Why are GA applied for mobile robot path planning

Question: I try to understand why most researchers are using GA for mobile robot path planning. In the Paper Path Planning for the Mobile Robot: A Review it shows its the most used. In the paper A Review of Optimization Algorithms for University Timetable Scheduling. They write that "GAs are particularly
applied to complex optimization problems, which are
challenges that have different parameters or characteristics that
need to be combined in search of the best solution and, at the
same time, cannot be represented mathematically"
Comment: Welcome to *Robotics* phiStackOverFlow, but I'm afraid that questions which are as broad as this are off-topic because answers would need to be too long. As it says in [ask] *If you can imagine an entire book that answers your question, you're asking too much*. We prefer *[practical, answerable questions based on actual problems that you face](http://robotics.stackexchange.com/help/dont-ask)*, so please take a look at [ask], [about] and the [*Robotics* question checklist](https://robotics.meta.stackexchange.com/q/1302/37) for advice on writing a good question.
Comment: Genetic algorithms are well-suited to problems where there are multiple solutions and/or no closed-form solution.  They are good at finding a solution that is good enough fairly quickly.  The downside is that no one really seems to know why they work.
Answer: That document claims

The results shows GA, PSO, APF, and ACO are the most used four
approaches to solve the path planning of mobile robot.

The survey shows GA (genetic algorithm), PSO (particle swarm
optimization algorithm), APF (artificial potential field), and ACO
(ant colony optimization algorithm) are the most used approaches to
solve the path planning of mobile robot

Which are both extremely suspect to me and given without evidence or a citation. Given the journal it is published in isn't even an engineering journal, let alone a robotics journal, I'm suspicious of anything written in that document that I don't already know is true. The author throws up a terrible straw man argument against search-based planners and suffocates other methods with only 1-3 sentences of lip service or ignores important methods like RRT and Navigation Functions.
I can say from personal experience at several robotics companies that I've never seen a GA algorithm being used for path planning across many domains of robotics. Its not to say they don't have their niche, but that niche is not the usual use-case. Traditional search and sampling based planners can yield high quality results in a fraction of the listed times in the GA papers and are widely seen across mobile, manipulation, and AUV navigation systems.
I believe this document is misleading and in many ways just factually incorrect, or at least inadequate.
Answer: Well, mobile robot path planning is a complex optimization problem, a challenge that has different parameters or characteristics that need to be combined in search of the best solution and, at the same time, cannot be represented mathematically.
Seems to me that makes the genetic algorithm approach worth exploring for a given application, although I'd want to see the citation for it being "the most used". If you need to get into detail about the parameters, characteristics, and what to optimize, you're getting into Ben's book.


CAT3 and CAT5 in the same conduit. Cross-talk potential?

Question: Can I run telephone cables and standard UTP CAT5/6 in the same conduit? Will it cause any interference or cross-talk?
Answer: You can mix UTP cable categories in the same conduit. The real reason not to is that it is harder to maintain because all the cable types exit the same place, and you need to separate them after they exit the conduit.
Be sure to maintain a fill ratio of no more than 40% to allow proper firestopping. There are calculators and tables for the National Electric Code to determine the number of cables you can fit in a particular size conduit to maintain the proper fill ratio.
Answer: I believe Cat5 and Cat6 are properly shielded (or can be, guess it depends on what you buy?) where Cat3 is not.  You shouldn't experience cross-talk between the cable types.
Comment: Category cable is specifically UTP (_Unshielded_ Twisted Pair). The immunity from noise is delivered by the cable twists, not shielding.
Answer: Yeah, you can use UTP cat5/6 in the conduit. Use one of the existing Cat5/6 cable to carry the audio to the speakers in various locations throughout the house. So in this case, the very same cable that's carrying ethernet is carrying amplified audio. The cross-talk would not happen.


Derivation of Coriolis acceleration before vectors got into use

Question: The Coriolis acceleration is known for ages, much before vectors started to be used. Even at the time when Gustave Coriolis was working, vectors were not well established as they are today. Nowadays, everyone uses vectors to derive the Coriolis acceleration, but how was it derived before, when vectors were still not used as they are now? Was it derived at all or the term was only empirically deduced and used for calculations?
Comment: The derivation is easier in some ways if you *don't* use cryptic vector calculus notation. It doesn't *need* anything more advanced than $x = r \cos\theta$, $y = r \sin\theta$.
Comment: @alephzero Yes, that's basically what was done before vector notation (except Coriolis works in 3D, so he also has a $z$).
Answer: Coriolis's original paper is:

G. Coriolis. Sur les équations du mouvement relatif des systèmes de corps. Journal de l'École Polytechnique, 15:142–154, 1835.

(cited in: Assis, André K. T. Relational Mechanics and Implementation of Mach's Principle with Weber's Gravitational Force. Montréal: Apeiron, 2014, p. 205 & 521.)
You can see that instead of cross product notation, he writes out all the components; and instead of vector notation, he writes three equations for $x$, $y$, and $z$.
(cf. Crowe's History of Vector Analysis)


Illustrator shape doesn't fill along path

Question: When looking very closely at my shapes, the fill is not following the paths I have defined. I have attached a screen shot where you see the blue does not go all the way to the red path. I have never seen this issue before.
Comment: To be sure that fill belongs to this path, select path, open Appearance panel and check stroke and fill.
Comment: are you sure you don't have 2 paths overlapping? Also is your path closed? Can we see more of the shape?
Answer: I know this question is 4 years old, but I thought I'd share an answer I discovered on the Adobe forum thread here: (https://community.adobe.com/t5/illustrator/fill-doesn-t-match-the-path-created/td-p/10474435)
The solution is:
View > View using CPU
For whatever reason, the GPU view was messing with some of my anchor points, extending the fill color out in an odd, squared-off way beyond the path (image 1 below). I switched it to CPU, and it cleared right up (image 2 below). Hope this helps anyone else coming here for an answer to this question!
Answer: If it steers anyone in the right direction, I can replicate it, having experienced it in the past. I can't remember if I managed to fix it.
For me, this only happens when creating a 72ppi RGB document, and then upscaling it (Effect > Document raster effects settings...) to 300ppi. For now, I can only view this at 17,000% zoom: https://postimg.org/image/w797ceuw3/
What % zoom do you have set to get this result, Jessica? If you can, it may be worth pasting everything in to a new, 300ppi document.
Comment: at that zoom level it's most probably just a rendering issue. If it exports fine for your intended purpose, than it's fine.
Comment: Uhn... The  Document Raster Effects item has *zero* effect on vector objects. As the title itself alludes to.. it's for raster elements. While I believe you may be able to recreate this anomaly.. I do not believe the Document Raster Effects setting has *anything* to do with it.


Can I get an outlet from this section of the open wall?

Question: There is a hole in one of the cabinets of the vanity, and I'd like to see if I can get an outlet installed through here. As a newbie who's never done electrical work, is it safe, and possible?
Answer: Can you take advantage of this hole to install an outlet nearby?  Yes probably.  The hole would probably make it easier to bring a cable to this location, and you could install an outlet in a surface-mount box inside the cabinet, or through a new hole cut for the purpose nearby in the back of the cabinet.
The harder question is where would the cable come from?  You need to tap off an existing outlet or your electrical panel and route a cable from there.  That needs some exploration and planning on your part.
Is it safe for a newbie to add an outlet in a wall?  IMO this is not a good first project, and is unlikely to be done safely without some on-site tutoring from someone knowledgeable.  There are too many details you need to learn in order to purchase the right materials and install them the right way.  If you have someone skilled who can watch and guide you, this could be safe but then you'd probably be asking them, not us.
Comment: No offense to any EEs out there, but in this case, somebody with experience fishing wires around plumbing is more valuable.
Comment: @jay613 - I was busy swearing at something else while he got on with that ;)) Both jobs got done.
Comment: Appreciate the response, and yes, due to it being a first time electrical project, I think I'll get an opinion of an EE friend and see if he can help out if anything.
Comment: ↑ @AloysiusDefenestrate - heartily agree. Just today had to defer to my friend's son, a mere snip of a lad [22] who successfully fished 240v mains & water through a [laughingly called] crawlspace 6" high over 30 ft to a 2" hole on an outside wall, passing all existing water, gas & power… without lifting a single floorboard. Pro job.
Comment: @Tetsujin in that situation I just swear a lot, and if that doesn't work, I swear some more, and eventually the job gets done. :)


Oberth Effect in deep space

Question: Does the Oberth effect only apply when in orbit of a planet or would a rocket generate more and more thrust (if kept on) even in deep space?
Wikipedia explains that the faster the rocket goes, the more useful energy it generates. But since speed depends from what point of reference you are measuring it, how can that be possible since the fuel doesn't know the rocket's speed?
Comment: OK, kinetic energy is *not* a frame independent idea, and you should be careful about applying any analysis that depends in KE. There will be times when it is useful, and other times when it simply enables you to fool yourself. The thing is, applied at the right time this analysis can lead to real insight, so it would be silly to dismiss them outright. The thing you need to figure out is *"It what frame would this mean something real?"*.
Answer: The Oberth effect takes advantage of when you add something to a quantity that is squared then the effect will be larger, the larger the quantity is initially. It works when a body is under the gravitational influence of another, usually larger e.g. a spacecraft around the Earth.
In the central body approximation, the energy equation of a (keplerian) orbit around a central body is, at a certain instant
$$E_0=\frac{v_0^2}{2}-\frac{\mu}{r_0}$$
where $v_0$ is the velocity, $r_0$ the distance to the central body and $\mu$ the gravitational constant (gravitational constant times the mass of the central body). The energy will remain constant while there is no maneuvers.
A sufficiently fast maneuver can be considered as an instantaneous change in velocity $\Delta v$, while $r_0$ remains approximately the same (around the Earth maneuvers usually take only a few minutes, which is much shorter than the orbital period around 100 minutes in low Earth orbit). So the energy after the maneuver is
$$E=\frac{(v_0+\Delta v)^2}{2}-\frac{\mu}{r_0}$$.
Now the larger the initial $v_0$, the larger the change in energy $E-E_0$.
Instantaneous maneuvers are an approximation. You can think that if the change in energy is different with the same maneuver (by making the maneuver at a different distance $r_0$) then something is wrong. Actually when performing the maneuver some propellant is expelled (and the mass of the spacecraft changes) and if one accounts for the energy of all, spacecraft and propellant, the change in energy is the same.
It can also work the other way round with a $\Delta v$ opposite to the initial $v_0$ (braking) and loosing more energy the larger the initial $v_0$.
Comment: Wiki also mentions that a faster rocket generates more energy, does that only apply when in a gravitational well?
Comment: "does that only apply when in a gravitational well?" No. Clearly you can set the gravitational term to zero and the energy difference $E-E_0$ doesn't change.
Comment: Edited the answer a little bit trying to be clear. A gravitational well is required for what it's called Oberth effect, as I see it, otherwise it will only be an effect of changing the kinetic energy by changing reference frames. The effect is hidden in the details as in reality the mass changes and so the potential energy is affected.
Comment: A gravitational well isn't the only way to define a reference frame. Whether you want to call it the Oberth effect or not in that case is, I guess, a question of semantics.

Oberth Effect in deep space


To take oneself's life is not an act of courage

Question: How do we make a reflexive using the "oneself" when referring to actions or inactions in a sentence.
For examples:

To take oneself's life is not an act of courage
Comment: The construction you're looking for is *To take **one's own** life is not an act of courage*.
Comment: The truth is that taking one's own life **is** sometimes an act of courage. Look up Masada, for example.
Answer: In English we often have to use a reflexive pronoun when we have two noun phrases that refer to the same person in the same (immediate) clause. In this post, I use a small < i > to show that two noun phrases refer to the same person.

Bob(i) kicked himself(i).
Bob(i) put a picture of himself(i) on the wall.

In example (1), above, the noun phrase Bob refers to the same person as the noun phrase himself. Because these two noun phrases are in the same clause, we can't just use a normal pronoun, him, as the Object of the verb kicked:

*Bob(i) kicked him(i). ("Him" cannot refer to the same person as "Bob")

We need to use a reflexive himself instead.
In the same way, we need to use the reflexive pronoun himself in (2), because it refers to the same person as the word Bob.
However, this rule does not apply if the second noun phrase is in Determiner function. In other words, it does not apply if the second noun phrase is a possessive:

Bob(i) kicked his(i) car. (grammatical)
Bob(i) put his(i) picture on the wall. (grammatical)

However, sometimes we want to emphasise  that the "possessor" is the same person as we just talked about. In this situation, we use the adjective own before the noun phrase:

Bob kicked his own car.
Bob put his own picture on the wall.

We cannot use a reflexive pronoun as a Determiner in English:

*Bob kicked himself's car. (ungrammatical)
*Bob put himself's picture on the wall. (ungrammatical)

The Original Poster's example

*To take oneself's life is not an act of courage.

Here the understood subject of the verb take is the same person as the person who owns the life. However, this example isn't grammatical, because it uses a reflexive pronoun as a Determiner.
Instead the writer needs to say:

To take one's own life is not an act of courage.

The writer could also write:

To take one's life is not an act of courage.

However, this does not put as much emphasis on the the fact that person is taking their own life. It does not have the same reflexive feeling as example (10).
It is fine to use oneself as a normal reflexive pronoun:

One shouldn't kick oneself.
It's nice to put a picture of oneself on the wall.
Answer: You can't make it more reflexive than it already is because oneself is as reflexive as it can possibly be. It's a reflexive pronoun and it's called that for a reason. In very simple terms, reflexive pronouns, apart from some other uses that they have, are used in situations where the effects of an action are reflected back in some way onto the doer of the action. For instance:

He hurt himself very badly.

The effects of the action of hurting are reflected back onto the person performing the action which is he in this case.
In the case of your example, it actually would be better to use the so-called impersonal you in its possessive form, your, as the sentence is talking about your life belonging to you as a generic person:

Taking your own life is not an act of courage.

For a more comprehensive explanation on what exactly the impersonal you is and how it's used, see the Wikipedia article I attached to this post. But loosely speaking, the impersonal you is not used to refer to you personally, but rather to people in general.
Answer: Oneself is really a shortening of one's self. It is not uncommon to see the phrase one's own self.
In isolation the word "self" refers to a person's nature, character, and individuality. It does not exclusively refer to a "physical" person.
For example if someone told you to "take care of yourself" it would refer to your whole person and perhaps looking after your physical, mental and emotional needs too. The inference is that one has or possesses a "self".
You should now be able to see why your sentence is incorrect:

To take oneself´s life is not an act of courage.

You mean to refer to "life" as the thing that is owned or possessed, but you have already essentially said "one's self". You wouldn't write or say "one's self's life", not because it is necessarily gramatically incorrect (you could just about get away with saying "your mother's father's brother"), but because it is a tautology.
You should just simply say:

To take one´s life is not an act of courage.
Answer:
oneself is a reflexive pronoun. Examples of reflexive use are:
to kick oneself, to berate oneself, to blame oneself, to declare oneself, to be oneself [idiom] . Not every verb can be used reflexively. They are, however, action or active verbs.
one's own [thing] means a thing that belongs to one. Own is an adjective.

As in: my own house, his own car, their own ideas
To kick oneself would be reflexive. [this is an idiom, but works in the same way as the OP's question, which is somewhat distasteful to work with here.]
Therefore:
To kick oneself for another's problems is not an act of courage.
You can kick yourself, but you cannot kick your own self. You could kick your own ball in your own garden.
kick oneself means to blame oneself for something.
One's own life may be full of problems but whose life isn't?


Cardano-Ethereum Bridge

Question: What is the best way to write a smart contract that will work across both Cardano and Ethereum? It doesn't have to be released yet but preferably something that will be usable by the end of the year. I believe that this is what the KEVM may allow?
Answer: This won't be possible, because Solidy and Plutus are both different languages and even the blockchain accounting system is different on both platforms.
There might be a side chain running KEVM in the future, where you will be able to run Ethereum smart contact and somehow interact with the Cardano mainnet, but this is still just in the planning at the moment and nothing specific has been shared to mention we will have this anytime soon.

Cardano-Ethereum Bridge


What's lacking in our understanding of the strong interaction?

Question: As far as I'm aware, our understanding of the strong interaction and strong nuclear force is pretty good. We can explain how particles move and stick together with good models. But from what I can find, I gather we do not have a mathematical theory that explains this in a precise manner. For example, for electromagnetism and gravitation, we have well established models that predict the phenomena precisely. My question is, is there anything lacking, such as a big hole in our knowledge, or is there any big problem or issue that has stopped us from establishing a mathematical model for the strong interaction?
Comment: *I gather we do not have a mathematical theory that explains this in a precise manner.* This is wrong. There is a precise mathematical model of the strong interaction between quarks. It has existed for about 50 years and is well-confirmed. The strong interaction between nucleons is a messy side-effect but is *in principle* explained by the same theory.
Comment: @G.Smith anywhere I could find it then? :)
Comment: The green box [here](https://en.wikipedia.org/wiki/Quantum_chromodynamics#Lagrangian) has the QCD Lagrangian for a single kind of quark. All six kinds of quarks are the same in how they feel the strong force; they just differ in mass (and electric charge, which is not relevant to the strong force). The entire theory flows from this expression!
Comment: If that kind of Yang-Mills Lagrangian is meaningless to you, then you should start by learning the quantum field theory of scalar fields, then QED, then QCD. If the entire concept of a Lagrangian is meaningless to you, you need to study advanced Newtonian mechanics.
Comment: I see in your profile that you are a high school student. Relativistic quantum field theory is generally graduate-school-level physics and is not easy to learn. If you want to eventually learn it, for now I suggest learning Special Relativity, classical EM, advanced classical mechanics, and nonrelativistic QM. If you try to plunge in to QFT without understanding these first, you will probably be lost by page 2 of a QFT textbook.
Comment: I would estimate understanding QCD as being 1000 times harder than understanding, say, Coulomb's Law. You can understand Coulomb's Law in a day. It usually takes four years of undergraduate physics before you are ready to start learning QFT.
Comment: @G.Smith Yeah, my dream would be to study physics, but thank you for the advice :)
Answer: Most of the calculations in quantum mechanics are made using the perturbation calculus. That is, we assume that the theory with no interactions that describes a free particle is an approximation of the full theory, take the classical solution of the free equations, and then add corrections. There are usually infinitely many quantum corrections that need to be calculated, but they often form a series in which every next term is much smaller than the previous one, and calculating just few initial terms gives a good approximation of a full result.
The problem with strong interaction is that the interaction is so strong we cannot reasonably approximate the real physical states with free-particle states. That means we fail at the first step, and we cannot use the perturbation approach that works in other cases.
Anther problem with QCD is that gluon fields interact directly with itself, making even the classical equations are non-linear, as opposed to linear equations of QED (in which electromagnetic field does not interact directly with itself, but only with charged matter). And we don't have the right mathematical tools to fully solve non-linear equations. This is similar to Generla Relativity, which also has non-linear equations. Because of that in GR we only know very few exact solutions. QCD has the same problem, and because of that we need to relay more on the simulations than on analytical solutions.
Comment: well and good,but I would like to draw the attention on the ampliduhedron which is another calculatonal view of  the dynamics of strong interactions , not perturbative ,https://arxiv.org/abs/1312.2007 and https://arxiv.org/abs/1810.08208
Comment: Dear @annav, sometimes you are spot on, sometimes you miss, but always with plenty references to back up your point. These smack of AI behavior. Please, please tell me that you are indeed human, or at least partial human.
Comment: @MadMax as I am turning 80 in april we can settle on the partially human :). Because of my age I do not trust my memory and look up as much as possible for references to what I think is a correct answer/comment , then it is a waste not to link what I found.
Comment: Thanks @annav. Superb job! I am impressed. You 80, Joe 77, Mike 78, and Bernie 78. "Do not go gentle into that good night".
Comment: @MadMax + anna v :) aww meep. ❤#meep. (that's meant to be a soft warm Good sound to wish soft Warm feels from my little Warmheart.)
Answer: Wikipedia has mentioned that in the high energy range which is the domain of particle physics the perturbation theory works fine which can result in sort-of-analytical form of predictions  which match the experiment results with good precision which is the main success of the theory of strong interaction come from for now.
But in the low energy range when quarks bind to together to form hadrons and hadron bind toether to form atomic nucleus, the perturbation theory fails and the only thing valid is sort-of-pure-numerical-framework solutions called lattice QCD.
With LQCD and enough computing power you can predict properties of hadrons and atomic nucleus and even nuclear reactions with high precision from the theory of strong interaction. But for now due to limited computation power LQCD can only predict hadron with some acceptable precision.
Due to the near to the end of the Moore's Law, maybe only small  atomic nucleus can be predicted finally in the future without model/algorithm/hardware breakthrough. Another breakthrough may come from Quantum Computing.
Another route is phenomenological model like the many models of atomic nucleus which has little to do with the theory of strong interaction.

For example, for electromagnetism and gravitation, we have well
  established models that predict the phenomena precisely

This is because the classical model - the Maxwell' equation which deal only with EM field in vacuum or simple material which can be treated as a continous bulk with some properties like dialetric constant which can be used in the equation. Once you begain to deal with "true EM problem" - like predicting structures and properties atom/molecule/liquid/solid from quantum mechanics, it soon become not that precise too, a lot of trade off and approximation is needed to make it computable on current generation of computers.
For gravity, there is not even a "true gravity"(quantum gravity) theory for now and you treat star/galaxy/Universe as a continuous bulk using GR, like in classical EM.

What’s lacking in our understanding of the strong interaction?


How high is too high with Cronbach's alpha?

Question: Someone in my organization just sent me a scale they developed (modified items from five separate scales used in published research) to measure an employee's readiness for change. They tested the internal consistency of the 15-item scale with Cronbach's alpha. The result was .995, and the alpha after each item was deleted was .995 (for each item). I'm pretty sure that results should not be this high and that there is a problem with the items themselves, the response scale, or perhaps the method of data collection. On the face of it, the individual items don't appear to be redundant. I know that a scale should also be tested for test-retest reliability, convergent and discriminant validity. What would be the first thing I should check to figure out what might be causing these results?
Comment: No, at face value the question items were different. They were pulled from different scales (multiple dimensions of the construct). He selected one or two items from each of the other scales and combined into a single index (trying to create a unidiminsional scale). Instead of the alpha being low (items should be representing multiple dimensions), it was essentially 1. This should indicate that something else is inflating the alpha, no? I assumed the result was due to CMB, social desireability, or something else related to his method of data collection, participant characteristics, etc.
Comment: It would be great to see some examples.  That high an alpha and that high interitem correlations suggest that the items are measuring the exact same construct. It appears that you only need to ask one of the items (any item). Are the items asking the same question but with slightly different format?
Comment: This is indeed a bit high even for an "individual testing" questionnaire. Do the usual alpha (based on covariances) and standardized alpha (based on correlations) differ much in your example?
Comment: Have you considered using IRT (http://en.wikipedia.org/wiki/Item_response_theory)?
Comment: Hi Tim, he provided a correlation matrix and several items are highly correlated >.97 and a few at .99. I don't have any information about the difference between the usual and standardized alpha's. He's also used a subset of the scale as the DV and regressed that on the other items. Not surprisingly the R square is over .90 for 5 of the items (.96 and .97 on two). Here I suspect that common method bias is a big problem. I don't and won't have access to the raw data to test the scale any further. I'm just leaning towards not using it based on the results he's provided. Thanks for your feedback.
Answer: When I have ran into this kind of error, I had made a mistake during the coding process (I'm using SPSS). I usually use numbers like 99 or 999 to mark missing values. Once I forgot to specify the missing values to be excluded at the variable view, and I begun the scale analysis. I got very high C-alphas, around 0.95, just like you.
Comment: To me this is a more plausible explanation than the otherwise good ideas about CMB, SD, etc.
Answer: I agree with @rolando2, as I believe mistakes made during the coding process could be the cause of such a high $\alpha$. Though my guess is that it is due to item redundancy - something you mentioned in your question. Another plausible cause could be your sample. I have analyzed survey data from many sources, and from my experience, it is clear that responses to organizational surveys are often quite lazy, in that it is common to see many respondents answer the same way across the entire survey. This is why I prefer organizational surveys that are both short and easy to read, as doing both makes it less likely for respondents to answer lazily.


Editing photoshop smart layers in fireworks

Question: If I import a psd file with smart layers into Fireworks, is it possible to edit one of those smart layers the same way you would be able to in Photoshop?
Comment: There are a lots of things in Photoshop that Fireworks can also do, but require different user actions to complete
Comment: Have you tried?
Comment: Yes, when you double-click the layer it doesn't open up a new window with the isolated layer as it does in Ps.
Comment: Doesn't that answer your question? Fireworks lacks the code structure to edit Smart Objects.
Answer: I don't understand why you even need to do this. Do your editing in Photoshop then go to Fireworks. K.I.S.S.
Comment: Not everyone has Photoshop installed. If you receive a file created in Photoshop and you only have Fireworks, this solution doesn't really work.


What is the difference between a web API and a web service?

Question: Is there any difference between a web API and a web service ? Or are they one and the same ?
Comment: An API is the published interface, while the service is the implementation running in the backend.
Comment: See also programmers.SE: [Difference between Web API and Web Service?](http://programmers.stackexchange.com/questions/38691)
Comment: Please read answers with caution. Some of them either outdated or invalid
Comment: See also: [API vs. Webservice \[closed\]](http://stackoverflow.com/questions/808421)
Comment: just adding one more brilliant explanation -  https://www.quora.com/What-is-the-difference-between-web-services-and-API
Answer: A web service typically offers a WSDL from which you can create client stubs automatically. Web Services are based on the SOAP protocol.
ASP.NET Web API is a newer Microsoft framework which helps you to build REST based interfaces. The response can be either JSON or XML, but there is no way to generate clients automatically because Web API does not offer a service description like the WSDL from Web Services.
So it depends on your requirements which one of the techniques you want to use. Perhaps even WCF fits your requirements better, just look at the MSDN documentation.
Comment: Web services are NOT necessarily based on the SOAP protocol.
Comment: technically outdated answer
Comment: "ASP.NET Web API" is a Microsoft framework, not "Web API" itself.
Comment: outdated answer, visit this link https://microsoft-techies.blogspot.com/2014/03/difference-between-api-and-web-service.html
Answer: The basic difference between Web Services and Web APIs
Web Service:
1) It is a SOAP-based service and returns data as XML.
2) It only supports the HTTP protocol.
3) It is not open source but can be used by any client that understands XML.
5) It requires a SOAP protocol to receive and send data over the network, so it is not a light-weight architecture.
Web API:
1) A Web API is an HTTP based service and returns JSON or XML data by default.
2) It supports the HTTP protocol.
3) It can be hosted within an application or IIS.
4) It is open source and it can be used by any client that understands JSON or XML.
5) It has light-weight architecture and good for devices which have limited bandwidth, like mobile devices.
Comment: A web service can be hosted on lots of places, not only IIS
Comment: Practically all the points are wrong. I can't understand how 40 users could have up-voted.
Comment: @horcrux I agree.  A Web Service is not necessary a SOAP based service.
Comment: the most confusing answer I  have ever seen.
Answer: API vs Web Service
Just pasted the summary of the linked article:

Summary:

All Web services are APIs but all APIs are not Web services.
Web services might not perform all the operations that an API would perform.
A Web service uses only three styles of use: SOAP, REST and XML-RPC for
  communication whereas API may use any style for communication.
A Web service always needs a network for its operation whereas an API doesn't need a network for its operation.
An API facilitates interfacing directly with an application whereas a Web service is a ...

Read more: Difference Between API and Web Service | Difference Between | API vs Web Service http://www.differencebetween.net/technology/internet/difference-between-api-and-web-service/#ixzz3e3WxplAv
See the above link for the complete answer.
Comment: But, question is about difference between WebAPI and WebService, not "API"
Comment: Furthermore, the point 3 is not correct. It is misleading, and it just helps to make confusion about the "SOAP vs. REST" topic.
Answer: for more detail visit this link
Comment: why?
from this image it seems that SOAP web services cannot be used on smartphones... or even on desktops?
really?  someone is forcing you to read JSON instead of XML on those platforms?
Comment: if reading xml it does not mean it SOAP base service REST also support Command Separated Value (CSV), JavaScript Object Notation (JSON) and Really Simple Syndication (RSS).
Answer: A Web Service if you want is a Web API. Specifically Web API usually means RESTful (HTTP based) web service and Web Service usually means SOAP+WSDL (+HTTP or SMTP or JMS..).
Tipically RESTful web services are opposed to Web Services (WSDL,SOAP) but recently it has been introduced the term RESTful Web services (with uppercase 'W') that means RESTful+WSDL+SOAP..
Check out this chart for differences among the three concepts:
http://www2.mokabyte.it/cms/figureproviderservlet?figureId=IUS-6NS-OBV_7f000001_19624184_5621ef4e--Fig02.jpg
Hope it helps!
Answer: Web service is absolutely the same as Web API - just a bit more restricted in terms of underlying data format. Both use HTTP protocol and both allows to create RESTful services.
And don't forget for other protocols like JSON-RPC - maybe they fit better.
Comment: Not "absolutely the same" if there are restrictions now are they?
Answer: API and Web service serve as a means of communication.
The only difference is that a Web service facilitates interaction between two machines over a network. An API acts as an interface between two different applications so that they can communicate with each other.
An API is a method by which third-party vendors can write programs that interface easily with other programs.
A Web service is designed to have an interface that is depicted in a machine-processable format usually specified in Web Service Description Language (WSDL)
All Web services are APIs but not all APIs are Web services.
A Web service is merely an API wrapped in HTTP.

This here article provides good knowledge regarding web service and API.
Answer:
Web service is a collection of open source protocols and standards used for exchanging data between systems
or applications whereas API is a software interface that allows two applications to interact with each other
without any user involvement.
Web service is used for REST, SOAP and XML-RPC for communication while API is used for any style of communication.
Web service supports only HTTP protocol whereas API supports HTTP/HTTPS protocol.
Web service supports XML while API supports XML and JSON.
All Web services are APIs but all APIs are not web services.
Answer: In the context of ASP.Net a Web API is a Controller whose base class is ApiController and does not use Views.
A Web Service is a class derived from WebService and has automatic WSDL generation.  By default it is a SOAP api, but you can also use JSON by adding a ScriptServiceAttribute.
Answer: Well, TMK may be right in the Microsoft world, but in world of all software including Java/Python/etc, I believe that there is no difference.  They're the same thing.
Answer: Difference between Web Service and Web API nicely explained here:
https://softwareengineering.stackexchange.com/questions/38691/difference-between-web-api-and-web-service
Text from the link:
Web Services - that's standard defined by W3C, so they can be accessed semi-automatically or automatically (WSDL / UDDI). The whole thing is based on XML, so anyone can call it. And every aspect of the service is very well defined. There's parameters description standard, parameter passing standard, response standard, discovery standard, etc. etc. You could probably write 2000 pages book that'd describe the standard. There are even some "additional" standards for doing "standard" things, like authentication.
Despite the fact that automatic invoking and discovery is barely working because clients are rather poor, and you have no real guarantee that any service can be called from any client.
Web API is typically done as HTTP/REST, nothing is defined, output can be for eg. JSON/XML, input can be XML/JSON/or plain data. There are no standards for anything => no automatic calling and discovery. You can provide some description in text file or PDF, you can return the data in Windows-1250 instead of unicode, etc. For describing the standard it'd be 2 pages brochure with some simple info and you'll define everything else.
Web is switching towards Web API / REST. Web Services are really no better than Web API. Very complicated to develop and they eat much more resources (bandwidth and RAM)... and because of all data conversions (REQUEST->XML->DATA->RESPONSE->XML->VALIDATION->CONVERSION->DATA) are very slow.
Eg. In WebAPI you can pack the data, send it compressed and un-compress+un-pack on the client. In SOAP you could only compress HTML request.
Answer: All WebServices is API but all API is not WebServices, API which is exposed on Web is called web services.
Comment: Web Service is the standard defined by W3C, well documented service for the 3rd party software to interact through XML (WSDL/UDDI). Web API is the API over HTTP, not well documented, has it's own standard. And API in general is something that can or can not have internet access to talk to other applications and can have other protocols too e.g. API for system calls to talk your terminal/cmd in OS.
Answer: Two things are very simple to understand,

API: It's an layer on application which can serve other application
request locally.
Webs Service:Is an API which can serve request and respond over the
network form remote system over the web or internet .

Note:
All Web Service is API's but not all API' is web services
Comment: On locally as well as on over the web


Using onboard graphics card instead of dedicated one on linux mint

Question: My dedicated graphics card (Radeon 6470) seems to have broke and I want to use the on board Intel graphics instead, but I can't figure out how to switch to it. The bios on my laptop (HP pavilion dm4) doesn't let me do it and I don't know how it's done on the OS, I'm using Linux Mint.
Answer: In general, you cannot. In most computers, the BIOS will disable the embedded the graphics when an expansion GPU is installed. For most PC's, the only way to use the embedded graphics is to physically remove the card from the computer.


the file osinstall.mpkg missing

Question: after updating this morning I ended up with the message on the screen that the osinstall.mpkg was missing, using Time Machine I managed to get everything back to normal without too much struggle, but what do I do now ? If I update is going to show the same mistake again ? How do I proceed ? Thanks
Answer: When you install from an "install application" on a primary-path disk, it guts the "install application" into an empty shell.
Copy the "install application" to an external drive.  When installed from there it does not end up gutted, or just use the external drive as a reusable copy.

the file osinstall.mpkg missing


What does weapon inertia mean?

Question: In Crysis and Crysis Warhead there is an option called weapon inertia with a slider. What is weapon inertia and how does it influence my gameplay when I put the the slider to lowest/middle/highest position?
Answer: As user98085 have already pointed out, this adds simulated inertia (delay on movement) to the weapons. However this really is just an aesthetic detail, as bullets will still instantaneously fly to the center of the screen, as illustrated by this video by aucoorslt on YouTube:
Answer: Referring to Inertia, this setting defines how much delay and resistance there is on moving the weapon. High weapon inertia results in sluggish, slightly delayed movement, while with a low setting the movement gets closer to instantaneous.
Both have their up- and downside, some of it may be considered "realism" and some can be about precision. Largely, this is up to personal preference, but obviously a low inertia setting gives you direct control where a high setting wouldn't.
Comment: Are you sure this effect actually ads delay? I've always thought that it's only cosmetic setting.

What does weapon inertia mean?


Understanding the relation of weak and weak star toplogy

Question: I'm working with Eberlein- Smulian Theorem fromm the book "Topics in Banach Space Theory". During the proof I have seen that there is used a lot the concept of weak topology and weak star topology. For a given Banach space X according to the definitions the weak topology is defined on X and the weak star topology is defined on the dual space X* . While trying to understand the proof I see that for  a set A in X there is considered the weak* closure W of A in X**  . *I don't understand how we can speak about the weak and weak-star closure of a set A in X, since the weak-star closure, to me, makes sense only for sets in X   **. I am really struggling with this issue! Is anybody who  can tell me which is the clue here? The set A to which I am referring is used to prove that (iii) implies (i) in the last paragraph of the theorem. Any advice would be really appreciated!
Comment: The author is thinking of $X$ embedded in $X^{\ast\ast}$ via the natural map $x \mapsto x^{\ast\ast}$, where $x^{\ast\ast}(f) = f(x)$
Comment: I have seen this embedding to be mentioned in several places. The nature of X and X** is different, so how is this embedding constructed ? Thank You!
Comment: The embedding is precisely as @PrahladVaidyanathan gave it above. In more detail: If $x\in X$ then you embed that as $x^{**}\in X^{**}$ via the given formula. So $x^{**}$ needs to be a linear functional on $X^*$; you pick some $f\in X^*$ to apply $x^{**}$ to, and discover that now you have $x\in X$ and $f\in X^*$, and you combine them in the only way that makes sense: $f(x)$. Thus arriving at $x^{**}(f)=f(x)$.
Answer: The short answer relies on two facts:

$X^{**}$ is a dual space, so it has a weak* topology.
$X$ can be considered a subspace of $X^{**}$.

As a side remark, the weak topology on $X$ coincides with the subscpace topology inherited from $X^{**}$ with the weak* topology, since both are derived from the functionals in $X^*$.
Comment: Yes, now I think I got the point! So, what is meant by weak* topology during the proof is the weak* topology on X**, since X can be embedded in X** and as you claim, X can be viewed as a linear subspace of X**. So, for a given a Normed Space X when speaking about weak* toplogy we may refer to it as the weak* toplogy defined on X** when we want to consider certain properties of sets in X such as compactness and closure. Now it makes sense to me talking about weak* closure and compactness of a set A in X. It seems like I'm repeating myself but I need to know if I got it right or not! Thank You!


How to fix a hole in the wall of a plastic shower/bathtub?

Question: I have a hole in the wall of my shower about 4 inches in diameter.  I think there is fiberglass underneath.  What is the best way to fix the wall and what kind of paint could I use to make it blend in with the rest of the tub?
Answer: You can actually repair it. Generally make it dry. Sand down the surface around the effected areas. If there is an actual hole try using plywood to fill the hole. Apply fibreglass (you can buy strips of it) and coat each piece entirely in epoxy resin. Let it cure and repeat until there is a correct thickness. You can then sand that down as well to make it smooth and flush with the rest of the structure. You can paint it over with an epoxy based paint that will stick and not peel.
Comment: Awesome! Tht's just what I was looking for.  I took a second look at the hole and I realized that just a bunch of cracks that caved in (like someone hit it with  a blunt object).  So in this case, I'm guessing I would just use the exact same method minus the plywood?
Comment: That is correct


Where do traders take their prices data from? How can it be different from their brokers'?

Question: I understand there are multiple sources for stocks or FX market prices, but what leaves me completely puzzled, is how can short term traders (speculators really) make their decisions based on price data from sources other than their broker; especially for forex. If one is tracking a particular currency pair with broker A, but data comes from source B, then they can't be sure that is the price they're going to get, right?
Comment: I'm not sure I understand the question, but I *think" you are starting from a false premise...
Comment: It may very well be so. I'm assuming the price data don't usually come directly from the broker. If trader now decides to buy X amount of assets from the broker, how does he know the unit price broker has, since price data came from elsewhere?
Answer: This is a complicated subject, because professional traders don't rely on brokers for stock quotes.  They have access to market data using Level II terminals, which show them all of the prices (buy and sell) for a given stock.
Every publicly traded stock (at least in the U.S.) relies on firms called "market makers".  Market makers are the ones who ultimately actually buy and sell the shares of companies, making their money on the difference between what they bought the stock at and what they can sell it for.  Sometimes those margins can be in hundreds of a cent per share, but if you trade enough shares...well, it adds up.
The most widely traded stocks (Apple, Microsoft, BP, etc) may have hundreds of market makers who are willing to handle share trades.  Each market maker sets their own price on what they'll pay (the "bid") to buy someone's stock who wants to sell and what they'll sell (the "ask") that share for to someone who wants to buy it.
When a market maker wants to be competitive, he may price his bid/ask pretty aggressively, because automated trading systems are designed to seek out the best bid/ask prices for their trade executions.  As such, you might get a huge chunk of market makers in a popular stock to all set their prices almost identically to one another.  Other market makers who aren't as enthusiastic will set less competitive prices, so they don't get much (maybe no) business.  In any case, what you see when you pull up a stock quote is called the "best bid/ask" price.  In other words, you're seeing the highest price a market maker will pay to buy that stock, and the lowest price that a market maker will sell that stock.  You may get a best bid from one market maker and a best ask from a different one.  In any case, consumers must be given best bid/ask prices.
Market makers actually control the prices of shares.  They can see what's out there in terms of what people want to buy or sell, and they modify their prices accordingly.  If they see a bunch of sell orders coming into the system, they'll start dropping prices, and if people are in a buying mood then they'll raise prices.
Market makers can actually ignore requests for trades (whether buy or sell) if they choose to, and sometimes they do, which is why a limit order (a request to buy/sell a stock at a specific price, regardless of its current actual price) that someone places may go unfilled and die at the end of the trading session.  No market maker is willing to fill the order.
Nowadays, these systems are largely automated, so they operate according to complex rules defined by their owners.  Very few trades actually involve human intervention, because people can't digest the information at a fast enough pace to keep up with automated platforms.
So that's the basics of how share prices work.  I hope this answered your question without being too confusing!
Good luck!
Answer: To add a bit to Daniel Anderson's great answer, if you want to 'peek' at what a the set of bid and ask spreads looks like, the otc market page could be interesting (NOTE:  I'm NOT recommending that you trade Over The Counter.  Many of these stocks are amusingly scary):  http://www.otcmarkets.com/stock/ACBFF/quote
You can see market makers essentially offering to buy or sell blocks of stock at a variety of prices.


Is this convex minimizer a continuous function?

Question: Consider the function $g: \mathbb R^n \rightarrow \mathbb R$ given by:
$$
g(x) = \arg\min_{y\in\mathbb R} \sum_{i=1}^n f_i(|y - x_i|)
$$
where $f_i$ are convex, strictly increasing and continuous. Further assume that at least one $f_i$ is strictly convex (so the minimizer is unique). Is $g$ a continuous function?
Comment: Just because the functions $f$ are convex does not mean their composition with absolute values will be.
Comment: I would start with the case $n=1$.  How would you treat the situation in which the functions $f_i$ do not have unique minimums?
Comment: Updated the question with more conditions on $f_i$'s. Thanks for pointing this out.
Answer: As you've written it, $g(x)$ appears to be a set valued function: the minimum can occur at many values of $y$. For instance, when each $f_i$ is constant we have $f(x)=\mathbb R$ for any value of $x$.
Comment: Updated the question with more conditions on $f_i$'s. Thanks for pointing this out.
Comment: This should be a comment, not an answer...


Restrict Content in iTunes

Question: I'd like to know if it is possible to restrict playback of certain content in iTunes. I know it can be done when using Apple TV 2/3 but can't seem to find a way to do it in iTunes itself. I can tag the media files using MetaX or MetaZ, these tags show up in iTunes but I can't seem to limit playback of films to only 'U' for example. Anyone got any ideas?
Answer: This used to be possible, but with the latest iteration of iTunes, it doesn't work.
The method was always as described above, and the same thing happened on the last major release of iTunes.  Apple eventually seemed to put things right, but it's happened again this time round.
I have movies stored on my Mac and Home share them via iTunes.  When my daughter accessed movies on her Mac, which had parental controls set in iTunes, anything over 12 (UK rating) was greyed out and unable to be played.  Now they're all accessible.
Perhaps Apple will resolve this issue too, if enough of us report it.
Answer: If the content was purchased from the iTunes Store, you can enable Parental Controls. See HT1904 iTunes: Using Parental Controls :

From the iTunes menu open Preferences ⌘ cmd ,
Click the Parental tab.
Select the checkbox next to any item you wish to disable or restrict.

Content not purchased from iTunes Store
When you purchase content from the iTunes Store it sets the MPAA content rating for that item. Unfortunately, you cannot modify (or set) the content rating from within iTunes itself, so you're going to have to get a little bit creative.
You can edit the metadata using an app such as iFlicks, which I strongly recommend. iDentify is a free alternate, however it does not appear as nice (although I have not used it myself). I'm going to provide instructions for iFlicks, but the process would be very similar for iDentify.

Drag the movie out of iTunes onto your Desktop, and delete the movie from within iTunes.
Drag the movie into iFlicks. iFlicks should recognise the movie and match it up with the right information.
Select the movie, and then click the cog in the bottom menu bar (it's the third from the left)
In the popover you can set the Content rating on the lower right, then hit OK.
Choose iTunes compatible as the preset, Current Location as the destination. Select Add to iTunes and Move Original to Trash

Click start, and then after a short file the file should be added into iTunes and it will be subject to the content ratings to set in iTunes preferences
Comment: David,

Blimey thanks for the rapid reply! Not all the content, which is mainly movies, has been bought from the store. Loads of them are movies I have ripped from DVD's I own. So I'd like to password protect anything nastier than a 'U' (I'm in the UK, that rating is for kids) so that my kids aren't subjected to swearing or violence inadvertently if I'm not around.
Comment: Its possible. I'm working on an edit. In the mean time, check out http://tidbits.com/article/13122
Comment: David, thanks for the info, I'm going to check it out.
Comment: David, you have pointed me in the direction of a couple of nifty pieces of software so thanks for that. But my original problem still remains - it seems that there is no way to restrict content played in iTunes. I was thinking along the lines that iOS uses for ATV, password protect files that are rated above a certain age limit. I may have to rethink the strategy I was going to employ for the media centre.

Restrict Content in iTunes


High-level overview of Razborov's method of approximations

Question: What is Razborov's method of approximations? Can someone give a high-level overview and the intuition behind it?
Comment: If you want to watch a lecture on the topic, Tim Gowers covers this in his complexity theory lectures: https://sms.cam.ac.uk/collection/545358
Answer: Let $f$ be a Boolean function on $n$-bits. Let $Z = f^{-1}(0) \subseteq 2^n$. Let $C$ be circuit on n bits and of size $m$ and gates $g_1, \ldots, g_m$. $g_i$ also denotes the function on $n$-bits computed by subcircuit with $g_i$ as the last gate. The first $n$ gates are for the input $x_1, \ldots, x_n$. The goal is to show that $C$ of size $m$ cannot compute $f$. Consider all computations of $C$ on inputs from $Z$. A computation assigns values to outputs of gates. Let $B$ be the Boolean algebra of $P(Z)$.
The idea is to consider for any function  $g$ on $n$-bits how well it approximates $f$ on $Z$. Let $||g|| = \{w \in Z \mid g(w) \neq 0 \}$.
For an ultrafilter $F \subseteq B$ we can define a new computation by ultraproduct from it: $c(g_i) = 0$ iff $||g_i|| \not\in F$. Because an ultrafilter is essentially a set of consistent computations for 0 values the resulting $c$ is a valid computation. It would follow that $f(c_1, \ldots, c_n) = 0$. We created a new computation from existing ones. Since all ultrafilters on finite sets are principal $c_1,\ldots,c_n \in Z$. This works for any circuit, we have not exploited the fact that the circuit is of size $m$.
The next idea is now to exploit the finiteness of the circuit to construct a new input that is outside $Z$ and $f(w) \neq 0$ but the circuit does not notice because of its limited size and therefore still outputs 0. So it does not compute $f$.
We need to relax the definition of ultrafilter so that we can get an input outside $Z$. In place of ultrafilters we use upward-closed subsets of $B$ ($a \in F$ and $a \subseteq b$ implies $b \in F$) that preserve meets($a,b \in F$ implies $a \cap b \in F$).
Let $W_F = \{w \in 2^n \mid w_i = 0 \to ||\lnot x_i|| \in F, w_i \neq 0 \to ||x_i|| \in F\}$. $W_F$ is the set of inputs consistent with $F$. If $F$ is prime ($a \cup b \in F$ implies $a \in F$ or $b \in F$) and nonfull ($\emptyset \not\in F$) then for each $i$, $F$ contains either  $||x_i||$ or $||\lnot x_i||$ and $W_F$ contains only a single input.
We are going to relax preservation of meets. In place of all meets in the Boolean algebra we will preserve a small number of them. Let $|f|$ be the smallest number $k$ of meets $M = (a_1 \cap b_1, \ldots, a_k \cap b_k)$ such that for all upward-closed, nonfull, $M$-preserving $F$, $W_F \subseteq Z$.
Let $m$ be the circuit complexity of $f$. Razborov proved that $\frac{1}{2}|f| \leq m \leq O(|f|^3 + n^3)$.
Note that this inequality holds for all functions. To prove a circuit size lower bound $m$ show that for all $m$-meets $M$, there is a $F$ that satisfies the conditions but its $W_F$ is not contained in $Z$. Moreover any strong circuit lower bound can be proven by this method because of the second inequality.
The actual part of a circuit lower bound proof is to show that for given $m$, for any $m$-meets there is such an $F$. In the case of monotone circuits the condition about $W_F$ simplifies to $w_i \neq 0 \to ||x_i|| \in F$ so coming up with $F$ is easier.
Alexander Razborov, On the Method of Approximation, 1989.
pdf
Mauricio Karchmer, On Proving Lower Bounds for Circuit Size, 1995.
Tim Gowers, Razborov's method of approximation, 2009. pdf
Comment: What is $|f|$? Is it $k$?
Answer: Disclaimer: This is only a high-level overview intended to give some intuition to the methods used in Blum's recent paper.
I will attempt to use notation that is closer to what is used in the aforementioned paper.
Let $f$ be a Boolean function on $n$ variables $x_1,\dots,x_n$. Suppose we want to prove that any Boolean network computing $f$ has large size.
Given some Boolean network $\beta$ computing $f$ at its output node, consider the following process.

Order the gates in $\beta$ according to some topological order $g_1,g_2,\dots,g_m$ where the last node is the output node.
For each time step $t=1,\dots,m$ we will approximate the function computed at gate $g_t$ by a "simple" function $f_{g_t}$. This approximation may change the functions computed at nodes downstream of $g_t$ (in particular, the function at the output node $g_m$ may have changed).

At the end of this process, we will have approximated the function computed at $g_m$ by a simple function $f_{g_m}$.
Next construct a group of test inputs $T\subseteq \{0,1\}^n$.
Suppose we can prove the following statements:

The approximation of each individual node is good (i.e., at most $e$-many mistakes are introduced on inputs from $T$ at each approximation step).
No simple function approximates $f$ well (i.e., for any simple function $f_{g_m}$, we have $f_{g_m}\neq f$ on more than a $d$-fraction of $T$).

Then by simply counting the number of errors we get that $\beta$ must have at least $\tfrac{d\lvert T\rvert}{e}$-many gates.
If this approximation scheme can be shown to work for any network $\beta$ computing the function $f$, then we arrive at a lower bound for the circuit complexity of $f$.
Comment: I don't think this answers the question, the question doesn't ask anything about that draft.
Comment: @Kaveh that is fair. I may have incorrectly assumed, due to the timing of the question, that it was asking about this technique in relation to the paper.


Am I taking the Right steps at Switching from Geoinformatics Bsc to Information Technology Msc?

Question: I am a Bsc degree holder in Geoinformatics from Nigeria intending to apply for Msc in Information Technology program in Germany, looking at the prerequisite its entirely a different ball game. So I decided to take some training for IT certificate courses like Network+, Cyber Ethical Hacking (CEH) and hoping to do Cisco certified Network Association (CCNA) and even planing on learning German language soon.
My question is will these certification acquisition give me a boost for admission to study Information Technology in Germany or anywhere in the UK.
Comment: Related: http://academia.stackexchange.com/questions/16013/what-is-the-best-way-to-take-missing-courses-before-applying-to-ms/18194
Answer: This heavily depends on the program you are applying for. Usually (in Germany) they require you to have an equivalent Bachelor to what they offer as Bachelor in the field, i.e., Information Technology in your case. Whether a Bachelor is equivalent is typically decided case by case. The whole procedure and detailed requirements are described in the Zugangsordnung of the faculty.
Since you are a student from a non-EU country there are most likely more requirements you need to fulfill, e.g., assessment of the German university entrance qualification, language requirements, visa, etc. You should get in contact with the international office of the university as soon as possible.
Comment: Interesting scenario. Smaller institutions in the U.S.A would usually be happy to accommodate scenarios like this, but of course, one would have to usually be self-financed, as is the case for most M.S. IT programs here in the USA.


Docking ports are not snapping

Question:
Why could two docking ports to not snap to each other? They a definitely close enough, speed is about 0.5 m/s and both ships have power. What i'm doing wrong?
Comment: That would be bugged "state" then, happens way too often, I wrote how to fix it in linked question. Its useful knowledge when building space station in KSP.
Comment: Interesting question! At that speed + from that distance, they should be glued by now.
Comment: Just to be sure. are ports enabled? Have you tried other docking ports on that orange tank and/or solution from [Docking Port Bug question](http://gaming.stackexchange.com/questions/258782/docking-port-bug) ?
Comment: @PTwr I double checked that, everything is enabled. I tried other ports, without any success. Restarting same(!) mission from the launchpad solved problem. Must be some bug.
Answer: Make sure that the ports are parallel to each other, their angle looks slightly off. Moving your ship sideways will help with getting the right angle.
Answer: The angle in the picture seems quite within norm for Clamp-o-tron standard. The Sr. ports are more sensitive about it (and Jr. - less.). The problem is that the game sometimes fails to notice ports are in position - a rather rare bug. You may need to repeat the approach - or save, quit, restart and load again.
Also, the "top" node on both ports needs to be empty. If you attached something to the port's top node, even if you moved it using the translation gizmo somewhere else, the node is still occupied and the port won't engage. Rightclick ports, "decouple node".
Also, if you just undocked, the port won't re-engage until you moved at least ~3m away from it.
Answer: One thing that helped me a lot, was to use the Docking Port Alignment Indicator mod.

Essentially, you set your docking port with "control from here" and then set the target's docking port with "set as target."  Then the indicators help you reduce your alignment angles to zero.
Here is a link to the tutorial on YouTube.
Playing with this mod helped me learn how to get the hang of docking, so much so that I don't need to install the mod any more.
Comment: If we talk about mods, I like to fly with Docking Helper backplate lights from [MRS](http://forum.kerbalspaceprogram.com/index.php?/topic/83959-12-modular-rocket-systems-v1131-2016-10-21-stock-alike-parts-pack/), much cleaner solution than bunch of spotlights.

Docking ports are not snapping


Why are there no global variables in Java?

Question: Why are there no global variables in Java?
Comment: @experimentX: For certain definitions of "fully". :)
Comment: Copy of [Java IAQ - Why are there no global variables in Java?](http://norvig.com/java-iaq.html#global) by Peter Norvig.
Comment: Too localized?  You closers realize he's talking about the programming language, not the island right?
Comment: you could circumvent that though using the GodObject pattern :)
Answer: Global variables are usually a design flaw.
Your components should be self-contained and should not need any global state.
Instead, use private static fields.
Comment: There are some legitimate cases where you need one and Java provides them using `static`
Answer: The answer is to your question is, because Java doesn't support global variables, by design. Java was designed with object-oriented principles in mind and as such, every variable in Java is either local or a member of a class.
Static class members are globally-accessible, which is certainly one possible definition of a global variable, depending upon your interpretation of the term. To be pedantic, whilst Static class members are accessible via the class name and therefore across multiple scopes, they are still class members; and therefore not truly global variables as such.
Java's lack of support for global variables is a good thing, as using global variables is a design anti-pattern.
Comment: @Ingo Wikipedia defines 'global' as 'accessible in every scope'. `out` is only accessible within the context of `System`, so it isn't global, and `System` itself isn't a variable. Ergo `System.out` is not a global variable. Wikipedia also says Java has [no explicit globals]('http://en.wikipedia.org/wiki/Global_variable#Java:_no_explicit_globals). If it said anything else when you read it, it was wrong.
Comment: @EJP The 2nd paragraph of the wiki page you cited lists the reasons we care about global variables in the first place. Note how this all applies to public static class members. The Wiki article is a bit deficient insofar it focusses on *global variables* (i.e names), which is just the usual way to feature global state, but not the only one.
Comment: I've chosen to interpret the question as "Why doesn't Java have global variables" (as in, variables which are truly global in scope, as opposed to variables like System.out which are scoped to a class but globally accessible because they are static) because it's the only context in which the question makes sense. I see what you mean though, as I've quoted Wikipedia and so contradicted that position. I'll edit.
Comment: @EJP This is utter formalism. Either that, or confusion of scoping rules of simple names with **accessibility** of data. One can access the data named by "System.out" precisely by writing that name. Where is it said that global data must have a *simple* name?
Comment: Java does, in fact, have global variables. Or how would `System.out` not be a global variable? If we go with the Wikipedia definition, then it is clear that Java *does* have global variables, hence the question cannot be answered, because it rests on faulty assumptions.
Comment: @Ingo `System.out` refers to the static field [`out`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/System.html#out) of type [`PrintStream`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/io/PrintStream.html) on the [`java.lang.System`](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/System.html) class.  This is exactly what this answer was referring to when it specifically called out `Static class members`.
Answer: Actually there is a certain similarity to global variables - you could use system properties, setting them in one class and reading them in another class. This is actually quite common for rather complex enterprise environments. JBoss for instance routinely provides a mechanism to define and access system properties.
Answer: If its a web application that you are working in, then you can use a session variable as a global variable....which will be available in all pages in the web app...
Answer: we can use static classe to hold Global/Application variables
Eg
<code>//Global Class
public class GlobalClass {
            public static String globalVariable = "globalValue";
    }

//Main Method
public static void main(String args[]){

      System.out.println("globalVariable:"+GlobalClass.globalVariable);
      GlobalClass.globalVariable = "newglobalValue";
      System.out.println("globalVariable:"+GlobalClass.globalVariable);

   }
</code>
Answer: The rational reason is that global variables are usually a bad idea so there is no downside to leaving them out of the language.
Then there is a practical syntactic reason: everything in Java needs to be defined within the scope of a class according to the syntax. So there isn't really anywhere "global" that you could put a named variable without changing Java's scoping rules. Arguably, the closest thing that Java allows within the syntax would be a "public static" member of a class which can be used like a global variable in many ways.
Finally there is an often forgotten principle of simplicity that comes in many guises: "if in doubt leave it out". Or "Keep It Simple, Stupid". Or YAGNI. In language design, often less is better in terms of features. On balance, Java is remarkably well designed and has stood the test of time from this perspective.


which is better, "We hope our close partnership can continue or can be continued well into the future"?

Question: which is better, "We hope our close partnership can continue well into the future" or "We hope our close partnership can be continued well into the future"?
Comment: We hope our close partnership *will* continue...
Comment: 'Continue' is used as a transitive verb, when a fair range of DO's such as partnership are available, as is the passive. This licenses the second variant grammatically. But 'continue' also has a middle usage. The partnership can continue. So the first variant is also grammatical.  Which is preferable is probably POB, but I'd choose a different phrasing as per some ('incorrect' as they give unsolicited workarounds) answers.
Answer: As @Lamar Latrell comments, it may be best to use will continue.
Of the two options given in the question, though:

"We hope our close partnership can continue well into the future"

is better. I say better, although both options make good sense, and are fine grammatically. It's just a matter of the nuanced implications of the sentences.
Using the passive voice, "can be continued", suggests that there is some doubt about the possibility of its continuing, and that there is effort involved in making it continue (that one or more of the parties in the partnership is the implied agent who makes it continue).
"can continue" is more suggestive that the partnership will continue naturally, as a matter of course (although there is still a chance that it won't).
So the most friendly, positive statement is to hope that it will continue.
Conversely, if you do in fact want to express doubt about the partnership, like if the person you're writing to has been breaking the terms of a deal, it may still be better to use the active voice and make your concern explicit: the passive form can sound passive-aggressive. Something like:

We hope you will work more closely with us in future, to continue our partnership...


Acts 11:20: Ἕλληνας or Ἑλληνιστάς?

Question: In Acts 11:20, of the words Ἕλληνας and Ἑλληνιστάς, which reading is more probable according to textual criticism? Which reading is more probable according to context? What is the meaning of each word?
Answer: Ἕλληνας or Hellene = Greeks. Ἑλληνιστάς refers to Hellenist, simply someone who is Greek in language and culture but was not from Greek ancestry (i.e. American Chinese who was born and has lived his/her whole life in the US). While some of the Hellenist might be of Jewish ancestry, some were not. This is consistent with the vision received by Peter in Chapter 10, that God is willing to reveal himself to the gentiles (non-Jewish).
Answer: If we take DBAG at face value then Ἑλληνιστάς refers to "Greek speaking Jews" then in context Ἕλληνας" is the most likely reading:
Acts 11:19-20 Now those who were scattered after the persecution that arose over Stephen traveled as far as Phoenicia, Cyprus, and Antioch, preaching the word to no one but the Jews only. But some of them were men from Cyprus and Cyrene, who, when they had come to Antioch, spoke to the Hellenists, preaching the Lord Jesus.
Why would the writer say as they travelled they preached to the Jews, but some preached to the Jews who spoke Greek? That seems a little redundant to me

Acts 11:20: Ἕλληνας or Ἑλληνιστάς?


MySQL Transaction Auto-Settler Calculation Query

Question: I'm creating a little auto-settler web app for people who share bills with each other.
Quick example, if Sam, Bill and Jim all live together and share common bills such as the Electricity Bill, Gas Bill and the Broadband Charge they should be able to input each transaction to the web app and then the app auto-calculates who should pay what to whom.
There are two tables concerned with this problem: 'transactions' and 'transactionusers'.
Transactions: ID, UserID, Retailer, Item, Date
Transactionusers: ID, TransactionID, Amount, UserID
When Sam adds a 'transaction' record for the Electricity Bill ($90) and splits the amount evenly across housemates, 3 records are added to the 'transactionusers' table.
I want to be able to write an SQL Query to work out the sum of all transactions between all users and then take away the reverse transactions (EG If Sam owes Bill $50 and Bill owes Sam $20, then the settlement is that Bill owes Sam $30)
My current query allows you to sum up total transaction value between each pair of users but not take away the reverse transaction - any help much appreciated:
SELECT transactionusers.userID AS debtor, SUM(amount) AS owes, transactions.userID AS toUser FROM transactionusers
INNER JOIN transactions ON transactions.ID = transactionusers.transactionID
WHERE transactions.userID <> transactionusers.userID
GROUP BY transactionusers.userID, transactions.userID

Example Data
Assume UserIDs are Sam (1), Bill (2), Jim (3)
Transactions:
1, 1, 'Electricity Co', 'Electricity Bill'
2, 2, 'Gas Co', 'Gas Bill'
3, 3, 'Broadband Co', 'Broadband Charge'
Transactionusers:
1, 1, 30, 1
2, 1, 30, 2
3, 1, 30, 3
4, 2, 20, 1
5, 2, 20, 2
6, 2, 20, 3
7, 3, 5, 1
8, 3, 5, 2
9, 3, 5, 3
What's not shown in the example records is the ability to split a bill unequally across users; for example: if Jim had been living in the house a month longer he may pick up a higher part of the bill
Comment: Can you show the data for your little example with Sam and Bill.  I do not see how this would be represented in your table structure.
Comment: Sure - have updated main question
Answer: Your query is good, you simply need to do a join on the very same query and deduct the results:
SELECT transactionusers.userID AS debtor, IF(SUM(amount)-r.owes < 0, 0, SUM(amount)-r.owes) AS owes, transactions.userID AS toUser FROM transactionusers
INNER JOIN transactions ON transactions.ID = transactionusers.transactionID
LEFT JOIN (
    SELECT transactionusers.userID AS debtor, SUM(amount) AS owes, transactions.userID AS toUser FROM transactionusers
    INNER JOIN transactions ON transactions.ID = transactionusers.transactionID
    WHERE transactions.userID <> transactionusers.userID
    GROUP BY transactionusers.userID, transactions.userID
) r ON r.debtor = transactions.userID AND r.toUser = transactionusers.userID
WHERE transactions.userID <> transactionusers.userID
GROUP BY transactionusers.userID, transactions.userID


Is there a way to validate a policy Id,and to check if a string is an actual policy id?

Question: im trying to build something in cardano, and i want to check if policy id provided by the user is an actual policyid?
after research i found that blake2b_224 is used for hashing the policy id,is there away to validate that a string was blake2b_224 hashed
Answer: Beyond the length of the hash digest (28 bytes in this case), no. Unless you have the pre-image (that is, the raw policy script) in which case you can rehash it and compare.
Answer: Depending on your usecase...
If you just need to know it exists, then you can scan the chain (db-sync, chain-index, blockfrost,...)
If you need to verify it against a minting policy, you'll obvs need access to that too and do the hashing like what KtoZ says. There are however resources listing currency symbols. (TBC, but) CardanoScan records and verifies native scripts (not plutus atm)


Did the Lord Buddha say anything about magic and fortune telling?

Question: Did the Lord Buddha say  anything about magic and fortune telling? I  just want to know because in this modern world everyone is following some astrology (Fortune tellers).  People believe what ever these people say. media also giving high priority to them.
Answer: These are examples of wrong livelihood. The Kevatta sutta discusses fortune telling and magic

"Whereas some brahmans and contemplatives, living off food given in
faith, maintain themselves by wrong livelihood, by such lowly arts as:
reading marks on the limbs [e.g., palmistry]; reading omens and signs;
interpreting celestial events [falling stars, comets];
interpreting dreams; reading marks on the body [e.g., phrenology];
reading marks on cloth gnawed by mice; offering fire oblations, oblations from a ladle, oblations of husks, rice powder, rice grains, ghee, and oil; offering oblations from the mouth; offering
blood-sacrifices; making predictions based on the fingertips;
geomancy; laying demons in a cemetery; placing spells on spirits;
reciting house-protection charms; snake charming, poison-lore, scorpion-lore, rat-lore, bird-lore, crow-lore; fortune-telling based on visions;
giving protective charms;
interpreting the calls of birds and animals —
he abstains from wrong livelihood, from lowly arts such as these.
Comment: Specially, wrong livelihood for monks.
Comment: wrong livelihood specifically for laity is defined in a different sutta http://www.accesstoinsight.org/tipitaka/an/an05/an05.177.than.html
Answer: The Buddha prohibits magic and fortune telling in the first sutta of the Digha Nikaya (therefore the first sutta of the Suttapitaka), referring to them as "base arts," along with astronomy, meteorology, medicine, accounting, mathematics, poetry, philosophy, surgery, and pediatrics.


Is it standard practice for an employer to make you pay for training costs if you've been fired?

Question: I signed a contract with my employer stating that for any and all reasons I am not working at that company before 2 years, I have to pay back x amount of dollars for the cost of training. Now this wasn't a small sum of money, but I got fired for reasons unknown (lack of "performance"). Is this common practice (and/or legal) in Ohio or elsewhere?
Comment: While I'm happy to see a very precise question, I'm afraid legal matters are outside of our scope. You should get a local lawyer.
Comment: Common practice or not, you read the contract and signed it. Now your only real question is whether the contract terms you agreed to are fundamentally illegal / not enforceable, so you can back out. The lesson here is: *Next* time you sign a contract, get these types of questions answered *before* you put your pen on the paper. You will have to contact a lawyer to resolve this, nobody here can really do much of anything besides make you feel better / worse about the situation you're in.
Comment: @JasonC totally agree that the OP is responsible for the terms of the contract and should have asked questions, but not everyone has leverage or the luxury to turn down an offer based on onerous terms. I guess that's part of the risk/opportunity.
Comment: I would be surprised if this was enforceable under the circumstances - but I'm no lawyer, least of all an Ohioan one
Comment: I've edited to shift away the focus on legality -- hopefully this brings it on topic.
Comment: @mcknz A valiant effort but it does still boil down to whether or not the OP can back out of a contract with unpleasant terms.
Comment: Definitely. Rephrasing: The lesson is: Next time you are about to sign a contract, ask the questions then and be prepared, so you're not in a panic looking for a lawyer and/or anxiously awaiting replies on this site when the time comes! Also @user56787, good luck! :)
Comment: Are they withholding your wages as a result of this claim? This "for any and all reasons..." clause sounds like a total scam to me. Have you googled for other instances of them doing the same to other employees?
Comment: Why did you agree to this contract?
Comment: @StephanBranczyk: In most countries, withholding wages would be illegal. The company has to pay the wages. They can take you to court to get money they want, but they cannot withold it.
Comment: @gnasher729, I know. That's why I asked.
Answer: This site cannot speak to whether or not this is a legal practice.
I do know of at least one time this has happened in Ohio -- a person was let go, changed jobs, and the person's original employer wanted the person (or new employer) to pay for the training.
Asking employees to pay for training when they voluntarily leave is one thing, but it makes no sense when the company releases an employee.
Agreed that a brief meeting with a lawyer would be valuable. The lawyer would be able to advise on the legality and enforceability, which are often two very different things.
Employers sometimes do put essentially illegal clauses in contracts, since they know the employee would have to go to court and pay legal fees to get a judgement in their favor. Often it's easier/cheaper for the employee to go along with a contract clause than try to fight it. And very few want to be the person who sued their last employer.
Comment: With these terms, an unscrupulous employer could just fire the trainee 23.5 months after the training, getting the advantages of the training for 23 months at zero cost.
Comment: @gnasher729 yep, seems like a shady practice to me overall.... Should be a cost of doing business. Not all investments pay off.
Comment: Unfortunately, shady/questionable does not invalidate a contract. If you didn't n like the terms, the time to negotiate them was before signing. Lesson to learn here is that you need to read, understand, and if necessary negotiate a contract before signing it -- and part of negotiation is deciding whether you care enough to be willing to walk away. If you decide to sign, don't complain later about being held to the terms of the contract.
Comment: @keshlam agreed. I think it's shady for the employer to put that in the contract in the first place. But once it's in there, you're right, the employee has agreed to it by signing.
Answer: You'd need to ask a lawyer about the legality. I have seen a lot of strange things in contracts and normally it's best to abide by them.
However once I leave a job I ignore anything the employer threatens me with. The last couple had sour grapes since many of their clients followed me out. Legal action is a costly exercise and I've never actually been prosecuted but I have been threatened twice. I wasn't sacked either time though, but I'd still ignore it if I was. This is probably your best strategy, don't answer emails, throw letters away unread, don't admit culpability for anything.
It would cost your employer quite a chunk of money (for a risk) just to get the process started against you. The longer you delay the more it costs them up front. If you're going to get prosecuted, then you're going to get prosecuted, there is no need to make it any easier or cheaper for the ex-employer and every reason to delay as long as possible.
Comment: I don't necessarily disagree, but consulting a lawyer can sometimes buy you peace of mind, if you're very worried about uncertainties. You seem not to mind uncertainty. :)
Comment: @gnasher729 I wouldn't spend two cents on anyone threatening me. It just validates their threats in a way. Let them spend the money and live with uncertainty. No point going through life flinching from shadows.
Comment: Yes in Span only government official can enforce financial fees so employers just dont have the authority to do so. It makes perfect sense I believe in all countries where law mean something should be in this way. Just thing about random pointless fees from employers for no reason, That doesn't make any sense.
Comment: I agree it's unlikely the employer is going to go so far as bring legal action, but you never know, which is why the OP should probably consult a lawyer on what the likelihood is, before getting rid of documentation.
Comment: @mcknz It's not documentation unless you read it, until then it's just an envelope a lawyer gave you unsolicited, you're under no obligation to do anything with it. Consulting lawyers costs money, easier said than done and changes nothing, either you get prosecuted or you don't, consulting a lawyer won't change that.
Comment: Consulting a lawyer also is a sign that you take it seriously as if you 'might' be culpable.
Comment: Fair enough, and yes, I don't get stressed
Comment: I'd think that ignoring a threat is unwise, and a lawyer should be contacted. As long as taking to a lawyer is cheaper than giving in to their demands.
Answer: A regular search, https://www.google.com/?ion=1&espv=2#q=recoup+training+costs+employee+after+firing+them+ohio might help you a little bit.
It appears that the answer is - it depends.
Most of the info is directed at employees who leave voluntarily.
Did you know that a fired employee can sue for wrongful termination?  I've seen employers agree to lots of things to avoid that suit.  Suits cost a lot of money, especially that one.  They may be willing to agree to not be sued and not sue you.  This is especially true if it is a large or tiny company.
Regardless of the wording of the question - including the legality part, it is best to get an employment attorney in the state in question.
Comment: While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - [From Review](/review/low-quality-posts/48359)
Comment: a) It is not a link-only answer.  b) It is a google search link - I pondered using LMGTFY for the link.


Ubuntu 12.10 won't use dhcp static lease from my router

Question: I have a Buffalo router running dd-wrt (came stock from the factory with it). I have a DHCP static lease setup for my computer which dual boots Windows 7 and Ubuntu 12.10.  When running Windows, there is no problem getting the IP address I assigned in the static lease.  However, when booting Ubuntu, it refuses to get the IP address I assigned and just gets the first available dhcp address.  Obviously the mac address is the same and the hostname is also set the same though I don't think hostname is used by the router.  This is not just isolated to one Ubuntu machine on my network.  My usual fix it to just configure the Ubuntu machine with a fixed ip address that matches the static lease address, but I found on this machine that is causing a problem with ssh connections dropping every few minutes (different issue, different question to come).
So, why does it seem every Ubuntu machine I have won't get the static lease address automatically and is there something I can do to fix it?
Answer: Turns out there was a NAS box on my network that had it's dhcp server turned on.  My Ubuntu machines were getting their dhcp addresses from the NAS instaed of the router.


Cannot access a disposed object

Question: I have a piece of code that throws an exception and error after running for a second time. Here it is:
static Form Window = new Form();
static public void Configuration()
{
    Window.Height = 800;
    Window.Width = 800;
    Window.Text = "Homework";

    Window.Paint += Window_Paint;

    Window.Show();
}

This code is inside a class and it throws an exception at "Window.Show();" saying that it:
ObjectDisposedException: Cannot access a disposed object.
Object name: 'Form'.

Please suggest a way that I can fix this so that it doesn't happen again.
Comment: " a way to fix this so that it doesn't happen again": don't use static `Form` object. create a new instance when necessary
Answer: The code you probably want to use is:
static public void Configuration()
{
    var window = new Form();

    window.Height = 800;
    window.Width = 800;
    window.Text = "Homework";

    window.Paint += Window_Paint;

    window.Show();
}

This will ensure that a new instance of Form is created every time that Configuration is called.

Cannot access a disposed object


Extract only GreasePencil lines

Question: I want to extract only the lines used in LineArt, is there a way to do this?
I tried setting the object path to GPencil, but it doesn't seem to be masked correctly.
The line will also be composited with other outputs ( LightGroup ).
Answer: I believe this Thread has a lot of relative value of what you're looking for.
For your case, you should move all the objects into a Holdout collection and make the background transparent. To activate Holdout, within the Outliner, select the Filter drop down menu and within the Restriction Toggles select the Holdout icon for your collection. To make the background transparent as well, go to Render Properties $\rightarrow$ Film $\rightarrow$ and select Transparent.

When you render your line art with the empty background, it should be usable in a Render Layers node within the compositor.

Extract only GreasePencil lines


What is an alternative to "Perpetrator" with a more neutral connotation?

Question: In the phrase "He criticized the revolution and its ______" I originally wrote "perpetrators," but that casts a negative connotation on the revolution, as if it is a crime. I don't want to use "revolutionaries"
as to avoid the sentence sounding too repetitive, so what is a more neutral word I can use for the revolutionaries in question?
Comment: Originators?  Instigators?
Comment: More context please. For all I know from your example, you could mean opponents. Are you talking about Lenin or members of the Comintern?
Answer: From a comment under the question, I see that adherents is what was being looked for. However, I think that followers is more natural in this context:

[Merriam-Webster, from the verb follow]
2 a : to engage in as a calling or way of life : PURSUE
       // wheat-growing is generally followed here
2 b : to walk or proceed along
       // follow a path
3 a : to be or act in accordance with
       // follow directions
3 b : to accept as authority : OBEY
       // followed his conscience

Using it in the example sentence:

He criticized the revolution and its followers.

The criticism of a revolution is often of the principles involved and the followers of those principles. These things can exist before, during, and after the revolutionary event itself.

Google Books Ngram Viewer indicates that and its followers is more common than and its adherents:
Comment: Somebody can be a follower only when there is something to follow. *Follower* may thus be an adequate term for those who joined a revolution that was already under way, but not for those who started a revolution.
Answer: You can use a straight up synonym for revolutionary such as insurgent:

For contemporary national revolutions, the capture and control of territory has virtually become a "territorial imperative." ... "Mobile war" is required when the insurgent is unable to establish a base in the cities and must continually move to avoid capture by government troops. —The Insurgent State: Territorial Bases of Revolution

Another option would be to use a generic word such as supporter or leader which might have a more relevant nuance.
Answer: If you mean its leaders, another word that would work here is "instigators," which has a negative connotation that goes with the criticism indicated in your sentence but is not as heavy-handed as, and better fitting than, "perpetrators."
If you don't mean the leaders, "participants" might be a better word than "followers;" as indicated in a comment above, it would seem more natural to say you are a follower of a revolution's principles than to say (about a revolutionary) you are a follower of the revolution itself, as in your sentence.
Answer: Would actor/enactors work? Although it is heavily used in legal contexts, I don't think it is restricted to this domain. It's thoroughly neutral also.
I was struggling to find alternatives to perpetrator myself - which is how I discovered this post. Negative connotations from terms such as instigator, insurgent, etc. I think present an unhelpful picture. I also agree that there are many followers who are leaders and the distinction doesn't work here.
Revolution in some people's eyes would warrant the positively connoted term hero. But that's also far too narrow, and definitely not what you're looking for.
I know this original question is three years old… I'm just exploring.


What are these white eggs behind my wall outlet?

Question: What type of animal eggs are these white eggs? Do I have something to worry about?
Comment: If they are made of silk thread then probably spider's egg cases.
Comment: I hope you will at least rake them out and mush them up a bit, so that you do not find out the hard way too soon. It may reveal some info at least. My Google Lens app only show mushrooms as a possibility. But that is a picture of a picture, not the same as using Lens at the place of concern.
Answer: Spider egg cases. Looks like they already hatched.


This question is downvoted but it has many answers which carry upvotes

Question:
I have a question about my Law Stack Exchange post: Can a country refuse to enforce international law even if it does not violate existing law?
Why did this question get downvotes when it was well-answered?
Answer: I can only speculate, since I'm not one of the people that downvoted it...but I'll give it a shot. My guess is that it was downvoted for a couple reasons:
The question in the title is somewhat unclear: it's not totally clear what you mean by "if it does not violate existing law."  The phrasing makes it sound like you're saying the law doesn't violate existing law, which doesn't really make sense.  A better title might be something like "Can a country refuse to enforce another country's laws forbidding conduct that is legal under the country's own laws?".
This lack of clarity is reinforced by a few comments mentioning that they found it unclear and asking clarifying questions, as well as a pending suggested edit trying to rephrase the title (you should either accept or reject it).
It's also somewhat of an unrealistic hypothetical.  No country would ever make a law demanding a $1 billion payment for the mere act of making a website accessible to its citizens, residents, or anyone within the borders of the country.  Compliance with such a law would be more or less impossible.  A more realistic hypothetical might have fared better.
Comment: I will keep the points in mind.
Answer: Apart from the aforementioned unnecessarily ridiculous nature of the statute and the unclarity of the question as asked, this is also a generally-asked-and-answered question: does every nation have to enforce the laws of every other nation (we've had a thousand variants of that question)? Tossing in the option to go to war is legal fantasy and irrelevant, but your question about treaties should have given you a start at self-answering the question (what kind of treaty?; why does it matter if there is a treaty?).