Is Revelation intended to be interpreted symbolically, or are certain elements meant to be taken literally? How are we to know which is which?

Question: When the book of Revelation is unpacked, it seems that there can be a certain haphazardness in interpreting the symbols it contains. Are there any principles that can serve as interpretative guideposts along the way?
Answer: Revelation is written in apocalyptic style and is therefore symbolic by nature. However, there are various techniques used in apocalyptic writing, each with its own 'saturation level' of symbolism.
Two of these techniques are often referred to by scholars as 'symbolic' and 'mythic realistic' writing. I would add a third: realistic.
Here is an example of a highly symbolic scene:

Rev. 13:1 – 2   The dragon stood on the shore of the sea. And I saw a beast coming out of the sea. It had ten horns and seven heads,
with ten crowns on its horns, and on each head a blasphemous name. The
beast I saw resembled a leopard, but had feet like those of a bear and
a mouth like that of a lion. The dragon gave the beast his power and
his throne and great authority.

This passage leads to the following sorts of questions:
What (or whom) does the dragon represent?
In this case, the answer is found directly from the text in the previous chapter:

Rev. 12:9a   The great dragon was hurled down – that ancient snake called the devil, or Satan, who leads the whole world astray.
(Emphasis added)

Is the sea significant? What does it represent, if anything?
Chapter 13's scene forms part of a series of visions contained in the so-called 'little scroll' which John is given:

Rev. 10:10 – 11   I took the little scroll from the angel's hand and ate it... Then I was told, 'You must prophesy again about many
peoples, nations, languages and kings.'

The vision of the prostitute sitting near many waters is in the same little scroll, and concerning these waters, the angel speaking to John says:

Rev. 17:15b   'The waters you saw, where the prostitute sits, are peoples, multitudes, nations and languages…'

So it would not be unreasonable to say that the sea (or waters) where the dragon stood in chapter 13 represents many nations, as does therefore the Danielesque 'multi-beast' which comes out of the sea. Likewise, it would not be unreasonable to see the 7-horned beast of chapter 13 as being synonymous with the 7-horned beast of chapter 17, given the proximity of the two visions.
What are the main ideas being communicated by this symbolic vision?
The answer is found at the end of the first part of the vision:

Rev 13:9 – 10   Whoever has ears, let them hear. 'If anyone is to go into captivity,
into captivity they will go. If anyone is to be killed with the sword,
with the sword they will be killed.' This calls for patient endurance and faithfulness on the part of God's people.

'Mythic realistic' writing, on the other hand, looks more like this:

Rev. 4: 2 – 3   At once I was in the Spirit, and there before me was a throne in heaven with someone sitting on it. And the one who sat
there had the appearance of jasper and ruby. A rainbow that shone like
an emerald encircled the throne.

Further on in the chapter, we see that the person on the throne is God:

Rev. 4:10b-11a   They lay their crowns before the throne and say: 'You are worthy, our Lord and God,… (Emphasis added)

We can think of mythic realistic descriptions as souped-up versions of the real thing (although 'souped-down' might be more to the point when describing God). So whilst there is no sea, dragon and prostitute per se, there really is a heavenly realm, and it really is where God the Creator and Redeemer dwell. There are angels serving God, and those who have died for the sake of the gospel are in their presence.
These two writing techniques are not always neatly compartmentalised. For example, in the relatively realistic heavenly scene of Rev. 4 - 5 we see God on the throne but we also encounter the Lion of Judah who is then described as a slain lamb with 7 horns and 7 eyes, so we need to stay flexible in terms of assigning one or the other type of metaphor to a particular passage.
As far as I can tell, when humans are involved in the narrative; when the human impact of God's wrath is being described, there is little or no 'decoding' required: it is written in a realistic manner. For example:

Rev. 6:15 – 17   Then the kings of the earth, the princes, the generals, the rich, the mighty, and everyone else, both slave and
free, hid in caves and among the rocks of the mountains. They called
to the mountains and the rocks, 'Fall on us and hide us from the face
of him who sits on the throne and from the wrath of the Lamb! For the
great day of their wrath has come, and who can withstand it?'

It does not seem necessary to ask questions like:
What does hiding in caves symbolise?
What is the meaning of calling to the rocks to fall on the human beings that are hiding?
Or even:
How is this passage using elements of mythic realism to add to the drama?
The whole point of the judgements in Revelation is that "the great day of [God's] wrath has come" (Rev. 6:17). We know from passages like 2 Peter 3 that this day will result in global catastrophe and that the chief mode of destruction will be searing heat, for example:

2 Peter 3:10   But the day of the Lord will come like a thief. The heavens will disappear with a roar; the elements will be destroyed by
fire, and the earth and everything done in it will be laid bare.

We know from Revelation itself that this prophecy (both the main book and the little scroll) concerns "many peoples, nations, languages and kings" (Rev. 10:11b). In this quoted verse, John is told that he "must prophesy again" (Rev. 10:11a, emphasis added) about these many nations, indicating that the entire book is really about the whole world – or, at the very least, the known world of the day.
Comment: Interesting. However you have 'missed' the 1000-1100 years which is after the day of wrath and before the searing heat! People have to be saved sometime - and this is when it happens for most.
Comment: Good answer. I saw a great sermon series from Pastor Robert Morris that dived into the symbology of the Bible and The book of Revelation. One thing that's stayed with me from that is his comment that "The Bible interprets itself". He basically showed that the symbology explains itself if you are willing to study scripture. The symbology is generally repeated and it will explicitly explain what each symbol represents if not in the book you are reading then another one Dragon = Satan, Cloud = Spirit, stars = Angelic Beings.
Comment: .... Continued.... Water/Sea is the interesting one as it has some flexibility. Water seems to be linked to nations/people but not just them as persons but also the "words" they speak. Water is symbolic of words in the bible. The "washing with the word" is hearing the word of God. Jesus is both "the word" and the "living water". The dragon spewing water is the torrent of attacks and accusations from the devil. The creatures coming out of the sea seems to be when humanity "speaks evil" and gives power to demonic forces. The water symbology is linked to what people hear and speak
Comment: @marshall Thank you for your extensive comments, not reading any books as yet, just a couple of papers, in particular one on the book of Enoch (part of a process to read more apocalyptic literature than just Revelation) but I can see the time approaching soon when I'll need to get into some books. I wanted to soak in the scripture itself first, so I wouldn't be 'formated' by the first couple of books I read! Also need to bring the rest of my NT familiarity up to speed, it's lagging behind now that there are these patches of highly familiar text. Some balance is required, I can feel!
Comment: @Ashley Roberts Yes there is lots of scripture to cover.  I think it's best to do what your doing and get a broad overall understanding. But once you have - its great to start doing "word studies". Pick a symbol/word and then go and search all the places it appears across scripture. Then read and meditate on all those sections together. Also the sermon series I spoke about is actually available in video form. Published by gateway church on YouTube. It's called "More then words" he basically does a deep dive on a specific word in each sermon and a more broad sermon covering multiple symbols
Comment: In the book of Revelation numbers convey ideas, not arithmetic. Forms display concepts, not shapes.  Words are clothed in mystery, not logic. Numbers in the Book of the Revelation have been shown to be spiritually and not arithmetically conceived. Therefore they must be spiritually and not arithmetically interpreted. And since this is a principle, of necessity it applies to every number wherever found in the Book of the Revelation.  From 'The Revelation of Jesus Christ' by John Metcalfe, published 1998 by the Apostolic Foundation of the Christian Church (p. 536) - ISBN 1 870039 77 7
Comment: @Lesley Many thanks for that quote, I feel the Lord using His servants this week to direct me to this book, it's being bought the day after January payday hehe!
Comment: Thank you Steve, yes I must look into post-millennialism and give it a serious wrestle.. I feel the earnestness of your comment, thank you.
Comment: Wonderful, thank you @xmarshallx
Answer: This question is almost certain to be closed (and deserves to be) but before it is let me offer a few quick comments:
The opening verses set the scene for interpreting Revelation:

Rev 1:1 (BLB) - The revelation of Jesus Christ, which God gave Him to
show to His bond-servants what things it behooves to take place in
quickness. And He signified it through having sent His angel to
His servant, John,

Then there is the long list of symbolic scenes and their elements such as:

a seven headed dragon who spews water to kill a woman (Rev 12)
a seven headed sea beast with 10 horns that is part lion, part bear and part leopard, who miraculously survives a fatal wound (Rev 13)
a two-horned land beast that calls fire from heaven (Rev 13)
Jesus represented by a seven-horned, wounded lamb (Rev 5)
a woman with the moon under her feet and clothed in the sun (Rev 12)
a great prostitute who rides the red beast and who trades in the bodies and souls of men (Rev 17 & 18)
The red beast of Rev 17 represents the seven hills of the great city
John eating a book that tastes like honey but turns his stomach sour (Rev 11)
the prostitute sits on waters representing people (Rev 17)
Jesus with seven stars in His hand walking among seven lamp-stands and sword coming from His mouth and legs like bronze (Rev 1)

... and so forth.  These are clearly highly symbolic and should not, must not, be taken literally but treated metaphorically.
However, the messages to the seven churches have some clearly literal elements but this should be the subject of a series of separate questions.
Comment: Thanks so much for your helpful insights!
Comment: Well-summarised nuggets like these don't readily betray the hours required to derive at them, thank you.
Answer: The letters to the churches probably aren't symbolic. The rest might be.
The opening of Revelations contains letters to seven churches from Jesus Christ, transcribed by the author of the text. While the rest of the book might or might not be symbolic, those sections of the text almost definitely aren't. They're just literal letters admonishing and/or praising certain early Christian churches located in what is now Turkey.
Comment: There are denominations that believe that in addition to being literal messages, these seven churches represent seven church eras throughout history, up to Christ's return. The messages both describe and inform the church during the seven eras. All denominations of course don't always have identical versions of what the messages represent.  An obvious example is the Philadelphia Church of God, which identifies itself as the remnant of the Philadelphian church era that is surviving through the current (and final) Laodicean era.
Answer: If it can't be interpreted literally, interpret it symbolically. John clearly stated that the purpose of the book was to show to the servants of Jesus Christ what would take place in the future. Rev. 1:1-2 If something is going to happen, that sounds pretty literal, and I want to try to figure it out.
There are 8 blessings mentioned in the book of Revelation so it really pays to read it and understand it. I recently talked about the significance of 8 here:
(https://hermeneutics.stackexchange.com/questions/69944/does-666-alludes-to-the-fact-that-man-was-created-on-the-6th-day?r=SearchResults&s=3|37.6512).
So even if the question gets closed, I'm voting it up because someone may be blessed by receiving the blessings of Revelation.
The first two blessings are found in 1:3.

3 Blessed is the one who reads aloud the words of this prophecy, and
blessed are those who hear it and take to heart what is written in it,
because the time is near.

Whether we take it literally or symbolically, we'd better take it seriously and put it into practice! As the 8th blessing reminds us,

Revelation 22:14: "Blessed are those who wash their robes, that they
may have the right to the tree of life and may go through the gates
into the city."
Comment: I think your answer highlights one of the most important "symbols" in revelation and the Bible in general. Water represents words. Jesus is given the titles of both "The word" and "living water". Washing with the word means to hear/read the word of God which cleanses and purifies us. (Thus the blessing for reading it aloud) Eg "you are already clean because of the words I have spoken to you." The torrent of water spewed by the dragon and also the "sea" in Revelation are other important symbols and point to the attacks, accusations, words of Satan and the words heard and spoken by the nations.
Comment: I sense that there are teachers / lecturers all over this site and really appreciate the time taken to respond. @Martin Your calm opening hermeneutic statement has the ring of experience, many thanks.
Comment: Thanks very much Martin, much appreciated.
Answer:
Are there any principles that can serve as interpretative guideposts along the way?

Divide into sections, studied separately.
@nick012000 pointed out that the letters to the churches are separate from the rest.  But even the remainder of the text is likely the result of redaction to merge multiple texts together.  John did not necessarily receive the entire revelation in one vision.  Most likely he had multiple intense prophetic experiences and wrote about them in either one or multiple texts that were later combined.
Completely ignoring the chapter/verse divisions, which were devised by Martin Luther as a convenience and are not original, create your own outline of the total text in sections.  Between the sections should be a clear 'break' in the text.  For example, when you see, "And I John saw these things ..." that is a break.  Such text may indicate a scribal redaction, used to merge originally separate texts into one, or it may be John's own words at the beginning of what was originally a separate work.  Study each of these sections as if it were a separate installment in a prophetic series.
The content is related, of course, but reading it in sections will help you to read it in a form likely closer to how John originally wrote it.
Interpret in terms of Hebrew Biblical prophetic language and symbolism.
You have no chance to understand much of the symbolism in Revelation without becoming familiar with the literary jargon it uses.  Some of the same symbols are used in the works of Daniel and other prophets.  Beware of untrustworthy sources for interpretation of prophetic symbols!  Some of the more obvious ones that emerge from studying the scriptures:

Mountain = looming threat or problem
Crown = authority
Head = ruler
Sword = division, infighting
River = sustenance, purification
Jordan river = death

Context will help you decide whether a term is meant literally or as a symbol.  And bear in mind, it is conceivable that a scribe somewhere along the line 'translated the symbol', changing the literal language to keep the symbolic meaning the same for the Greek reader.
Another example, 'prophecy time'.  Rev 11:2 says the Gentiles will tread down the Set Apart (holy) city for 42 months.  11:3 says the two witnesses will prophesy 1260 days wearing sackcloth.  These are equal amounts of time because each month has 30 days.  This allows the Metonic cycle to be simplified somewhat; by using 3.5 year units of time, only one leap month every 6th year and another every 39th year are required.  This system is also used in Daniel.  This method of counting time is not exact, but it is close and appears to be the norm for Biblical prophetic counting of time.
Using the wrong cultural symbolism or calendar system to interpret the symbols or times will result in vastly different interpretation.  To an American today, the eagle means liberty; but not to a Jew in that time.
Interpret according to Aramaic/Hebrew idioms of the time, not modern or Greek ones.
The oldest surviving manuscripts of Revelation are in Greek, but that by no means proves that John wrote in Greek.  Yeshua (Jesus) and all the Shlichim (Apostles) spoke Aramaic natively.  Especially for such an abstract and prophetic work as Revelation, it is important to treat the text as having been translated from Aramaic into Greek and then from Greek into English.  Even if John wrote originally in Greek, which is not certain, that means only that he was the original translator from Aramaic into Greek, in much the same way that a non-native English speaker would translate their thoughts from their native language into English to write.
For example, when you read, "Eat this book," you should not imagine a codex book but a scroll.  And you should be aware of the Aramaic idiom, when you eat something, you make it a part of you.  Now you can properly consider what it means for the book to be sweet on the tongue and bitter in the belly.
Another example, when "trumpets" are sounded, is that to announce the entrance of royalty, as in Europe, or a march to war?  Or are shofars blown to announce the new moon or Yom Teruah, or to summon war-fighters to the camp, as commanded in Torah?
Comment: Ah… this was enormously helpful, thank you! Some of your concepts (like looking to the OT and ancient Jewish culture to point to the meaning of unexplained symbols) I have actually already begun to apply.. others (like considering the natural breaks in the book, plus insights into how it might have been compiled) I will start considering and using as points of departure. Thanks again!
Comment: I should thank you again for this answer. A few months down the line and it's still proving most useful!
Comment: Thanks!  Glad to be of help.  Revelation is so mysterious, and we are so far removed from the original cultural context.  And analysis of the Greek and Aramaic texts indicates that it was likely written originally in Hebrew Aramaic (aka 'Palestinian' Aramaic) then translated to Greek then translated **back** into Syriac Aramaic from Greek to give us what we have now.
Comment: An invaluable guide to Aramaic idioms is New Testament Light by Dr George Lamsa.
Comment: Thanks so much for that, I will buy this book
Answer: Revelation is to be interpreted literally
And where symbols are mentioned,
interpretation is given
e.g. The mystery woman is a city.
Rev 17:18
When imagery of the spirit realm is described,  these are not symbols but actual appearances.
These Spiritual entities are
Invisible to the physical realm,  but their influences affect the physical realm
King Saul was influenced to murder. 1 Samuel 19:9
Judas was influenced to betray John 13:27
These entities were not observed in the physical realm but their influence was devastating.
Comment: Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Answer: Principles What principles are there to serve as interpretive guides?1) The first Principle to determine how to interpret the Book of Revelation is to determine which GENRE of literature it is. This falls into the Apocalypse genre.  It is not a direct Prophetic book ala Old Testament prophecy, so its method of interpreting is different.
2)The second guiding Principle would be an admonition to read other Jewish Apocalypes to see how they incorporated imagery to portray the messages relevant to their cultural and spiritual situation. Seeing their style would be most enlightening.
3)Thirdly, Discover the purpose and motive for the writing of this Johannine Apocalypse. What political, social, and religious milieu existed at the time of writing?  Was their religious persecution, expansive church growth, a need for hope or correction in theology, etc.?
4)Check out the origins of the various interpretations of Revelation. Knowing the circumstances of the authors of the interpretations can be very revealing...as well as Who they are. Sometimes church dynamics (intrigue) skew interpretations. Often, "times that are out of joint" influence interpretations. E.g. End-time expectations caused by alleged "signs" have undue influence, quite often.
5)Since Revelation draws heavily from Old Testament imagery and passages of scripture, a good guide is to look up and read those O.T. scriptures in their setting. Familiarity with the Old Testament is a must.
THEN, pray like a house afire and ask the Holy Spirit for enlightenment, or direction to a well-versed teacher in the Body (Or acquisition of his books) that will lead to Truth.


How to run bibtex in texstudio (or otherwise) on \included files

Question: Apologies for the newbie question, I am trying to use chapterbib for multiple bibliographies in my thesis. Each chapter is in the main file with \include and has its own bibliography from the same .bib file. I understand that for chapterbib I need to build the main file, then bibtex on each of the subfiles then build the main file again. However, when I try to run bibtex on each of the subfiles, it just runs on the main file again, not the subfiles. I am using Texstudio, how do I run bibtex just on the subfiles so that chapterbib will work?
Answer: Running your LaTeX complier (e.g. PDFLaTeX) on your main file will create aux files for each of the included files. Open each aux file and run BibTex on each of them (press F8 in TeXStudio). You must open each aux file and run BibTex on each aux file to generate the bbl files for each included file. Then, go back to the main file. Rerun your LaTeX compiler twice to generate the citations and bibliography for each chapter.
Comment: Thank you for the tip. When I run the LaTeX compiler it doesn't create the aux file for each chapter included. Any idea on what is going on? Weirdly enough, bibliography on the first chapter is working, but not on the second.
Answer: You dont need to install parallel toolbox as har-wradim stated. Simply type:
sh -c "for f in *.aux; do bibtex ${f}; done"

in your BibTeX textbox of TeXstudio configuration window (i.e. Configure --> Commands --> BibTeX) and you are good to go.
This perfectly works for Linux/Mac, for windows we need a different command:
cmd /C "FOR %f in (*.aux); DO bibtex %f"

Explanation:

Har-wradim code: What parallel bibtex -- ?*.aux does is that it runs a different thread for each file it finds with *.aux extension. While it works, running a task using multiple threads requires parallel package.
My script: It simply removes the aforementioned requirement by:

List of all files that end with aux (using a for statement).
Run bibtex <file>.aux for each individual file separately using single core.
Comment: Thanks a lot, it works... this has been so hard to debug!!
Answer: The easiest solution is to use parallel bibtex -- ?*.aux as the BibTeX command under Configure → Commands. This implies that parallel is installed and available in the PATH, which is almost certainly true by default if you use a Linux distribution. Installation on OSX is straightforward with brew. No idea how it might work on Windows.
This solution would not work for aux files with spaces in their names, but using spaces in file names is arguably a bad practice in the first place.


GUI won't load properly after update 19.04

Question: After upgrading to 19.04 my gui no longer loads normally. After booting I get stuck on a purple screen (with some distortion). Booting in recovery mode however goes really smoothly.
The kernel has the following error messages:
<code>dmesg -l err
[    4.877660] ucsi_ccg 0-0008: i2c_transfer failed -6
[    4.879379] ucsi_ccg 0-0008: ucsi_ccg_init failed - -6
[   80.431815] debugfs: File 'le_min_key_size' in directory 'hci0' already present!
[   80.431819] debugfs: File 'le_max_key_size' in directory 'hci0' already present!
[   80.907771] iwlwifi 0000:70:00.0: Unhandled alg: 0x707
</code>
Are any of these error messages relevant to my issue? Why are things working in recovery  mode, but not in regular mode?
Answer: Software Updater --> Settings... --> Additional drivers --> NVIDIA: Change using X.Org X server to NVIDIA driver from nvidia-driver-435, fixed my issue.


Linear equivalence and Hilbert function

Question: Let $X \subset \mathbb{P}^3$ be a smooth degree $d$ surface containing two irreducible curves $C_1, C_2$ linearly equivalent to each other. If we assume that $X$ is general (among all degree $d$ smooth surfaces in $\mathbb{P}^3$) then is it true that $I_d(C_1)=I_d(C_2)$?
Comment: What does $I_d(C_i)$ denote? The Hilbert function of the curve $C_i$?
Comment: Yes. I meant the d-th graded part of the homogeneous ideal $I(C_i)$, the ideal of the curve $C_i$.
Answer: Let me show that the answer to this question is positive for $d>3$. Indeed, for a general surface $X$ of degree $d>3$ its Picard group is $\mathbb Z$
and is generated by $O(1)$. It follows that both curves $C_1$ and $C_2$ are complete intersections, and so they have the same Hibert function (see for example Section 13 pages 172-173 in book of Harris "first course in algebraic geometry"). Hence the statement is proved.

Linear equivalence and Hilbert function


Construct PDA for $Σ^* -\{(a^nb) ^n, n>0\}$

Question: I want to construct a PDA for $Σ^* -\{(a^nb) ^n, n>0\}$ where $Σ=\{a, b\}$. Here is my try:
I know that context-free languages are closed under union operation. Also I know how to make a PDA for union. So I tried to decompose the given language to some parts. For example, the language of the strings starting by $b$, the language of strings ending with $a$, the language of strings containing $bab$ as a substring.
I made a context-free grammar for these languages. Then I made PDAs based on each grammar and I combined them to get a PDA for the union of them.
But I know that the union of these languages does not cover all strings in the given language. Could you help me find what I'm missing and how to make a context-free grammar for that?
Answer: If a word is not of the form $(a^nb)^n$ for $n > 0$, then one of the following must happen:

The word is not of the form $(a^*b)^+$, i.e., it is either empty or ends in $a$.
The word is of the form $a^ib(a^*b)^*a^jb(a^*b)^*$ for some $i \neq j$.
The word is of the form $a^nb (a^*b)^k$, where $n \neq k+1$.

Each of these can be checked by a PDA or generated by a CFG. It might help to break a condition of the form $i \neq j$ into two alternatives, $i > j$ and $i < j$.
To see why this case distinction holds, let us assume that the word is of the form $(a^*b)^+$. We can write it as
$$
a^{i_1} b a^{i_2} b \cdots a^{i_m} b.
$$
The word is of the form $(a^nb)^n$ if $i_1 = \cdots = i_m = m$, which is equivalent to
$$
i_1 = i_2 \text{ and } i_1 = i_3 \text{ and } \cdots \text{ and } i_1 = i_m \text{ and } i_1 = m.
$$
Hence the word is not of the form $(a^nb)^n$ if
$$
i_1 \neq i_2 \text{ or } i_1 \neq i_3 \text{ or } \cdots \text{ or } i_1 \neq i_m \text{ or } i_1 \neq m.
$$
The case $i_1 \neq i_j$ is handled by the second bullet above, and the case $i_1 \neq m$ is handled by the third bullet.
(Thank you to Hendrik Jan for help with simplifying the cases.)
Comment: Can you explain how you reached to this decomposition? Also how to make a CFG for each of them? It doesn't look easy.
Comment: It's a case analysis. As to how to construct CFGs, it doesn't look too hard. I trust that you can do it.
Comment: But I couldn't do it.
Comment: Well, I'm not going to do that for you.


Pickoff fake a throw disengaged

Question: If a pitcher fake a throw to a base is he considered disengaged? So technically then could he fake a throw to first base?
Answer: Faking a throw is illegal when touching the plate ("engaged").  6.02(a)(2):

If there is a runner, or runners, it is a balk when:

(2) The pitcher, while touching his plate, feints a throw to first or third base and fails to complete the throw;

However, a pitcher not touching the plate is a fielder and can do any normal fielder thing, including feint throws.  So once a pitcher has stepped off (i.e., his back foot is no longer on the plate), sure, he can do whatever he wants.
Regardless, I think the answer to the question you intend is effectively no; if the pitcher, while engaged, fakes a throw to a base, that is a balk. The pitcher would have to remove his foot from the plate (at which point no sane runner would be going anywhere other than back to the bag).

Pickoff fake a throw disengaged


How did SCP-3848 affect human morality?

Question: I was reading the SCP Foundation wiki as well as TVTropes and read about the interesting story of the ED-K-Class Lethe Scenario: a scenario where a memetic phenomenon called scp-3848 causes people to forget basic activities and act strangely because of it. The TvTropes entry described how the phenomenon was able to "erase the concepts that make up normal human morality, having some of the infected exhibit Blue and Orange Morality". I, however, was not able to identify instances of moral behavior being changed by the virus, just instances of people acting silly because they forgot how to fly fish and those not affected calling the infected people weird. Am I missing something from this particular SCP tale and are there any specific instances in these stories of scp-3848 changing human morality or causing 'Blue and Orange Morality' that I overlooked?
Comment: Links to TVTropes should perhaps be marked with a warning that any such link constitutes "memetic activity" that "causes people to forget basic activities". ;)
Comment: Besides, I don't understand what you are saying. Where does it indicate that the phenomenon is a virus? Where do people decide to flee Earth?
Comment: "*Description of Concept Affected: The fact that murder is illegal, as well as the fact that it is generally regarded as amoral.*" - This seems like a fairly big change in morality
Comment: @Adamant: sorry, I fixed it. There was another story connected to scp-3848 where it was described as 'like a virus' and people left Earth because of it in an alternate reality.  I edited this out since it is not relevant to the current question and what I was asking for.
Answer: There are different items in the story of SCP-3848 that show a difference in morality or at least personal behavior. One instance of SCP-3848 in Wisconsin, for example, led to everyone forgetting the existence of canines, causing people to become fearful of dogs and unable to care for their own pets. Their reaction to all dog breeds, even friendly ones, became fear and/or fascination with the concept of dogs in a way many people (especially in the United States where dogs are plentiful and generally considered 'man's best friend') would find very peculiar. Also, in Ontario, Canada on January 3rd, 2017 -as another contributor pointed out - a select group of people started killing their neighbors and fellow townsmen while forgetting that murder is illegal and generally considered amoral.

How did SCP-3848 affect human morality?


Preventing SSL strip attack

Question: Is it possible to detect a SSL strip attack by checking whether the page delivered is HTTPS or HTTP using JavaScript? I am assuming that the response page is HTTPS page instead of HTTP?
Answer: You may want to look into setting your webserver to HSTS (Strict Transport Security) which uses a special response header to tell the browser to only accept https traffic.  Full Disclosure:  As you might have expected, IE support < 11 I believe is limited.  If you must use something client-side to check for https I think you could use window.location.protocol.
Comment: This helps if the first access to the site is done without sslstrip, otherwise sslstrip could remove the HSTS header.
Comment: The HSTS header does not need to be removed. See my comments on the answer here: http://security.stackexchange.com/a/70934/35267
To prevent attacks during the first access, the owner of the website should include its website into the preloaded HSTS list of the browser (ofc this is only possible if the browser supports this, like for example with firefox and chrome).
Comment: First, HSTS is not even available for a large part of browsers (Internet Explorer). And you really believe that *preloaded* HSTS is possible for all sites in the world containing sensitive data? I doubt it.
Answer: You might try the following:

Create a cookie with Javascript. Set the secure flag on the cookie, so that it is only usable for https connections.
Make a https request to the server and check if the secure cookie was received. If it was not received then you can assume that the request on the client side was not done with https, i.e. something like sslstrip was active.
Comment: You mean that you check at the webserver if the secure cookie was received, right? Maybe my understanding of cookies is incorrect, but what if the user sends a request to the webserver for the first time? It hasn't been instructed yet to send a cookie, so it cannot send a cookie. That means that the webserver would not respond to the request?

Furthermore, assuming the sslstrip attack takes place when the user requests the site for the first time, the attacker could modify the "Set-Cookie" header, or the javascript code which should have created the secure cookie, coudn't he?
Comment: Set-Cookie header is to weak, that's why I proposed creating the cookie with Javascript. If you expect an attacker which targets a specific web site and knows up front how the Javascript will look like and how to modify it then you have lost anyway.  This protection is more against a broad sslstrip and not a site-specific attack. And you could simply only provide sensitive data on the site if you've got the https-only cookie. It's probably a good thing to combine this idea with HSTS (see the other answer) so you get protection on the client side (if HSTS is supported) and on the server side.
Comment: What about my first point? How can the client reach the website at all, if the first attempt does not work (because it cannot send the cookie as he does not have it, thus he won't get a response) and thus the subsequent also won't?
Regarding your new statement: I think I see what you mean, but an attacker could connect to the most famous 1000 sites via HTTPS, capture the javascript code used for generating the cookie, and include the site specific javascript code deletion into his broad sslstrip-attack. You could generate unique javascript code each, but this is solution is kind of hacky. 1/2
Comment: For browsers which support HSTS, to prevent sslstrip attacks sending the HSTS header and using the HSTS preloaded list is the way to go. 2/2
Comment: Maybe we understand the question different. For me it is a question of a smaller provider, which wants to make sure that clients can only get access to the sensitive part if the connection is not ssl-stripped. Preloaded HSTS is probably the best way if available (which excludes IE!), but I doubt that it is reachable for a small provider to be included included into all browsers this way. On the other hand it is not inside the most important 1000s sites too, so chances are high that its own script based sslstrip detection will not be specifically evaded by the attacker.
Comment: @SteffenUllrich, that smells like security by obscurity ;)
Comment: @Michael: While security by obscurity sounds bad it works in real life for non-targeted attacks. If you have better things like preloaded HSTS you should use it but often you don't. You will also not find too much details about the heuristics used in virus scanners and other security products because otherwise evasion would be too easy.
Answer: You can use window.location.protocol to check what protocol is in use. But the attacker can deliver page without this tag, so you will need a check for existence of this script in page. Personally, I would use HSTS for eliminating this type of attack, not by checking the protocol.

Preventing SSL strip attack


Limit selectable file-types or show error messages?

Question: some users try to upload img/heic although only jpg, png or pdf are allowed.
in the best case our backend should also support img/heic.
However, our backend system will not support img/heic for a long time. A conversion of the file format is legally not possible, because we have to archive the file unchanged.
Currently, the user receives an error message after the upload that the file format img/heic is not supported.
From a user experience point of view, should it only be possible to select jpg, png or pdf?
So that the user can't select img/heic in the first place?
Answer: It generally is better to help the user avoid making an error in the first place, yes. You already have listed the possible actions you could take to achieve that in order of usefulness:

Support the file format in question
Convert from the file format to something that's supported behind the scenes
Prevent the user from selecting anything that's unsupported
Allow the user to upload something unsupported and error out afterwards, requiring them to resubmit only the erroring fields in question
worst case - allow anything, error out and have the user fill out the entire form again from the beginning

As 1 and 2 are impossible for you, 3 is the way to go.


Turing Machine to Accept String from a 3 character alphabet

Question: I need to create a turing machine that accepts the language $a^ib^jc^k$ where $i \ge j \ge k$, but I am not even really sure how to start. Turing machines in this context are a hard concept for me to grasp for some reason.
Answer: One idea is to delete characters, to make it easier let me introduce @ character - it will denote empty space after scratching characters.
For example let input string be $BaabccB$, where $B$ is blank symbol.
At first check for $a$ and create state, say $qa$ which looks for $a$ and then replaces it with $@$ switches to $qb$ moves right until it finds $b$.
Then it replaces $b$ with $@$ switches state to $qc$ and moves right until it finds $c$.
Here again replaces $c$ with $@$ and switches to state $ql$ moves to the left until $a$ is found.
While moving right if blank symbol is encountered, it means that there are less symbols of particular character, this is good according to given language, if the next character is also missing otherwise it breaks inequality and we reject. Also when we seek $b$ but encounter $c$ we reject. After consecutive $c$ if there are other symbols, we reject (it is something like $abca$
When moving left, when blank is encountered, we are finished and accept.
It may happen that there are not sufficient number of $a$ or any character, so after reaching blank character we move right to delete $@$ characters. If we clear all and hit blank, we accept, otherwise we reject as some characters broke inequality.
Example: $BaabccB$
$B@abccB$ move right, switch state, replace $b$
$B@a@ccB$ move right, switch state, switch $c$.
$B@a@@cB$ move left until $a$ replace
$B@@@@cB$ move right, switch state, $c$ is encountered in $qb$ state, it means that $#c > #b$ reject.
Excersise 1:
Try to solve similar question where $i \ge j \le k$
Excersise 2:
Try to solve similar question where $i = 2j = 3k$
Answer: There are two things you need to do when designing a Turing machine (or, in fact, writing any computer program). The first is to decide what algorithm you're going to use, and the second is to express that as a Turing machine/Java program/whatever.  I'll cover the first part.
Turing machines were inspired by what a human could compute using a pencil and paper so, usually, the best way to figure out an algorithm is to think, "How would I do this if somebody gave me a really long string written on a piece of paper and asked me to determine if the string is in the language?"  First, you'd scan the input to check that it really is a bunch of $a$s followed by a bunch of $b$s followed by a bunch of $c$s. Then what?

You could count the $a$s, $b$s and $c$s, call those numbers $i$, $j$ and $k$, and check that $i\geq j\geq k$. That's all very well but the numbers are big so you'll lose count unless you write down the numbers step by step.  As in, there are $1$, $2$, $3$, ..., $45\,387\,298$ $a$s. And then you need to figure out how to compare if one number is bigger than another and this is all rather tricky and tedious.
You don't actually care what the numbers are, as long as they're in the right pattern, so why bother computing them at all? If you had a big pile of stones and you wanted to know if it was an odd or even number, you could count, or you could just arrange the stones into pairs and see if there's one left over. The same idea applies here: go through the string and repeatedly cross out an $a$, a $b$ and a $c$. If you run out of $c$s first, there are more $a$s and $b$s than $c$s.  Then cross out $a$s and $b$s and check that you run out of $b$s next. What is "crossing out"? Well, looking at it kinda literally, you're replacing a character $a$ with $\not{\!a}$, etc., and you can always add $\not{\!a}$, $\not{b}$ and $\not{\!c}$ to your alphabet. Or you can make your life easier by interpreting "cross out" as "replace with $\times$" since, once a character is crossed out, you don't actually care what it used to be.


File Upload(what type of file)

Question: While I was learning about file upload vulnerability one question come to my mind. What type of file do I use while hunting file upload vulnerability ? Do I need to detect which programming language is used on the backend ? Php extension files are used in most examples.
Answer: When testing for RCE via arbitrary file upload vulnerability, it's essential to be certain about the backend otherwise server won't be able to understand your file.
There are multiple ways to detect the backend language used in the application, most are listed in the response here.
For more general tests, in which you want to see how many types of file extension does the application allows, you can use this extension list in intruder and see how many file extension does the application support and then you can craft an attack from the allowed extension. Like for example, if upload functionality supports SVG extension then you can look for XSS via SVG.
Most of the times file upload restrictions are not applied via extension only, but they can also be done based on the content type and other properties. You can read more about it in here.
Answer: It's a broad question and hence hard to answer correctly but I will look into it one by one.
What type of file do I use while hunting file upload vulnerability ?
Answer : Try to identify the file parsing in the application. As mentioned the best match is to identify the backend language and upload a file in the same language. PHP extensions are used in most scenarios is a wrong assumption because enterprise core applications are relying on JSP or .Net and uploading a PHP file on these applications might not yield the expected results.
Diving deep : Even though PHP , JSP or ASP files are the extensions that can potentially produce a critical impact on the application server, other file extensions are also dangerous. A few of them are listed below

Excel and Word can lead to XXE
Postscripts files like  PDF, EPS, PS, XPS
GIF files leaking memory
SVG files leading to SSRF, XXE and XSS
HTML file leading to XSS

This GitHub repo has lots of image related public exploits found so far
https://github.com/barrracud4/image-upload-exploits
Final Note : Understanding the file parsing and application behaviour is important to identify the file upload test cases that can be performed on the application. File upload bypass techniques will aid in overcoming certain extension limitations and content-type validation.
More and more threat vectors are revealed in file parsing libraries, so moving forward file upload testing can go beyond expectations.

File Upload(what type of file)


Is linear discriminant analysis (LDA) more likely to overfit than support vector machine (SVM)?

Question: I went to a short talk and the speaker quickly mentioned something like 'LDA (linear discriminant analysis) is more likely to be overfitted than SVM (support vector machine)'. Is this true? And why?
Comment: Could be some insight here: http://stats.stackexchange.com/questions/35276/svm-overfitting-curse-of-dimensionality?rq=1
Comment: Also, see here some illustrations of overfitting in LDA: http://stats.stackexchange.com/questions/106121.
Answer: I do not believe it is the inverse either. Both approaches are very different.
LDA is optimal (in a Bayes sense) whenever the assumptions under which it is derived are met, namely: data is generated from two multivariate Gaussians with equal covariance matrices. This assumptions are very restrictive.
Linear SVM on the other side, makes no assumptions on the distribution of the data, and has parameters which allow one to control the number of outliers directly. This seems a quite more flexible approach.
Further, LDA has numerical problems in high dimensions. SVMs are more robust in that setting. So, in general, yes, SVMs will behave better.
As an example (more like a starting point to experiment with) you can take a look at this notebook in R. There you can see how in a general case (where assumptions are no longer warranted and for a higher dimensional problem) linear SVMs usually perform better.
Answer: I suspect the reason for the claim that LDA is more likely to overfit than the SVM is because the SVM incorporates regularisation (i.e. a penalty term) that allows you to control the complexity of the model, and hence avoid over-fitting.  However, there are also regularised versions of LDA (the Least-Squares SUpport Vector Machine is equivalent to one form of regularised LDA and uses the same form of regularisation as the SVM).  So strictly speaking the claim is probably incorrect.
As to non-linear SVMs, as mentioned by Jacques, there are non-linear variants of LDA as well (e.g. Kernel Fisher Discriminant analysis), so for a fair comparison, you would compare SVM and KFD with Gaussian kernels, and in that case I'd say that neither was a-priori more likely to overfit, as both have the same form of regularisation to avoid over-fitting.
Answer: I think it is the reverse.
SVM specially with a Gaussian kernel have a much higher probability of overfitting the data than LDA which is LINEAR on the data space!. SVM with a Gaussian Kernel will map the data into a infinite dimension space, and in that space the data is linearly separable. If one uses a very high C, the cost of errors (placing data in the wrong side of the margin) will be unbearable, and the SVM will find the hyperplane that separates the classes (since there is one - they are linearly separable!). That plane (linear on the infinite dimension space) will be a very convoluted manifold in the data space, that separates the classes exactly - the very definition of overfitting!!
For SVM with a linear kernel, I dont know, but if the data is generated by two Gaussians of the same shape (same covariance matrix) the LDA is the optimal solution, which would mean the least overfitting. A Linear SVM can at most match the LDA! For other cases, I dont know.
Comment: (-1) I am sorry for the downvote, but this answer is currently the top one in this thread and I am afraid it can be misleading. As others replies have already pointed out, in high dimensions LDA tends to overfit *badly*, because its computations rely on inversion of the within-class covariance matrix that is very difficult to estimate reliably unless $N>>k$. [See my illustrations here](http://stats.stackexchange.com/questions/106121). Of course one can use a regularized version of it, but "vanilla" LDA does not use any regularization, whereas SVM always does.
Comment: @amoeba: in contrast, you'd say that vanilla SVM have a soft margin, though? I think one could argue that the plainest thinkable SVM is hard margin. Which I'd guess to have at least as much overfitting problems in high dimensions as LDA (possibly more: unregularized LDA gives equal weight to all available cases, whereas the [hard margin] SVM focuses on few cases at the boundary)
Comment: @cbeleites: No, I guess vanilla SVM is the one with hard margin, I agree with you here. But I don't know enough about its behaviour in high dimensions to comment on overfitting. I think, though, that if the classes are perfectly separated, then hard margin SVM is unlikely to  overfit (because maximum margin itself acts as a regularizer), but LDA still might. In a more realistic case of non-perfect separation, I do not know. In any case, my primary objection to the answer above was that LDA does **not** result in (quote) "the least overfitting".


Is 4D $\phi^4$ theory with a complex mass term UV finite?

Question: Consider the path integral expression for the (unrenormalised) propagator in $\phi^4$ theory with a real scalar field $\phi$ on 4D Minkowski space and with a complex mass term:
$$
G[f,g] = \int\mathcal{D}\phi\,{\textstyle(\int f\phi)(\int g\phi)\exp(i\int[\frac12(\partial_\mu\phi)(\partial^\mu\phi) - \frac12(m^2 - i\epsilon)\phi^2 - \frac1{4!}\lambda\phi^4]})
$$
where $f$ and $g$ are smooth, square-integrable functions on Minkowski space. In the limit $\epsilon\to0$ this is just the propagator of $\phi^4$ theory which I know is UV divergent. My question is whether this expression is also divergent for finite $\epsilon>0$.
I have one argument which shows that $G[f,g]$ is finite and one which shows that it is infinite and I can't figure out which one is wrong:
Argument 1: I know that $\mathcal{D}\phi$ is just a sloppy physicist notation for an ill-defined functional integration measure, but if my understanding of Gaussian functional integration measures (which is somewhat limited and comes mostly from math-ph/0510087) is correct then
$$
d\mu_\epsilon(\phi)\equiv\mathcal{D}\phi{\textstyle\exp(-\frac12\epsilon\int\phi^2)}
$$
can be regarded as a well-defined functional integration measure which satisfies
$$
\int d\mu_\epsilon(\phi) = 1
\quad,\quad
\int d\mu_\epsilon(\phi){\textstyle(\int f\phi)(\int g\phi)} = \frac1\epsilon{\textstyle\int fg}
$$
If this is true we may write
$$
G[f, g] = \int d\mu_\epsilon(\phi){\textstyle(\int f\phi)(\int g\phi)\exp(i\int[\frac12(\partial_\mu\phi)(\partial^\mu\phi) - \frac12m^2\phi^2 - \frac1{4!}\lambda\phi^4]})
$$
and since the expression in the exponent is now purely imaginary the exponential has magnitude 1 and we have
$$
|G[f,g]| \leq \left|\int d\mu_\epsilon(\phi){\textstyle(\int f\phi)(\int g\phi)}\right| = \frac1\epsilon|{\textstyle\int fg}| < \infty
$$
Argument 2: The integrals we encounter when we calculate $G[f, g]$ in perturbation theory have the same UV divergences irrespective of whether $\epsilon$ is zero or not. For example, the one-loop 'tadpole' integral is
$$
\int d^4l \frac1{l^2 - m^2 + i\epsilon}
= -i\int_0^\infty dr\frac{2\pi^2r^3}{r^2 + m^2 - i\epsilon}
$$
where we obtained the right-hand side by Wick rotating and integrating out the angular variables. The UV divergence is associated with the behaviour of the integrand for $r\to\infty$ and for this the value of $\epsilon$ is irrelevant. Thus, if $G[f, g]$ is UV divergent for $\epsilon\to0$ it should be UV divergent for all $\epsilon>0$.
My instinct is to trust the non-perturbative argument 1 over the perturbative argument 2, but this would mean that a complex mass term can serve as a UV regulator and I've never heard of anyone use or even discuss such a regularisation.
Comment: Ah, nevermind. I found the answer with the help of [these](http://www.math.ucsd.edu/~bdriver/247A-Winter2012/Lecture%20Notes/topclass.pdf) lecture notes. (Example 2.6, to be specific.) It's Argument 1 which is flawed. The expression is UV divergent. Since this got upvoted I'll post a proper answer later.
Answer: Argument 1 is incorrect because (without additional regularisations) the functional integral is still ill-defined. The reason is that the the derivatives in the integrand are only defined on a dense subspace of $L^2(\mathbb{R}^4)$ (the space of square fields on Minkowski space) but we are trying to integrate over the whole space $L^2(\mathbb{R}^4)$. The issue is discussed in detail in Example 2.6 of these lecture notes.


Uses for dry bread

Question: Currently I have a lot of bread. It's not bad, only dry because it's a bit old. I don't want to throw it out. What can I do with it?
Comment: See faq:  http://meta.cooking.stackexchange.com/questions/740/can-i-ask-about-how-to-use-a-specific-ingredient-aka-culinary-uses-guidelines  This question is considered
Comment: This is a somewhat general question more suited to a traditional forum than here. There is no one right answer to your question, and any answer would be purely subjective.
Comment: Also, I don't ask for recipes, just for ways to use an ingredient.
Comment: possible duplicate of [Uses for stale bread?](http://cooking.stackexchange.com/questions/5279/uses-for-stale-bread)
Answer: Whenever I have some very dry leftover bread I run it through the blender and make it into breadcrumbs, whose uses are legion. In particular, I find that they are a necessary component of frittata and meatballs. After blending, sift the crumbs to remove the bigger chunks and store in an airtight container. Discard if it becomes moldy, but if you store it properly it will keep for weeks.
If the bread is not very dry (let's say that you can still cut it without it turning into a cloud of crumbs), you can make bruschetta: lightly toast it, rub garlic on the cut surface with a heavy hand, add olive oil and a sprinkling of salt. Yummy, not so good for your social life.
Old bread is also the basis of the panzanella salad and of bread soups like panada, ribollita and pappa al pomodoro. Yes, the Tuscans do love their bread.
Not-too-dry bread can also be cut into little cubes that you can dry in the oven (the microwave also works, but be careful lest you set them on fire) to make croutons, the best friends of boring vegetable soups.
Oh, I realized that there is a canonical entry on the many uses of stale bread,
Comment: Panzanella doesn't look hard, so maybe I'm gonna try to make that. I know croutons too, however I don't eat soup often since I'm living in a hostel. Thank you anyway!
Comment: I don't see what living in a hostel has to do with not eating soup! Dry bread can make acceptable toast. The classic British use for stale bread is bread and butter pudding (butter the bread, cut into cubes, layer with some raisins, pour on a mixture of hot milk, sugar and eggs, bake).
Comment: Of course I'd be able to make and eat soup. I'm just too lazy to do that! =D

Uses for dry bread


Considering automation parameters, which is better: relative Xpath or absolute xpath?

Question: I want to perform automation (selenium) using Xpath.  Which one gives better results?
Comment: Welcome to SQA.SE - perhaps you'd like to expand your question, to explain what you ARE trying to achieve? At the moment, it just seems brusque.
Comment: I have to agree with Andrew here. If you could elaborate on what the business problem you're trying to solve is, perhaps this could be salvaged into a keepable question. You can still edit the question even though it is closed, and I'll be more than happy to reopen it when it's ready for consumption! :)
Answer: I assume you use the terms as defined in the Xpath specification.  In that sense, absolute and relative paths are not interchangeable.  You use a relative path when you refer to something relative to another element.  The rest of the time, you use an absolute path.
It is possible that you really want to understand the relative merits of an absolute path and an abbreviated absolute path.  The former starts with a single slash, whereas the latter starts with a double slash followed by a relative path.  You use an abbreviated absolute path when you want to describe a location relative to the root but you do not want to specify all of the ancestor elements.
It is possible that your web page may change someday, e.g. because a developer updates it or because it contains dynamically generated id's.  An abbreviated absolute path may be more likely to still work with the changed page than an absolute path.  It may also be easier to read.


Difference between MABs and full MDPs

Question: As far as Im aware, the difference between Multi-armed Bandit problems and full MDPs is that in
MABs the full distribution over the results of action are known. Is this true?
Answer: It is untrue.
The MAB setting can be interpreted as a one-state MDP (thus a MAB is stateless). In MAB you are given a set of K distributions (whose structure is usually known while the mean of the distribution is unknown).
The goal in MAB is either to identify the arm with the highest mean (best arm) with the smallest number of arm pulls or to maximize the cumulative regret.
An MDP is much more complex: the action you choose determines a new state in which you could have completely different distributions (and best arms). In MAB you are always in the same state).

Difference between MABs and full MDPs


"Ich werde aus ihm nicht klug"

Question: I know that "Ich werde aus ihm nicht klug" means "I can't make him out" or "I can't understand him".
Could someone please explain why?
The literal translation "I become out of him/from him not smart" is hard to understand from a construction point of view.
Btw., is my literal translation right?
Answer:
Ich werde aus [Person/Sache/Information] nicht klug.

is a figure of speech meaning you can't figure something or someone out.
The literal translation would be

I won't become smart out of him/her/it.

It is a way to say that you cant get information out of something that could make you become smart enough to understand it.
"Ich werde aus diesem Lehrbuch nicht klug" might be easier to understand, the pattern is simply applied 1:1 to other objects and people.
Comment: In Swedish we have almost exactly the same expression, but with another preposition, "on" rather than "out of". "Jag blir inte klok på honom". This shows that the exact meaning of the  preposition isn't important, it's just used to establish some sort of relation to the object.
Comment: Incorrect. The "aus" doesn't just express an undefined relation, but also specifies a direction, in this case picturing the (desired) direction of understanding-fostering information flow, whereas "on" is... well, I'm not good enough at speaking Swedish to make a proper statement on that, so I'll have to trust you that it's unimportant. In any case, drawing conclusions between languages, especially for figures of speech, is not a good idea.
Answer: "Ich werde aus ihm nicht klug/schlau." = I fail to read him / can't make him out. Expressing a sense of being puzzled by the person's words, behaviours, etc. Literally perhaps: "I'm not getting smart (out) of him."
It's a collocation of the idiomatic expression 'klug werden' or 'schlau werden' in the meaning of 'learning something, understanding it' with the preposition 'aus' + dative.
This also occurs for things that need to be understood to be of use, e.g., user instructions or machines: "Ich werde aus dieser Anleitung einfach nicht schlau." – "I just don't get these instructions."
A related proverbial phrase is "Aus Schaden wird man klug.", literally: "from damage one gets smart", used in the sense of "you live and you learn" or "once bitten, twice shy" depending on the context.
Also related is the expression "aus etwasᴰᴬᵀ lernen" – to learn a lesson from something, usually a damage/misfortune suffered by someone.

"Ich werde aus ihm nicht klug"


UITableView datasource methods called before database open

Question: I am writing an application that uses a Core Data database to store data which I then want to display using a UITableView. I have everything working, but was a little curious if there is a way around one small point that is bugging me...
When the app runs I do the following:

Create a NSManagedDocument
Create a NSFetchedResultsController
Open the Core Data database.

I am using ...
[[self testDatabase] openWithCompletionHandler:^(BOOL success) {
    if(success) {
        ...
    }
}];

to open the database but my problem is that by the time the block has executed the UITableView dataSource has already called -[TableViewController tableView:numberOfRowsInSection:] and returned rows=0
My solution so far has been to ignore this first "automatic" call and  instead add a performFetch and a reloadData to the block that executes when the database is open.
[[self testDatabase] openWithCompletionHandler:^(BOOL success) {
    if(success) {
        [[self fetchedResultsController] performFetch:nil];
        [[self tableView] reloadData];
    }
}];

My question, is there a way to stop or delay that first call? or is there something I should add to -[TableViewController tableView:numberOfRowsInSection:] to manage that first call, or does it simply not matter and its fine as it is?
Answer: You can try starting with nil for tableView.dataSource and setting it after fetch.


How do I gain land through conquest?

Question: I have played many games of CK2 now but cannot figure out why when I win a war I NEVER gain any territory, but when I lose I often lose a county or two!
Even when I siege all the cities/temples/castles/etc on that land it never ends up belonging to me even when I have a valid claim (casus beli) to it!
So HOW do I gain land and WHY am I losing it?
Comment: I just surrended in a war i couldn't win i had 3/4 demesne and suddenly its game over. when i offered surrender it didnt say anywhere in the surrender conditions that would be i lose all my land... so why did it do that? is it some random catastrophe of surrender?
Comment: That depends on the what the war was fought over, or who was doing the fighting. For example, if your 3/4 was three holdings in one county (castle, town and church) and someone attacked you for a religious cause (Norse, Islamc etc), then you'd lose all the holdings in that county if you surrender.
Answer: There are a variety of ways to go to war. When you declare war, read the Casus Belli very carefully. It turns out that while the Medieval and Renaissance eras didn't have a United Nations or equivalent, they did have to deal with similar fallout: if you went to war because you're a warmongering monster bent on conquering the world, the countries near you would probably form a temporary alliance and beat you senseless. Therefore, wars were usually fought for "valid"† reasons: somebody had a claim on a bit of land (discovered by carefully reading family trees‡, being a scholar of genealogy, and/or making one up!), because their opponents were heretics/heathens, or because they were rising in rebellion.
Some Common Cassus Belli
Here are a few common CBs and their results if you win:

Your claim (possibly multiple): you get that county/duchy, and no others. Regardless of how many castles you siege and how many armies you destroy, you're only going to get the county/duchy that you went to war over. (You can go to war over multiple claims that you have at the same time, but not a combination of your claims and your vassals' claims.)
Your vassal's claim: Once you win, your vassal gets the land (and loves you dearly). This will expand your kingdom, but it won't expand your personal demesne. (Note: if the title you're taking is equal to your rank, your vassal will become independent! If you're a duke, don't press your vassals' claims on duchies; if you're a king, don't press your vassals' claims on kingdoms.)
A claim from a member of your court: When you win, that courtier is going to take over the title. If they have no other titles, then they're just going to be independent. (This is why, if you use courtiers' claims, you should give them some minor title first: a city, church, or castle is enough for them to still be your vassal afterwards.)
Opponent is excommunicated: Once you win, your opponent abdicates, and his heir takes over. You'll only get things if you're the heir.
De jure claim: You kingdom/duchy will definitely expand, but the title can go to one of three possible people. If it's the last county owned by someone, then they become a vassal (of you or your vassal, depending on who owns the duchy). If it's not their last county, then either you or your vassal gain the county.
Wars over independence, deposing your liege, or refusing arrest (a.k.a. war against tyranny): In all cases, nobody gains anything. Deposing your liege just means his heir takes over, losing against tyranny just means you're arrested (and the liege, as a separate action, can revoke a title), and winning against tyranny just lowers the crown laws.
Holy War: The person pressing the holy war takes the named title as part of their personal demesne, including all lower titles. If you wage holy war to take a duchy, you'll have plenty of titles to hand out afterward. (Again, if you destroy other castles/armies/kingdoms, you still only get the bit of land you mentioned in your initial Casus Belli.)
Crusade/Jihad/Great Holy War: These are called by the leader of a religion, regarding a Kingdom. If the war is successful, the land is handed over to the noble whose armies contributed most to the war.

Why you might have lost everything on losing a war
On a separate note, when you lost your war, it would depend on what the war was about. If they had a claim on your duchy (I'm assuming you had a single duchy with three counties in it), then that's it: you lose everything. Also keep in mind that the holder of the duchy title can revoke counties, it just causes a hit to the duke's opinion with his other vassals. If he has no other vassals, then he can simply revoke everything and you're out of a job. Similarly, if they were simply deposing you, and you had no heirs, then that's it: your dynasty has ended. And if it was a Holy War for your last duchy/county, then surrendering means that you lose all of the titles in that duchy/county.
Footnotes
†: One historical example: in 1215, a bunch of English barons rebelled against King John. The barons won, but John remained King afterward; they just limited some of his kingly powers via the Magna Carta, a document that they made him sign. In Crusader Kings II terms, this is a War Against Tyrrany/Resisting Arrest, which reduces crown authority.
‡: One more example, because I can't resist: The Hundred Years' War was kicked off in 1337 at least partially because the King of England had a better claim on the Kingdom of France than the current King of France did!
Comment: +1. Also (you may have mentioned it but I missed it), you can't have vassals of the same rank as you, so if you're a king, and go to war on another kingdom on behalf of your vassal's claim, when you win the war he will be king, and since you're also a king, he will be independent and you didn't gain anything (except a friendly fellow king)
Answer: When you go to war, you must have a valid Casus Belli. There are many different CB types. When you select the CB upon declaring war, look at who you are going to war for, and why. This will determine not only what the "prize" or goal of the war is, but who recieves it - in many cases, a member of your court who may or may not be a direct vassal.
I would reccomend reading up on the different CB types and reference this page before going to war.
http://www.ckiiwiki.com/Casus_Belli
Comment: Generally speaking, if the person you're fighting for is of your dynasty (has a little blood drop on their picture) and/or you have a 'de jure' claim on the title (is part of a duchy, kingdom or empire you control) then you'll gain that territory when you win.
Answer: Yeah, you need to read VERY VERY VERY carefully what the reason for the war is, because that is EXACTLY what is at stake.
Most likely if you're fighting wars and not getting anything, you've been challenging on other people's claims who then get the territory and most likely leave your realm since they're probably equal or higher tier then you or weren't landed to your realm yet.
It's also possible that they were fighting in another war that was related that would nullify the war when they lost that one. (It'll usually warn you that this is a possible outcome before you declare the war if it applies).

How do I gain land through conquest?


Best reagents state for air free chemistry. Choosing halide for grignard synthesis

Question: I am planning to synthesize a grignard and I have a choice between the iodo or chloro aryl halide. The iodo is a solid and the chloro is borderline. For my previous reaction I melted the chloro and then tranfered it using a flushed sringe. As an alternative I could just weigh out the iodo and then pull vacuum on it a few times before running my reaction. Is there a better option between the two or they are just the same?
Answer: The chloride can be a bit slow to react, particularly if the aryl halide is hindered. You might need a small amount of iodine to get the reaction started. (Maybe you ran into this already?)
Once you form the Grignard, they should be identical for most applications.
Personally, I would just go with iodide because the chloride is probably a bit less reactive, and frankly, weighing out substances that are almost solid is extremely annoying. Strongly prefer the actual solid.
The main reason I would elect the chloride over the iodide in this case is if the cost of the chloride were much lower, and even then only if the reactivity weren't seriously impeded by using the chloride.
Comment: Also, I should point on that the air-free part doesn't matter in terms of the choice. You'll going to pull vacuum on the substrate, and if you really need to avoid oxygen/water vapor, you'd backfill with an nitrogen/argon and then transfer into your reaction vessel with a cannula.
Answer: While I haven't done this with halocarbons to create Grignards, I have performed quite a large number of reactions where I either had a very highly viscous liquid or a solid.
If you have a choice, my advice is to go for the solid for these reasons:

If a compound is 'borderline', it'll typically be rather viscous as a liquid just above its melting point.
Viscous liquids are a pain to deal with. Taking them into a syringe is hard.
Getting exact amounts of liquids is harder than getting exact amounts of solids. Typically, the scale on a syringe is too broad to adequately determine how much substance you have added. You would have to weigh the syringe with its contents. Adding or removing a few milligrams is much harder than just picking a few crystals/needles.
Solids, having relatively high melting points, are unlikely to evaporate notably when being subjected to HV conditions. (But this applies to viscous liquids, too.) This makes them easy to handle as you can simply add them to a flask and then evacuate.


Faking a network communication to test client/server on one computer

Question: I have a course project where I'm suppose to present some networking stuff. There are great chances that I have to do it on one computer. So my question is, how do I show a communication between tcp/ip or tcp/udp? I'm not a networking expert, I understand the concept of sending data which is red. And I think I need two IP addresses.
Answer: You don't need two IP addresses.  Just start the server on the machine, and have the client connect to address 127.0.0.1 and the appropriate port.  (This address always refers to the same machine the program is running on.)
Answer: You can run a virtual machine on your computer and work on network between them.


In my Canon t5, how much can I bring up the ISO without getting unacceptable noise?

Question: Would you feel comfortable at 3200?  Or maybe at 1600?
Comment: possible duplicate of [How much "noise" is acceptable in a photograph?](http://photo.stackexchange.com/questions/1421/how-much-noise-is-acceptable-in-a-photograph)
Answer: It is not noise that matters but its visibility. Each ISO has inherent noise, greater than the one before it. However, the smaller the noise, the less visible it is. So, the acceptable ISO depends on the viewing or printing size.
For a moderately large print, I would stick to ISO 800 or less on the T5. For a mid-size one, say a 12" x 8", possibly use ISO 1600 but no more. And if I had to make a small print, then ISO 3200 or 6400 would be acceptable.
Each time I review a camera, I show a sample crop from an image taken at each ISO. Here is the Canon T5 Review and this page shows a crop from an image taken at each ISO with it. From there, if you go to the Images page, you can see images taken at each ISO. Underneath you can click on the 4x6 or 8x12 label to see a scaled down version of the image image. If you do that with some of the high ISO images, you will clearly see that how noise is perceived is quite different once an image is scalled down.
Comment: > Each ISO has inherent noise, greater than the one before it. -- this is totally wrong.
Comment: It is so simply because of the way sensors implement ISO. You see, there is only one true sensitivity of the silicon. In order to get higher sensitivities, one simply reduces the saturation point the resulting charge is sampled at a different scale when converted to digital. This effectively means that each ISO other than the base is an amplification of the native sensitivity.
Comment: you can look at noise graphs for different ISO settings (very easy to plot, or you can use Bill Claff's - something like http://www.photonstophotos.net/Charts/PDR_Shadow.htm#Canon%20EOS%207D%20Mark%20II,Nikon%20D810 ) to see what is really happening. Well-designed analogue stages, including in-camera PGAs, are why. What happens is low light increases the relative photon shot noise (it is square root of the signal, if the level is 100, photon noise is about 10, or 10%, with SNR 10:1; but if the signal is 2 stops higher, 400, photon shot noise is 20, or 5%, with SNR 20:1, acceptable).
Answer: The ISO boost decreases noise on Canon cameras. The noise is because exposure is low (due to low light, for example, and inability to open the lens wider and/or use slower shutter speed, or lack of experience) which means the signal is low and drowning in noise.
Comment: Where did you hear such a thing? Maybe low exposure creates noise, but the ISO will always increase it.
Comment: @Emilios1995 : Please see my response to Itai above. ISO setting is sort of amplification (in pro video cameras it is rated directly in dB). When you have low signal and poor signal-to-noise ratio, your volume control does not increase noise level - it simply makes noise more audible. But the root cause is not volume control, it is low SNR at the input.
Comment: Thanks for the info! I never thought about ISO that way. I mark Itai's answer because it is more practical. But +1 to you and your valuable insight!


LDA VS LOGISTIC REGRESSION

Question: Can Linear Discriminant Analysis be used to classify data the way that logistic regression can be used to classify an outcome of something?
Answer: This question has been answered, at least, for binary classification here: Logistic regression vs. LDA as two-class classifiers , where the significant comment is:

LDA works when all the independent/predictor variables are continuous (not categorical) and follow a Normal distribution. Whereas in Logistic Regression this is not the case and categorical variables can be used as independent variables while making predictions.

Now, per this source , 'Comparison of Logistic Regression and Linear Discriminant Analysis: A Simulation Study', to quote:

Contrary to the popular beliefs, both methods can be applied to more than two categories (Hosmer and Lemeshow, 1989, p. 216).

Hosmer and Lemeshow provide technical details in their online book, Applied logistic regression, on page 56, freely available here.
So, in the multi-categorical case, both techniques can be employed and the underlying comments in the binary case remain essentially applicable.
Comment: Note that logistic regression is not intended to be used as a classifier but rather to estimate probabilities.  And classification without an explicit and appropriate utility function is arbitrary and inconsistent with optimum decision making.

LDA VS LOGISTIC REGRESSION


Why does MATLAB's dualtree3 function not return the lowpass subband of the imaginary tree?

Question: MATLAB has a function named dualtree3 which computes 3-D dual-tree complex wavelet transform. This function only retains the last low-pass coefficients/subband of the real tree. And, it does not save the low-pass subband of the imaginary tree. How can you justify this?
Comment: In [1], the authors say that when the input signal is real, there is a symmetry between imaginary and real parts. However, you should note that this symmetry exists for detail subbands (or highpass coefficients). This MATLAB's function seems to remove the computations for the lowpass coefficients.

----
[1]    Selesnick, Ivan W., Richard G. Baraniuk, and Nick C. Kingsbury. "The dual-tree complex wavelet transform." IEEE signal processing magazine 22.6 (2005): 123-151.
Comment: I don't clearly see the link between the title (complexity reduction) and the low-pass vs Hilbert behavior
Comment: You are right @Laurent. At first, I thought that when the function does not return one of the two low-pass parts, it actually reduces the amount of computations. Now, I changed the title to better show my question.
Answer: Prof. Nick Kingsbury kindly provide an answer to my question!.

In 1-D, the lowpass basis functions (scaling functions) from the two
trees (a) and (b) of the dual tree WT tend to look very similar to
each other, apart from a shift of half the output sample period
between them. Hence it usually makes most sense to regard the two sets
of lowpass samples as interleaved samples from a single 2x
over-sampled real basis function.
On the other hand, the highpass basis functions (wavelets) from (a)
and (b) look approximately like a Hilbert pair of functions. so they
are most logically interpreted as the real and imaginary parts of an
analytic basis function.
Hence the over-sampling by 2 in the lowpass channel replaces the
spitting into real + imaginary channels for the bandpass channels of a
multi-scale wavelet transform.  Similar things apply when 4 trees are
used for the 2-D dual-tree WT, or when 8 trees are used for the 3-D
version.
I hope this helps.  Do refer to our 2005 paper in IEEE Signal
Processing Magazine for more details.

[UPDATE at 9/18/2020]
Since I quoted Prof. Kingsubury's answer above, I should also note one more thing. He mentioned in his email that he is not familiar with dualtree3 function in MATLAB. However, based on my question, he gave the above general answer.
Comment: Not fully convinced by now because the inversion result is close to perfect. I have updated my contribution
Comment: I added an update. Still I am working on your answer. Thanks.
Answer: TL,DR: the low-pass component (approximation coefficients, a) has a size bigger than expected ($2^3$ times). So I guess that the 8 avatars of the approximation subbands are gathered into one.
First, I did not take enough time to check the codes, so this may be a partial answer. While performing a dualtree3 decomposition:
zr = rand(64,64,64);
[a,d] = dualtree3(zr,2);

and its inversion:
xrec = idualtree3(a,d);

the $\ell_\infty$ norm is very low, typically of the order of $10^{-15}$. So, numerically speaking, the reconstruction is "perfect". As such, I won't go for the ideas that the low-pass approximations are "very similar". This would yield higher relative differences. It may not matter a lot for practical volume processing
Now, let us look at the subbands. For d, th details subbands, one gets:
  1×2 cell array
    {32×32×32×28 double}    {16×16×16×28 double}

so you recover the $28$ directional details, that's okay. Their size are respectively $2^3$ and $4^3$ those of the original data. Now, look at the approximation:
a         32x32x32            262144  double

Oddly, the size does corresponds to what we could expect. Each of the low-pass approximations (8 in 3D) ought to be of size 16×16×16, similarly to the 2nd level of details. Instead, it looks like the 8 low-pass approximations are packed into a $2^3$ bigger array.
Finally, if you consider that the high-pass subbands are complex (hence have twice the array size), the global size of the 3D dual-tree, divided by the size of the orignal cube, is
(2*prod(size(d{1}))+2*prod(size(d{2}))+prod(size(a)))/prod(size(zr))

which yields $8$, as expected. I obtained the same results with three level of decomposition. To me, all the information is here, with the expected redundancy. No savings, unfortunately. Gathering approximation coefficients is not uncommon. It is rare in 2D (because one gets a shape factor). This is possible in 3D because the $8$ instances of approximations can nicely fit into a cube. I have no mention of that in the literature in mind.
Answer: The @LaurentDuval is right.
The MATLAB's dualtree3 function returns all detail and approximation subbands which are expected when performing 3D dual-tree complex wavelet transform (cplxdual3D). However, instead of returning separate approximation subbands, dualtree3 function groups them all in a single cube.
In the following, I explain it by using both MATLAB's built-in dualtree3 function and cplxdual3D function from Prof. Ivan Selesnick's Wavelet toolbox.
Example 1: One stage decomposition
We know that real 3D discrete wavelet transform (DWT) returns $1$ approximate subband and $7$ detail subbands.
In practice, cplxdual3D is implemented using eight real 3D discrete wavelet transforms. Therefore, after performing one stage of cplxdual3D, we expect to have $1\times8$ approximate subbands and $7\times8$ detail subbands.
J = 1; % number of decomposition stage
[Faf,Fsf] = FSfarras; % filterbanks used in the first stage
[af,sf] = dualfilt1; % filterbanks used in the remaining stages

zr = rand(64,64,64); % Input volume

w = cplxdual3D(zr,J,Faf,af);

This function returns all subbands in a cell array named w, in which the approximate subbands can be accessed by w{J+1}{m}{n}{p}, where $m,n,p\in\{1,2\}$.
For the above example:
m = 1; n = 1; p = 1;
size(w{J+1}{m}{n}{p})

ans =
    32    32    32

So, we have $32 \times 32 \times 32 \times 8$ entries as approximate coefficients.
NOTE: I do not know why but MATLAB's dualtree3 function could not support one stage decomposition.
Example 2: Two stage decomposition
J = 2
w = cplxdual3D(zr,J,Faf,af);

size(w{J+1}{1}{1}{1})

ans =
    16    16    16

As mentioned in the above example, here we also have $8$ approximate subbands. So we have $16 \times 16 \times 16 \times 8$ entries as approximate coefficients.
If we run a similar experiment with MATLAB's dualtree3 function, we see that dualtree3 groups all approximate coefficients in a cube of size $32 \times 32 \times 32$:
J = 2;
[a,d] = dualtree3(zr,J);
size(a)

ans =
    32    32    32

Additional Note: At this time, I do not know in which order dualtree3 puts the approximate coefficients into the cube. In order to find it, you should perform cplxdual3D and dualtree3 with the same filter banks and compare the results of decompositions for a small and simple example.
Comment: Yes, this one level impossibility is weird. I should have thought it was from Selesnick word (the Farras filter).


Got an error 1120 ~ Access of undefined property

Question: This is not your typical 1120. I know better than to have buttons/MCs without instance names on the timeline.
Nope, this problem resides in a I timer I built from script I found online. The undefined property is related to the timer class delay I want to implement.
What I'm trying to achieve is have the user click the next button, wait 1 sec., then scroll through the next content. I have the code sitting inside a conditional statement to reduce the amount of code.
One thing to note, I am using TweenLite for the transitions, if that makes any difference
Now, the following code will show you the timer only working work one next position. I want to eventually add this to the remaining next position and all the previous positions so that there will be a slight delay when scrolling through the content.
Also, I want to reuse the same code so when the user reaches a particular position, there will be a slight delay and load, and/or, make an image or text visible.
How would I solve my initial problem and then simplify the code to reuse the code throughout the project?
Thanks for the help in advance!
import gs.TweenLite;
import gs.easing.*;

var timer:Timer = new Timer(1500, 1);

next_mc.addEventListener(MouseEvent.CLICK, nextListener);
prev_mc.addEventListener(MouseEvent.CLICK, prevListener);
timer.addEventListener(TimerEvent.TIMER, delay); //I get the error here with "delay"

prev_mc.visible = false;

function nextListener(event:MouseEvent):void {

 if (this.content_mc.slider_mc.x == 0) {

  function delay(event:TimerEvent):void {
   TweenLite.to(this.content_mc.slider_mc, 1, {x:-923.2, y:0, ease:Quart.easeInOut});
   prev_mc.visible = true;
  }
 } else {
  TweenLite.to(this.content_mc.slider_mc, 1, {x:-1872, y:0, ease:Quart.easeInOut});
  next_mc.visible = false;
 }
}

function prevListener(event:MouseEvent):void {
 if (this.content_mc.slider_mc.x == -1872) {
  TweenLite.to(this.content_mc.slider_mc, 1, {x:-923.2, y:0, ease:Quart.easeInOut});
  next_mc.visible = true;
 } else {
  TweenLite.to(this.content_mc.slider_mc, 1, {x:0, y:0, ease:Quart.easeInOut});
  prev_mc.visible = false;
 }
}

next_mc.buttonMode = true;
prev_mc.buttonMode = true;

timer.start();

Answer: The problem is that the "delay" function is defined within your nextListener function, so it is not accessible in your timer.addEventListener(TimerEvent.TIMER, delay); code.  I think you meant to move the timer.addEventListener(TimerEvent.TIMER, delay) inside of the next button handler.
Answer: This is a scoping issue. You are calling the 'delay' function from this line:
timer.addEventListener(TimerEvent.TIMER, delay); //I get the error here with "delay"

but the delay function is defined in another function, nextListener.
That means that this line cannot see the delay function. To fix this issue, just put this line inside the nextListener function:
function nextListener(event:MouseEvent):void {
// newly added ---v
timer.addEventListener(TimerEvent.TIMER, delay); //I get the error here with "delay"
// rest of code
}


Why a verb "to be" has a lot forms

Question: I really can't understand why this verb changes to "am", "is", etc. The common answer is "just became as historical legacy", but how actually it happend?
Comment: The "verb _be_" doesn't change to anything. That's just a way of talking about paradigms. The fact is that people say _I am_ instead of *_I is_ or *_I be_. You can say there's a special verb "am" that means "be" but is used only in the first person singular and in the present tense, while the verb _be_ is never used in the first person singular present tense. That sounds kind of silly, so we say they're the "same verb", but they aren't, really. They're just two different forms in the same paradigm. The story of how they got into the same paradigm is another matter.
Comment: Welcome to Linguistics.SE! This is due to a process known as [suppletion](https://en.wikipedia.org/wiki/Suppletion) which causes several roots to merge, leading to this kind of 'mixed paradigms'. In the question I linked the factors playing a role in suppletion are discussed.
Comment: There are a lot of details specific to "be": is that what you are looking for?
Comment: @user6726 true. I have retracted my close vote.
Answer: The basic intuition here is that the most common verbs are on average the most irregular.  It is very hard for people to remember irregular forms of uncommon verbs, we tend to regularise them over time.
Well, to be is the most common verb of all.
Comment: This explains how the situation is maintained, not how it came to be.
Comment: Depends.  Do we consider it the default natural state does of things that words used in different contexts have different roots, or that they share roots via some paradigm?  Which one requires explanation?

Why a verb "to be" has a lot forms


Is it safe to force shutdown a mac while booting?

Question: So I have the 2015 "13 MacBook so I read some articles to update firmware by holding the power button so i tried to try it for fun but I misunderstood the article and I held the power button while my mac had completed 1/4 of booting process. So I accidentally force shutdown my mac while it was booting. So should I worry about some firmware error or some sort of software error which I can't notice?
Answer: Any forced shutdown can leave a file in a bad state. At boot, you would only corrupt a system file, so that's usually easy to reinstall the OS so I suppose if you care about user data - that's the best time to force a stop.
High Sierra supports internet recovery and bootable install media, so the options to reinstall are much better than the old days where you needed a CD or DVD to reinstall and it took a long time.
Comment: Thanks for the immediate response actually i don't care that much about a system file because maybe the system itself may rebuild it. And also I don't notice any type of problem in my mac!
Comment: But I believe no system file would have been corrupted because in the 1/4 boot process only the kexts are loaded.


Swap red and blue channels in application

Question: I have an old application which renders with the red and blue channels swapped. Is there a way I can use a color filter or display profiles or something else to fix this? I'm willing to use a solution that's either specific to the application or global to the system so long as it can be easily toggled.
Comment: What application? I doubt this is fixable at OS-level; changing any aspect of the display profile would not be capable of literally swapping two input/output channels, afaik. It could possibly be done through a video 'effect', LUT etc, but idk how you would inject that to the app's output.
Answer: Depending on how often you need the application you could use OBS to capture the window and aplly a filter like the streamfx color filter to the image to fix it and then view the output in the preview window. This is pretty unpractical if you want to use the application a lot, but for using it seldomly this should work.