A list comprehension is a special syntax in some programming languages to describe lists. It is similar to the way mathematicians describe sets, with a set comprehension, hence the name.

Some attributes of a list comprehension are:

 They should be distinct from (nested) for loops and the use of map and filter functions within the syntax of the language.
 They should return either a list or an iterator (something that returns successive members of a collection, in order).
 The syntax has parts corresponding to that of set-builder notation. 


Task

Write a list comprehension that builds the list of all Pythagorean triples with elements between   1   and   n.

If the language has multiple ways for expressing such a construct (for example, direct list comprehensions and generators), write one example for each.




flatten = (arr) -> arr.reduce ((memo, b) -> memo.concat b), []
 
pyth = (n) ->
  flatten (for x in [1..n]
    flatten (for y in [x..n]
      for z in [y..n] when x*x + y*y is z*z
        [x, y, z]
    ))
 
console.dir pyth 20