====== List comprehension ======

  * syntactic sugar to apply set operations to lists
  * syntax := "[" //output expression// "|" //variable / binding// = //input set// "," //predicate// "]"
  * e.g. ''[ 1 / x | x <- [-1, -0.75 .. 1], x /= 0 ]''
    * creates a list 
      * of reciprocal numbers (''1 / x'')
      * from the set {-1, -0.75, -0.5, -0.25, 0, 0.25, 0.5, 0.75, 1} (''[-1,-0.75..1]'')
      * except 0 (''x /= 0'')
    * code:<code Haskell>
main :: IO ()
main = print x

x = [ 1 / x | x <- [-1,-0.75..1], x /= 0 ]
</code>
      * excutes, with output:<code>
[-1.0,-1.3333333333333333,-2.0,-4.0,4.0,2.0,1.3333333333333333,1.0]
</code>
  * binding can be applied to pattern matching to filter out sums
    * example:<code Haskell>
import Prelude hiding (Maybe(..))

main :: IO ()
main = print x

data Maybe a = Just a | Nothing

x = [ch | (Just ch) <- [Just '3', Nothing, Just '4']]</code>
      * excutes, with output:<code>
"34"
</code>


===== ✎ =====
~~DISCUSSION~~