intersect package:xmonad-contrib

The intersect function takes the list intersection of two lists. It is a special case of intersectBy, which allows the programmer to supply their own equality test.

Examples

>>> [1,2,3,4] `intersect` [2,4,6,8]
[2,4]

If equal elements are present in both lists, an element from the first list will be used, and all duplicates from the second list quashed:

>>> import Data.Semigroup

>>> intersect [Arg () "dog"] [Arg () "cow", Arg () "cat"]
[Arg () "dog"]

However if the first list contains duplicates, so will the result.

>>> "coot" `intersect` "heron"
"oo"

>>> "heron" `intersect` "coot"
"o"

If the second list is infinite, intersect either hangs or returns its first argument in full. Otherwise if the first list is infinite, intersect might be productive:

>>> intersect [100..] [0..]
[100,101,102,103...

>>> intersect [0] [1..]
* Hangs forever *

>>> intersect [1..] [0]
* Hangs forever *

>>> intersect (cycle [1..3]) [2]
[2,2,2,2...

interface to the X11 library function XIntersectRegion().

The intersectBy function is the non-overloaded version of intersect. It is productive for infinite arguments only if the first one is a subset of the second.

True if the intersection of the set of points comprising each rectangle is not the empty set. Therefore any rectangle containing the initial points of an empty rectangle will never intersect that rectangle - including the same empty rectangle.

uses intersect