Haskell Language List Comprehensions Nested Generators
Example
List comprehensions can also draw elements from multiple lists, in which case the result will be the list of every possible combination of the two elements, as if the two lists were processed in the nested fashion. For example,
[ (a,b) | a <- [1,2,3], b <- ['a','b'] ]
-- [(1,'a'), (1,'b'), (2,'a'), (2,'b'), (3,'a'), (3,'b')]
