break, applied to a predicate
p and a list
xs, returns a tuple where first element is longest prefix
(possibly empty) of
xs of elements that
do not satisfy
p and second element is the remainder of the list:
>>> break (> 3) [1,2,3,4,1,2,3,4]
([1,2,3],[4,1,2,3,4])
>>> break (< 9) [1,2,3]
([],[1,2,3])
>>> break (> 9) [1,2,3]
([1,2,3],[])
break p is equivalent to
span (not .
p).