Like map, but drops elements that raise exceptions.
DESCRIPTION
Applies a function to every element of a list, returning a list of
results for those elements for which application succeeds. The
function is applied to the elements of the list from left to right
(which is significant if its action includes side effects).
FAILURE
If f x raises Interrupt for some element x of l, then
mapfilter f l fails (with an Interrupt exception).
EXAMPLE
- mapfilter hd [[1,2,3],[4,5],[],[6,7,8],[]];
> val it = [1, 4, 6] : int list