[procedure] count pred clist1 clist2 ...

SRFI-1: pred is a procedure taking as many arguments as there are lists and returning a single value. It is applied element-wise to the elements of the lists, and a count is tallied of the number of elements that produce a true value. This count is returned. count is "iterative" in that it is guaranteed to apply pred to the list elements in a left-to-right order. The counting stops when the shortest list expires.

See also fold, reduce.