count_if

csp/utils.rkt

@@ -1,3 +1,12 @@
 #lang racket/base
+(require racket/list racket/bool)
 
-(provide (all-defined-out))
+(provide (all-defined-out))
+
+(module+ test (require rackunit))
+
+(define (count_if pred xs)
+  (length (filter-not false? (map pred xs))))
+
+(module+ test
+  (check-equal? (count_if procedure? (list 42 null max min)) 2))