X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=blobdiff_plain;f=utils.scm;fp=utils.scm;h=ea8900f51cf989caa59fc9ed6d4168d354621545;hp=e063b85d08625500f5bbeb6e124214d98a464688;hb=fff1029008b7399f597e0227fff2bf05b8a27b3c;hpb=f4b0d5c1b14a1890e1b88398e256b272595346b2

diff --git a/utils.scm b/utils.scm
index e063b85..ea8900f 100644
--- a/utils.scm
+++ b/utils.scm
@@ -25,3 +25,20 @@
     ((_ s) (let ([x (car s)])
 	     (set! s (cdr s))
 	     x))))
+
+(define (any p x)
+  (fold-left
+   (lambda (acc y) (if acc #t (p y)))
+   #f
+   x))
+
+(define (all xs) (fold-left (lambda (acc x) (and acc x)) #t xs))
+
+					; (combinations '(1 2) '(3)) => '((1 3) (2 3))
+(define (combinations . lists)
+  (case (length lists)
+    [0 '()]
+    [1 (map (lambda (x) (list x)) (car lists))]
+    [else (flat-map (lambda (x)
+		      (map (lambda (y) (cons x y))
+			   (apply combinations (cdr lists)))) (car lists))]))