trie: add with test

1 files changed, 35 insertions, 0 deletions

diff --git a/util.scm b/util.scm
new file mode 100644
index 0000000..fa361f7
--- /dev/null
+++ b/util.scm
@@ -0,0 +1,35 @@
+;;; Utilities.
+
+;;; ;;;;;;;;;;;;;;;;
+;;; Versions of FOLD
+;;; ;;;;;;;;;;;;;;;;
+
+(define fold
+  (lambda (f init lst)
+    (if (null? lst)
+        init
+        (fold f (f (car lst) init) (cdr lst)))))
+
+(define fold-vector
+  (lambda (f init vec)
+    (if (list? vec)                    ; Support MiniScheme
+        (fold f init vec)
+        (letrec
+            ((loop
+              (lambda (i val)
+                (if (= i (vector-length vec))
+                    val
+                    (loop (+ i 1) (f (vector-ref vec i) val))))))
+          (loop 0 init)))))
+
+;;; ;;;;;;;;;;;;;;;;;;;;
+;;; Misc. list functions
+;;; ;;;;;;;;;;;;;;;;;;;;
+
+(define all
+  (lambda (f lst)
+    (cond
+      ((null? lst) #t)
+      ((not (f (car lst))) #f)
+      (else (all f (cdr lst))))))
+