Closure, coin sums, & number spiral generator

1 files changed, 32 insertions, 0 deletions

diff --git a/closure/closure.scm b/closure/closure.scm
new file mode 100644
index 0000000..9dec47e
--- /dev/null
+++ b/closure/closure.scm
@@ -0,0 +1,32 @@
+(define-module (closure)
+  #:export (iterative-add
+            set-store
+            peek-store
+            advance-char))
+
+(define (iterative-add)
+  "Given NUM, returns NUM plus the previous
+supplied NUM."
+  (let ((prev-num 0))
+    (lambda num
+      (let ((result
+             (+ (car num) prev-num)))
+        (set! prev-num (car num))
+        result))))
+
+(define set-store #f)
+(define peek-char #f)
+(define advance-char #f)
+
+(let ((store '()))
+  (set! set-store
+        (lambda (lst)
+          (set! store lst)))
+  (set! peek-char
+        (lambda ()
+          (car store)))
+  (set! advance-char
+        (lambda ()
+          (let ((ret (car store)))
+            (set! store (cdr store))
+            ret))))