net: Add (net ricketyspace sicp one thirtytwo)

* net/ricketyspace/sicp/one/thirtytwo.scm: New file.

1 files changed, 36 insertions, 0 deletions

diff --git a/net/ricketyspace/sicp/one/thirtytwo.scm b/net/ricketyspace/sicp/one/thirtytwo.scm
new file mode 100644
index 0000000..6287353
--- /dev/null
+++ b/net/ricketyspace/sicp/one/thirtytwo.scm
@@ -0,0 +1,36 @@
+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one thirtytwo)
+  #:export (factorial simpson))
+
+(define (accumulate combiner null-value term a next b)
+  (if (> a b)
+      null-value
+      (combiner (term a)
+                (accumulate combiner null-value term (next a) next b))))
+
+(define (product term a next b)
+  (accumulate * 1 term a next b))
+
+(define (factorial n)
+  (let ((term (lambda (x) x))
+        (next (lambda (x) (1+ x))))
+    (product term 1 next n)))
+
+(define (sum term a next b)
+  (accumulate + 0 term a next b))
+
+(define (simpson f a b n)
+  (let* ((h (/ (- b a) (* 1.0 n)))
+         (y (lambda (k) (+ a (* k h))))
+         (ce (lambda (k) ;coefficient
+               (cond ((or (= k 0) (= k n)) 1)
+                     ((even? k) 2)
+                     (else 4))))
+         (term (lambda (k)
+                 (* (ce k) (f (y k)))))
+         (next (lambda (k) (1+ k))))
+    (* (/ h 3.0)
+       (sum term 0 next n))))