net: Add (net ricketyspace sicp one thirtyfive).

net/ricketyspace/sicp/one/thirtyfive.scm: New file.

1 files changed, 28 insertions, 0 deletions

diff --git a/net/ricketyspace/sicp/one/thirtyfive.scm b/net/ricketyspace/sicp/one/thirtyfive.scm
new file mode 100644
index 0000000..04713fa
--- /dev/null
+++ b/net/ricketyspace/sicp/one/thirtyfive.scm
@@ -0,0 +1,28 @@
+;;;; Under Creative Commons Attribution-ShareAlike 4.0
+;;;; International. See
+;;;; <https://creativecommons.org/licenses/by-sa/4.0/>.
+
+(define-module (net ricketyspace sicp one thirtyfive)
+  #:export (golden-ratio))
+
+(define tolerance 0.00001)
+
+(define (fixed-point f first-guess)
+  (define (close-enough? v1 v2)
+    (< (abs (- v1 v2)) tolerance))
+  (define (try guess)
+    (let ((next (f guess)))
+      (if (close-enough? guess next)
+          next
+          (try next))))
+  (try first-guess))
+
+(define (golden-ratio )
+  (fixed-point  (lambda (x) (+ 1 (/ 1.0 x))) 1.0))
+
+;;; Guile REPL
+;;;
+;;; scheme@(guile-user)> ,use (net ricketyspace sicp one thirtyfive)
+;;; scheme@(guile-user)> (golden-ratio)
+;;; $1 = 1.6180327868852458
+