From 5778a7251f6a09a74bb896503c11f2f686b1f09b Mon Sep 17 00:00:00 2001
From: rsiddharth <s@ricketyspace.net>
Date: Wed, 25 Jan 2017 03:50:34 +0000
Subject: (taocp utils math) Add fibonacci functions.

* guile/taocp/utils/math.scm (fib, fib-range): New functions.
---
 guile/taocp/utils/math.scm | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

(limited to 'guile')

diff --git a/guile/taocp/utils/math.scm b/guile/taocp/utils/math.scm
index 768d30d..7d49c10 100644
--- a/guile/taocp/utils/math.scm
+++ b/guile/taocp/utils/math.scm
@@ -2,8 +2,10 @@
 ;;;; under gnu general public license version 3 or higher.
 
 (define-module (taocp utils math)
-  #:export (compute-exp1-n))
-
+  #:use-module (srfi srfi-1)
+  #:export (compute-exp1-n
+            fib
+            fib-range))
 
 (define (compute-exp1-n fx n)
   "Evaluate function FX for `x` equals 1 to N and return all results
@@ -15,3 +17,15 @@ For instance `(lambda (x) (* x x))` is a valid FX.
 "
   (cond ((= n 0) '())
         (else (cons (fx n) (compute-exp1-n fx (1- n))))))
+
+(define (fib n)
+  "Returns Fibonacci of N."
+  (cond ((= n 0) 0)
+        ((= n 1) 1)
+        (else (+ (fib (- n 1)) (fib (- n 2))))))
+
+(define (fib-range start end)
+  "Returns Fibonacci sequence between START and END."
+  (let ((f (lambda (x) (cons x (fib x))))
+        (count (1+ (- end start ))))
+  (map f (iota count start))))
-- 
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