diff options
Diffstat (limited to 'net')
| -rw-r--r-- | net/ricketyspace/sicp/one/thirtyone.scm | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/net/ricketyspace/sicp/one/thirtyone.scm b/net/ricketyspace/sicp/one/thirtyone.scm new file mode 100644 index 0000000..a88dc1d --- /dev/null +++ b/net/ricketyspace/sicp/one/thirtyone.scm @@ -0,0 +1,43 @@ +;;;; Under Creative Commons Attribution-ShareAlike 4.0 +;;;; International. See +;;;; <https://creativecommons.org/licenses/by-sa/4.0/>. + +(define-module (net ricketyspace sicp one thirtyone) + #:export (product factorial pi)) + +(define (product term a next b) + (if (> a b) + 1 + (* (term a) + (product term (next a) next b)))) + +(define (factorial n) + (let ((term (lambda (x) x)) + (next (lambda (x) (1+ x)))) + (product term 1 next n))) + +(define (pi precision) + (let* ((n (lambda (x) (* (+ (quotient x 2) 1) 2))) ; numerator of term. + (d (lambda (x) (+ (* (quotient (1+ x) 2) 2) 1))) ; denominator of term. + (term (lambda (x) (/ (* (n x) 1.0) (* (d x) 1.0)))) + (next (lambda (x) (1+ x)))) + (* (product term 1 next precision) 4))) + +;;; Guile REPL +;;; scheme@(guile-user)> ,use (net ricketyspace sicp one thirtyone) +;;; scheme@(guile-user)> (factorial 5) +;;; $9 = 120 +;;; scheme@(guile-user)> (factorial 10) +;;; $7 = 3628800 +;;; scheme@(guile-user)> (factorial 20) +;;; $8 = 2432902008176640000 +;;; scheme@(guile-user)> (pi 1000) +;;; $10 = 3.143160705532257 +;;; scheme@(guile-user)> (pi 10000) +;;; $11 = 3.1417497057379635 +;;; scheme@(guile-user)> (pi 100000) +;;; $12 = 3.1416083612780903 +;;; scheme@(guile-user)> (pi 1000000) +;;; $13 = 3.1415942243828017 + + |