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| -rw-r--r-- | net/ricketyspace/sicp/one/twentyone.scm | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/net/ricketyspace/sicp/one/twentyone.scm b/net/ricketyspace/sicp/one/twentyone.scm new file mode 100644 index 0000000..9d1c94f --- /dev/null +++ b/net/ricketyspace/sicp/one/twentyone.scm @@ -0,0 +1,42 @@ +;;;; Under Creative Commons Attribution-ShareAlike 4.0 +;;;; International. See +;;;; <https://creativecommons.org/licenses/by-sa/4.0/>. + +(define-module (net ricketyspace sicp one twentyone) + #:export (sm-divisor-of-199 + sm-divisor-of-1999 + sm-divisor-of-19999)) + +(define (small-divisor n) + (find-divisor n 2)) + +(define (find-divisor n test-divisor) + (cond ((> (square test-divisor) n) n) + ((divides? test-divisor n) test-divisor) + (else (find-divisor n (+ test-divisor 1))))) + +(define (divides? a b) + (= (remainder b a) 0)) + +(define (square x) + (expt x 2)) + +(define (sm-divisor-of-199) + (small-divisor 199)) + +(define (sm-divisor-of-1999) + (small-divisor 1999)) + +(define (sm-divisor-of-19999) + (small-divisor 19999)) + +;;; +;;; scheme@(guile-user)> ,use (net ricketyspace sicp one twentyone) +;;; ... +;;; scheme@(guile-user)> (sm-divisor-of-199) +;;; $3 = 199 +;;; scheme@(guile-user)> (sm-divisor-of-1999) +;;; $4 = 1999 +;;; scheme@(guile-user)> (sm-divisor-of-19999) +;;; $5 = 7 +;;; |