diff options
Diffstat (limited to 'modular.scm')
| -rw-r--r-- | modular.scm | 32 |
1 files changed, 15 insertions, 17 deletions
diff --git a/modular.scm b/modular.scm index e836100..052bf92 100644 --- a/modular.scm +++ b/modular.scm @@ -245,20 +245,18 @@ ;;@args modulus n2 n3 ;;Returns (@var{n2} ^ @var{n3}) mod @var{modulus}. -(define modular:expt - (let ((integer-expt (and (provided? 'inexact) expt))) - (lambda (m n xpn) - (cond ((= n 1) 1) - ((= n (- m 1)) (if (odd? xpn) n 1)) - ((and (zero? m) integer-expt) (integer-expt n xpn)) - ((negative? xpn) - (modular:expt m (modular:invert m n) (- xpn))) - ((zero? n) 0) - (else - (do ((x n (modular:* m x x)) - (j xpn (quotient j 2)) - (acc 1 (if (even? j) acc (modular:* m x acc)))) - ((<= j 1) - (case j - ((0) acc) - ((1) (modular:* m x acc)))))))))) +(define (modular:expt m n xpn) + (cond ((= n 1) 1) + ((= n (- m 1)) (if (odd? xpn) n 1)) + ((zero? m) (expt n xpn)) + ((negative? xpn) + (modular:expt m (modular:invert m n) (- xpn))) + ((zero? n) 0) + (else + (do ((x n (modular:* m x x)) + (j xpn (quotient j 2)) + (acc 1 (if (even? j) acc (modular:* m x acc)))) + ((<= j 1) + (case j + ((0) acc) + ((1) (modular:* m x acc)))))))) |