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-rw-r--r--modular.scm32
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))))))))