Modular arithmetic: Difference between revisions
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}</syntaxhighlight>
=={{header|Scheme}}==
{{works with|Gauche Scheme|0.9.12}}
{{works with|Chibi Scheme|0.10.0}}
{{works with|CHICKEN Scheme|5.3.0}}
The program is for R7RS Scheme.
<syntaxhighlight lang="scheme">
(cond-expand
(r7rs)
(chicken (import r7rs)))
(import (scheme base))
(import (scheme write))
(define *modulus*
(make-parameter
#f
(lambda (mod)
(if (or (not mod)
(and (exact-integer? mod)
(positive? mod)))
mod
(error "not a valid modulus")))))
(define-syntax enhanced-op
(syntax-rules ()
((_ op)
(lambda args
(let ((mod (*modulus*))
(tentative-result (apply op args)))
(if mod
(floor-remainder tentative-result mod)
tentative-result))))))
(define enhanced+ (enhanced-op +))
(define enhanced-expt (enhanced-op expt))
(define (f x)
;; Temporarily redefine + and expt so they can handle either regular
;; numbers or modular integers.
(let ((+ enhanced+)
(expt enhanced-expt))
;; Here is a definition of f(x), in the notation of Scheme:
(+ (expt x 100) x 1)))
;; Use f on regular integers.
(display "No modulus: ")
(display (f 10))
(newline)
;; Use f on modular integers.
(parameterize ((*modulus* 13))
(display "modulus 13: ")
(display (f 10))
(newline))
</syntaxhighlight>
{{out}}
<pre>$ gosh modular_arithmetic_task.scm
No modulus: 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011
modulus 13: 1
</pre>
=={{header|Sidef}}==
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