racket/collects/math/private/number-theory/modular-arithmetic.rkt
Neil Toronto f2dc2027f6 Initial math library commit. The history for these changes is preserved
in the original GitHub fork:

  https://github.com/ntoronto/racket

Some things about this are known to be broken (most egregious is that the
array tests DO NOT RUN because of a problem in typed/rackunit), about half
has no coverage in the tests, and half has no documentation. Fixes and
docs are coming. This is committed now to allow others to find errors and
inconsistency in the things that appear to be working, and to give the
author a (rather incomplete) sense of closure.
2012-11-16 11:39:51 -07:00

145 lines
5.0 KiB
Racket

#lang racket/base
(require "modular-arithmetic-base.rkt")
(provide with-modulus
current-modulus
modular-inverse
modular-expt
mod+
mod-
mod*
mod/
modsqr
modexpt
mod
mod=
mod<
mod<=
mod>
mod>=)
(module typed-defs typed/racket/base
(require racket/performance-hint
racket/flonum
"divisibility.rkt"
"modular-arithmetic-base.rkt")
(provide (all-defined-out))
(define-syntax-rule (define-comparison-op name op)
(begin
(: name (case-> (Integer -> Boolean)
(Integer Integer Integer * -> Boolean)))
(define name
(case-lambda:
[([a : Integer]) #t]
[([a : Integer] [b : Integer])
(define n (current-modulus))
(op (modulo a n) (modulo b n))]
[([a : Integer] [b : Integer] . [cs : Integer *])
(define n (current-modulus))
(let ([a (modulo a n)] [b (modulo b n)])
(and (op a b)
(let loop ([b b] [cs cs])
(or (null? cs)
(let ([c (modulo (car cs) n)])
(and (op b c) (loop c (cdr cs))))))))]))))
(begin-encourage-inline
(: mod+ (case-> (-> Natural)
(Integer -> Natural)
(Integer Integer Integer * -> Natural)))
(define mod+
(case-lambda:
[() 0]
[([a : Integer]) (modulo a (current-modulus))]
[([a : Integer] [b : Integer]) (modulo (+ a b) (current-modulus))]
[([a : Integer] [b : Integer] . [cs : Integer *])
(define n (current-modulus))
(for/fold: ([a : Natural (modulo (+ a b) n)]) ([c (in-list cs)])
(modulo (+ a c) n))]))
(: mod- (case-> (Integer -> Natural)
(Integer Integer Integer * -> Natural)))
(define mod-
(case-lambda:
[([a : Integer]) (modulo (- a) (current-modulus))]
[([a : Integer] [b : Integer]) (modulo (- a b) (current-modulus))]
[([a : Integer] [b : Integer] . [cs : Integer *])
(define n (current-modulus))
(for/fold: ([a : Natural (modulo (- a b) n)]) ([c (in-list cs)])
(modulo (- a c) n))]))
(: mod* (case-> (-> Natural)
(Integer -> Natural)
(Integer Integer Integer * -> Natural)))
(define mod*
(case-lambda:
[() (modulo 1 (current-modulus))]
[([a : Integer]) (modulo a (current-modulus))]
[([a : Integer] [b : Integer]) (modulo (* a b) (current-modulus))]
[([a : Integer] [b : Integer] . [cs : Integer *])
(define n (current-modulus))
(for/fold: ([a : Natural (modulo (* a b) n)]) ([c (in-list cs)])
(modulo (* a c) n))]))
(: mod/ (case-> (Integer -> Natural)
(Integer Integer Integer * -> Natural)))
(define mod/
(case-lambda:
[([a : Integer]) (modular-inverse a (current-modulus))]
[([a : Integer] [b : Integer]) (define n (current-modulus))
(modulo (* a (modular-inverse b n)) n)]
[([a : Integer] [b : Integer] . [cs : Integer *])
;; It's ridiculous that `cs' has to be split here
(mod/ a (apply mod* b (car cs) (cdr cs)))]))
(: modsqr (Integer -> Natural))
(define (modsqr a) (modulo (* a a) (current-modulus)))
(: modexpt (Integer Integer -> Natural))
(define (modexpt a b)
(define n (current-modulus))
(cond [(b . < . 0) (modular-expt (modular-inverse a n) (- b) n)]
[else (modular-expt a b n)]))
(: mod (Exact-Rational -> Natural))
(define (mod a)
(cond [(integer? a) (modulo a (current-modulus))]
[else (mod/ (numerator a) (denominator a))]))
(define-comparison-op mod= =)
(define-comparison-op mod< <)
(define-comparison-op mod<= <=)
(define-comparison-op mod> >)
(define-comparison-op mod>= >=)
) ; begin-encourage-inline
)
(module untyped-defs racket/base
(require (for-syntax racket/base)
"../syntax-utils.rkt"
"modular-arithmetic-base.rkt"
(prefix-in typed- (submod ".." typed-defs)))
(provide (all-defined-out))
(define-inline-op mod+ inline-mod+ typed-mod+ (a ...))
(define-inline-op mod* inline-mod* typed-mod* (a ...))
(define-inline-op mod- inline-mod- typed-mod- (a b ...))
(define-inline-op mod/ inline-mod/ typed-mod/ (a b ...))
(define-inline-op modsqr inline-modsqr typed-modsqr (a))
(define-inline-op modexpt inline-modexpt typed-modexpt (a b))
(define-inline-op mod inline-mod typed-mod (a))
(define-inline-op mod= inline-mod= typed-mod= (a b ...))
(define-inline-op mod< inline-mod< typed-mod< (a b ...))
(define-inline-op mod<= inline-mod<= typed-mod<= (a b ...))
(define-inline-op mod> inline-mod> typed-mod> (a b ...))
(define-inline-op mod>= inline-mod>= typed-mod>= (a b ...))
)
(require (submod "." untyped-defs))