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;;; srfi-114 - comparators
;;;
;;; Copyright (c) 2014-2016 Shiro Kawai <shiro@acm.org>
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;;
;;; 1. Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;;
;;; 2. Redistributions in binary form must reproduce the above copyright
;;; notice, this list of conditions and the following disclaimer in the
;;; documentation and/or other materials provided with the distribution.
;;;
;;; 3. Neither the name of the authors nor the names of its contributors
;;; may be used to endorse or promote products derived from this
;;; software without specific prior written permission.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;; "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;;; LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
;;; A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
;;; OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
;;; SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
;;; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
;;; PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
;;; LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
;;; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
;;; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;;;
;; Basic support of comparators are built-in, for the built-in
;; data structures such as hashtables would make use of them.
;; This module provides complete set of srfi-114
;; TODO: Importing srfi-114 shadows make-comparator, but many procedures
;; here are generally useful. We might want to split those procs
;; in separate module so that they can be used without worring
;; different make-comparator APIs.
;; TODO: Comparator combinators are written for srfi-114 and assumes
;; the given comparator has comparison proc. We might be able to optimize
;; it by checking if the passed one is srfi-128.
(define-module srfi-114
(use gauche.uvector)
(export comparator? ;builtin (srfi-128)
comparator-comparison-procedure?
comparator-hash-function?
boolean-comparator char-comparator char-ci-comparator
string-comparator string-ci-comparator symbol-comparator
exact-integer-comparator integer-comparator rational-comparator
real-comparator complex-comparator number-comparator
pair-comparator list-comparator vector-comparator
bytevector-comparator uvector-comparator ;all builtin
default-comparator ;builtin
(rename make-comparator/compare make-comparator) ;builtin
make-car-comparator make-cdr-comparator
make-inexact-real-comparator
make-vector-comparator ; builtin
make-bytevector-comparator
make-list-comparator ; builtin
make-vectorwise-comparator make-listwise-comparator
make-pair-comparator ; builtin
make-improper-list-comparator
make-selecting-comparator make-refining-comparator
make-reverse-comparator make-debug-comparator
eq-comparator ;builtin
eqv-comparator ;builtin
equal-comparator ;builtin
comparator-type-test-procedure
comparator-equality-predicate ;builtin
comparator-comparison-procedure ;builtin
comparator-hash-function ;builtin
comparator-test-type ;builtin
comparator-check-type ;builtin
comparator-equal?
comparator-compare ;builtin
comparator-hash ;builtin
make-comparison< make-comparison> make-comparison<=
make-comparison>= make-comparison=/< make-comparison=/>
if3 if=? if<? if>? if<=? if>=? if-not=?
=? <? >? <=? >=? ;builtin
make=? make<? make>? make<=? make>=?
in-open-interval? in-closed-interval?
in-open-closed-interval? in-closed-open-interval?
comparator-min comparator-max))
(select-module srfi-114)
;;;
;;; Predicates
;;;
(define (comparator-comparison-procedure? c)
(comparator-ordered? c)) ;srfi-128
(define (comparator-hash-function? c)
(comparator-hashable? c)) ;srfi-128
(define (comparator-type-test-procedure c)
(comparator-type-test-predicate c)) ;srfi-128
(define (comparator-equal? c a b) (=? c a b))
;;;
;;; Inexact comparator
;;;
(define (((%make-scaler rounder) epsilon) num) (rounder (/ num epsilon)))
(define %scale-round (%make-scaler round))
(define %scale-ceiling (%make-scaler ceiling))
(define %scale-floor (%make-scaler floor))
(define %scale-truncate (%make-scaler truncate))
(define (%handle-nan which num nan-handling)
(case nan-handling
[(min) (if (eq? which 'a) -1 1)]
[(max) (if (eq? which 'a) 1 -1)]
[else
(if (applicable? nan-handling <real>)
(nan-handling num)
(error "nan-handling argument must be either a procedure taking one argument, or a symbol min or max, but got:" nan-handling))]))
(define (make-inexact-real-comparator epsilon rounding nan-handling)
(define scaler
(case rounding
[(round) (%scale-round epsilon)]
[(ceiling) (%scale-ceiling epsilon)]
[(floor) (%scale-floor epsilon)]
[(truncate) (%scale-truncate epsilon)]
[else (if (applicable? rounding <real> <real>)
(^[num] (rounding num epsilon))
(error "make-inexact-comparator requires `rounding' argument to be either a procedure taking two real numbers, or one of the symbols 'round, 'ceiling, 'floor or 'truncate, but got:" rounding))]))
(define nan-handler
(case nan-handling
[(min) (^[which num] (if (eq? which 'a) -1 1))]
[(max) (^[which num] (if (eq? which 'a) 1 -1))]
[(error) (^[which num]
(error "attempt to compare NaN with non-NaN: ~a" num))]
[else
(if (applicable? nan-handling <real>)
(^[which num] (nan-handling num))
(error "make-inexact-comparator requires `nan-handling' argument to be either a procedure taking one real number, or one of the symbols 'min or 'max, but got:" nan-handling))]))
(make-comparator/compare real?
#t
(^[a b]
(if (nan? a)
(if (nan? b)
0
(nan-handler 'a b))
(if (nan? b)
(nan-handler 'b a)
(compare (scaler a) (scaler b)))))
(^[a] (if (nan? a) 0 (eqv-hash (scaler a))))))
;;;
;;; Comparator transformers
;;;
(define (make-car-comparator comparator)
(make-key-comparator comparator pair? car))
(define (make-cdr-comparator comparator)
(make-key-comparator comparator pair? cdr))
(define (make-listwise-comparator test elt-comparator null? car cdr)
(make-list-comparator elt-comparator test null? car cdr)) ; srfi-128
(define (make-vectorwise-comparator test elt-comparator len ref)
(make-vector-comparator elt-comparator test len ref)) ; srfi-128
(define (make-bytevector-comparator elt-comparator)
(make-vectorwise-comparator u8vector? elt-comparator
u8vector-length u8vector-ref))
(define (make-improper-list-comparator elt-comparator)
($ make-comparator/compare #t
(^[a b] (cond [(null? a) (null? b)]
[(pair? a)
(and (pair? b)
(comparator-equal? elt-comparator (car a) (car b))
(comparator-equal? elt-comparator (cdr a) (cdr b)))]
[else (comparator-equal? elt-comparator a b)]))
(and (comparator-comparison-procedure? elt-comparator)
(^[a b] (cond [(null? a) (if (null? b) 0 -1)]
[(pair? a)
(if (pair? b)
(let1 r (comparator-compare elt-comparator
(car a) (car b))
(if (= r 0)
(comparator-compare elt-comparator
(cdr a) (cdr b))
r))
-1)]
[else (comparator-compare elt-comparator a b)])))
(and (comparator-hash-function? elt-comparator)
(^x (if (pair? x)
(combine-hash-value (comparator-hash elt-comparator (car x))
(comparator-hash elt-comparator (cdr x)))
(comparator-hash elt-comparator x))))))
(define (make-selecting-comparator cmp . cmps)
(define (selector x) ; returns a comparator
(let loop ([cmp cmp] [cmps cmps])
(cond [(comparator-test-type cmp x) cmp]
[(null? cmps) #f]
[else (loop (car cmps) (cdr cmps))])))
(define (selector2 a b) ; returns a comparator
(let loop ([cmp cmp] [cmps cmps])
(cond [(and (comparator-test-type cmp a)
(comparator-test-type cmp b))
cmp]
[(null? cmps) #f]
[else (loop (car cmps) (cdr cmps))])))
(make-comparator/compare
(^x (boolean (selector x)))
(^[a b] (and-let* ([cmp (selector2 a b)])
(comparator-equal? cmp a b)))
(^[a b] (if-let1 cmp (selector2 a b)
(comparator-compare cmp a b)
(error "argument isn't comparable")))
(^x (if-let1 cmp (selector x)
(comparator-hash cmp x)
(error "argument isn't hashable:" x)))))
(define (make-refining-comparator cmp . cmps)
(define (selector x) ; returns a comparator
(let loop ([cmp cmp] [cmps cmps])
(cond [(comparator-test-type cmp x) cmp]
[(null? cmps) #f]
[else (loop (car cmps) (cdr cmps))])))
(define (selector2 a b cmps) ; returns a comparator and the rest
(let loop ([cmps cmps])
(cond [(null? cmps) (values #f #f)]
[(and (comparator-test-type (car cmps) a)
(comparator-test-type (car cmps) b))
(values (car cmps) (cdr cmps))]
[else (loop (cdr cmps))])))
(make-comparator/compare
(^x (boolean (selector x)))
(^[a b] (receive (cmp _) (selector2 a b (cons cmp cmps))
(if cmp
(comparator-equal? cmp a b)
#f)))
(^[a b] (let loop ([cmps (cons cmp cmps)]
[r #f])
(receive (cmp cmps) (selector2 a b cmps)
(if cmp
(let1 r (comparator-compare cmp a b)
(if (= r 0)
(loop cmps r)
r))
(or r (error "argument isn't comparable"))))))
(^x (if-let1 cmp (selector x)
(comparator-hash cmp x)
(error "argument isn't hashable:" x)))))
(define (make-reverse-comparator cmp)
(make-comparator/compare (comparator-type-test-procedure cmp)
(comparator-equality-predicate cmp)
(and (comparator-comparison-procedure? cmp)
(^[a b] (- (comparator-compare cmp a b))))
(and (comparator-hash-function? cmp)
(comparator-hash-function cmp))))
(define (make-debug-comparator cmp)
cmp) ;WRITEME
(define (make-comparison< pred)
(^[a b] (cond [(pred a b) -1]
[(pred b a) 1]
[else 0])))
(define (make-comparison> pred)
(^[a b] (cond [(pred a b) 1]
[(pred b a) -1]
[else 0])))
(define (make-comparison<= pred)
(^[a b] (if (pred a b) (if (pred b a) 0 -1) 1)))
(define (make-comparison>= pred)
(^[a b] (if (pred a b) (if (pred b a) 0 1) -1)))
(define (make-comparison=/< eq-pred lt-pred)
(^[a b] (cond [(eq-pred a b) 0]
[(lt-pred a b) -1]
[else 1])))
(define (make-comparison=/> eq-pred gt-pred)
(^[a b] (cond [(eq-pred a b) 0]
[(gt-pred a b) 1]
[else -1])))
(define-syntax if3
(syntax-rules ()
[(_ expr less equal greater)
(let1 r expr
(cond [(= r 0) equal]
[(< r 0) less]
[else greater]))]
[(_ . x) (syntax-error "malformed if3:" (if3 . x))]))
(define-syntax define-ifx
(syntax-rules ()
[(_ name op)
(define-syntax name
(syntax-rules ()
[(_ expr then . opt) (if (op expr 0) then . opt)]))]))
(define (!= a b) (not (= a b)))
(define-ifx if=? =)
(define-ifx if<? <)
(define-ifx if>? >)
(define-ifx if<=? <=)
(define-ifx if>=? >=)
(define-ifx if-not=? !=)
(define (make=? comparator)
(rec (cmp a b . args)
(and (comparator-equal? comparator a b)
(or (null? args)
(apply cmp b args)))))
(define (gen-make-x op)
(^[comparator]
(rec (cmp a b . args)
(let1 r (comparator-compare comparator a b)
(and (op r 0)
(if (null? args)
#t
(apply cmp b args)))))))
(define make<? (gen-make-x <))
(define make>? (gen-make-x >))
(define make<=? (gen-make-x <=))
(define make>=? (gen-make-x >=))
(define in-open-interval?
(case-lambda
[(cmp a b c) (<? cmp a b c)]
[(a b c) (<? default-comparator a b c)]))
(define in-closed-interval?
(case-lambda
[(cmp a b c) (<=? cmp a b c)]
[(a b c) (<=? default-comparator a b c)]))
(define in-open-closed-interval?
(case-lambda
[(cmp a b c) (and (<? cmp a b) (<=? cmp b c))]
[(a b c) (in-open-closed-interval? default-comparator a b c)]))
(define in-closed-open-interval?
(case-lambda
[(cmp a b c) (and (<=? cmp a b) (<? cmp b c))]
[(a b c) (in-closed-open-interval? default-comparator a b c)]))
(define (comparator-min cmp x . xs)
(let loop ([r x] [xs xs])
(cond [(null? xs) r]
[(<? cmp (car xs) r) (loop (car xs) (cdr xs))]
[else (loop r (cdr xs))])))
(define (comparator-max cmp x . xs)
(let loop ([r x] [xs xs])
(cond [(null? xs) r]
[(>? cmp (car xs) r) (loop (car xs) (cdr xs))]
[else (loop r (cdr xs))])))
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