105 lines
3.1 KiB
Scheme
105 lines
3.1 KiB
Scheme
;;; Ikarus Scheme -- A compiler for R6RS Scheme.
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;;; Copyright (C) 2006,2007 Abdulaziz Ghuloum
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;;;
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;;; This program is free software: you can redistribute it and/or modify
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;;; it under the terms of the GNU General Public License version 3 as
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;;; published by the Free Software Foundation.
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;;;
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;;; This program is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;;; General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with this program. If not, see <http://www.gnu.org/licenses/>.
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(library (ikarus.sort)
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(export list-sort vector-sort vector-sort!)
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(import
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(ikarus system $fx)
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(except (ikarus) list-sort vector-sort vector-sort!))
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(define (merge1 <? a1 ls1 ls2)
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(cond
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[(null? ls2) ls1]
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[else
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(let ([a2 (car ls2)])
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(cond
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[(<? a2 a1)
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(cons a2 (merge1 <? a1 ls1 (cdr ls2)))]
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[else
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(cons a1 (merge2 <? a2 (cdr ls1) ls2))]))]))
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(define (merge2 <? a2 ls1 ls2)
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(cond
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[(null? ls1) ls2]
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[else
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(let ([a1 (car ls1)])
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(cond
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[(<? a2 a1)
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(cons a2 (merge1 <? a1 ls1 (cdr ls2)))]
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[else
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(cons a1 (merge2 <? a2 (cdr ls1) ls2))]))]))
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(define (merge <? ls1 ls2)
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(cond
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[(null? ls2) ls1]
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[else
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(let ([a1 (car ls1)] [a2 (car ls2)])
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(cond
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[(<? a2 a1)
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(cons a2 (merge1 <? a1 ls1 (cdr ls2)))]
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[else
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(cons a1 (merge2 <? a2 (cdr ls1) ls2))]))]))
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(define (sort-head <? ls n)
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(cond
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[($fx= n 0) (values '() ls)]
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[($fx= n 1)
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(values (cons (car ls) '()) (cdr ls))]
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[else
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(let-values ([(sorted-head tail)
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(sort-head <? ls ($fxsra n 1))])
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(let-values ([(sorted-tail tail)
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(sort-head <? tail ($fx- n ($fxsra n 1)))])
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(values (merge <? sorted-head sorted-tail) tail)))]))
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(define (sort-tail <? ls n)
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(cond
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[($fx<= n 1) ls]
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[else
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(let-values ([(sorted-head tail)
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(sort-head <? ls ($fxsra n 1))])
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(merge <? sorted-head (sort-tail <? tail ($fx- n ($fxsra n 1)))))]))
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(define (list-sort <? ls)
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(unless (procedure? <?)
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(error 'list-sort "not a procedure" <?))
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(sort-tail <? ls (length ls)))
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(define (vector-sort <? v)
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;;; FIXME: improve
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(unless (procedure? <?)
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(error 'vector-sort "not a procedure" <?))
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(unless (vector? v)
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(error 'vector-sort "not a vector" v))
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(list->vector
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(sort-tail <? (vector->list v) (vector-length v))))
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(define (vector-sort! <? v)
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(unless (procedure? <?)
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(error 'vector-sort! "not a procedure" <?))
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(unless (vector? v)
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(error 'vector-sort! "not a vector" v))
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(let f ([i 0] [v v]
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[ls (sort-tail <? (vector->list v) (vector-length v))])
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(unless (null? ls)
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(vector-set! v i (car ls))
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(f (fx+ i 1) v (cdr ls)))))
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)
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