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original commit: 64a031ee92049895fd5977b71c098a909f98a6f3
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Robby Findler
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350
collects/mzlib/plt-match.ss
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350
collects/mzlib/plt-match.ss
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;; (documentation (name plt-match))
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;; <pre>Pattern Matching Syntactic Extensions for Scheme
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;;
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;; All bugs or questions concerning this software should be directed to
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;; Bruce Hauman <bhauman@cs.wcu.edu>. The latest version of this software
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;; can be obtained from http://sol.cs.wcu.edu/~bhauman/scheme/pattern.html.
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;;
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;; Special thanks go out to:
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;; Robert Bruce Findler for support and bug detection.
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;; Doug Orleans for pointing out that pairs should be reused while
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;; matching lists.
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;;
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;;
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;; Originally written by Andrew K. Wright, 1993 (wright@research.nj.nec.com)
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;; which in turn was adapted from code written by Bruce F. Duba, 1991.
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;;
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;; This software is in the public domain. Feel free to copy,
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;; distribute, and modify this software as desired. No warranties
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;; nor guarantees of any kind apply. Please return any improvements
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;; or bug fixes to bhauman@cs.wcu.edu so that they may be included
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;; in future releases.
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;;
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;; This macro package extends Scheme with several new expression forms.
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;; Following is a brief summary of the new forms. See the associated
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;; LaTeX documentation for a full description of their functionality.
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;;
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;;
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;; match expressions:
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;;
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;; exp ::= ...
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;; | (match exp clause ...)
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;; | (match-lambda clause ...)
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;; | (match-lambda* clause ...)
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;; | (match-let ((pat exp) ...) body)
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;; | (match-let* ((pat exp) ...) body)
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;; | (match-letrec ((pat exp) ...) body)
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;; | (match-define pat exp)
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;;
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;; clause ::= (pat body) | (pat => exp)
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;;
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;; patterns: matches:
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;;
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;; pat ::=
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;; identifier this binds an identifier if it
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;; doesn't conflict with ..k or _
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;; | _ anything
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;; | #t #t
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;; | #f #f
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;; | string a string
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;; | number a number
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;; | character a character
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;; | 'sexp an s-expression
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;; | 'symbol a symbol (special case of s-expr)
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;; | (list lvp_1 ... lvp_n) list of n elements
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;; | (list-rest lvp_1 ... lvp_n pat) an improper list of n elements
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;; plus a last element which represents
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;; the last cdr of the list
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;; | (vector lvp_1 ... lvp_n) vector of n elements
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;; | (box pat) box
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;; | (struct struct-name (pat_1 ... pat_n)) a structure
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;; | (list-no-order pat ...) matches a list with no regard for
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;; the order of the
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;; items in the list
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;; | (list-no-order pat ... pat_n ooo) pat_n matches the remaining
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;; unmatched items
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;; | (hash-table pat ...) matches the elements of a hash table
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;; | (hash-table pat ... pat_n ooo) pat_n must match the remaining
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;; unmatched elements
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;; | (app field pat) a field of a structure (field is
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;; an accessor)
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;; Actually field can be any function
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;; which can be
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;; applied to the data being matched.
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;; Ex: (match 5 ((= add1 b) b)) => 6
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;;
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;; | (and pat_1 ... pat_n) if all of pat_1 thru pat_n match
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;; | (or pat_1 ... pat_n) if any of pat_1 thru pat_n match
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;; | (not pat_1 ... pat_n) if all pat_1 thru pat_n don't match
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;; | (? predicate pat_1 ... pat_n) if predicate true and all of
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;; pat_1 thru pat_n match
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;; | (set! identifier) anything, and binds setter
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;; | (get! identifier) anything, and binds getter
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;; | `qp a quasi-pattern
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;;
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;; lvp ::= pat ooo greedily matches n or more of pat,
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;; each element must match pat
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;; | pat matches pat
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;;
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;; ooo ::= ... zero or more
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;; | ___ zero or more
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;; | ..k k or more
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;; | __k k or more
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;;
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;; quasi-patterns: matches:
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;;
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;; qp ::= () the empty list
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;; | #t #t
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;; | #f #f
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;; | string a string
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;; | number a number
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;; | character a character
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;; | identifier a symbol
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;; | (qp_1 ... qp_n) list of n elements
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;; | (qp_1 ... qp_n . qp_{n+1}) list of n or more
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;; | (qp_1 ... qp_n qp_n+1 ooo) list of n or more, each element
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;; of remainder must match qp_n+1
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;; | #(qp_1 ... qp_n) vector of n elements
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;; | #(qp_1 ... qp_n qp_n+1 ooo) vector of n or more, each element
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;; of remainder must match qp_n+1
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;; | #&qp box
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;; | ,pat a pattern
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;; | ,@(lvp . . . lvp-n)
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;; | ,@(lvp-1 . . . lvp-n . pat)
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;; | ,@`qp qp must evaluate to a list as
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;; so that this rule resembles the
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;; above two rules
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;;
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;; The names (quote, quasiquote, unquote, unquote-splicing, ?, _, $,
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;; and, or, not, set!, get!, list-no-order, hash-table, ..., ___)
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;; cannot be used as pattern variables.</pre>
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;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(module plt-match mzscheme
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(provide
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match
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match-lambda
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match-lambda*
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match-let
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match-let*
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match-letrec
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match-define
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match:test-no-order
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)
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(require-for-syntax (lib "stx.ss" "syntax")
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(lib "etc.ss")
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;(lib "pretty.ss")
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(lib "list.ss")
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(lib "include.ss"))
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(require (lib "etc.ss")
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(lib "list.ss"))
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(define-struct (exn:misc:match exn:misc) (value))
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(define match:error
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(case-lambda
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((val)
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(raise
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(make-exn:misc:match
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(format "match: no matching clause for ~e" val)
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(current-continuation-marks)
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val)))
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((val expr)
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(raise
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(make-exn:misc:match
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(format "match: no matching clause for ~e: ~s" val expr)
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(current-continuation-marks)
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val)))))
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(define-syntax-set (match
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match-lambda
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match-lambda*
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match-let
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match-let*
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match-letrec
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match-define)
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(include "private/plt-match/match-inc.scm")
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(define match/proc
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(lambda (stx)
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(syntax-case stx (=>)
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((_ exp clause ...)
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(quasisyntax/loc
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stx
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(let ((x exp)) #,(gen-match (syntax x)
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'()
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(syntax (clause ...))
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stx)))))))
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(define match-lambda/proc
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(lambda (stx)
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(syntax-case stx ()
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[(k clause ...)
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(syntax/loc
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stx
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(lambda (exp) (match exp clause ...)))])))
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(define match-lambda*/proc
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(lambda (stx)
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(syntax-case stx ()
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[(k clause ...)
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(syntax/loc stx (lambda exp (match exp clause ...)))])))
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(define match-let/proc
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(lambda (stx)
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(syntax-case stx ()
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[(_ name () body1 body ...)
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(syntax/loc stx (let name () body1 body ...))]
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[(_ name ([pat1 exp1] [pat exp]...) body1 body ...)
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(identifier? (syntax name))
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(let ((pat-list (syntax-object->datum (syntax (list pat1 pat ...))))
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(real-name (syntax-object->datum (syntax name))))
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(if (andmap pattern-var? pat-list)
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(syntax/loc
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stx
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(let name ([pat1 exp1] [pat exp] ...) body1 body ...))
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(syntax/loc
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stx
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(letrec ([name
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(match-lambda* ((list pat1 pat ...)
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body1 body ...))])
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(name exp1 exp ...)))))]
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[(_ () body1 body ...)
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(syntax/loc stx (begin body1 body...))]
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[(_ ([pat1 exp1] [pat exp]...) body1 body ...)
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(syntax/loc
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stx
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((match-lambda* ((list pat1 pat ...) body1 body ...))
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exp1 exp ...))])))
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(define match-let*/proc
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(lambda (stx)
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(syntax-case stx ()
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((_ () body body1 ...)
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(syntax/loc stx (let* () body body1 ...)))
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((_ ([pat exp] rest ...) body body1 ...)
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(if (pattern-var? (syntax-object->datum (syntax pat)))
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(syntax/loc
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stx
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(let ([pat exp]) (match-let* (rest ...) body body1 ...)))
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(syntax/loc
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stx
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(match exp [pat (match-let* (rest ...) body body1 ...)])))))))
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(define match-letrec/proc
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(lambda (stx)
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(syntax-case stx ()
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((_ () body body1 ...)
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(syntax/loc stx (let () body body1 ...)))
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((_ ([pat exp] ...) body body1 ...)
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(andmap pattern-var?
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(syntax-object->datum (syntax (pat ...))))
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(syntax/loc stx (letrec ([pat exp] ...) body body1 ...)))
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((_ ([pat exp] ...) body body1 ...)
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(let* ((**match-bound-vars** '())
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(compiled-match
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(gen-match (syntax the-exp);(syntax (list exp ...))
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'()
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(syntax (((list pat ...) never-used)))
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stx
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(lambda (sf bv)
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(set! **match-bound-vars** bv)
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(quasisyntax/loc
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stx
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(begin
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#,@(map (lambda (x)
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(quasisyntax/loc
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stx
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(set! #,(car x) #,(cdr x))))
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(reverse bv))
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body body1 ...))))))
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(quasisyntax/loc
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stx
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(letrec (#,@(map
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(lambda (x) (quasisyntax/loc stx (#,(car x) #f)))
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(reverse **match-bound-vars**))
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(the-exp (list exp ...)))
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#,compiled-match)))))))
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(define match-define/proc
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(lambda (stx)
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(syntax-case stx ()
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[(_ pat exp)
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(identifier? (syntax pat))
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(syntax/loc stx (begin (define pat exp)))]
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[(_ pat exp)
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(let* ((**match-bound-vars** '())
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(compiled-match
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(gen-match (syntax the-exp)
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'()
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(syntax/loc (syntax pat) ((pat never-used)))
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stx
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(lambda (sf bv)
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(set! **match-bound-vars** bv)
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(quasisyntax/loc
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stx
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(begin
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#,@(map (lambda (x)
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(quasisyntax/loc
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stx
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(set! #,(car x) #,(cdr x))))
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(reverse bv))))))))
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(quasisyntax/loc stx
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(begin #,@(map
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(lambda (x) (quasisyntax/loc
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stx
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(define #,(car x) #f)))
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(reverse **match-bound-vars**))
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(let ((the-exp exp))
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#,compiled-match))))])))
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)
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;;!(function match:test-no-order
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;; (form (match:test-no-order tests l last-test ddk-num)
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;; ->
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;; bool)
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;; (contract (list list test integer) -> bool))
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;; This is a recursive depth first search for a sequence of
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;; items in list l which will satisfy all of the tests in list
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;; tests. This is used for list-no-order and hash-table patterns.
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;; This function also handles ddk patterns by passing it the last
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;; test before the ddk and the value of k.
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(define (match:test-no-order tests l last-test ddk-num)
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(define (handle-last-test test l)
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(and (>= (length l) ddk-num)
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(andmap test l)))
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(define (dep-first-test head rest tests)
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(cond ((null? tests)
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(if last-test
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(handle-last-test last-test (cons head rest))
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#f))
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((null? rest)
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(if last-test
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(and (= 0 ddk-num)
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(= 1 (length tests))
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((car tests) head))
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(and (= 1 (length tests))
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((car tests) head))))
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(else (and (pair? tests)
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((car tests) head)
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(match:test-no-order (cdr tests)
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rest
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last-test
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ddk-num)))))
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(let loop ((lst l))
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(if (null? lst)
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#f
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(or (dep-first-test (car lst) (remove (car lst) l) tests)
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(loop (cdr lst))))))
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)
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