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README.org

Match module for Youtoo 0.93

#

Copyright

Youtoo is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version.

Youtoo is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Youtoo in the file COPYING. If not, see http://www.gnu.org/licenses/.

EuLisp index

General Description

Modulized version of match-slib.scm badly hacked for eulisp.

Original: Pattern Matching Syntactic Extensions for Scheme

Version 1.18, July 17, 1995”

Report bugs to wright@research.nj.nec.com. The most recent version of this software can be obtained by anonymous FTP from ftp.nj.nec.com in file pub/wright/match.tar.Z. Be sure to set “type binary” when transferring this file.

Written by Andrew K. Wright, 1993 (wright@research.nj.nec.com). Adapted from code originally written by Bruce F. Duba, 1991. This package also includes a modified version of Kent Dybvig’s define-structure (see Dybvig, R.K., The Scheme Programming Language, Prentice-Hall, NJ, 1987).

This software is in the public domain. Feel free to copy, distribute, and modify this software as desired. No warranties nor guarantees of any kind apply. Please return any improvements or bug fixes to wright@research.nj.nec.com so that they may be included in future releases.

This package extends Scheme with several new expression forms. Following is a brief summary of the new forms. See the associated LaTeX documentation for a full description of their functionality.

Pattern Matching Syntactic Extensions for EuLisp

This package extends EuLisp with several new expression forms. Following is a brief summary of the new forms.

match expressions:
exp ::= ...
      | (match exp clause ...)
      | (match-lambda clause ...)
      | (match-lambda* clause ...)
      | (match-let ((pat exp) ...) body)
      | (match-let* ((pat exp) ...) body)
      | (match-letrec ((pat exp) ...) body)
      | (match-define pat exp)

clause ::= (pat body) | (pat => exp)
patterns:                               matches:

pat ::= identifier                      anything, and binds identifier
      | _                               anything
      | ()                              the empty list
      | t                               t
      | string                          a string
      | number                          a number
      | character                       a character
      | 'sexp                           an s-expression
      | 'symbol                         a symbol (special case of s-expr)
      | (pat_1 ... pat_n)               list of n elements
      | (pat_1 ... pat_n . pat_{n+1})   list of n or more
      | (pat_1 ... pat_n pat_n+1 ooo)   list of n or more, each element
                                        of remainder must match pat_n+1
      | #(pat_1 ... pat_n)              vector of n elements
      | #(pat_1 ... pat_n pat_n+1 ooo)  vector of n or more, each element
                                        of remainder must match pat_n+1
      | #&pat                           box
      | ($ struct-name pat_1 ... pat_n) a structure
      | (= field pat)                   a field of a structure
      | (and pat_1 ... pat_n)           if all of pat_1 thru pat_n match
      | (or pat_1 ... pat_n)            if any of pat_1 thru pat_n match
      | (not pat_1 ... pat_n)           if all pat_1 thru pat_n don't match
      | (? predicate pat_1 ... pat_n)   if predicate true and all of
                                        pat_1 thru pat_n match
      | (set! identifier)               anything, and binds setter
      | (get! identifier)               anything, and binds getter
      | `qp                             a quasi-pattern

ooo ::= ...                             zero or more
      | ___                             zero or more
      | ..k                             k or more
      | __k                             k or more

quasi-patterns:                         matches:
qp  ::= ()                              the empty list
      | t                               t
      | ()                              ()
      | string                          a string
      | number                          a number
      | character                       a character
      | identifier                      a symbol
      | (qp_1 ... qp_n)                 list of n elements
      | (qp_1 ... qp_n . qp_{n+1})      list of n or more
      | (qp_1 ... qp_n qp_n+1 ooo)      list of n or more, each element
                                        of remainder must match qp_n+1
      | #(qp_1 ... qp_n)                vector of n elements
      | #(qp_1 ... qp_n qp_n+1 ooo)     vector of n or more, each element
                                        of remainder must match qp_n+1
      | #&qp                            box
      | ,pat                            a pattern
      | ,@pat                           a pattern

The names (quote, quasiquote, unquote, unquote-splicing, ?, _, $, and, or, not, set!, get!, ..., ___) cannot be used as pattern variables.

structure expressions:
exp ::= ...
      | (define-structure (id_0 id_1 ... id_n))
      | (define-structure (id_0 id_1 ... id_n)
                          ((id_{n+1} exp_1) ... (id_{n+m} exp_m)))
      | (define-const-structure (id_0 arg_1 ... arg_n))
      | (define-const-structure (id_0 arg_1 ... arg_n)
                                ((arg_{n+1} exp_1) ... (arg_{n+m} exp_m)))

arg ::= id | (! id) | (@ id)

match:error-control controls what code is generated for failed matches.
Possible values:

  • unspecified - do nothing, ie., evaluate (cond [() ()])
  • fail - call match:error, or die at car or cdr
  • error - call match:error with the unmatched value
  • match - call match:error with the unmatched value and the quoted match expression

match:error-control is set by calling match:set-error-control with the new value.

match:error is called for a failed match. match:error is set by calling match:set-error with the new value.

match:structure-control controls the uniqueness of structures.
Possible values:

  • vector - (default) structures are vectors with a symbol in position 0
  • disjoint - structures are fully disjoint from all other values

match:structure-control is set by calling match:set-structure-control with the new value.

match:runtime-structures controls whether local structure declarations generate new structures each time they are reached.
Possible values:

  • t - (default) each runtime occurrence generates a new structure
  • () - each lexical occurrence generates a new structure

End of user visible/modifiable stuff.

Notes:

  • Vectors probably don’t work right.
  • Why doesn’t #(a b c …) match what PLT Scheme gives for the same thing?
  • Structures certainly don’t.
  • Use of modified vector-ref – should original be changed?

Installation

  • Run ‘make’ in directory Modules/Match.
  • Run ‘make test’ in directory Modules/Match.