Package: guile;
Reported by: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Date: Sun, 17 Sep 2023 18:18:01 UTC
Severity: normal
Message #11 received at 66057 <at> debbugs.gnu.org (full text, mbox):
From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com> To: Jean Abou Samra <jean <at> abou-samra.fr> Cc: 66057 <at> debbugs.gnu.org Subject: Re: bug#66057: (ice-9 match) allows invalid usages of ... or ..1 Date: Sun, 17 Sep 2023 20:59:23 -0400
Hello,
Jean Abou Samra <jean <at> abou-samra.fr> writes:
> Le dimanche 17 septembre 2023 à 14:17 -0400, Maxim Cournoyer a écrit :
>> Hi,
>>
>> After attempting the following:
>>
>> --8<---------------cut here---------------start------------->8---
>> (match (string-split "./Bootloaders/Printer/Documentation/html" #\/)
>> (("." path ..1 "Documentation" "html")
>
>
> For a start, where does that "..1" syntax come from? To my knowledge, no such
> syntax is supported by Guile's pattern matcher, which AFAIK is the one described
> in SRFI-204.
>
> https://srfi.schemers.org/srfi-204/srfi-204.html
It's mentioned in the Guile Reference manual; see info "(guile) Pattern
Matching":
--8<---------------cut here---------------start------------->8---
-- Scheme Syntax: match exp clause1 clause2 ...
Match object EXP against the patterns in CLAUSE1 CLAUSE2 ... in the
order in which they appear. Return the value produced by the first
matching clause. If no clause matches, throw an exception with key
‘match-error’.
Each clause has the form ‘(pattern body1 body2 ...)’. Each PATTERN
must follow the syntax described below. Each body is an arbitrary
Scheme expression, possibly referring to pattern variables of
PATTERN.
The syntax and interpretation of patterns is as follows:
patterns: matches:
pat ::= identifier anything, and binds identifier
| _ anything
| () the empty list
| #t #t
| #f #f
| 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
| ($ record-name pat_1 ... pat_n) a record
| (= field pat) a ``field'' of an object
| (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
| (identifier *** pat) matches pat in a tree and binds
identifier to the path leading
to the object that matches pat
ooo ::= ... zero or more
| ___ zero or more
| ..1 1 or more
quasi-patterns: matches:
qp ::= () the empty list
| #t #t
| #f #f
| 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!’, ‘...’, and ‘___’ cannot be
used as pattern variables.
--8<---------------cut here---------------end--------------->8---
>
> So your example is just binding the string "Printer" to the variable "..1":
> since "..1" doesn't have any special meaning, it's just a pattern variable.
Unless I misread the doc, it should '..1' is a special case '...', which
means "one or more" instead of "zero or more".
>
>> (pk 'path path)))
>>
>> => ;;; (path "Bootloaders")
>>
>> Expected (and works with '...'):
>> ;;; (path "Bootloaders" "Printer")
>> --8<---------------cut here---------------end--------------->8---
>>
>> and asking about it in #scheme or #guile, it seems the '..1' and '...'
>> patterns *must* be used strictly to match at the end of lists,
>
>
> ??
>
> This is not what SRFI 204 says, and it's not consistent with syntax-rules and
> syntax-case patterns either.
OK! I hope it's just a bug in Guile that can be addressed then.
Thanks for tipping in.
--
Maxim
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