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Re: ‘match’ and “k or more” patterns
From: |
Ludovic Courtès |
Subject: |
Re: ‘match’ and “k or more” patterns |
Date: |
Wed, 08 Sep 2010 14:06:00 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) |
Hi,
Alex Shinn <address@hidden> writes:
> On Mon, Sep 6, 2010 at 9:12 PM, Ludovic Courtès <address@hidden> wrote:
>>
>> Well, since there are only 9 of them, they could probably be implemented
>> as special cases, with an augmented ‘match-gen-ellipses’, which would be
>> told the minimum number of elements expected?
>
> Oh, the Wright syntax limited you to 9 forms, so "..10" is illegal?
>From Wright’s 1995 paper & doc I thought k > 9 wasn’t supported but
apparently it is:
--8<---------------cut here---------------start------------->8---
guile> (use-modules (ice-9 match)) ;; <- Wright’s code
guile> (match (iota 30) ((a ..10) a))
$1 = (0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
28 29)
guile> (match (iota 30) ((a ..22) a))
$2 = (0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
28 29)
guile> (version)
$3 = "1.8.7"
--8<---------------cut here---------------end--------------->8---
:-(
> "..1" is actually useful - it's the analog of "+" in regular
> expressions, and allows simplifying many syntax-rules
> patterns you see written (elt0 elt1 ...) as (elt ..1). If
> the elements are more complex patterns this is a big
> win.
Agreed.
So perhaps one solution would be to:
1. Have a special case for ‘..1’, since it’s quite handy.
2. Have a new syntax form, like ‘.. k’, as you suggested.
What do you think?
Thanks,
Ludo’.
- ‘match’ and “k or more” patterns, Ludovic Courtès, 2010/09/05
- Re: ‘match’ and “k or more” patterns, Alex Shinn, 2010/09/06
- Re: ‘match’ and “k or more” patterns, Ludovic Courtès, 2010/09/06
- Re: ‘match’ and “k or more” patterns, Alex Shinn, 2010/09/07
- Re: ‘match’ and “k or more” patterns,
Ludovic Courtès <=
- Re: ‘match’ and “k or more” patterns, Andy Wingo, 2010/09/08
- Re: ‘match’ and “k or more” patterns, Ludovic Courtès, 2010/09/19
- Message not available
- Re: ‘match’ and “k or more” patterns, Ludovic Courtès, 2010/09/27
- Re: ‘match’ and “k or more” patterns, Alex Shinn, 2010/09/27
- Message not available
- Re: ‘match’ and “k or more” patterns, Ludovic Courtès, 2010/09/28