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From: Phillip Wood <phillip.wood123@gmail.com>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Johannes Sixt" <j6t@kdbg.org>
Cc: Atharva Raykar <raykar.ath@gmail.com>,
	git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
Subject: Re: [GSOC][PATCH] userdiff: add support for Scheme
Date: Mon, 29 Mar 2021 15:06:27 +0100	[thread overview]
Message-ID: <7edaee06-2149-a547-4fa9-c91b241ff966@gmail.com> (raw)
In-Reply-To: <87wntqm7dj.fsf@evledraar.gmail.com>

On 29/03/2021 14:12, Ævar Arnfjörð Bjarmason wrote:
> 
> On Mon, Mar 29 2021, Johannes Sixt wrote:
> 
>> Am 29.03.21 um 12:18 schrieb Phillip Wood:
>>> It would be nice to include indented define forms but including them
>>> means that any change to the body of a function is attributed to the
>>> last internal definition rather than the actual function. For example
>>>
>>> (define (f arg)
>>>    (define (g x)
>>>      (+ 1 x))
>>>
>>>    (some-func ...)
>>>    ;;any change here will have '(define (g x)' in the hunk header, not
>>> '(define (f arg)'
>>>
>>> I don't think this can be avoided as we rely on regexs rather than
>>> parsing the source so it is probably best to only match toplevel defines.
>>
>> There can be two rules, one that matches '(define-' that is indented,
>> and another one that matches all non-indented forms of definitions. If
>> that is what you mean.
> 
> Yes, but that doesn't help in these sorts of cases because what a rule
> like that really wants is some version of "don't match this line, but
> only if you can reasonably match this other rule".
> 
> We can only do rule precedence on a per-line basis via the inverted
> matches.
> 
> So for languages like cl/elisp/scheme and others where it's common to
> have nested function definitions (then -W would like the top-level) *OR*
> similarly looking nested function definitions, but the top-level isn't a
> function but a (setq) or whatever we're basically stuck with picking one
> or the other.

Exactly

> I've pondered how to get around this problem in my userdiff.c hacking
> without resorting to supporting some general-purpose Turing machine, and
> have so far come up with nothing.

I think using an indentation heuristic would probably work quite well 
for most languages - see 
https://public-inbox.org/git/20200923215859.102981-1-rtzoeller@rtzoeller.com/ 
for a discussion from last year (from memory there were some problems 
with the approach in those patches but I think there are some suggestion 
from Peff and me later in the thread on how they could be overcome)

Best Wishes

Phillip


> You can see lots of prior art by grepping Emacs's source code for
> beginning-of-defun, it solves this problem by exposing a Turing machine
> :)
> 

  reply	other threads:[~2021-03-29 14:07 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-27 17:39 [GSOC][PATCH] userdiff: add support for Scheme Atharva Raykar
2021-03-27 22:50 ` Junio C Hamano
2021-03-27 23:09   ` Junio C Hamano
2021-03-28  3:16     ` Ævar Arnfjörð Bjarmason
2021-03-28  5:37       ` Junio C Hamano
2021-03-28 12:40       ` Atharva Raykar
2021-03-29 10:08         ` Phillip Wood
2021-03-30  6:41           ` Atharva Raykar
2021-03-30 12:56             ` Ævar Arnfjörð Bjarmason
2021-03-30 13:48               ` Atharva Raykar
2021-03-28 12:45     ` Atharva Raykar
2021-03-28 11:51   ` Atharva Raykar
2021-03-28 18:06     ` Junio C Hamano
2021-03-29  8:12       ` Atharva Raykar
2021-03-29 20:47         ` Junio C Hamano
2021-03-29 10:12     ` Phillip Wood
2021-03-27 23:46 ` Johannes Sixt
2021-03-28 12:23   ` Atharva Raykar
2021-03-29 10:18     ` Phillip Wood
2021-03-29 10:48       ` Johannes Sixt
2021-03-29 13:12         ` Ævar Arnfjörð Bjarmason
2021-03-29 14:06           ` Phillip Wood [this message]
2021-03-30  7:04       ` Atharva Raykar
2021-03-30 10:22         ` Atharva Raykar
2021-04-05 10:04           ` Phillip Wood
2021-04-05 17:58             ` Johannes Sixt
2021-04-06 12:29             ` Atharva Raykar
2021-04-06 19:10               ` Phillip Wood
2021-04-03 13:16 ` [GSoC][PATCH v2 0/1] userdiff: add support for scheme Atharva Raykar
2021-04-03 13:16   ` [GSoC][PATCH v2 1/1] " Atharva Raykar
2021-04-05 10:21     ` Phillip Wood
2021-04-06 10:32       ` Atharva Raykar
2021-04-08  9:14   ` [GSoC][PATCH v3 0/1] " Atharva Raykar
2021-04-08  9:14   ` [GSoC][PATCH v3 1/1] userdiff: add support for Scheme Atharva Raykar
2021-04-12 23:04     ` Junio C Hamano

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