From: Mikael Magnusson <mikachu@gmail.com>
To: Bart Schaefer <schaefer@brasslantern.com>
Cc: zsh workers <zsh-workers@zsh.org>
Subject: Re: Aliasing separators (Re: grammar triviality with '&&')
Date: Fri, 6 Mar 2015 05:13:28 +0100 [thread overview]
Message-ID: <CAHYJk3Sr90FhHjup+-K0OdcsHuOAFS4imTAJtaXX9gFfw3oY6A@mail.gmail.com> (raw)
In-Reply-To: <150305174240.ZM8732@torch.brasslantern.com>
On Fri, Mar 6, 2015 at 2:42 AM, Bart Schaefer <schaefer@brasslantern.com> wrote:
> On Mar 5, 5:40pm, Peter Stephenson wrote:
> }
> } Personally, I don't see why allowing someone to alias \& but not &&
> } is logical; either you give users enough rope to hang themselves (and we
> } do), or you limit it to non-metacharacters (and we don't).
>
> It has nothing to do with metacharacters and everything to do with tokens.
>
> "*" is not intrinsically a token; it's only a token when delimited by
> whitespace or other tokens. Similarly "\&" is not intrinsically a token.
> If you write "**" it becomes a different thing and any alias for "*" no
> longer applies.
>
> But (unless quoted, when aliasing doesn't apply anyway) "&&" always is
> a token; further it's in the class of tokens that separate other parts
> of the lexical space into tokens. Allowing separators to be aliased
> doesn't just change the outcome of a parse (in the way that, say, an
> alias for "fi" would), it changes the rules for constructing other
> aliasable tokens.
>
> Furthermore, ignoring "alias -g" issues which I agree are an entirely
> smellier kettle of fish, it changes the definition of "in command
> position". With input like
>
> torch% &&bar
>
> I would argue that the "&&" is NOT "in command position" because in the
> normal lexical situation "command position" ENDS just to the left of any
> separator. There's NOTHING in "command position" in that example.
>
> Either "&&" is a separator token and should act like one, or it isn't
> and in that example the alias for "&&bar" should be looked up instead.
>
> } > Aliasing only of STRING tokens is exactly the right thing and this
> } > change is simply wrong. The doc only says "before parsing" as a
> } > shorthand instead of a long explaination about how the alias is
> } > replaced and then parsed all over again.
> }
> } If you can produce an alternative patch describing the previous position
> } properly, go ahead. I don't think anyone is actually screaming to use
> } this change.
>
> I'll think about a documation patch if that's what you mean.
You could argue that the documentation is already right, it uses
"before parsing", and && is interpreted in the "lexing" stage, right?
However, I don't think users can know that... :)
--
Mikael Magnusson
next prev parent reply other threads:[~2015-03-06 4:13 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <54F33934.2070607@eastlink.ca>
[not found] ` <13666281425228233@web7o.yandex.ru>
[not found] ` <54F345D3.9010204@eastlink.ca>
[not found] ` <D0509295-7DA9-4F18-9E3D-D50C0A756998@larryv.me>
[not found] ` <20150302022754.GA7449@xvii.vinc17.org>
[not found] ` <CABx2=D8efL3X2tfB+_+VweY2yye6EhaMNbJa3b3jJeVMp=7gaQ@mail.gmail.com>
[not found] ` <20150302104619.GC6869@xvii.vinc17.org>
[not found] ` <20150302110610.2e2c7e86@pwslap01u.europe.root.pri>
[not found] ` <CAH+w=7YoHjN85hqOZVywOfYGZqvU74vZrbE84Ln+V2HQi-6nSA@mail.gmail.com>
[not found] ` <20150304144756.GA27231@ypig.lip.ens-lyon.fr>
2015-03-04 15:18 ` grammar triviality with '&&' Peter Stephenson
2015-03-04 21:13 ` Daniel Shahaf
2015-03-04 22:05 ` Mikael Magnusson
2015-03-05 9:46 ` Peter Stephenson
[not found] ` <150304175112.ZM19818@torch.brasslantern.com>
[not found] ` <20150305100638.55631238@pwslap01u.europe.root.pri>
2015-03-05 17:07 ` Aliasing separators (Re: grammar triviality with '&&') Bart Schaefer
2015-03-05 17:40 ` Peter Stephenson
2015-03-06 1:42 ` Bart Schaefer
2015-03-06 4:13 ` Mikael Magnusson [this message]
2015-03-06 16:43 ` Vincent Lefevre
2015-03-06 9:40 ` Peter Stephenson
2015-03-06 19:26 ` Bart Schaefer
2015-03-07 15:52 ` Peter Stephenson
2015-03-07 17:18 ` Ray Andrews
2015-03-07 21:10 ` Bart Schaefer
2015-03-09 11:46 ` Vincent Lefevre
2015-03-09 16:33 ` Peter Stephenson
2015-03-09 17:03 ` Bart Schaefer
2015-03-09 17:39 ` Peter Stephenson
2015-03-09 17:47 ` Ray Andrews
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