From: Ammar Ali <ammarabuali@...>
Date: 2010-11-23T20:39:55+09:00
Subject: Re: gsub and backslashes

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On Tue, Nov 23, 2010 at 11:17 AM, Robert Klemme
<shortcutter@googlemail.com>wrote:

> On Mon, Nov 22, 2010 at 10:06 PM, Ammar Ali <ammarabuali@gmail.com> wrote:
> >
> > I guess I took issue with the word tolerance. I don't think of lexers
> > and parsers as tolerant. They are quite ruthless and dictatorial. It's
> > either their way, or their way in a way one did not expect. :)
>
> :-)  But rules can be made to allow for some flexibility (just think
> of method calls with or without brackets in Ruby).


That's a good example, and I know understand what you meant by tolerance.



> >> This is not an "escaped newline" but merely a backslash followed by
> >> character "n".  Whether that is considered "escaped" in some way depends
> on
> >> the code that processes this string.  If at all this is an escaped "n".
> :)
> >
> > You are correct sir. For someone who was nitpicking, I misspoke. :)
>
> No problem.  Apparently we both enjoy nitpicking. :-))


:)


> I agree, but this long "heritage" that goes back to the 60s is
> > probably very hard to shake. Maybe a new language can break away from
> > it.
>
> In Ruby's case the heritage does not go back to the sixties but rather
> to the nineties (1997) if I am not mistaken.


I was thinking of C, which I believe introduced these escapes, but I'm not
sure.



> > Out of curiosity, what could these beasts be replaced with? Constants?
>
> I'd leave everything as is except drop special cases like '\1' (this
> would either be an octal escape as in a double quoted string or rather
> just "1").  In single quoted strings only ' would be special if
> preceded by a backslash.  In double quoted strings I would have those
> characters which are special currently (", n, r, a, t and probably
> others I'm not thinking of right now).  I am undecided whether I would
> make all others errors or tolerant (e.g. "\z" would either by a syntax
> error or just "z").  I have a slight tendency to the more strict
> variant though because otherwise people might be left wondering what
> \z means when it is just "z"; also, this would help detect typing
> errors (maybe someone wanted to type "\t" which is just a key away in
> my German keyboard).



I like the idea of treating unnecessary escapes as syntax errors, or at
least warnings. I see this a lot in regular expressions, especially in
character sets. Characters that don't need to be escaped (like ? and *) are
preceded with a backslash, just to be safe I guess, making for a harder to
code, as you noted.

Regards,
Ammar

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