Re: "Raw" string literals for elisp

[tomas]

On Wed, Sep 08, 2021 at 04:18:23PM -0400, Stefan Monnier wrote:
> > I just think these are two separate dimensions which happen to align
> > in the "regexp and backslash" case.
> 
> BTW, they can align in somewhat funny ways sometimes.
> E.g. the raw-string version of the regexp "[ \t\n]" turns into something like
> 
>     #r"[
> ]"

Actually I was using "align" in a rather metaphorical sense, but you
are making a very good point: one might want to have some ot the
"classical C escapes" (\n, \r and some of its ilk, perhaps even \b),
but then `raw' wouldn't be raw anymore.

> which is not ideal in terms of clarity.  Similarly a regexp that matches
> the NUL character will be problematic when written as a raw string
> because it will need to embed the NUL character in the source code,
> which in turn will cause tools like `grep` to treat the file as binary.
> 
> For the first problem above we can/should extend our regexp syntax to
> include \t and \n as regexps that match TAB and LF respectively (that
> would also be handy when writing regexps in the minibuffer).

For regexps proper there's an escape hatch, since there is a language "on
top" that could be extended a bit (e.g. via the [:...:] character class
notation or something). But that would be unwieldy indeed.

> But \0 is already used for other things so there's no such "obvious"
> workaround for the second case :-(

Yes, the very handy `\x' notation has much history. Hard to move whithin
that cupboard without breaking anything :-)

Cheers
 - t

signature.asc
Description: Digital signature