Emacs version and LISP interpretation

Emacs version and LISP interpretation

[richard.christensen]

Hi,

I was transferring a new mode and .emacs file from my PC to my work
linux box.  My PC is running 23.1.1 and my linux box is running
21.3.1.  Anyway I was getting the following error from the Linux
version "Invalid escape character syntax".  I was able to trace it
down to instances like (insert ?\s). My PC will insert a space and on
the linux box will give an error.  I did try (insert " ") and this
works just fine as well as (insert ?\t).  Why isn't \s recognized?  Is
this common problem from older versions?  What would be the best work-
around?  Have the current version of emacs installed?

Thanks.

Richard.

Re: Emacs version and LISP interpretation

[Stefan Monnier]

> version "Invalid escape character syntax".  I was able to trace it
> down to instances like (insert ?\s). My PC will insert a space and on

?\s is a "new" syntax for the space character, introduced in Emacs-22.


        Stefan

Re: Emacs version and LISP interpretation

[Stefan Monnier]

> So the answer is that you need to change (insert ?\s) to (insert ?\s ).
> That is, leave at least one space after the \s.

No, ?\s is new, so ?\s won't work even if you add a space after it.
The old syntax is ?\  (where the space after the backslash is important).

> I've seen more than one library broken this way (broken for older Emacs
> versions).

We (Emacs maintainers) only changed the code of the files distributed
along with Emacs, so we don't get to introduce such bugs directly.
Of course, some of those changes are then fed back upstream and the
upstream maintainer may either fail to notice the incompatibility
introduced, or consider it to be minor.


        Stefan

RE: Emacs version and LISP interpretation

[Drew Adams]

> > So the answer is that you need to change (insert ?\s) to 
> > (insert ?\s ).  That is, leave at least one space after the \s.
> 
> No, ?\s is new, so ?\s won't work even if you add a space after it.
> The old syntax is ?\  (where the space after the backslash is 
> important).

Right, my bad; good catch.  What you say is what I meant to say:
change (insert ?\s) to (insert ?\ ), where, as you point out, the space is
important.

(I was no doubt confusing the SPC char syntax with the regexp syntax for
matching a whitespace char, which is `\s ' or `\s-'.)