font-lock in rexx-mode

font-lock in rexx-mode

[Bob Babcock]

I'm using rexx-mode.el from 
http://www.sve.man.ac.uk/General/Staff/perrin/rexx.html
In rexx, I could say
  foo = "\"
and the backslash is just a character in quotes.  But with font-lock-mode 
enabled, the backslash breaks recognition of the end of the string and 
syntax coloring breaks.  Is there a way to turn off the special meaning of 
backslash when in rexx mode?

If it matters, I'm using Emacs 21.3.1 under Windows.

Re: font-lock in rexx-mode

[Stefan Monnier]

> I'm using rexx-mode.el from 
> http://www.sve.man.ac.uk/General/Staff/perrin/rexx.html
> In rexx, I could say
>   foo = "\"
> and the backslash is just a character in quotes.  But with font-lock-mode 
> enabled, the backslash breaks recognition of the end of the string and 
> syntax coloring breaks.  Is there a way to turn off the special meaning of 
> backslash when in rexx mode?

Of course: each mode sets up its own `syntax-table' where the meaning of
each char is described.  So if in Rexx a \ should not escape the next char,
the syntax-table should be changed.
Currently rexx-mode.el does:

  (modify-syntax-entry ?\\ "\\" rexx-mode-syntax-table)

which as that \ should be treated as an escape char.  So either this line is
in error, or the \ should sometimes be treated as an escape char and
sometimes not.  I don't know anything about the syntax of Rexx, so I have no
idea when \ escapes and when it doesn't.  E.g. how do you escape a " inside
a string in Rexx?


        Stefan

Re: font-lock in rexx-mode

[Bob Babcock]

Stefan Monnier <monnier@iro.umontreal.ca> wrote in
news:jwv8xhhg6m1.fsf-monnier+gnu.emacs.help@gnu.org: 

> So if in Rexx a \ should not escape the
> next char, the syntax-table should be changed.
> Currently rexx-mode.el does:
> 
>   (modify-syntax-entry ?\\ "\\" rexx-mode-syntax-table)
> 
> which as that \ should be treated as an escape char.  So either this
> line is in error, or the \ should sometimes be treated as an escape
> char and sometimes not.  I don't know anything about the syntax of
> Rexx, so I have no idea when \ escapes and when it doesn't.  E.g. how
> do you escape a " inside a string in Rexx?

Thanks for the response.  I don't understand why, but commenting out the 
above line and restarting emacs doesn't change the behavior.  (I do not 
have a rexx-mode.elc.  If I start emacs with --no-init-file, rexx-mode is 
not recognized.)

Backslash is never an escape in Rexx.  Rexx allows either single or double 
quotes to delimit a string, so '"' would be a double quote.  A string 
containing both kinds of quote could be built by concatenation.

Re: font-lock in rexx-mode

[Stefan Monnier]

>> So if in Rexx a \ should not escape the
>> next char, the syntax-table should be changed.
>> Currently rexx-mode.el does:
>> 
>> (modify-syntax-entry ?\\ "\\" rexx-mode-syntax-table)
>> 
>> which as that \ should be treated as an escape char.  So either this
>> line is in error, or the \ should sometimes be treated as an escape
>> char and sometimes not.  I don't know anything about the syntax of
>> Rexx, so I have no idea when \ escapes and when it doesn't.  E.g. how
>> do you escape a " inside a string in Rexx?

> Thanks for the response.  I don't understand why, but commenting out the 
> above line and restarting emacs doesn't change the behavior.  (I do not 
> have a rexx-mode.elc.  If I start emacs with --no-init-file, rexx-mode is 
> not recognized.)

It's normal: this line is superfluous since it just repeats the default
setting of \.  Instead of removing it, you want to replace it with another
line such as

   (modify-syntax-entry ?\\ "." rexx-mode-syntax-table)

where the "." means "punctuation".  See C-h f modify-syntax-entry RET
for a bit more documentation.


        Stefan

Re: font-lock in rexx-mode

[Stefan Monnier]

> It's normal: this line is superfluous since it just repeats the default
> setting of \.  Instead of removing it, you want to replace it with another
> line such as

>    (modify-syntax-entry ?\\ "." rexx-mode-syntax-table)

> where the "." means "punctuation".  See C-h f modify-syntax-entry RET
> for a bit more documentation.

Oh and if it's really a bug in rexx-mode, as you seem to imply, then please
send it to the maintainer and/or post it somewhere for others to use (the
maintainer seem to have quit his job, so maybe you want to distribute your
own version, virtually improvising yourself maintainer).


        Stefan

Re: font-lock in rexx-mode

[Bob Babcock]

Stefan Monnier <monnier@iro.umontreal.ca> wrote in
news:jwv4ps5dutz.fsf-monnier+gnu.emacs.help@gnu.org: 

> It's normal: this line is superfluous since it just repeats the
> default setting of \.  Instead of removing it, you want to replace it
> with another line such as
> 
>    (modify-syntax-entry ?\\ "." rexx-mode-syntax-table)

I thought I had tried this last night and it didn't work, but today it 
works.  It was late and I was tired...  Thanks.

I will send an email about this to the (retired) rexx-mode maintainer.  
Perhaps he will consider making this small change.  If not, I'll try to put 
the revised version on a web page so search engines can find it.