CoCoA » CoCoA-5

Around line 335 in cocoa5.el there is this

  ; -- comments 
  (modify-syntax-entry ?- ". 12"    cocoa5-mode-syntax-table)
  ; // and /* */ comments 
  (modify-syntax-entry ?/  ". 124" cocoa5-mode-syntax-table)

At the moment I have no idea how to interpret this, but suspect that the problem could well be here.

Here is some doc about emacs;

http://www.gnu.org/software/emacs/manual/html_node/elisp/Syntax-Flags.html

This is probably not solvable :-(

I changed the emacs syntax declaration for "minus" into just a plain "." (punctuation, without any special flags about being a marker for the start of a comment)
and the unexpected colouring went away... but of course, minus-minus was no longer recognised as a comment start.

I did also try setting the syntax description to ". 12c" which means first & second char of a comment of class "c", but that did not solve the unexpected colouring.

It seems to me that problem stems from emacs wanting to give context-independent descriptions of the syntax of single chars.
I have no idea how to solve this.

A possible way to address the problem is to discourage users from typing /- by making it issue a warning.

As already stated in issue #1538 I do not much like allowing input such as 2*-3 or 2/-3 (and also 2*+3 and 2/+3),
because they look more like typos to me. A leading plus or minus would be allowed only at the very start of an expr (e.g. also inside brackets);
in other contexts we could issue a warning...

John Abbott wrote:

A possible way to address the problem is to discourage users from typing /- by making it issue a warning.

that's a good point ;-)