$ in identifiers -- poll

[Oliver Boliver Butt]

> For what it's worth, the current ANSI C draft (12 Nov 1984) says that
> dollar signs aren't in C's vocabulary at all (except for the usual
> exemption for comments and strings), but adds the following in the
> "Common extensions" discussion in appendix E:
> 
> 	E.4.4.1 Specialized identifiers
> 	
> 	Characters other than the underscore _, letters, and digits, that
> 	are not defined in the required source character set (such as the
> 	dollar sign $) may appear in an identifier.

    *
Yacc  uses $$ and $n to allow for manipulations on its parsing stack.  In this
case, $$ & $n are used as pseudo identifiers for the stack in the C code actions
which get executed when a rule gets reduced.  Therefore, there is an ambiguity
problem with yacc and the proposed $ operators when you try to compile the code
yacc generates.   So you either have to change yacc, or forget about the $ ops.

Paul van de Graaf	U. C. San Diego		sdcsvax!sdcc3!85488116

* If you don't know, yacc stands "for yet another compiler compiler" It is a tool
  which generates a compiler given a LR(1) grammar and some supporting code that 
  the programmer writes.