argv ==> stdin (fast)

[scabel at diku.UUCP]

In article <2972 at rsch.WISC.EDU> mcvoy at rsch.WISC.EDU (Lawrence W. McVoy) writes:
>Hi there.  I'm using lex & yacc to do some work for me and I can't 
>quite get it.   The scanner & parser part works, but only if it's 
>getting input from stdin.  I diddled lex.yy.c to change the getc(yyin)
>call in the input() define to call my routine which feed sit characters 
>from argv.  This works if I call yylex() from main, but if yyparse calls 
>it then I get a "syntax error".  The same program works if I don't
>diddle the input() routine.  And I can't figure out what's wrong
>with my diddling.....

I have made a program using lex and yacc, which either reads from a
argument to the program, or from stdin.

Here is the important parts from the lex file..
%C
%{
#ifdef input
#undef input
#endif
# define input() (((yytchar=yysptr>yysbuf?U(*--yysptr):nextchar())==10?(yylineno++,yytchar):yytchar)==EOF?0:yytchar)

extern int ARGEXPR;
extern char *argexpr;
%}

%%
/* The lex program */
%%
int nextchar()
{
	static int i = 0;

	if (ARGEXPR) {
		if (*argexpr == '\0')
		    return(i++ == 0?'\n':EOF);
		return(*argexpr++);
	} else
	    return(getc(yyin));
}

-- 

Niels Schachtschabel,
Institute of Datalogy, University of Copenhagen
E-mail: scabel at diku.uucp / ...!seismo!mcvax!diku!scabel