Supporting C Routines[adapted from slide by John Werth.]

A lexical analyzer named yylex() must be provided in the third section. This can be user-written or generated by lex.

yylex must return two values:

• ``what is it?'', a small integer that is the return value, e.g. return(NUMBER);
• the actual value of the item, by setting the value of yylval, e.g. yylval = tok;