What is the meaning of yytext[0]?

Question

What is the meaning of yytext[0]? And why should we use in the lex and yacc program? I'm learner so don't mind if it is a silly question.

Answer 1

yytext holds the text matched by the current token. So yytext[0] holds the first character of the text matched by the current token. Sometimes you have a rule which can match different texts so you need to get the real text matched like for variable names or you have a rule to match all arithmetic operations.

A good source is the Flex manual.

For beginners the best starting point is trying the sample projects.