Create a Print Function

Question

I'm learning Bison and at this time the only thing that I do was the rpcalc example, but now I want to implement a print function(like printf of C), but I don't know how to do this and I'm planning to have a syntax like this print ("Something here");, but I don't know how to build the print function and I don't know how to create that ; as a end of line.
Thanks for your help.

Answer 1

You first need to ask yourself:
  What are the [sub-]parts of my 'print ("something");' syntax ?

Once you identify these parts, "simply" describe them in the form of grammar syntax rules, along with applicable production rules. And then let Bison generate the parser for you; that's about it.

To put you on your way:
The semi-column is probably a element you will use to separate statemements (such a one "call" to print from another).
'print' itself is probably a keyword, or preferably a native function name of your language.
The print statement appears to take a literal string as [one of] its arguments. a literal string starts and ends with a double quote (and probably allow for escaped quotes within itself)
etc. The bolded and italic expressions above are some of the entities (the 'symbols' in parser lingo) you'll likely need to define in the syntax for your language. For that you'll use Bison grammar rules, such as

stmt : print_stmt ';' | input_stmt ';'| some_other_stmt ';' ;
prnt_stmt : print '(' args ')' 
     { printf( $3 ); }
    ;

args : arg ',' args;
...

Since the question asked about the semi-column, maybe some confusion was from the different uses thereof; see for example above how the ';' belong to your language's syntax whereby the ; (no quotes) at the end of each grammar rule are part of Bison's language.

Note: this is of course a simplistic implementation, aimed at showing the essential. Also the Bison syntax may be a tat off (been there / done it, but a long while back ;-) I then "met" ANTLR never to return to Bison, although I do see how its lightweight and fully self contained nature can make it appropriate in some cases)