Recursive Decent Parsing:Actions in the Parsing Functions

• Here is one of the augmented grammar productions that make up the translation scheme, with the semantic action symbols inserted as before:

<> --> ID {enter} ‘=’ <> {pop;copy} ‘;’

• The code for the recursive-descent parsing function that implements the semantic actions for this production looks something like this:

Boolean stmt(){

if( tokentype != ID ){

errprint(“Missing identifier”);

return FALSE;

}

\\ {enter} action goes here: Call a function that

\\ returns a pointer to the identifier in the

\\ symbol table. If not found there, enter it.

. . . usual code to match EQUALS goes here . . .

if( ! item() )

return FALSE;

\\ {pop;copy} action goes here: Pop the top value

\\ off the value stack and copy it into the

\\ symbol table at the location of the identifier

if( tokentype != SEMICOLON ){

errprint("Missing ‘;’");

return FALSE;

}

scanner();

return TRUE; /* parsing succeeded */

}