CS606 Short Notes Lecture 15

Lecture 15

Let’s consider the implementation of the C++ classes for the non-terminals. We start with Expr.

bool Expr::isPresent() · Term* op1 = new Term(s); · Eprime* op2 = new Eprime(s, tree); · bool Eprime::isPresent() · if(op==PLUS || op==MINUS){ s->advance(); · Term* op2=new Term(s); · Eprime* op3 = new Eprime(s, tree); · bool Term::isPresent() · bool Tprime::isPresent() · if(op == MUL || op == DIV){ s->advance(); · bool Factor::isPresent() · if(op == ID || op == NUM)

tree = new TreeNode(op,s->tokenValue()); s->advance();

if( op == LPAREN ){ · s->advance(); · Expr* opr = new Expr(s); if(!opr->isPresent() ) · if(s->nextToken() != RPAREN) · s->advance(); · tree = opr->AST();