Question

Consider the following grammar for variable and class declarations in Java:

<Decl>      -> <VarDecl>
             | <ClassDecl>

<VarDecl>   -> <Modifiers> <Type> <VarDec> SEM

<ClassDecl> -> <Modifiers> CLASS ID LBRACE <DeclList> RBRACE

<DeclList>  -> <Decl>
             | <DeclList> <Decl>

<VarDec>    -> ID
             | ID ASSIGN <Exp>
             | <VarDec> COMMA ID
             | <VarDec> COMMA ID ASSIGN <Exp>

Indicate any problems in this grammar that prevent it from being parsed by a recursive-descent parser with one token lookahead.

Transform this grammar into a form that can be parsed with a recursive-descent parser with one token lookahead. Make as few changes to the grammar as possible. Do not use EBNF.

Answer 1

The problem here is that return is done from right to left here.

the following is the recursive descent parser grammar expression

<E> --> <T> <E*>

<E*> --> + <T> <E*> | - <T> <E*> | epsilon

<T> --> <F> <T*>

<T*> --> * <F> <T*> | / <F> <T*> | epsilon

<F> --> ( <E> ) | number