Chapter 4

1. A terminal symbol is not defined by a production rule in terms of other symbols. This is the opposite of a non-terminal symbol, which can be replaced by or constructed from the sequence of symbols on the right-hand side of a production rule that defines that non-terminal symbol.
2. A shift removes the current symbol from the input and pushes it onto the parse stack. A reduce pops zero or more symbols from the top of the parse stack that match the right-hand side of a production rule and pushes the corresponding non-terminal from the left side of the production rule in their place.
3. YACC gives you a chance to execute some semantic action code only when a reduce operation takes place.
4. The integer categories returned from yylex() in the previous chapter are exactly the sequence of terminal symbols that the parser sees and shifts on during parsing. A successful parse shifts all the available input symbols and gradually reduces them back to the starting non-terminal...