Where f is any index symbol, is any string of terminals and / or non-terminal symbols, and x is a terminal is a terminal symbol.
22.
Where f is any index symbol, is any string of terminals and / or non-terminal symbols, and x is a terminal is a terminal symbol.
23.
The basic rewrite operation of an LMG is very similar to that of a CFG, with the addition of " arguments " to the non-terminal symbols.
24.
Where the grammar generates a terminal symbol, the PDA reads a symbol from input when it is the topmost symbol on the stack ( " match " ).
25.
The leaves of a derivation tree for a formal grammar " G " are the terminal symbols of that grammar, and the internal nodes the nonterminal or variable symbols.
26.
ERROR, then, represents a configuration where the state at the top of the stack, and the lookahead terminal symbol " is not " within the subject grammar.
27.
LR parsers can generate somewhat helpful error messages for the first syntax error in a program, by simply enumerating all the terminal symbols that could have appeared next instead of the unexpected bad lookahead symbol.
28.
An occurrence of a non-terminal symbol is rewritten using rewrite rules as in a context-free grammar, eventually yielding just compositions ( composition functions applied to string tuples or other compositions ).
29.
The third rule form, the push rule, should be pointed out, as it differs from the pop rule in requiring that all push operations introduce at least one new terminal symbol to the derivation string.
30.
STOP, then, represents a configuration where the state at the top of the stack and the lookahead terminal symbol " is " within the subject grammar, and represents the ending of the program:
