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4.3.3 Finding Tokens by String Literals

If the grammar uses literal string tokens, there are two ways that yylex can determine the token kind codes for them:

• If the grammar defines symbolic token names as aliases for the literal string tokens, yylex can use these symbolic names like all others. In this case, the use of the literal string tokens in the grammar file has no effect on yylex.

  This is the preferred approach.

• yylex can search for the multicharacter token in the yytname table. This method is discouraged: the primary purpose of string aliases is forging good error messages, not describing the spelling of keywords. In addition, looking for the token kind at runtime incurs a (small but noticeable) cost.

  The yytname table is generated only if you use the %token-table declaration. See Bison Declaration Summary.