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10.1.5.2 Complete Symbols

If you specified both %define api.value.type variant and %define api.token.constructor, the parser class also defines the class parser::symbol_type which defines a complete symbol, aggregating its type (i.e., the traditional value returned by yylex), its semantic value (i.e., the value passed in yylval, and possibly its location (yylloc).

Method on symbol_type: symbol_type (token_type type, const semantic_type& value, const location_type& location)

Build a complete terminal symbol which token type is type, and which semantic value is value. If location tracking is enabled, also pass the location.

This interface is low-level and should not be used for two reasons. First, it is inconvenient, as you still have to build the semantic value, which is a variant, and second, because consistency is not enforced: as with unions, it is still possible to give an integer as semantic value for a string.

So for each token type, Bison generates named constructors as follows.

Method on symbol_type: make_ token (const value_type& value, const location_type& location)
Method on symbol_type: make_ token (const location_type& location)

Build a complete terminal symbol for the token type token (not including the api.token.prefix) whose possible semantic value is value of adequate value_type. If location tracking is enabled, also pass the location.

For instance, given the following declarations:

%define api.token.prefix {TOK_}
%token <std::string> IDENTIFIER;
%token <int> INTEGER;
%token COLON;

Bison generates the following functions:

symbol_type make_IDENTIFIER(const std::string& v,
                            const location_type& l);
symbol_type make_INTEGER(const int& v,
                         const location_type& loc);
symbol_type make_COLON(const location_type& loc);

which should be used in a Lex-scanner as follows.

[0-9]+   return yy::parser::make_INTEGER(text_to_int (yytext), loc);
[a-z]+   return yy::parser::make_IDENTIFIER(yytext, loc);
":"      return yy::parser::make_COLON(loc);

Tokens that do not have an identifier are not accessible: you cannot simply use characters such as ':', they must be declared with %token.


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