Hi Hans - thanks - that looks good. On 08/05/2019 22:10, Hans Åberg wrote:
On 8 May 2019, at 22:30, EML <eml-bi...@cyconix.com> wrote: Sometimes, to make the grammar manageable, the lexer has to *dynamically* return 'typename' instead of 'identifier'. Only semantic analysis can determine what is a user-defined type (say 'foo'), so the lexer must be told at runtime that 'foo' is a 'typename' and not an 'identifier'.That is done by the method I indicated. In flex have a rule: identifier [[:alpha:]][[:alnum:]]+ %% {identifier} { std::optional<std::pair<token_type, semantic_type>> x = lookup_table.find(yylval.text); if (!x) return my::yyparser::token::identifier; // Set semantic value return to x->second. return x->first; } The Bison parser will then get the token of whatever the identifier has been defined to. It will have rules like: %token int_definition %token int_variable %token identifier %% definition: int_definition identifier[x] value[v] { lookup_table.push($x, {my::yyparser::token::int_variable, $v}); } use_value: … int_variable[x] … { … $x … }
_______________________________________________ help-bison@gnu.org https://lists.gnu.org/mailman/listinfo/help-bison
