在yacc中将多种数据类型分配给非终端 [英] Assigning multiple data types to a non-terminal in yacc
问题描述
我正在为一个项目设计类,我们必须在其中构建一个解析器.我们目前处于使用yacc构建解析器的阶段.目前让我感到困惑的是,我读到您需要为每个非终端分配一个类型.在某些情况下,我会有类似的东西:
I'm working on a project for class in which we have to build a parser. We're currently in the stage of building the parser in yacc. The thing currently confusing me is I've read that you need to assign a type to each nonterminal. In some cases though I'll have Something like:
...
%union {
Type dataType;
int integerConstant;
bool boolConstant;
char *stringConstant;
double doubleConstant;
char identifier[MaxIdentLen+1]; // +1 for terminating null
Decl *decl;
List<Decl*> *declList;
}
%token <identifier> T_Identifier
%token <stringConstant> T_StringConstant
%token <integerConstant> T_IntConstant
%token <doubleConstant> T_DoubleConstant
%token <boolConstant> T_BoolConstant
...
%%
...
Expr : /* some rules */
| Constant { /* Need to figure out what to do here */ }
| /* some more rules */
;
Constant : T_IntConstant { $$=$1 }
| T_DoubleConstant { $$=$1 }
| T_BoolConstant { $$=$1 }
| T_StringConstant { $$=$1 }
| T_Null { $$=$1 }
...
由于有时不能是整数,双精度或bool等,如何将类型赋给expr?
How can you assing a type to expr since can't it sometimes be an integer or double, or bool, etc?
推荐答案
您可以通过以下方式在规则中添加类型:
You can add the type in the rule by
TypesConstant : T_IntConstant { $<integerConstant>$=$1 }
| T_DoubleConstant { $<doubleConstant>$=$1 }
| ...
请参见 http://www.gnu .org/software/bison/manual/html_node/Action-Types.html#Action-Types 了解更多详细信息.
See http://www.gnu.org/software/bison/manual/html_node/Action-Types.html#Action-Types for more details.
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