我正在学习弹/野牛。我写了以下程序,但收到错误。
%{
#include <stdio.h>
typedef struct node
{
struct node *left;
struct node *right;
char *token;
}node;
node *mknode( node *left, node *right, char *token);
void printtree(node *tree);
#define YYSTYPE struct node *
%}
%union
{
char* str;
int num;
}
%start lines
%token <str> WORD
%token <str> PLUS MINUS TIMES DIVIDE POWER
%token <str> LEFT_PARENTHESIS RIGHT_PARENTHESIS
%token <str> END
%left PLUS MINUS
%left TIMES DIVIDE
%right POWER
%type <str> exp term factor line lines
%%
lines: /* empty */
| lines line;
line: exp END { printtree($1); printf("\n");}
;
exp: term {$$=$1; }
| exp PLUS term { $$=mknode($1,$3,"+"); }
| exp MINUS term { $$=mknode($1,$3,"-"); }
;
term: factor { $$=$1; }
|term TIMES factor { $$=mknode($1,$3,"*"); }
;
factor: WORD { $$=mknode(0,0, (char*)yylval); }
|LEFT_PARENTHESIS exp RIGHT_PARENTHESIS
{ $$=$2; }
;
%%
int main(void)
{
return yyparse();
}
node *mknode(node *left, node *right, char *token)
{
/* malloc the node */
node *newnode = (node *)malloc(sizeof(node));
char *newstr = (char *)malloc(strlen(token)+1);
strcpy(newstr, token);
newnode->left = left;
newnode->right = right;
newnode->token = newstr;
return(newnode);
}
void printtree(node *tree)
{
int i;
if (tree->left || tree->right)
printf("(");
printf(" %s ", tree->token);
if (tree->left)
printtree(tree->left);
if (tree->right)
printtree(tree->right);
if (tree->left || tree->right)
printf(")");
}
int yyerror(char *s )
{
fprintf (stderr, "%s\n", s);
}
挠曲:
%{
#include <stdlib.h>
#include "y.tab.h"
%}
%%
[a-zA-Z0-9]+ { yylval.str = strdup( yytext ); return WORD; }
/* cast pointer to int for compiler warning */
[ \t] ;
"+" return(PLUS);
"-" return(MINUS);
"*" return(TIMES);
"/" return(DIVIDE);
"^" return(POWER);
"(" return(LEFT_PARENTHESIS);
")" return(RIGHT_PARENTHESIS);
\n return(END);
%%
int yywrap (void) {return 1;}
我得到的错误:
C:\flexbison>recomp example2
example2.y:40.6: warning: empty rule for typed nonterminal, and no action
conflicts: 5 reduce/reduce
example2.y:43: error: request for member `str' in something not a structure or union
example2.y:46: error: request for member `str' in something not a structure or union
example2.y:46: error: request for member `str' in something not a structure or union
example2.y:47: error: request for member `str' in something not a structure or union
example2.y:47: error: request for member `str' in something not a structure or union
example2.y:47: error: request for member `str' in something not a structure or union
example2.y:48: error: request for member `str' in something not a structure or union
example2.y:48: error: request for member `str' in something not a structure or union
example2.y:48: error: request for member `str' in something not a structure or union
example2.y:51: error: request for member `str' in something not a structure or union
example2.y:51: error: request for member `str' in something not a structure or union
example2.y:52: error: request for member `str' in something not a structure or union
example2.y:52: error: request for member `str' in something not a structure or union
example2.y:52: error: request for member `str' in something not a structure or union
example2.y:55: error: request for member `str' in something not a structure or union
example2.y:56: error: request for member `str' in something not a structure or union
example2.y:58: error: request for member `str' in something not a structure or union
example2.y:58: error: request for member `str' in something not a structure or union
知道我为什么会收到此错误?
答案 0 :(得分:2)
第一个明显的问题是,如果您使用的是yacc,则不应该定义YYSTYPE
。 Yacc从您的YYSTYPE
定义%union
。如果您使用YYSTYPE
但未使用lex
,则需要定义yacc
。
您的%union
解析堆栈项类型仅包含int
和str
成员。示例:您已将exp
语法符号定义为类型str
,然后您就拥有了这个产品:
exp: term {$$=$1; }
| exp PLUS term { $$=mknode($1,$3,"+"); }
| exp MINUS term { $$=mknode($1,$3,"-"); }
;
mknode
函数返回node *
,但$$
符号的类型为char *
,因为它代表左侧的exp
,您输入的内容为str
,str
的{{1}}成员为%union
。
char *
的参数也必须是mknode
。但node *
和$1
没有该类型。