如何读取lex和yacc中的多行输入? [英] How to read multiple lines of input in lex and yacc?

问题描述

我希望输出为:

a=3   mov a,3
a=fs  mov b,fs
b=32  mov b,32

3地址中间代码生成程序-为词法分析编写的 lex 文件从命令行读取输入并传递标记:

Program for 3 address intermediate code generation - the lex file written for lexical analysis reads the input from command line and passes tokens:

%{
#include "y.tab.h"
#include "string.h"
#include <math.h>
%}
%%
[a-zA-Z]+ { yylval.var=(char *)malloc(sizeof(char *));
          strcpy(yylval.var,yytext);
         return ID;}
"="       return EQUALS;
[0-9]+    {yylval.num=atoi(yytext);return DIGIT;}


%%

对应的yacc文件:

%{

#include "stdio.h"

#include "string.h"

int yywrap()
{
return 1;
}
%}


%union
{char *var;
 int num;
}


%token <var> ID 
%token <num> EQUALS DIGIT




%%
start : line 

line : ID EQUALS DIGIT {printf("MOV %s, %d\n",$1, $3);}
     | ID EQUALS ID    {printf("MOV %s, %s\n",$1, $3);}
     ;


%%

main()

{

yyparse();

return 0;

}

int yyerror(char *s)

{
fprintf(stderr,"%s\n",s);

}

运行上述代码的输出(在lex和yacc链接之后):

The output of running the above code (after linking between lex and yacc):

dsa=32                
MOV dsa, 32                // 3 address code generated

ds=342                     // but does not parse this line why??
syntax error

如何获得所需格式的输出?

How do I get the output in the desired format?

推荐答案

你的语法只读取一行 line

也许你想要:

start : line
      | start line
      ;

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