LALR Using YACC Compiler

Compiler Construction Lab Manual / LALR Using YACC Compiler

Program Name

Write a Compiler Construction Program for LALR Using YACC Compiler.

Theory
LALR Using YACC Compiler.

Program Code


//LALR.L
%{
#include "y.tab.h"
extern int yylval;
%}
%%
[0-9]+ {yylval=atoi(yytext);
return num;}
\n return 0;
. return yytext[0];
%%
yywrap()
{
return 1;
}
//LALR.Y
%{
#include<stdio.h>
%}
%token num;
%%
cmd:E {printf("%d\n",$1);}
E:T'+'E {$$=$1+$3;}
|T{$$=$1;}
;
T:F'*'T{$$=$1*$3;}
|F{$$=$1;}
;
F:'('E')'{$$=$2;}
|num{$$=$1;}
;
%%
main()
{
yyparse();
}
yyerror(char *s)
{
printf("%s",s);
}

Saving: vi lalr.l

Compiling and Running
yacc -d lalr.y
lex.yy.c y.tab.c
./a.out

Input
2+3
2++

Output
5
Syntax Error

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