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%{
#include <stdio.h>
int yylex();
int yyerror(const char* error);
#define YYDEBUG 0
#include <iostream>
#include <string>
using namespace std::string_literals;
%}
%start input
%define api.value.type {std::string}
%token NUMBER
%token IDENT
%token PLUS
%token MINUS
%token MULT
%token DIV
%token ASSIGN
/* Define both - precedence and associativity */
%right ASSIGN
%left PLUS MINUS
%left MULT DIV
%%
input: /* empty */
| expr { std::cout << $1 << std::endl; }
;
expr: NUMBER { $$ = $1; }
| IDENT { $$ = $1; }
| '(' expr ')' { $$ = "( "s + $2 + " )"; }
| expr PLUS expr { $$ = "{ "s + $1 + " + " + $3 + " }"; }
| expr MINUS expr { $$ = "{ "s + $1 + " - " + $3 + " }"; }
| expr MULT expr { $$ = "{ "s + $1 + " * " + $3 + " }"; }
| expr DIV expr { $$ = "{ "s + $1 + " / " + $3 + " }"; }
| expr ASSIGN expr { $$ = "{ "s + $1 + " = " + $3 + " }"; }
%%
int yyerror(const char* error)
{
extern int current_line;
fprintf(stderr, "input:%d: error: %s\n", current_line, error);
return 0;
}
int main()
{
#if YYDEBUG
yydebug = 1;
#endif
yyparse();
return 0;
}
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