%{
extern int yylval;
extern int sym[];
extern int yyerror(char *s);
#include "y.tab.h"
%}

%%

[a-z]   {
           yylval = *yytext - 'a';
           return VARIABLE;
        }

[0-9]+  {
           yylval = atoi(yytext);
           return INTEGER;
        }

[(),]   { return *yytext; }

":="    return ASSIGN;
"+"     return PLUS;
"-"     return MINUS;
"/"     return DIVIDE;
"%"     return MODULO;
"*"     return TIMES;
"<"     return SMAS;
"<="    return SMGAS;
"=="    return IS;
"!="    return NOTIS;
">="    return BGGAS;
">"     return BGAS;

"min"   return MIN;
"max"   return MAX;

"n"    return NEWLINE;

[ t]   ;

.       yyerror("Invalid character");

%%

int yywrap() {
 return 1;
}

%{
#include <stdio.h>
int sym[26];
int yylex();
int yyerror(char *s);
%}

%token VARIABLE ASSIGN INTEGER NEWLINE
%left PLUS
%left TIMES
%left MINUS
%left DIVIDE
%left MODULO
%left UMINUS
%left UPLUS
%left SMAS SMGAS IS NOTIS BGAS BGGAS
%left MIN MAX

%%

program: program statement
       |
       ;

statement: expr NEWLINE
             { printf("%dn", $1); }
         | VARIABLE ASSIGN expr NEWLINE
             { sym[$1] = $3; }
         ;

expr: INTEGER            { $$ = $1; }
      | VARIABLE         { $$ = sym[$1]; }
      | expr PLUS expr   { $$ = $1 + $3; }
      | expr TIMES expr  { $$ = $1 * $3; }
      | expr MINUS expr  { $$ = $1 - $3; }
      | expr DIVIDE expr { $$ = $1 / $3; }
      | expr MODULO expr { $$ = $1 % $3; }
      | '(' expr ')'     { $$ = $2;      }

      | MINUS expr %prec UMINUS { $$ = -$2; }
      | PLUS expr %prec UPLUS { $$ = $2; }

      | expr SMAS  expr   { $$ = $1 < $3;  }
      | expr SMGAS expr   { $$ = $1 <= $3; }
      | expr IS    expr   { $$ = $1 == $3; }
      | expr NOTIS expr   { $$ = $1 != $3; }
      | expr BGGAS expr   { $$ = $1 >= $3; }
      | expr BGAS  expr   { $$ = $1 > $3;  }

      | MIN '(' expr ',' expr ')' { if ($3 < $5){ $$ = $3; } else if ($3 > $5){ $$ = $5; }; }
      | MAX '(' expr ',' expr ')' { if ($3 > $5){ $$ = $3; } else if ($3 < $5){ $$ = $5; }; }

      ;

%%

int yyerror(char *s) {
  fprintf(stderr, "%sn", s);
  return 0;
}

int main() {
  yyparse();
  return 0;
}