/**

 * test/demos/parser/parser.yy

 * Copyright (C) 2008 Markus Broeker

 */

%{

   #include <stdio.h>

   #include <ctype.h>

   int regs[26];

   int base;

   int yyerror();

   int yylex();

%}

%start list

%token DIGIT LETTER

%left MINUS PLUS MUL DIV

%left UMINUS

%%

list:

    /* empty */

    | list stat '\n'

    | list error '\n' { yyerrok; };

stat:

    expr { (void) printf( "RESULT: %d\n", $1 ); }

    | LETTER '=' expr { regs[$1] = $3; }

    ;

expr:

    '(' expr ')'

    {

        $$ = $2;

    }

    | expr PLUS expr

    {

        $$ = $1 + $3;

    }

    | expr MINUS expr

    {

        $$ = $1 - $3;

    }

    | expr MUL expr

    {

        $$ = $1 * $3;

    }

    | expr DIV expr

    {

            $$ = $1 / $3;

    }

    | MINUS expr  %prec UMINUS

    {

        $$ = -$2;

    }

    | LETTER

    {

        $$ = regs[$1];

    }

    |  number

    ;

number:

    DIGIT

    {

        $$ = $1; base = ($1==0) ? 8 : 10;

    }

    | number DIGIT

    {

        $$ = base * $1 + $2;

    }

    ;

%%

int yyerror()

{

    printf("ERROR\n");

    return 0;

}

int yywrap()

{

    return 1;

}