%{
#include <cstdio>
#include <string>
#define YYDEBUG 1						<-- set debug on
%}

%start input
%token DIGIT
%left '+' '-'
%left '*' '/'
%name-prefix="Scalc"						<-- classname prefix (ScalcPushParser)
%%
input:  /* empty */						|
        | input line						|
        ;							|
								|
line:   '\n'							|
        | exp '\n'              { printf ("\t%d\n", $1); }	|
        ;							|
								|	pull grammar == push grammar
exp:    DIGIT                   { $$ = $1;           }		|
        | exp '+' exp           { $$ = $1 + $3;      }		|
        | exp '-' exp           { $$ = $1 - $3;      }		|
        | exp '*' exp           { $$ = $1 * $3;      }		|
        | exp '/' exp           { $$ = $1 / $3;      }		|
        | '-' exp               { $$ = -$2;          }		|
        ;							|
%%

class MyScalcPushParser:public ScalcPushParser			<-- implement debugPrint(...) and yyerror(...)
{
    private:
    virtual void debugPrint(int aInt) const
    {
	printf("%d",aInt);
    }
    virtual void debugPrint(std::string s) const
    {
	printf("%s",s.c_str());
    }
    public:
    MyScalcPushParser() {}
    virtual void yyerror(const char* s) const
    {
        printf("%s\n",s);
    }
};

void lex(MyScalcPushParser *parser)		
{
    MyScalcPushParser::SemanticType token;
    while((token=fgetc(stdin))!=EOF) {
        if(isblank(token)) {
            continue;
        }
        if(isdigit(token)) {
            ungetc(token,stdin);
            scanf("%d",&token);
            parser->parseToken(DIGIT,token);			<-- instead of return(...) parseToken(...)
        } else {
            parser->parseToken(token,token);
        }
    }
    parser->parseToken(0,token);				<-- parse EOF
    return;
}

int main()
{
    MyScalcPushParser *parser=new MyScalcPushParser();
    parser->setDebug(1);
    lex(parser);
    delete parser;
    return 0;
}