Visual C++ update

[Stark Mathews]

Here is the new code. Sorry about spamming like this:

/*BEGIN BISON PARSER SECTION */

%{
  #define YYSTYPE int
  int yylex();
  void yyerror(char *error);

  #include <math.h>
  #include <MALLOC.h>
%}

%token NUM
%left '+' '-'
%left '*' '/'
%left NEGATE
%right '^'

%%
input: /* empty */;
input: input line;

line: '\n' { printf("ping.\n"); };
line: exp '\n'  { printf("result: %d\n", $1); };

exp: NUM                                { $$ = $1; };
exp: exp '+' exp            { $$ = $1 + $3; };
exp: exp '-' exp                  { $$ = $1 - $3; };
exp: exp '*' exp                              { $$ = $1 * $3; };
exp: exp '/' exp                              { $$ = $1 / $3; };
exp: '-' exp %prec NEGATE   { $$ = -$1; };
exp: exp '^' exp            { $$ = (int)pow($1, $3); };
%%

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <ctype.h>
#include <conio.h>

int yylex(){
  int result = ' ';

  while (result == ' ' || result == '\t') result = getchar();

  if (isdigit(result)){
    ungetch(result);
    scanf("%d", &yylval);
    return NUM;
  }

  if (result == '^') return 0;

  return result;
};

void yyerror(char *error){
  printf(error);
};


/*END BISON PARSER SECTION*/

void main(void){
  yyparse();
};

I have gotten this to compile and run, but nothing is printed to the screen
except what I type. Why is this process so easy for Linux users?