Thread: long problem

I have this problem i solved from a book. When i try to compile it using turbo C i get output #1 , while with MVC++ i get output #2. Obviously the first output has a problem. has turbo C has a long variable problem or did i just do something wrong here?

Output #1
(1) Total: 0
(2) Total: 0
(3) Total: 0
(4) Total: 0
(5) Total: 0
(6) Total: 0
(7) Total: 0
(8) Total: 0
(9) Total: 0
(10) Total: 0
(11) Total: 0
(12) Total: 0

Output #2
(1) Total: 0
(2) Total: 1051
(3) Total: 2024
(4) Total: 3027
(5) Total: 4018
(6) Total: 4869
(7) Total: 6018
(8) Total: 5007
(9) Total: 3968
(10) Total: 2979
(11) Total: 2012
(12) Total: 1027

PHP Code:

#include<stdio.h>
#include<time.h>
#include<stdlib.h>

#define TOTAL_ROLL 36000

int main()
{
    long result[12] = { 0 };
    long rollnum = 0, ipos;
    int dice1, dice2, ires;

    clrscr(); /* removed in mvc++ */
    srand( time( 0 ) );

    for( rollnum = 0; rollnum != TOTAL_ROLL; rollnum++ ){
        dice1 = ( rand() % 6 ) + 1;
        dice2 = ( rand() % 6 ) + 1;
        ires = dice1 + dice2;
        result[ires-1]++;
    }

    for( ipos = 0; ipos != 12; ipos++ ){
        printf( "(%d) Total: %d\n", ipos+1, result[ipos] );
    }

    getch(); /* removed in mvc++ */
    return 0;
} 


What Microsoft Visual are you using there, is it 6.0, 2003 or 2005?

Im using 6.0

result array holds junk

What do you mean it holds junk?

This is better code:

Code:

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#define	NITER	36000
#define	NRES	12

int main(void)
{
	long	result[NRES];
	size_t	i;
	
	srand(time(0));
	memset(result, 0, sizeof(result));

	for (i = 0; i < NITER; i++)
		result[rand() % NRES]++;

	for(i = 0; i < NRES; i++)
		printf("(%d) Total: %d\n", i, result[i]);

	return (EXIT_SUCCESS);
}

when I say it holds junk, i mean exactly what I said.
uninitialized variables hold junk. Read your C book.

Originally Posted by valenok

This is better code:

Code:

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#define	NITER	36000
#define	NRES	12

int main(void)
{
	long	result[NRES];
	size_t	i;
	
	srand(time(0));
	memset(result, 0, sizeof(result));

	for (i = 0; i < NITER; i++)
		result[rand() % NRES]++;

	for(i = 0; i < NRES; i++)
		printf("(%d) Total: %d\n", i, result[i]);

	return (EXIT_SUCCESS);
}

This doesnt output the desired output though it works.

The problem is though. I have 2 dice. A dice has 1 to 6 value.
The value of the result of the 2 dice should be added. So there should be no incrementation on index 1 and 2 coz the lowest value you could get from 1 dice is 1, so 1 + 1 = 2. Your code increments even those indexes. Value 7 has the highest result rate.

result[12] is out of bounds. increase the array size.
if you want to duplicate the logic, do:

Code:

result[(rand() % 6) + (rand() % 6) + 2]++;

yeah. printf modifier for long is %ld, so use

Code:

printf("(%d) Total: %ld\n", i, result[i]);

Originally Posted by valenok

result[12] is out of bounds. increase the array size.
if you want to duplicate the logic, do:

Code:

result[(rand() % 6) + (rand() % 6) + 2]++;

That was a lot lesser code than mine and it works perfect.
So what do you think i did wrong with mine though?

Just the ipos declaration. Stupid turbo C

1. you did not initialize result array properly
2. you wrote behind array bounds (result[12])
3. you printed results using %d, not %ld, that's why it did not work with Turbo C.

Originally Posted by valenok

1. you did not initialize result array properly
2. you wrote behind array bounds (result[12])
3. you printed results using %d, not %ld, that's why it did not work with Turbo C.

1. i didnt write out of bounds. the dice result would only generate 2 to 12 minus 1. Thats just enough for the array. There is no way i could have written out of bounds

2. Whats the proper way to initialize an array?

3. Yeah i forgot about that.

I redeclared ipos as int for some stupid reason it worked.

Originally Posted by loko

1. i didnt write out of bounds. the dice result would only generate 2 to 12 minus 1. Thats just enough for the array. There is no way i could have written out of bounds

yes you did. maximum index you had was 12.
for array of size 12 maximum index is 11.

2. Whats the proper way to initialize an array?

either declare it static, which implicitely zeroes the array,
or call memset().