whats the deal with break ?????

Hi !

I am newbie c programmer trying to understand some concepts. Here is a program i wrote which connects two pairs on integers in an array

for eg if u enter 2 3 i will link the two nodes
lets say u enter 3 4 next then i will link 3-4 and also 2-4 since 2 is already linked to 3.

PROBLEM :

I am confused over the break in line 33, when i enter a choice n the program should exit the while loop and display the changed array but infact it exits main() ??????????

maybe my concepts on break are wrong can anyone help me on this ????


Here is the code :

Code:

#include<stdio.h>

/*  ******************************************************************************************************** */
/*  This program creates new connection pairs b/w two elments and ignores if a connection (direct or indirect)
    already exists */
/*  ******************************************************************************************************** */


#define size 10
#define TRUE 1


int main()
{
    int i, p, q, t, id[size];                                         /* vairables used for spanning the array */
    char c;                                                           /* variable used to store the users choice to continue */
    
    for(i = 0; i < size; id[i] = i, printf("%d ", id[i]), i++);       /* initialize array to index and print it */   
    printf("\n");
    
    while(TRUE)
    {
            scanf("%d %d", &p, &q);                                   /* read two entries and check if they are connected */
            if(id[p] == id[q])
            {
                     printf("node %d-%d already exists\n", p, q);     /* if they are connected then ask for choice from user */
                     printf("do you wish to continue : y/n");
                     fflush(stdin);                                   /* flush newline in input buffer from scanf() */
                     c = getchar();
                     if('y' == c)
						 continue;
                     else
                         break;
            }
            else                                                      /* if not connected, connect them and all elements */
            {                                                         /* connected to them as well */
                for(t = id[p], i = 0; i < size; i++)
                      if(id[i] == t)
                               id[i] = id[q];
                printf("%d-%d node created\n", p, q);                 /* print the new node created and the new array */
                for(printf("new arrary is : "),i = 0; i < size; printf("%d ", id[i]), i++);
                printf("\n");
            }
    }
    
    for(printf("new arrary is : "),i = 0; i < size; printf("%d ", id[i]), i++);
    printf("\n");             
    return 0;
}

[EDIT]:
removed incorrect information.
[/EDIT]

Also search the FAQ for why using fflush(stdin); is bad.

This is the output I had -- what did you expect to be different?

C:\Test>test
0 1 2 3 4 5 6 7 8 9
2 3
2-3 node created
new arrary is : 0 1 3 3 4 5 6 7 8 9
3 4
3-4 node created
new arrary is : 0 1 4 4 4 5 6 7 8 9
3 4
node 3-4 already exists
do you wish to continue : y/nn
new arrary is : 0 1 4 4 4 5 6 7 8 9

[edit]getchar returns an int.

Originally Posted by nonpuz

break; will break out of one level of nesting...meaning

Code:

while (something)
  if (something)
    break;

will break out of the while, however this:

Code:

while (something)
  if (something)
    if (something)
      break;

Will break out of the first if statement and return to the while statement.

No.

A break statement terminates execution of the smallest enclosing switch or iteration statement.

hi !

the program behaves different when run from dos prompt and when run from dev-C++ compiler,

on the dev-C++ compiler when i enter a choice 'n' it just exits and does not display the final array instead the new window just closes ?????

oh and whay is fflush() bad and what could i used instead of that ???

Originally Posted by gemini_shooter

the program behaves different when run from dos prompt and when run from dev-C++ compiler,

on the dev-C++ compiler when i enter a choice 'n' it just exits and does not display the final array instead the new window just closes ?????

FAQ > How do I... (Level 1) > Stop my Windows Console from disappearing everytime I run my program?
FAQ > How do I... (Level 1) > How do I get my program to wait for a keypress?

Originally Posted by gemini_shooter

oh and whay is fflush() bad and what could i used instead of that ???

FAQ > Explanations of... > Why fflush(stdin) is wrong
FAQ > How do I... (Level 2) > Flush the input buffer

hi !

thanks for the links about the windows console,

i found a way to flush without using fflush as suggested by the faq but unfortunately i didn't really understand the explantion of why fflush(stdin) is bad, if someone could give me a simpler explanation, I am pretty new at this , sorry !!!!

Originally Posted by gemini_shooter

i didn't really understand the explantion of why fflush(stdin) is bad

fflush(stdin) is undefined behavior, just like integer overflow: it might appear to do exactly what you want, it might not.