Thread: break in for loop not working

Simple: a "break" breaks only the loop that is in, no other. Here you have two loops!

EDIT: Use something like:

Code:

for (i = 0; i < 10; i++){
    for (j = 0; j < 10; j++){
        // Break however you want in here
    }

    if (j < 10)
        break;
}

That is of course only one of the ways to do it.

Originally Posted by dylan

Just before the break set the i to 10 (or greater).
Then the first for loop will stop.

Dylan

Nice trick. But remember that it's a good programming practice to not change the value of counters inside the loops.

Originally Posted by Sipher

Nice trick. But remember that it's a good programming practice to not change the value of counters inside the loops.

Like most things described as "good practice", there are multiple views on what "good" really means.

A technique, if you want to avoid changing counters inside their loops, is

Code:

for(i = 0, barrel_on = true; barrel_on && i <10; i++)
{      
        for(j = 0; barrel_on && j <cols; j++)
        {    
          scanf("%d", &matrix[i][j]);
          if(isalpha(matrix[i][j])) barrel_on = false;
         }
}

Or (at the risk of encouraging cries of horror from the "goto is evil" crowd)

Code:

for(i = 0; i <10; i++)
{      
        for(j = 0; j <cols; j++)
        {    
          scanf("%d", &matrix[i][j]);
          if(isalpha(matrix[i][j]))  goto break_out;
         }
}
break_out:

How is isalpha ever going to be true for something that was read in using %d inside scanf!
It's never going to break because an int is never an alphabetical character. Try checking the return value of scanf instead.

Originally Posted by iMalc

How is isalpha ever going to be true for something that was read in using %d inside scanf!

Easily. Assuming your machine has an ASCII character set, the letter 'A' has a value of 65. isalpha() accepts a value of type int, and it is fairly easy for a user to enter 65 into an int via scanf's %d format.

I suspect the actual question you wanted to ask is: why you would want to check integral values entered by the user with isalpha()?

Ahem ... %d doesn't read alphabetical characters ... ahem ( Damm this cold! )

Ohh the number is a letter trick, e? What if my PC does run on ASCII?!

Originally Posted by CommonTater

Most do...

Sorry, I meant "doesn't".

Anyway, what I said earlier is that because scanf("%d", ...) doesn't accept letters such as 'a' or 'Z', there is no point at checking for them with isalpha afterwards.

Originally Posted by Sipher

Sorry, I meant "doesn't".

Anyway, what I said earlier is that because scanf("%d", ...) doesn't accept letters such as 'a' or 'Z', there is no point at checking for them with isalpha afterwards.

Then it would false trigger on different values...

I agree using isalpha() in that situation is wrong... what if the value 65 (continuing the example) is a valid entry for his int matrix[][] array? The isalpha() function would falsely terminate the loop...