Why infinite loop for input elements, bigger than single digit.

astrogeek · 07-24-2023, 08:44 PM

Quote:

Originally Posted by ajiten

Thanks, but had no idea that only the first element of the array (i.e., spacing) would be picked up; if not specified the dimension of the array. Seems due to one pass compilation, C-language has this constraint. But, wouldn't there be garbage value for the variable: total_elements, rather than just containing the value = 1, each time the code is compiled & run (or might be it is specific to the www.onlinegdb.com compiler only); or is it that if the static array's dimension is un-specified, then only the first element is taken? Confused about that part.

What do you mean by static array?

It is all about the runtime value of total_elements, and the fact that it is indeterminate when first used. So you cannot make any assumptions about the runtime state of the spacing array either. If you think you saw some "default" C language behavior compensating for your error, you are likely mistaken.

Quote:

Originally Posted by ajiten

Also, if the last line of the code below is changed to the one shown below, then the array contents are not displayed. The ordering of the two statements (i.e., '++i', & 'printf(" %d ", *(int *) vals[i])') in the 3rd part of the for-loop is important, but unclear as why that matters?:

EDIT: I believe NevemTeve may have part of the actual answer to this part of your question in the next post.

Consider also that putting the printf(...) after increment of the loop control variable in the update expression may have unintended consequences. Using your example:

Code:

 for (int i=0; i<total_elements; ++i, printf(" %d ", *(int *) vals[i]))

The complete update expression, including the printf(...) will be executed before the incremented loop control is tested and will likely result in a missed first array member and at least one printf(...) execution (and use of illegal array index) beyond the bounds of the loop. It is confusing at best.

I think you have more than one problem with that loop construct and should probably rethink it. Again, I would suggest working that out in isolation from the rest of your code.

NevemTeve · 07-24-2023, 11:19 PM

> Also, if the last line of the code below is changed to the one shown below, then the array contents are not displayed. The ordering of the two statements (i.e., '++i', & 'printf(" %d ", *(int *) vals[i])') in the 3rd part of the for-loop is important, but unclear as why that matters?

There is a difference between printing vals[0]..vals[num-1] and printing elements vals[1]..vals[num], especially that there is no vals[num], that is an invalid index.

ntubski · 07-25-2023, 07:51 AM

Quote:

Originally Posted by pan64

that printf is not invoked at all, because the comma operator cannot invoke functions, just evaluate expressions.

A function call is an expression.

ajiten · 07-28-2023, 08:52 AM

Quote:

Originally Posted by ntubski

A function call is an expression.

Very sorry, but you seem to contradict what is quoted in your answer.

NevemTeve · 07-28-2023, 08:56 AM

That's what one call 'correction'.
Anyways, could you solve the digit-counting problem?