c# for loop wrong number of iterations

Question

I am writing a function that iterates through string[] array and adds some objects into lists. It is a part of loading saved game system. It has a lot of buggs yet, because I wrote a lot of code, before can test any of it. But in this debugging phase I found some weird bug, that am not able to explain or fix.
I cant access some of data. If I have original code, for-loop iterates 1 time less then needed. If I add +1 to iterator limit, it acts normally. To conclude, I can iterate either -1 or +1 times, but not as much as I need.
This is the original code, which iterates one time less than expected:

string str = " start at " + Convert.ToInt32(s[k]) + " " + k;
        for (int i = 0; i < Convert.ToInt32(s[k]); i++)
        {
            k++;
            landOwned.Add(setle.civil.land[Convert.ToInt32(s[k]), Convert.ToInt32(s[k+1])]);
            k++;
            str += "  iteration "+i + " finish " + k;
        }
        throw new ArgumentException(str);

This is the line in text file:

f 4894 0 250 -523058 0 0 0 0 0 0 0 0 0 0 0 0 0 35 35 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4 3 4 2 4 3 3 4 4 1 0 1 0 1 0 1 2

Here are screenshots of exeptions catched:

enter image description here

your for loop end point changes throughout the loop is that intended? — Sayse
– Sayse, Commented Jul 4, 2013 at 21:31

competent_tech · Accepted Answer · 2013-07-04 21:33:08Z

6

The problem is that a variable that is used in your loop end test (k) is incremented within the loop.

Changing the loop to the following should resolve the problem:

    var endIndex = Convert.ToInt32(s[k]);
    for (int i = 0; i < endIndex; i++)

answered Jul 4, 2013 at 21:33

competent_tech

45.1k12 gold badges96 silver badges114 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Sayse Over a year ago

I should just go with gut instinct more often than waiting for more from OP; +1

Kiaurutis Over a year ago

U mean for-loop checks i < Convert.ToInt32(s[k]) every iteration? That would mean for-loop has to hold this function in call stack for every iteration D: I need to know more about this behavior. Always thought, that parameter of function is passed by value or reference, but not as a whole function. Should I start new question to know about this stuff, or someone can give a hint for what to search to know more about it?

Sayse Over a year ago

@user1742303 - I've added an answer to explain

Sayse · Accepted Answer · 2013-07-05 08:26:25Z

2

In answer to your comment,

you can treat a for loop as the following

int i = 0;
while(i < something){
//...


i++
}

every iteration, the check within the while loop will be checked again to see if I is still less than a value, this means in your situation it is converting "something" into an integer every iteration. @competent_techs solution will store the initial value of this into a separate variable that will then just store the value for the check to look at

answered Jul 5, 2013 at 8:26

Sayse

43.4k14 gold badges85 silver badges150 bronze badges

1 Comment

Kiaurutis Over a year ago

Thank U very much. Now I understand that for-loop is not a method, but a packed up set of basic instructions (user level instructions). Something like inlined method.

Collectives™ on Stack Overflow

c# for loop wrong number of iterations

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related