c++ variable keeps resetting instead of incrementing? [closed] - c++

Question

Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers.
This question was caused by a typo or a problem that can no longer be reproduced. While similar questions may be on-topic here, this one was resolved in a way less likely to help future readers.
Closed 8 years ago.
Improve this question
void RetailerOrder::addItem(Product* p)
{
bool space = false;
int counter = 0;
while ((space == false) && (counter < manifest.size()))
{
if (manifest[counter] == nullptr);
{
manifest[counter] = p;
space = true;
}
counter++;
}
if (space == false)
{
cout << "no space" << endl;
}
}
Why does the counter reset to zero with each pass through the while loop? If I use it as it is, only the last product that I enter gets stored in the array because i is always 1. Is there a way to let the counter increase.

Answer 1

if (manifest[counter] == nullptr); // << see here
{
manifest[counter] = p;
space = true;
}
That semi-colon at the end of your if statement means "if condition, do nothing".
Then the braced scope following that executes always.
It should instead be:
if (manifest[counter] == nullptr)
{
manifest[counter] = p;
space = true;
}
As an aside, I'm not a big fan of things like:
if (space == false) ...
since, if you name you boolean values intelligently, you can avoid the comparisons:
if (! foundSpace) ...
The intelligent naming means that the boolean variable itself should be readable, such as with foundSpace or haveFinished or userIsClinicallyInsane. Once it is, you don't need to compare it to boolean constants at all.
That greatly reduces the code size and avoids the reductio-ad-absurdum situation where you don't know when to stop comparing booleans to constants:
if ((((haveFinished == true) == true) != false) == true) ...
As a second aside, I value my vertical space greatly when looking at code and there are ways to simplify your code which make it shorter and, in my opinion, easier to understand.
Since you're only using space as a way to insert the item and exit the loop prematurely, you could use something like:
void RetailerOrder::addItem (Product* p) {
// Check every possible slot.
for (int i = 0; i < manifest.size(); i++) {
// If one free, use it and exit.
if (manifest[i] == nullptr) {
manifest[i] = p;
return;
}
}
// None were free, complain bitterly.
cout << "no space" << endl;
}
Still, that's a stylistic approach of mine and you should feel free to ignore it if you disagree.
The "multiple return points are bad" crowd may not like it but that's usually because they don't understand the reason why it's considered suspect, the inability to easily see the many code paths. With a function of this size, it's not really a issue.