a problem of iterator

evenstar

string str="this IS A example";
for(string::iterator iter=str.begin();
iter!=str.end();++iter)
{
if(isupper(*iter))
{str.erase(iter);
--iter;}
}

cout<<str<<endl;
after "str.erase(iter);" i think iter will be an ivalidated iterator .But the code is correct.Why?Thank you~

JosAH

Quote:

Originally Posted by evenstar

string str="this IS A example";
for(string::iterator iter=str.begin();
iter!=str.end();++iter)
{
if(isupper(*iter))
{str.erase(iter);
--iter;}
}

cout<<str<<endl;
after "str.erase(iter);" i think iter will be an ivalidated iterator .But the code is correct.Why?Thank you~

On your implementation it seems to run but on other implementations it can make daemons fly out of your nose. Better make your loop do this:

Expand|Select|Wrap|Line Numbers

 
for(string::iterator iter=str.begin(); iter!=str.end(); ) 

   if (isupper(*iter))

      iter= str.erase(iter);

   else

      iter++;

kind regards,

Jos

evenstar

I know use iterator like "iter= str.erase(iter);"is a good custom.But i puzzle that use a vector<int>::iterator like

Quote:

vec.erase(iter); //vec is a object of vector
iter--;

will lead a RUNTIME ERROR. Why this kind of error would not happen to object of string .(in Visual Studio 2008)

JosAH

Quote:

Originally Posted by evenstar

I know use iterator like "iter= str.erase(iter);"is a good custom.But i puzzle that use a vector<int>::iterator like

will lead a RUNTIME ERROR. Why this kind of error would not happen to object of string .(in Visual Studio 2008)

That can also happen with the string class, it depends on its implementation; suppose the string class reallocates its buffer after it had become less than half full; the buffer probably ends up somewhere else in memory leaving any pointers to the old buffer (kept by the iterator) invalid.

Simply assume that all iterators become invalid after an erase() operation and use the iterator returned by that erase() operation instead.

kind regards,

Jos

evenstar

I see，and appreciate your help very much.

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