a problem of iterator

[evenstar]

string str="this IS A example";
for(string::ite rator iter=str.begin( );
iter!=str.end() ;++iter)
{
if(isupper(*ite r))
{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?Tha nk you~

[JosAH]

string str="this IS A example";
for(string::ite rator iter=str.begin( );
iter!=str.end() ;++iter)
{
if(isupper(*ite r))
{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?Tha nk 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:

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>::it erator like

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]

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