Vectors

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Vectors

 
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  #1
Dec 7th, 2009
Hey everyone,
im trying to get to know vectors but i came to a point that my current knowledge stops and i need more help,
i found a program which i would like to understand but i couldn't figure it out.
here is the code:
C++ Syntax (Toggle Plain Text) 
  1. #include<iostream>
  2. #include<vector>
  3. #include<string>
  4. #include<iterator>
  5. using namespace std;
  6.  
  7. bool islowerCase(char c)
  8. {
  9.   return islower(c);
  10. }
  11.  
  12. int main()
  13. {
  14.   const int size=10;
  15.   vector<char>v1;
  16.   vector<char>::iterator lastElem;
  17.  
  18.  
  19.   const char charList[size]={'w','W','b','B','C','E','w','F','B','m'};
  20.  
  21.  
  22.   for(int i=0;i<size; i++)
  23.     {
  24.       v1.push_back(charList[i]);
  25.  
  26.     }
  27.   lastElem =remove_if(v1.begin(), v1.end(), islowerCase);//line1
  28.   ostream_iterator<char> screen(cout, "");//line2
  29.  
  30.  
  31.   copy(v1.begin(), lastElem, screen);//line3
  32.   cout<<endl;
  33. }

can somebody explain to me line 1,2 and three (where it is shown as comments)
in detail because i am really struggling to understand how it works thanks a lot
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  #2
Dec 7th, 2009
Did you check your handy C++ library reference? Because it's all explained there, and a more specific question than "can you tell me everything I want to know?" is likely to encourage high quality answers.
In case you were wondering, yes, I do hate you.
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  #3
Dec 7th, 2009
C++ Syntax (Toggle Plain Text) 
  1. lastElem =remove_if(v1.begin(), v1.end(), islowerCase);//line1

Line 1 : remove_if(...), if the containers contains a lower case character
the function removes it. It does this, and returns the a pointer that
points to the new end since some elements has been deleted.

C++ Syntax (Toggle Plain Text) 
  1. ostream_iterator<char> screen(cout, "");//line2
Line 2 : creates an iterator. Just like the vector::iterator, ostream_iterator is an iterator. It can insert elements into the
ostream object, cout. When you do :
C++ Syntax (Toggle Plain Text) 
  1.  cout << 'a';
Its almost the same as if you do :
C++ Syntax (Toggle Plain Text) 
  1.  screen = 'a';
Its just doing it in a different way.

C++ Syntax (Toggle Plain Text) 
  1. copy(v1.begin(), lastElem, screen);//line3

Remember what I said, if you do screen = 'a'; It will print out a into the
console. So the above code roughly does screen = vec[0] ... vec[lastElement]. That means everything inside the vector is getting
printed to the screen.


Also check this out for some reference : remove_if , istream_iterator using std::copy 
Go ahead and try to solve  this  euler problem, if u can. Check with me for hints and 
answers. Good Luck
Solved by:tux4life, "your name here"
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  #4
Jan 5th, 2010
thank you guys for your help thanks a lot
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