DaniWeb Forum Index > Software Development > C++

C++ RSS

STL <map> question?

Please support our C++ advertiser: Intel Parallel Studio Home

•

Join Date: Sep 2004

Posts: 421

Reputation: JoBe is on a distinguished road

Solved Threads: 4

JoBe

Offline

Posting Pro in Training

STL <map> question?

Aug 27th, 2005

Hello ladies and gents,

Im reading about working with maps and there is small programm example shown in this chapter. Now, when I write this code into the MS VC C++ compiler and compile the code, I get like over 90 warnings, however, when pressing compile again, they all are gone

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <string>
#include <map>
 
using namespace std;
 
int main()
{
	typedef map<string, int, less<string> > maptype;
	maptype M;
 
	M["Jan"]   = 1234;
	M["Piet"]  = 9999;
	M["Piet"]  = 3456;
	M["Klaas"] = 5678;
 
	for(maptype::iterator i = M.begin(); i != M.end(); ++i)
		cout<< (*i).first <<" "<< (*i).second <<endl;
 
	cout<<"Press any key to continue!\n";
	cin.get();
 
	return 0;
}
#include <iostream>
#include <string>
#include <map>

using namespace std;

int main()
{
	typedef map<string, int, less<string> > maptype;
	maptype M;

	M["Jan"]   = 1234;
	M["Piet"]  = 9999;
	M["Piet"]  = 3456;
	M["Klaas"] = 5678;

	for(maptype::iterator i = M.begin(); i != M.end(); ++i)
		cout<< (*i).first <<" "<< (*i).second <<endl;

	cout<<"Press any key to continue!\n";
	cin.get();

	return 0;
}

Some examples of warning messages:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
main.cpp
c:\program files\microsoft visual studio\vc98\include\xtree(120) : warning C4786: 'std::_Tree<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::pair<std::basic_string<char,std::char_traits<char>,std::allocator<char> > const ,
int>,std::map<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,int,std::less<std::basic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<int> >::_Kfn,std::less<std::basic_string<char,std::char_traits<cha
r>,std::allocator<char> > >,std::allocator<int> >' : identifier was truncated to '255' characters in the debug information
        c:\program files\microsoft visual studio\vc98\include\map(46) : see reference to class template instantiation 'std::_Tree<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::pair<std::basic_string<char,std::char_traits<
char>,std::allocator<char> > const ,int>,std::map<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,int,std::less<std::basic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<int> >::_Kfn,std::less<std::ba
sic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<int> >' being compiled
        C:\Program Files\Microsoft Visual Studio\MyProjects\LAVbBoek\main.cpp(12) : see reference to class template instantiation 'std::map<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,int,std::less<std::basic_string<char,std
::char_traits<char>,std::allocator<char> > >,std::allocator<int> >' being compiled
main.cpp
c:\program files\microsoft visual studio\vc98\include\xtree(120) : warning C4786: 'std::_Tree<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::pair<std::basic_string<char,std::char_traits<char>,std::allocator<char> > const ,
int>,std::map<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,int,std::less<std::basic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<int> >::_Kfn,std::less<std::basic_string<char,std::char_traits<cha
r>,std::allocator<char> > >,std::allocator<int> >' : identifier was truncated to '255' characters in the debug information
        c:\program files\microsoft visual studio\vc98\include\map(46) : see reference to class template instantiation 'std::_Tree<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::pair<std::basic_string<char,std::char_traits<
char>,std::allocator<char> > const ,int>,std::map<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,int,std::less<std::basic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<int> >::_Kfn,std::less<std::ba
sic_string<char,std::char_traits<char>,std::allocator<char> > >,std::allocator<int> >' being compiled
        C:\Program Files\Microsoft Visual Studio\MyProjects\LAVbBoek\main.cpp(12) : see reference to class template instantiation 'std::map<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,int,std::less<std::basic_string<char,std
::char_traits<char>,std::allocator<char> > >,std::allocator<int> >' being compiled

Questions are:

1) What is causing these warnings the first time I compile?
2) How can I make sure that these warnings aren't shown from the first time I compile the code?
3) Why do those warnings don't appear the second time I compile this code?

•

Join Date: Sep 2004

Posts: 7,646

Reputation: Narue has a reputation beyond repute

Solved Threads: 721

Narue

Offline

Code Goddess

Re: STL <map> question?

Aug 27th, 2005

>1) What is causing these warnings the first time I compile?
The complete identifier is saved for debugging purposes when you compile in debug mode. However, because the internal identifier for templates can be ridiculously long, and the compiler only allows a length of 255 characters, everything after 255 characters has been cut off. The warning simply notifies you of that, and can be safely ignored.

>2) How can I make sure that these warnings aren't shown from the first time I compile the code?
Compile in release mode, or disable the warning with a pragma:

Help with Code Tags

C++ Syntax (Toggle Plain Text)

#pragma warning(disable:4786)

>3) Why do those warnings don't appear the second time I compile this code?
Probably because no changes were made to the source, so the file wasn't actually compiled because the current compilation was up to date.

I'm here to prove you wrong.

•

Join Date: Sep 2004

Posts: 421

Reputation: JoBe is on a distinguished road

Solved Threads: 4

JoBe

Offline

Posting Pro in Training

Re: STL <map> question?

Aug 27th, 2005

Thanks Narue

•

Join Date: Feb 2005

Posts: 466

Reputation: winbatch is on a distinguished road

Solved Threads: 18

winbatch

Offline

Posting Pro in Training

Re: STL <map> question?

Aug 27th, 2005

Also,

I think some of the warning messages go away with a newer version of visual studio (looks like 6.0/98 based on the paths in your warnings...)

•

Join Date: Jul 2005

Posts: 164

Reputation: Stoned_coder is an unknown quantity at this point

Solved Threads: 5

Stoned_coder Stoned_coder is offline

Offline

Junior Poster

Re: STL <map> question?

Aug 27th, 2005

use STLFilt

Give your C++ a BOOST
Need a Windows Compiler. Get one here.
Guru of the Week
Did you do all right at GOTW? Try these then!

•

Join Date: Sep 2004

Posts: 421

Reputation: JoBe is on a distinguished road

Solved Threads: 4

JoBe

Offline

Posting Pro in Training

Re: STL <map> question?

Aug 28th, 2005

Thanks for the additional information gentlemen :!:

Ive got another question and alltough it's not related to <map>, it is related towards STL.

There's a program shown in wich the uses of find_first_of and find_end are explained, now, I understand what find_first_of is doing, but can't figure out what the actual function of find_end is

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <algorithm>
#include <iostream>
 
using namespace std;
 
int main()
{
	int a[10] = {3, 2, 5, 7, 5, 8, 7, 5, 8, 5},
		b[2] = {5, 8}, *p1, *p2;
 
	p1 = find_first_of(a, a + 10, b, b + 2);
	p2 = find_end(a, a + 10, b, b + 2);
 
	cout<< p1 - a <<" "<< p2 - a <<endl;
 
	cout<<"Press any key to continue!\n";
	cin.get();
 
	return 0;
}
#include <algorithm>
#include <iostream>

using namespace std;

int main()
{
	int a[10] = {3, 2, 5, 7, 5, 8, 7, 5, 8, 5},
		b[2] = {5, 8}, *p1, *p2;

	p1 = find_first_of(a, a + 10, b, b + 2);
	p2 = find_end(a, a + 10, b, b + 2);

	cout<< p1 - a <<" "<< p2 - a <<endl;
	
	cout<<"Press any key to continue!\n";
	cin.get();

	return 0;
}

Output: 2 7

I understand where 2 comes from because comparing a[5] with b[5] puts it on the second place of a, starting from 0.

But, how does 7 becomes the output for find_end, I don't understand, is it also a position that is determined

The explanation that is given isn't really clear and doesn't really make sense, could someone explain what find_end actually does

•

Join Date: Sep 2004

Posts: 7,646

Reputation: Narue has a reputation beyond repute

Solved Threads: 721

Narue

Offline

Code Goddess

Re: STL <map> question?

Aug 28th, 2005

>could someone explain what find_end actually does
find_end is actually the reverse of search. search finds the first occurance of the second range in the first range, and find_end finds the last occurance of the second range in the first range. find_end is admittedly poorly named. This example may make more sense:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <algorithm>
#include <iostream>
 
using namespace std;
 
int main()
{
  int a[10] = {3, 2, 5, 7, 5, 8, 7, 5, 8, 5},
    b[2] = {5, 8}, *p1, *p2;
 
  p1 = search(a, a + 10, b, b + 2);
  p2 = find_end(a, a + 10, b, b + 2);
 
  cout<< p1 - a <<" "<< p2 - a <<endl;
 
  return 0;
}
#include <algorithm>
#include <iostream>

using namespace std;

int main()
{
  int a[10] = {3, 2, 5, 7, 5, 8, 7, 5, 8, 5},
    b[2] = {5, 8}, *p1, *p2;

  p1 = search(a, a + 10, b, b + 2);
  p2 = find_end(a, a + 10, b, b + 2);

  cout<< p1 - a <<" "<< p2 - a <<endl;

  return 0;
}

search looks for the first occurance of {5, 8}, which is at index 4. find_end does the opposite and looks for the last occurance of {5, 8}, which is at index 7.