problem with iterator (map iterator)

Newsgroup: comp.lang.c++

Subject: problem with iterator (map iterator)

From: Jim Anderson <jjanderson52000@...>

Date: Fri, 10 Jan 2014 08:52:20 -0500



I'm writing a small program that will use a map (i.e. map<string,int>).

it has been a while since I have written in c++, so I found an example

on the internet and modified it for my own use. But when I try to

compile my program, I get a compile error.



The code looks ok to me, so I did a search on the internet to see if

others had the same problem. I found 3 or 4 examples, but the solutions

were all related to using an iterator, when infact a const_iterator

should be used. That is not the cause of my problem, as near as I can tell.



I have reduced my code to a simple example:



1

2 #include <iostream>

3 #include <map>

4 #include <string>

5

6 using namespace std;

7

8 int main()

9 {

10 map<string, int> totals;

11

12 totals.insert(std::pair<string,int>("NJ",10));

13 totals.insert(std::pair<string,int>("NY",20));

14 totals.insert(std::pair<string,int>("PA",30));

15 totals.insert(std::pair<string,int>("CT",40));

16

17 map<int,string>::iterator iter;

18 for(iter = totals.begin(); iter != totals.end(); ++iter) {

19 cout << (*iter).first << ": " << (*iter).second << endl;

20 }

21 }





I'm using the GNU compiler g++ version 4.4.5 on crunchbang linux. The

compile error messages are:



1 g++ -g -Wall -I/home/jja/bfs/include -DLINUX -c problem.cc

2 problem.cc: In function ?int main()?:

3 problem.cc:18: error: no match for ?operator=? in ?iter =

totals.std::map<_Key, _Tp, _Compare, _Alloc>::begin [ with _Key =

std::basic_string<char, std::char_traits<char>, std::allocator<char> >,

_Tp = int, _Compare = std:: less<std::basic_string<char,

std::char_traits<char>, std::allocator<char> > >, _Alloc =

std::allocator<std::pai r<const std::basic_string<char,

std::char_traits<char>, std::allocator<char> >, int> >]()?

4 /usr/include/c++/4.4/bits/stl_tree.h:154: note: candidates are:

std::_Rb_tree_iterator<std::pair<const int, std ::basic_string<char,

std::char_traits<char>, std::allocator<char> > > >&

std::_Rb_tree_iterator<std::pair<const int, std::basic_string<char,

std::char_traits<char>, std::allocator<char> > > >::operator=(const

std::_Rb_tree _iterator<std::pair<const int, std::basic_string<char,

std::char_traits<char>, std::allocator<char> > > >&)

5 problem.cc:18: error: no match for ?operator!=? in ?iter !=

totals.std::map<_Key, _Tp, _Compare, _Alloc>::end [ with _Key =

std::basic_string<char, std::char_traits<char>, std::allocator<char> >,

_Tp = int, _Compare = std:: less<std::basic_string<char,

std::char_traits<char>, std::allocator<char> > >, _Alloc =

std::allocator<std::pai r<const std::basic_string<char,

std::char_traits<char>, std::allocator<char> >, int> >]()?

6 /usr/include/c++/4.4/bits/stl_tree.h:216: note: candidates are:

bool std::_Rb_tree_iterator<_Tp>::operator!=(co nst

std::_Rb_tree_iterator<_Tp>&) const [with _Tp = std::pair<const int,

std::basic_string<char, std::char_trai ts<char>, std::allocator<char>

> >]

7 make: *** [problem.o] Error 1





Can anyone help explain the compile errors/



Jim Anderson

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