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Mar 5th, 2009

map in STL

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hi guys, im trying to do map in cpp using STL and when i ran a simple program it was showing error that:
error:
nomatchfor'operator<<'in'std::cout<<(&mp0_iter)->std::_Rb_tree_iterator<_Tp>::operator* [with _Tp = std::pair<const int, int>]()'....
my program was like this:

c++ Syntax (Toggle Plain Text)
#include<map.h>
#include<iostream.h>
 
int main()
{
        map<int,int>::iterator mp0_iter;
        map<int,int>mp0;
        map<int,int>mp1;
 
        mp1.insert(1,13);
        mp1.insert(2,16);
        mp1.insert(3,17);
 
        for(mp0_iter=mp1.begin();mp0_iter!=mp1.end();mp0_iter++)
                {
                        cout<<*mp0_iter<<' ';
                }
        cout<<endl;
 
        return(0);
}
#include<map.h>
#include<iostream.h>

int main()
{
        map<int,int>::iterator mp0_iter;
        map<int,int>mp0;
        map<int,int>mp1;

        mp1.insert(1,13);
        mp1.insert(2,16);
        mp1.insert(3,17);

        for(mp0_iter=mp1.begin();mp0_iter!=mp1.end();mp0_iter++)
                {
                        cout<<*mp0_iter<<' ';
                }
        cout<<endl;

        return(0);
}

Last edited by karthik.c; Mar 5th, 2009 at 8:07 am.

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Hash in STL in C++
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karthik.c

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Mar 5th, 2009

Re: hash map in STL

The map as a whole can not displayed using cout. Try

Quote ...

cout << *mp0_iter.first() << *mp0_iter.second() << '\n';

kbshibukumar

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Mar 5th, 2009

Re: hash map in STL

>cout << *mp0_iter.first() << *mp0_iter.second() << '\n';
This won't work, for several reasons. To begin with, first and second are not member functions. Also, the member operator binds more tightly than the indirection operator, so you're trying to call the first and second member functions (which still don't exist) on the iterator itself rather than the value type. You need to wrap the indirection in parens:

C++ Syntax (Toggle Plain Text)
cout << (*mp0_iter).first << (*mp0_iter).second << '\n';
cout << (*mp0_iter).first << (*mp0_iter).second << '\n';

In sufficiently conforming versions of the standard library, the -> operator is defined and you can use that instead:

C++ Syntax (Toggle Plain Text)
cout << mp0_iter->first << mp0_iter->second << '\n';
cout << mp0_iter->first << mp0_iter->second << '\n';

>mp1.insert(1,13);
>mp1.insert(2,16);
>mp1.insert(3,17);
The map class doesn't have an overload of the insert member function that takes a key/value pair as two arguments. You'd have to create your own pair object first:

C++ Syntax (Toggle Plain Text)
mp1.insert ( make_pair ( 1, 13 ) );
mp1.insert ( make_pair ( 2, 16 ) );
mp1.insert ( make_pair ( 3, 17 ) );
mp1.insert ( make_pair ( 1, 13 ) );
mp1.insert ( make_pair ( 2, 16 ) );
mp1.insert ( make_pair ( 3, 17 ) );

But that's effort you can avoid by taking advantage of the subscript operator overload:

C++ Syntax (Toggle Plain Text)
mp1[1] = 13;
mp1[2] = 16;
mp1[3] = 17;
mp1[1] = 13;
mp1[2] = 16;
mp1[3] = 17;

Narue

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Mar 6th, 2009

Re: hash map in STL

thanks narue ,i tried out both ways of inserting:using pair object and operator overload and program is working fine.

karthik.c

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Mar 6th, 2009

Re: hash map in STL

hi again,im having some problem while coding with hash_map
my coding was like this:

c++ Syntax (Toggle Plain Text)
#include<iostream>
#include<hash_map>
using namespace std;
 
int main()
{
        typedef pair<int,int>make_pair;
        hash_map<int,int>::iterator hmp0_iter;
 
        hash_map<int,int>hmp0;
 
        hmp0.insert(make_pair(1,78));
        hmp0.insert(make_pair(3,34));
 
        for(hmp0_iter=hmp0.begin();hmp0_iter!=hmp0.end();hmp0_iter++)
        {
                cout<<(*hmp0_iter).second<<' ';
        }
        cout<<endl;
 
        return(0);
}
#include<iostream>
#include<hash_map>
using namespace std;

int main()
{
        typedef pair<int,int>make_pair;
        hash_map<int,int>::iterator hmp0_iter;

        hash_map<int,int>hmp0;

        hmp0.insert(make_pair(1,78));
        hmp0.insert(make_pair(3,34));

        for(hmp0_iter=hmp0.begin();hmp0_iter!=hmp0.end();hmp0_iter++)
        {
                cout<<(*hmp0_iter).second<<' ';
        }
        cout<<endl;

        return(0);
}

error was like this:
hashdemo.cpp:2:19: hash_map: No such file or directory
hashdemo.cpp: In function `int main()':
hashdemo.cpp:8: error: `hash_map' was not declared in this scope
hashdemo.cpp:8: error: expected primary-expression before "int"
hashdemo.cpp:8: error: expected `;' before "int"
hashdemo.cpp:10: error: expected primary-expression before "int"
hashdemo.cpp:10: error: expected `;' before "int"
hashdemo.cpp:12: error: `hmp0' was not declared in this scope
hashdemo.cpp:15: error: `hmp0_iter' was not declared in this scope

but when i replaced #include<hash_map>with #include<hash_map.h>the program ran and printed the output but it did showed some warnings saying im using deprecated header.

im workin in linux using gcc(version3.4.6)so does it support hashmap??

karthik.c

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Mar 6th, 2009

Re: hash map in STL

I don't know if there is any stl hash_map. U need to use just map instead, with a #include <map>

Quote ...

map<int,int>::iterator hmp0_iter;
map<int,int>hmp0;

kbshibukumar

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Mar 6th, 2009

Re: hash map in STL

hi shibukumar, i actually was trying to program the code which was given in a site where they are using hash_map at the same time they are also saying hashtable Datastructure is not part of c++ standard library.

http://www.tenouk.com/Module29a.html
so what if their is any way to do it??

karthik.c

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Jan 8th, 2010

Re: hash map in STL

Click to Expand / Collapse Quote originally posted by karthik.c ...

hi again,im having some problem while coding with hash_map
my coding was like this:
c++ Syntax (Toggle Plain Text)
#include<iostream>
#include<hash_map>
using namespace std;
 
int main()
{
        typedef pair<int,int>make_pair;
        hash_map<int,int>::iterator hmp0_iter;
 
        hash_map<int,int>hmp0;
 
        hmp0.insert(make_pair(1,78));
        hmp0.insert(make_pair(3,34));
 
        for(hmp0_iter=hmp0.begin();hmp0_iter!=hmp0.end();hmp0_iter++)
        {
                cout<<(*hmp0_iter).second<<' ';
        }
        cout<<endl;
 
        return(0);
}
#include<iostream> #include<hash_map> using namespace std; int main() { typedef pair<int,int>make_pair; hash_map<int,int>::iterator hmp0_iter; hash_map<int,int>hmp0; hmp0.insert(make_pair(1,78)); hmp0.insert(make_pair(3,34)); for(hmp0_iter=hmp0.begin();hmp0_iter!=hmp0.end();hmp0_iter++) { cout<<(*hmp0_iter).second<<' '; } cout<<endl; return(0); }
error was like this:
hashdemo.cpp:2:19: hash_map: No such file or directory
hashdemo.cpp: In function `int main()':
hashdemo.cpp:8: error: `hash_map' was not declared in this scope
hashdemo.cpp:8: error: expected primary-expression before "int"
hashdemo.cpp:8: error: expected `;' before "int"
hashdemo.cpp:10: error: expected primary-expression before "int"
hashdemo.cpp:10: error: expected `;' before "int"
hashdemo.cpp:12: error: `hmp0' was not declared in this scope
hashdemo.cpp:15: error: `hmp0_iter' was not declared in this scope

but when i replaced #include<hash_map>with #include<hash_map.h>the program ran and printed the output but it did showed some warnings saying im using deprecated header.

im workin in linux using gcc(version3.4.6)so does it support hashmap??

Hash_map signature is wrong refer <ext/hash_map>
5 parameter need to be passed

ambi_

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Apr 2nd, 2010

Re: hash map in STL

The namespaceof hash_map is not std. Check the include file <hash_map>.

Click to Expand / Collapse Quote originally posted by karthik.c ...

hi again,im having some problem while coding with hash_map
my coding was like this:
c++ Syntax (Toggle Plain Text)
#include<iostream>
#include<hash_map>
using namespace std;
 
int main()
{
        typedef pair<int,int>make_pair;
        hash_map<int,int>::iterator hmp0_iter;
 
        hash_map<int,int>hmp0;
 
        hmp0.insert(make_pair(1,78));
        hmp0.insert(make_pair(3,34));
 
        for(hmp0_iter=hmp0.begin();hmp0_iter!=hmp0.end();hmp0_iter++)
        {
                cout<<(*hmp0_iter).second<<' ';
        }
        cout<<endl;
 
        return(0);
}
#include<iostream> #include<hash_map> using namespace std; int main() { typedef pair<int,int>make_pair; hash_map<int,int>::iterator hmp0_iter; hash_map<int,int>hmp0; hmp0.insert(make_pair(1,78)); hmp0.insert(make_pair(3,34)); for(hmp0_iter=hmp0.begin();hmp0_iter!=hmp0.end();hmp0_iter++) { cout<<(*hmp0_iter).second<<' '; } cout<<endl; return(0); }
error was like this:
hashdemo.cpp:2:19: hash_map: No such file or directory
hashdemo.cpp: In function `int main()':
hashdemo.cpp:8: error: `hash_map' was not declared in this scope
hashdemo.cpp:8: error: expected primary-expression before "int"
hashdemo.cpp:8: error: expected `;' before "int"
hashdemo.cpp:10: error: expected primary-expression before "int"
hashdemo.cpp:10: error: expected `;' before "int"
hashdemo.cpp:12: error: `hmp0' was not declared in this scope
hashdemo.cpp:15: error: `hmp0_iter' was not declared in this scope

but when i replaced #include<hash_map>with #include<hash_map.h>the program ran and printed the output but it did showed some warnings saying im using deprecated header.

im workin in linux using gcc(version3.4.6)so does it support hashmap??

alvinyang

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