STL question

STL question

[Alexander Samoilov]

STL experts!

Could you help me?

The following code compiles ok:
----------------------------------------------
#include <set.h>
#include <map.h>
#include <multimap.h>
#include <list.h>
#include <hash_set.h>
#include <hash_map.h>


struct ltstr {
    bool operator() (char* const s1, char* const s2) const {
	return strcmp(s1, s2) < 0;
    }
};

typedef map<char* const, int, ltstr> hmap;

inline bool cmp(pair<char* const,int> p1, pair<char* const,int> p2)
{
    return strcmp(p1.first, p2.first) != 0;
}


int main()
{
    hmap ins1, ins2, ins_diff;

    insert_iterator<hmap> ii1(ins_diff,ins_diff.begin());

    set_difference(ins1.begin(), ins1.end(),
	           ins2.begin(), ins2.end(),
		   ii1, cmp);
}
----------------------------------------------------

But if we substitute map for hash_map, the compiler refuses
to compile point-blank:

----------------------------------------------------

#include <set.h>
#include <map.h>
#include <multimap.h>
#include <list.h>
#include <hash_set.h>
#include <hash_map.h>


struct eqstr {
    bool operator() (char* const s1, char* const s2) const {
	return strcmp(s1, s2) == 0;
    }
};

typedef hash_map<char* const, int, hash<char*>, eqstr> hmap;

inline bool cmp(pair<char* const,int> p1, pair<char* const,int> p2)
{
    return strcmp(p1.first, p2.first) != 0;
}


int main()
{
    hmap ins1, ins2, ins_diff;

    insert_iterator<hmap> ii1(ins_diff,ins_diff.begin());

    set_difference(ins1.begin(), ins1.end(),
	           ins2.begin(), ins2.end(),
		   ii1, cmp);
}
--------------------------------------------------------------

with the following messages:

--------------------------------------------------------------
home/spike/egcs-gas-bin/include/g++/stl_iterator.h: In method `class insert_iterator<hash_map<char *const,int,hash<char *>,eqstr,__default_alloc_template<false,0> > > & insert_iterator<hash_map<char *const,int,hash<char *>,eqstr,__default_alloc_template<f
alse,0> > >::operator =<hmap>(const struct pair<char *const,int> &)':
/home/spike/egcs-gas-bin/include/g++/stl_algo.h:2213:   instantiated from `set_difference<__hashtable_iterator<pair<char *const,int>,char *const,hash<char *>,select1st<pair<char *const,int> >,eqstr,__default_alloc_template<false,0> >, __hashtable_iterator
<pair<char *const,int>,char *const,hash<char *>,select1st<pair<char *const,int> >,eqstr,__default_alloc_template<false,0> >, insert_iterator<hash_map<char *const,int,hash<char *>,eqstr,__default_alloc_template<false,0> > >, bool (*)(pair<char *const,int>,
 pair<char *const,int>)>(__hashtable_iterator<pair<char *const,int>,char *const,hash<char *>,select1st<pair<char *const,int> >,eqstr,__default_alloc_template<false,0> >, __hashtable_iterator<pair<char *const,int>,char *const,hash<char *>,select1st<pair<ch
ar *const,int> >,eqstr,__default_alloc_template<false,0> >, __hashtable_iterator<pair<char *const,int>,char *const,hash<char *>,select1st<pair<char *const,int> >,eqstr,__default_alloc_template<false,0> >, __hashtable_iterator<pair<char *const,int>,char *c
onst,hash<char *>,select1st<pair<char *const,int> >,eqstr,__default_alloc_template<false,0> >, insert_iterator<hash_map<char *const,int,hash<char *>,eqstr,__default_alloc_template<false,0> > >, bool (*)(pair<char *const,int>, pair<char *const,int>))'
hm1.cc:32:   instantiated from here
/home/spike/egcs-gas-bin/include/g++/stl_iterator.h:398: no matching function for call to `hash_map<char *const,int,hash<char *>,eqstr,__default_alloc_template<false,0> >::insert (__hashtable_iterator<pair<char *const,int>,char *const,hash<char *>,select1
st<pair<char *const,int> >,eqstr,__default_alloc_template<false,0> > &, const pair<char *const,int> &)'
/home/spike/egcs-gas-bin/include/g++/stl_hash_map.h:139: candidates are: hash_map<char *const,int,hash<char *>,eqstr,__default_alloc_template<false,0> >::insert<char *const, int, hash<char *>, eqstr, alloc>(const pair<char *const,int> &)
--------------------------------------------------------------

Could you give me some advice how to remedy the situation?

Best regards.

Alexander Samoilov

Re: STL question

[Alexandre Oliva]

Alexander Samoilov <spike@Gambit.Msk.SU> writes:

> typedef hash_map<char* const, int, hash<char*>, eqstr> hmap;

> int main() { hmap ins_diff;
>     insert_iterator<hmap> ii1(ins_diff,ins_diff.begin());

Unlike map, hash_map does not support insert(pos,x), so insert
iterators do not work on it :-(

Instead, you may want to replace ii1 with:

      bind1st(mem_fun(insert_meth), &ins_diff)

   given:

      pair<hmap::iterator,bool> (hmap::*insert_meth)(const hmap::value_type&)
	= &hmap::insert;
      
Perhaps insert iterators should be specialized for hash maps...

-- 
Alexandre Oliva
mailto:oliva@dcc.unicamp.br mailto:aoliva@acm.org
http://www.dcc.unicamp.br/~oliva
Universidade Estadual de Campinas, SP, Brasil

Re: STL question

[Joe Buck]

Alexandre Oliva writes:

> Unlike map, hash_map does not support insert(pos,x), so insert
> iterators do not work on it :-(

I think that this is a design bug.  STL containers should be as orthogonal
as possible.  (and since hash_map is an extension, it can be fixed without
having to worry about violating the standard.

> Perhaps insert iterators should be specialized for hash maps...

Or perhaps insert(iterator, value) should be implemented for hash maps,
in an analogous way as for maps (the iterator position is only taken as
a hint, which can be ignored if necessary).

Re: STL Question.

[Chris Dern]

The program dumps core, when run. If I use -frepo, it won't link correctly
after collect2 decideds to re-compile (-fpreo), the linker complains of
missing functions.

Joe Buck wrote:

> > Quick question.
> > I'm trying to nest a STL list in a map, like so.
> >
> > typedef list<Base*> BaseList;
> >
> > map<String,BaseList> itsMap;
> >
> >
> > However this won't compile correctly if I use the repo, and if I just
> > try and compile it, I get a core dump. Anyone else have problems with
> > this?
>
> What dumps core, the program or the compiler?
>
> While we should investigate the problem, there is no good reason to use
> -frepo on your platform.  You'll get pretty much the same executable
> without it (if your binutils is recent enough: 2.8.0.x or newer).

Re: STL Question.

[Joe Buck]

> The program dumps core, when run. If I use -frepo, it won't link correctly
> after collect2 decideds to re-compile (-fpreo), the linker complains of
> missing functions.

I suspect that the core dump is a bug in your program: putting pointers
in STL objects can be a bit tricky, as you must do your own memory 
management.  As for the missing functions, this could be a bug, or
it could be that the functions are actually missing (template definitions
not visible).  One way to test that is to build without -frepo and
see if you are missing anything.

Re: STL Question.

[Joe Buck]

> Quick question.
> I'm trying to nest a STL list in a map, like so.
> 
> typedef list<Base*> BaseList;
> 
> map<String,BaseList> itsMap;
> 
> 
> However this won't compile correctly if I use the repo, and if I just
> try and compile it, I get a core dump. Anyone else have problems with
> this?

What dumps core, the program or the compiler?

While we should investigate the problem, there is no good reason to use
-frepo on your platform.  You'll get pretty much the same executable
without it (if your binutils is recent enough: 2.8.0.x or newer).

STL Question.

[Chris Dern]

Quick question.
I'm trying to nest a STL list in a map, like so.

typedef list<Base*> BaseList;

map<String,BaseList> itsMap;


However this won't compile correctly if I use the repo, and if I just
try and compile it, I get a core dump. Anyone else have problems with
this?

This is on a RH 4.0 Egcs 1.01, i486

Chris