Map-like container?

Hi!

I'm looking for something similar to the map container, but with a
slight modification, a unique key, with multiple assignments to each
one. I think some container in the STL has it, but I cannot see it.

So I can assign to a key like a map:

// pseudo c++ code
container<int, int> m;

// 1: <2, -3, 5>
m[1] = 2;
m[1] = -3;
m[1] = 5;

// 2: <7, 1, 0, -1, 8>
m[2] = 7;
m[2] = 1;
m[2] = 0;
m[2] = -1;
m[2] = 8;

And get an iterator for each key:

for (it = m[1].begin(); it != m[1].end(); it++)
cout << "this is " << (*it) << endl;


The result would be something like a

map< key_T, list<data_T> >

without hassles :)

Thanks to anyone!!

--
Sensei <senseiwa@mac.com>

The optimist thinks this is the best of all possible worlds.
The pessimist fears it is true. [J. Robert Oppenheimer]

Sensei <senseiwa@mac.com> wrote:[color=blue]
> Hi!
>
> I'm looking for something similar to the map container, but with a
> slight modification, a unique key, with multiple assignments to each
> one. I think some container in the STL has it, but I cannot see it.
>
> So I can assign to a key like a map:
>
> // pseudo c++ code
> container<int, int> m;
>
> // 1: <2, -3, 5>
> m[1] = 2;
> m[1] = -3;
> m[1] = 5;
>
> // 2: <7, 1, 0, -1, 8>
> m[2] = 7;
> m[2] = 1;
> m[2] = 0;
> m[2] = -1;
> m[2] = 8;
>
> And get an iterator for each key:
>
> for (it = m[1].begin(); it != m[1].end(); it++)
> cout << "this is " << (*it) << endl;
>
>
> The result would be something like a
>
> map< key_T, list<data_T> >[/color]

So why not use just that?

regards
--
jb

(reply address in rot13, unscramble first)

Sensei wrote:[color=blue]
> Hi!
>
> I'm looking for something similar to the map container, but with a
> slight modification, a unique key, with multiple assignments to each
> one. I think some container in the STL has it, but I cannot see it.
>
> So I can assign to a key like a map:
>
> // pseudo c++ code
> container<int, int> m;
>
> // 1: <2, -3, 5>
> m[1] = 2;
> m[1] = -3;
> m[1] = 5;
>
> // 2: <7, 1, 0, -1, 8>
> m[2] = 7;
> m[2] = 1;
> m[2] = 0;
> m[2] = -1;
> m[2] = 8;
>
> And get an iterator for each key:
>
> for (it = m[1].begin(); it != m[1].end(); it++)
> cout << "this is " << (*it) << endl;
>
>
> The result would be something like a
>
> map< key_T, list<data_T> >
>
> without hassles :)
>[/color]

Sounds like a multimap to me. ;-)

HTH,
--ag


--
Artie Gold -- Austin, Texas
http://goldsays.blogspot.com
"You can't KISS* unless you MISS**"
[*-Keep it simple, stupid. **-Make it simple, stupid.]

Sensei wrote:[color=blue]
> I'm looking for something similar to the map container, but with a
> slight modification, a unique key, with multiple assignments to each
> one.[/color]

What does "multiple assignments to each one" mean? Are you trying to
create some kind of hash table? Use 'hashtable' from SGI. Or use
std::map<int, std::vector<int> >.
[color=blue]
> I think some container in the STL has it, but I cannot see it.
>
> So I can assign to a key like a map:
>
> // pseudo c++ code
> container<int, int> m;
>
> // 1: <2, -3, 5>
> m[1] = 2;
> m[1] = -3;
> m[1] = 5;
>
> // 2: <7, 1, 0, -1, 8>
> m[2] = 7;
> m[2] = 1;
> m[2] = 0;
> m[2] = -1;
> m[2] = 8;
>
> And get an iterator for each key:
>
> for (it = m[1].begin(); it != m[1].end(); it++)
> cout << "this is " << (*it) << endl;
>
>
> The result would be something like a
>
> map< key_T, list<data_T> >
>
> without hassles :)[/color]

<rant>
What's a "hassle"? Do you want to avoid calling "push_back"? Why don't
you try to avoid programming at all, just think harder of what you want
and it might just happen...
</rant>

Well, you could you invent your own class that when assigned to would grow
its own internal collection:

template<class T> struct auto_list
{
std::list<T> collection;
public:
auto_list& operator=(T t) { collection.push_back(t); }
// ... whatever else you need
};

and then use it in your 'map':

std::map<key_T, auto_list<data_T> >

Remember that free cheese is only found in the mousetrap.

V
--
Please remove capital As from my address when replying by mail

Sensei skrev:[color=blue]
> Hi!
>
> I'm looking for something similar to the map container, but with a
> slight modification, a unique key, with multiple assignments to each
> one. I think some container in the STL has it, but I cannot see it.
>
> So I can assign to a key like a map:
>
> // pseudo c++ code
> container<int, int> m;
>
> // 1: <2, -3, 5>
> m[1] = 2;
> m[1] = -3;
> m[1] = 5;
>
> // 2: <7, 1, 0, -1, 8>
> m[2] = 7;
> m[2] = 1;
> m[2] = 0;
> m[2] = -1;
> m[2] = 8;
>
> And get an iterator for each key:
>
> for (it = m[1].begin(); it != m[1].end(); it++)
> cout << "this is " << (*it) << endl;
>
>
> The result would be something like a
>
> map< key_T, list<data_T> >
>
> without hassles :)
>
> Thanks to anyone!!
>[/color]

class SetWrapper {
private:
typedef std::set<int> seti;
seti d_set;
public:
void operator=(int i) {
d_set.insert(i);
}
seti::iterator begin() {
return d_set.begin();
}
seti::iterator end() {
return d_set.end();
}
};

int main() {
std::map<int,SetWrapper> m;

m[1] = 2;
m[1] = -3;
m[1] = 5;

m[2] = 7;
m[2] = 1;
m[2] = 0;
m[2] = -1;
m[2] = 8;

for (it = m[1].begin(); it != m[1].end(); it++) {
cout << "this is " << (*it) << endl;
}
return 0;
}

--
TB @ SWEDEN

On 2006-03-14 16:40:47 +0100, Victor Bazarov <v.Abazarov@comAcast.net> said:
[color=blue][color=green]
>> I'm looking for something similar to the map container, but with a
>> slight modification, a unique key, with multiple assignments to each
>> one.[/color]
>
> What does "multiple assignments to each one" mean? Are you trying to
> create some kind of hash table? Use 'hashtable' from SGI. Or use
> std::map<int, std::vector<int> >.[/color]

I come from C and ASM, where nothing is defined, no lists, nothing more
than memory allocation. I thought there were containers helping the
programmer. This construct seems quite useful, that's why I'm asking.
[color=blue]
> <rant>
> What's a "hassle"? Do you want to avoid calling "push_back"? Why don't
> you try to avoid programming at all, just think harder of what you want
> and it might just happen...
> </rant>[/color]

A simple ``no'' would suffice, I don't really like classes and
siblings, I feel better with memset and alike... but unfortunately for
me, C++ is required, and I must adapt myself. Hassle (to me of course)
is caring about copy constructors and whatever is more than
malloc()/memmove()... that is hassle :)
[color=blue]
> Well, you could you invent your own class that when assigned to would grow
> its own internal collection:
>
> template<class T> struct auto_list
> {
> std::list<T> collection;
> public:
> auto_list& operator=(T t) { collection.push_back(t); }
> // ... whatever else you need
> };
>
> and then use it in your 'map':
>
> std::map<key_T, auto_list<data_T> >[/color]

The class seems the same as a map of int and list<something> to me :)
except of course, the = operator.
[color=blue]
> Remember that free cheese is only found in the mousetrap.[/color]

This is very true.

--
Sensei <senseiwa@mac.com>

The optimist thinks this is the best of all possible worlds.
The pessimist fears it is true. [J. Robert Oppenheimer]

Sensei wrote:
[color=blue]
> On 2006-03-14 16:40:47 +0100, Victor Bazarov <v.Abazarov@comAcast.net>
> said:
>[color=green][color=darkred]
>>> I'm looking for something similar to the map container, but with a
>>> slight modification, a unique key, with multiple assignments to each
>>> one.[/color]
>>
>> What does "multiple assignments to each one" mean? Are you trying to
>> create some kind of hash table? Use 'hashtable' from SGI. Or use
>> std::map<int, std::vector<int> >.[/color]
>
> I come from C and ASM, where nothing is defined, no lists, nothing more
> than memory allocation. I thought there were containers helping the
> programmer.[/color]

There are.
[color=blue]
> This construct seems quite useful, that's why I'm asking.
>[color=green]
>> <rant>
>> What's a "hassle"? Do you want to avoid calling "push_back"? Why don't
>> you try to avoid programming at all, just think harder of what you want
>> and it might just happen...
>> </rant>[/color]
>
> A simple ``no'' would suffice, I don't really like classes and
> siblings, I feel better with memset and alike... but unfortunately for
> me, C++ is required, and I must adapt myself. Hassle (to me of course)
> is caring about copy constructors and whatever is more than
> malloc()/memmove()... that is hassle :)[/color]

Hmm, the idea is actually the other way round. The constructors and that
stuff do things automatically for you that you usually would have to care
about yourself. You just push_back the object into your container and
you're done. No malloc, no memmove needed.
A copy constructor is mostly needed if you're handling some raw resources
that themselves aren't represented by a class with a proper copy
constructor.
[color=blue][color=green]
>> Well, you could you invent your own class that when assigned to would
>> grow its own internal collection:
>>
>> template<class T> struct auto_list
>> {
>> std::list<T> collection;
>> public:
>> auto_list& operator=(T t) { collection.push_back(t); }
>> // ... whatever else you need
>> };
>>
>> and then use it in your 'map':
>>
>> std::map<key_T, auto_list<data_T> >[/color]
>
> The class seems the same as a map of int and list<something> to me :)
> except of course, the = operator.[/color]

Well, it's still unclear what you want. What's wrong with the map of int and
list<int> (or int and vector<int>)?

[color=blue]
> Sounds like a multimap to me. ;-)[/color]

a multimap has several identical entries for the key values. That's
not what he wanted. He just wanted a map of array data:
std::map<int, std::vector<int> >
e.g.

Gernot Frisch wrote:
[color=blue]
>[color=green]
>> Sounds like a multimap to me. ;-)[/color]
>
> a multimap has several identical entries for the key values. That's
> not what he wanted. He just wanted a map of array data:
> std::map<int, std::vector<int> >
> e.g.[/color]

Hmm, what would be the difference? You store several values of the same type
under one key.

[color=blue]
> ... I feel better with memset and alike... but unfortunately for
> me, C++ is required, and I must adapt myself.[/color]

Oh boy! Get a C++ book and start thinking. You don't know what you're
missing. It's not C++ because classes and ineritance makes it more
complex, it's because it's more powerful and easier to maintain. I
know a good FORTRAN programmer can write FORTRAN code in any
language - but do you really want to?

C++ is _not_ C(++)

it is rather:

class Cpp : public C
{
public:
virtual Cpp& operator++() {return C::data++;}
};


-Gernot

[color=blue][color=green]
>>[color=darkred]
>>> Sounds like a multimap to me. ;-)[/color]
>>
>> a multimap has several identical entries for the key values. That's
>> not what he wanted. He just wanted a map of array data:
>> std::map<int, std::vector<int> >
>> e.g.[/color]
>
> Hmm, what would be the difference? You store several values of the
> same type
> under one key.[/color]

....now that I think of it... forget all I said.

On 2006-03-14 16:35:45 +0100, Artie Gold <artiegold@austin.rr.com> said:

[color=blue]
> Sounds like a multimap to me. ;-)[/color]


Can you explain this?

Following the SGI documentation, I understand it is possible to use
multimap with pairs, so the only way to achieve what I want is to be
tricky:

multimap<int, int> adj;

multimap<int, int>::iterator it_adj;

/*
1:
2, 4, 1

2:
6, 9, 4, 2, 1, 0
*/

adj.insert(pair<int,int>(1,2));
adj.insert(pair<int,int>(1,4));
// ``2'' inserted before ending the key ``1''
adj.insert(pair<int,int>(2,6));
adj.insert(pair<int,int>(2,9));
adj.insert(pair<int,int>(2,4));
adj.insert(pair<int,int>(2,1));
adj.insert(pair<int,int>(2,0));
// insert last ``1''
adj.insert(pair<int,int>(1,1));
adj.insert(pair<int,int>(2,2));

it_adj = adj.find(1);

while ((*it_adj).first == 1)
{
cout << "that's 2 key and value " << (*it_adj).second << endl;
it_adj++;
}



So I feel like there's no other way than this and a by-hand use of
map/lists... am I right? :)

--
Sensei <senseiwa@mac.com>

The optimist thinks this is the best of all possible worlds.
The pessimist fears it is true. [J. Robert Oppenheimer]

On 2006-03-14 17:54:50 +0100, "Gernot Frisch" <Me@Privacy.net> said:
[color=blue]
>[color=green]
>> ... I feel better with memset and alike... but unfortunately for
>> me, C++ is required, and I must adapt myself.[/color]
>
> Oh boy! Get a C++ book and start thinking. You don't know what you're missing.[/color]

I bought C++, third edition, from Bjarne Stroustrup himself... not that
I bought it from him I mean :)
[color=blue]
> It's not C++ because classes and ineritance makes it more complex, it's
> because it's more powerful and easier to maintain. I know a good
> FORTRAN programmer can write FORTRAN code in any language - but do you
> really want to?[/color]

Possibly not. So, I think I'm writing C code in C++...
[color=blue]
> C++ is _not_ C(++)
>
> it is rather:
>
> class Cpp : public C
> {
> public:
> virtual Cpp& operator++() {return C::data++;}
> };[/color]

Better read that book pronto, since that & at the end of Cpp for the ++
operator dazzles me :)

--
Sensei <senseiwa@mac.com>

The optimist thinks this is the best of all possible worlds.
The pessimist fears it is true. [J. Robert Oppenheimer]

Sensei wrote:[color=blue]
> On 2006-03-14 17:54:50 +0100, "Gernot Frisch" <Me@Privacy.net> said:
>[color=green]
>> C++ is _not_ C(++)
>>
>> it is rather:
>>
>> class Cpp : public C
>> {
>> public:
>> virtual Cpp& operator++() {return C::data++;}
>> };[/color]
>
> Better read that book pronto, since that & at the end of Cpp for the ++
> operator dazzles me :)[/color]

It's a reference. A bit like a pointer, but different.

Ben Pope
--
I'm not just a number. To many, I'm known as a string...

Ben Pope wrote:[color=blue]
> Sensei wrote:[color=green]
>> [..]
>> Better read that book pronto, since that & at the end of Cpp for the
>> ++ operator dazzles me :)[/color]
>
>
> It's a reference. A bit like a pointer, but different.[/color]

Heh... "It's like a pointer, only it's not."

Victor Bazarov wrote:[color=blue]
> Ben Pope wrote:[color=green]
>> Sensei wrote:[color=darkred]
>>> [..]
>>> Better read that book pronto, since that & at the end of Cpp for the
>>> ++ operator dazzles me :)[/color]
>>
>>
>> It's a reference. A bit like a pointer, but different.[/color]
>
> Heh... "It's like a pointer, only it's not."[/color]

Just trying to pique his curiosity without giving too much away ;)

Ben Pope
--
I'm not just a number. To many, I'm known as a string...

Sensei wrote:
[color=blue]
> On 2006-03-14 16:35:45 +0100, Artie Gold <artiegold@austin.rr.com> said:
>
>[color=green]
>> Sounds like a multimap to me. ;-)[/color]
>
>
> Can you explain this?
>
> Following the SGI documentation, I understand it is possible to use
> multimap with pairs, so the only way to achieve what I want is to be
> tricky:
>
> multimap<int, int> adj;
>
> multimap<int, int>::iterator it_adj;
>
> /*
> 1:
> 2, 4, 1
>
> 2:
> 6, 9, 4, 2, 1, 0
> */
>
> adj.insert(pair<int,int>(1,2));[/color]

adj.insert(make_pair(1,2));
[color=blue]
> adj.insert(pair<int,int>(1,4));
> // ``2'' inserted before ending the key ``1''
> adj.insert(pair<int,int>(2,6));
> adj.insert(pair<int,int>(2,9));
> adj.insert(pair<int,int>(2,4));
> adj.insert(pair<int,int>(2,1));
> adj.insert(pair<int,int>(2,0));
> // insert last ``1''
> adj.insert(pair<int,int>(1,1));
> adj.insert(pair<int,int>(2,2));
>
> it_adj = adj.find(1);
>
> while ((*it_adj).first == 1)[/color]

Use equal_range instead:

typedef multimap<int, int>::iterator iter;

pair<iter, iter> b = adj.equal_range(1);
for (iter it = b.first; it != b.second; ++it)
cout << "that's 2 key and value " << (*it).second << endl;
}
[color=blue]
> So I feel like there's no other way than this and a by-hand use of
> map/lists... am I right? :)[/color]