[c++] set of values returned from a function

[ZikO]

Hi

What would you do to return the set of values from a function
1) the list of values
2) a couple values of different types

Something like in LUA:
-- lua code
function f()
-- something to do
return 1, 2, "name";
end

after running
a,b,c = f();

a = 1, b = 2, c = "name".

I know c++ is different than LUA but sometimes I need to get a set of
values from a function. I know there is the pair<T1, T2> type by which I
could have a pair of different values but this is only 2.
I would use one of the containers like the vector, the list or the
deqeue etc. like in example

vector<string> f() {
// something to do
vector<string> list = {"aaa","bbb","ccc"};
return list;
}

But this is not quite efficient Im affraid. Second, vector<> seems to be
difficult to deal with if there's an error and the list can't be generated.

Any suggestions appreciated very much =)
Regards.

[Kai-Uwe Bux]

ZikO wrote:

> Hi
>
> What would you do to return the set of values from a function
> 1) the list of values
> 2) a couple values of different types
>
> Something like in LUA:
> -- lua code
> function f()
> -- something to do
> return 1, 2, "name";
> end
>
> after running
> a,b,c = f();
>
> a = 1, b = 2, c = "name".
>
> I know c++ is different than LUA but sometimes I need to get a set of
> values from a function. I know there is the pair<T1, T2> type by which I
> could have a pair of different values but this is only 2.

There will be tuples in C++0X, I think.

> I would use one of the containers like the vector, the list or the
> deqeue etc. like in example
>
> vector<string> f() {
> // something to do
> vector<string> list = {"aaa","bbb","ccc"};
> return list;
> }
>
> But this is not quite efficient Im affraid. Second, vector<> seems to be
> difficult to deal with if there's an error and the list can't be
> generated.
>
> Any suggestions appreciated very much =)

It all values have the same type, you can try an output iterator:

template < typename OutIter >
OutIter some_function ( OutIter where, ... );

Best

Kai-Uwe Bux

[Thomas J. Gritzan]

ZikO wrote:
> Hi
>
> What would you do to return the set of values from a function
> 1) the list of values
> 2) a couple values of different types
>
> Something like in LUA:
> -- lua code
> function f()
> -- something to do
> return 1, 2, "name";
> end

You can use

* a struct, which is good because you can name the values and define
operations on it (member functions)

* boost::tuple and boost::tie, with those you can do similar to what you
do in Lua.

* boost::array (or tr1::array) for homogenous lists of a fixed length.

* output parameters

--
Thomas