Re: How to pass STL containers (say a vector) ?
In article <1148070525.301764.67280@u72g2000cwu.googlegroups.com>,
"peter koch" <peter.koch.larsen@gmail.com> wrote:
Daniel T. skrev:
In article <1148063503.729070.325510@j33g2000cwa.googlegroups.com>,
"peter koch" <peter.koch.larsen@gmail.com> wrote:
Daniel T. skrev:
In article <Wahbg.228$D_5.37@fe12.lga>,
Sanjay Kumar <nospam-hypertree@yahoo.com> wrote:
Folks,
I am getting back into C++ after a long time and I have
this simple question: How do pyou ass a STL container
like say a vector or a map (to and from a function) ?
The same way the standard algorithms do. 'std::copy' for example accepts
a container as an input param, and another container as an output param.
Well.... that one is a bad example. std::copy does not return a
collection. Actually, i can't remember a single std::algorithm that
does so (but I am tired and might well be wrong).
In my opinion you need very strong arguments (and those arguments
include measured improvements) in order to not return by value.
I beg to differ, std::copy does return a container in its own way...
vector<int> foo;
copy( istream_iterator<int>( cin ), istream_iterator<int>(),
back_inserter( foo ) );
The data in foo was returned...
So you mean that the data was returned in foo? In that case we simply
have a different perception of "returning values". To me, std::copy
does not return data in foo.
What about transform?
Perhaps this example better demonstrates what i mean?
vector<int> foo;
foo.push_back(117);
copy( istream_iterator<int>( cin ), istream_iterator<int>(),
back_inserter( foo ) );
copy definitely does not return its data in foo.
How so? All the data collected inside the copy function is given to the
caller through foo...
In other words when you want to pass in a container:
tempalte < typename InIt >
void func( InIt first, InIt last );
Fine! And now let func remove the second element.
The same way std::remove does it.
when you want to return a container:
template < typename OutIt >
void func( OutIt first );
It still does not return a container.
template <class container> void normalise_container(container const&
c);
template <class container> void print_container(container const& c);
print_container(normalise_container(func(???)));
template < typename FwIt > void normalize( FwIt first, FwIt last );
template < typename FwIt > void print( FwIt first, FwIt last ) {
copy( first, last, ostream_iterator<int>( cout, " " ) );
}
normalize( vec.begin(), vec.end() );
print( vec.begin(), vec.end() );