[cfe-dev] initializer_list deduction

[Fernando Pelliccioni]

On Wed, May 9, 2012 at 3:27 PM, David Blaikie <dblaikie at gmail.com> wrote:

> On Wed, May 9, 2012 at 11:18 AM, Fernando Pelliccioni
> <fpelliccioni at gmail.com> wrote:
> > Hi all,
> >
> > Is it this behavior correct ?
> >
> > //Code ----------------------
> > #include <initializer_list>
> > #include <iostream>
> > #include <string>
> > #include <vector>
> >
> > using namespace std;
> >
> > void foo( initializer_list<typename vector<string>::value_type> list )
> > {
> >     for (auto& item : list)
> >     {
> >         cout << item << endl;
> >     }
> > }
> >
> > int main( /* int argc, char* argv[] */ )
> > {
> >     foo( { {"k0", "v0"}, {"k1", "v1"} } );
> >     return 0;
> > }
> >
> > //End code ----------------------
> >
> >
> > $ clang++ --version
> > clang version 3.1 (trunk 155038)
> > Target: i386-pc-linux-gnu
> > Thread model: posix
> >
> > $ clang++ -std=c++11 initializer_list_test.cpp
> > $ ./a.out
> > k0
> > k1
> >
> > ------------------------------------------
> >
> > I would have expected that the initializer_list be deduced to something
> like
> > an associative container (a compile time error).
>
> I believe you're calling the std::string(Iterator begin, Iterator end)
> constructor. As you could with this code:
>
> std::string s{"k0", "v0"};
>
> (or even C++03 code: std::string s("k0", "v0"); )
>


Oh, you're right!


>
> You probably got luck with the string constant layout & ran into "v0"
> from "k0" - but I suspect the length of your strings is 3, not 2
> (including the null character between "v0" and "k0")
>


But... I'm  concerned about the ambiguous resolution in this case ...


//Code ----------------------
#include <initializer_list>
#include <iostream>
#include <string>
#include <vector>
#include <map>

using namespace std;

void foo( initializer_list<typename vector<string>::value_type> list )
{
for (auto& item : list)
{
cout << item << endl;
}
}

void foo( initializer_list<typename map<string, string>::value_type> list )
{
for (auto& item : list)
{
cout << item.first << endl;
}
}

int main( /* int argc, char* argv[] */ )
{
foo( { {"k0", "v0"}, {"k1", "v1"} } );
return 0;
}

//End code ----------------------


It seems that no solution.

Regards,
Fernando.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20120509/9da5c2b0/attachment.html>