transfer loop into C++03 for_each

Question

Possible Duplicate:
Using bind1st for a method that takes argument by reference

I have the following traditional C++03 loop (using auto for stack overflow space efficiency only):

for (auto it = some_vector.begin(); it != some_vector.end(); ++it)
{
    foobar.method(*it);
}

In C++11, I managed to rewrite this into the following for_each invocation which works perfectly well:

std::for_each(some_vector.begin(), some_vector.end(),
              std::bind(&Foobar::method, std::ref(foobar), _1));

(Of course I could just use a lambda in C++11, but that's not the point.) Unfortunately, std::bind is not part of C++03, so I tried simulating it with std::bind1st and std::mem_fun_ref:

std::for_each(some_vector.begin(), some_vector.end(),
              std::bind1st(std::mem_fun_ref(&Foobar::method), std::ref(foobar)));

But this triggered a C2535 error in Visual Studio ("member function already defined or declared"):

// inside class binder1st in header xfunctional

result_type operator()(const argument_type& _Right) const
{   // apply functor to operands
    return (op(value, _Right));
}

result_type operator()(argument_type& _Right) const
{   // apply functor to operands   <--- ERROR C2535 HERE
    return (op(value, _Right));
}

Is this a const-correctness bug in Visual Studio, or have I done something wrong?

Also, std::ref does not seem to be part of C++03. Is there any workaround?

`std::tr1::bind` is part of TR1 -- is that sufficient for your needs? — ildjarn, Jan 10 '12 at 17:42
Might be of interest: [Is it possible to create function-local closures pre-C++11?](http://stackoverflow.com/questions/5723619/is-it-possible-to-create-function-local-closures-pre-c11). — Xeo, Jan 10 '12 at 17:44
@ildjarn I'm probably just going to keep the traditional loop for simplicity's sake. Just curious as to what exactly caused the error. — fredoverflow, Jan 10 '12 at 17:44
As a note, can anyone explain me, _why_?! Given so pretty clear peace of code, TS finished with such a _mess_! — Lol4t0, Jan 10 '12 at 17:47
@Xeo: I have nothing against Boost. Sometimes I just go traditional for old time's sake and wonder why it doesn't work is all ;) — fredoverflow, Jan 10 '12 at 17:47
Is the error the same using `std::transform` rather than `std::for_each`? — Barry, Jan 10 '12 at 17:50
GCC also rejects your `for_each`, so there's a good chance this isn't just a VS bug. Also your use of `auto` in the traditional loop is C++11, not C++03. — bames53, Jan 10 '12 at 18:03

score 3 · Accepted Answer · answered Jan 10 '12 at 17:59

3

Why not simply use std::mem_fun? It expects a pointer as the first parameter, as such:

#include <functional>
#include <algorithm>
#include <vector>

struct foo{
    void method(int){}
};

int main(){
    std::vector<int> v;
    foo f;
    std::for_each(v.begin(), v.end(),
        std::bind1st(std::mem_fun(&foo::method), &f));
}

answered Jan 10 '12 at 17:59

Xeo

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+1 I proved it http://ideone.com/AAR4S – Antonio Pérez Jan 11 '12 at 16:14

transfer loop into C++03 for_each

1 Answers1