CODEWITHSUNDEEP
visual-c++c++11tuples
Petter
Petter

Reputation: 38644

Map indexed by tuples in VC++

Consider the following code:

#include <tuple>

template <typename Map, typename K>
void mymapfunc(Map& m, const K& key) 
{
    m[key] = 1;
}

void f() 
{
    typedef std::tuple<int,int> Pair;
    std::map<Pair,int> m;
    mymapfunc(m, Pair(1,2));
}

This code fails in VC++ 2010, but compiles fine in gcc 4.5 (without warnings with -Wall and -pedantic). The error is somewhere inside <tuple> and hard to decipher.

If std::tuple is changed to std::pair, everything works. What is going on here?

Upvotes: 3

Views: 951

Answers (2)

Howard Hinnant
Howard Hinnant

Reputation: 218900

N3242, 20.4.2.7 [tuple.rel] defines the relational operators for tuple.

If you add #include <map>, this example also compiles fine in libc++.

Upvotes: 1

James McNellis
James McNellis

Reputation: 355079

There is a bug in Visual C++ 2010 when using a std::tuple as a key type in an associative container (like std::map).

The workaround (mentioned in the linked bug report) is to construct a temporary std::tuple:

m[K(key)] = 1;

Upvotes: 4

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