Initialze a tuple of tuples

Asked May 12 '16 at 13:34

Active May 12 '16 at 13:40

Viewed 586 times

I can initialize a std::tuple like this

std::tuple<int,float> t1{ 1,2.2 }; // works

If I want to initialize a tuple of tuples:

std::tuple<std::tuple<int,float> > t2{ 1,2.2}; // fails on gcc5.2.0 & gcc6.1.0
std::tuple<std::tuple<int,float> > t2{{ 1,2.2}}; // works on gcc6.1.0, fails for gcc5.2.0

So I am a bit confused if one of the above lines is correct c++14 code or not.

Simple question: Is it possible to direct initialize a tuple of tuples without using std::make_tuple or other helper types?

I am a bit in fear because of other problems found today like: Confusion while deriving from std::tuple, can not handle std::get

edited May 23 '17 at 11:59

Community

asked May 12 '16 at 13:34

Klaus

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TL;DR: wait for C++17. :) – erip May 12 '16 at 13:45
@erip Maybe this is the reason while gcc 6.1.0 compiles in c++14 mode without an error :-) – Klaus May 12 '16 at 13:47
I think that's probably a bug... C++14 shouldn't have any C++17 features - standard features aren't backwards compatible, nor are bug fixes. – erip May 12 '16 at 13:49
That is a definitely a bug. But it looks that a new feature for c++17 has opened that door. That's why I write a ":-)". I will prepare a bug report for that later... – Klaus May 12 '16 at 19:09
tuple> t1 = tuple>{tuple{1,2.2}}; – fmnijk Oct 30 '19 at 10:41
works on gcc4.9.2 – fmnijk Oct 30 '19 at 10:42

Initialze a tuple of tuples

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