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2301. Why isstd::tie notconstexpr?

Section: 22.4.5[tuple.creation]Status:C++14Submitter: Rein HalbersmaOpened: 2013-09-11Last modified: 2016-01-28

Priority:2

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Discussion:

InN3471, a bunch of routines from header<tuple> were madeconstexpr.

make_tuple/tuple_cat/get<>(tuple)/relational operators — all these were "constexpr-ified".

But nottie. This is similar to Issue2275⁽ⁱ⁾, where the same observation was made aboutforward_as_tuple.

[2014-02-13 Issaquah: Move as Immediate]

Proposed resolution:

This wording is relative to N3691.

1. Change the header<tuple> synopsis, 22.4.1[tuple.general] p2 as indicated:

   template<class... Types>constexpr tuple<Types&...> tie(Types&...) noexcept;

2. Change 22.4.5[tuple.creation] around p7 as indicated:

   template<class... Types>constexpr tuple<Types&...> tie(Types&... t) noexcept;