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std::ignore constexprSection: 22.4.1[tuple.general]Status:C++17Submitter: Vincent ReverdyOpened: 2016-09-10Last modified: 2017-07-30
Priority:0
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Discussion:
Currentlystd::ignore is not specifiedconstexpr according to the C++ draft N4606 in the paragraph 22.4.1[tuple.general]. It prevents some use inconstexpr context: for example declaring aconstexpr variable equals to the result of a function to whichstd::ignore has been passed as a parameter:
constexpr int i = f(std::ignore); // Won't compile
If there is no fundamental reason preventingstd::ignore to beconstexpr, then we propose to declare it asconstexpr instead of asconst.
[Issues processing Telecon 2016-10-7]
P0; set to Tentatively Ready
Proposed resolution:
This wording is relative to N4606.
Modify 22.4.1[tuple.general] as indicated:
// 20.5.2.4, tuple creation functions:constconstexprunspecified ignore;