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parse
manipulator without abbreviation is not callableSection: 29.13 [time.parse] Status: C++20 Submitter: Tomasz Kamiński Opened: 2019-07-10 Last modified: 2021-02-25
Priority: 0
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Discussion:
The parse
overload that does not accept the abbreviation but does accept an offset,
because the expression in the Remarks: clause:
from_stream(declval<basic_istream<charT, traits>*>(), fmt.c_str(), tp, nullptr, &offset)
is not valid. This is caused by deduction failure for the basic_string<charT, traits, Alloc>*
from nullptr
(see this link):
[2019-08-17 Issue Prioritization]
Status to Tentatively Ready and priority to 0 after six positive votes on the reflector.
Proposed resolution:
This wording is relative to N4830.
[Drafting note: As a drive-by fix the Remarks element is also converted to a Constraints element.]
Modify 29.13 [time.parse] as indicated:
template<class charT, class traits, class Alloc, class Parsable> unspecified parse(const basic_string<charT, traits, Alloc>& fmt, Parsable& tp, minutes& offset);-6-
RemarksConstraints:This function shall not participate in overload resolution unlessThe expressionfrom_stream(declval<basic_istream<charT, traits>&>(), fmt.c_str(), tp, declval<basic_string<charT, traits, Alloc>*>()nullptr, &offset)is
-7- Returns: A manipulator that, when extracted from aa validwell-formedexpressionwhen treated as an unevaluated operand.basic_istream<charT, traits> is
, callsfrom_stream(is, fmt.c_str(), tp, static_cast<basic_string<charT, traits, Alloc>*>(nullptr), &offset)
.