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723.basic_regex should be moveable

Section: 28.6.7[re.regex]Status:C++11Submitter: Daniel KrüglerOpened: 2007-08-29Last modified: 2016-01-28

Priority:Not Prioritized

View all otherissues in [re.regex].

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Discussion:

Addresses UK 316

According to the current state of the standard draft, the classtemplatebasic_regex, as described in 28.6.7[re.regex]/3, isneitherMoveConstructible norMoveAssignable.IMO it should be, because typical regex state machines tendto have a rather large data quantum and I have seen severaluse cases, where a factory function returns regex values,which would take advantage of moveabilities.

[Sophia Antipolis:]

Needs wording for the semantics, the idea is agreed upon.

[Post Summit Daniel updated wording to reflect new "swap rules".]

[2009-07 Frankfurt:]

Move to Ready.

Proposed resolution:

In the class definition ofbasic_regex, just below 28.6.7[re.regex]/3,perform the following changes:

1. Just afterbasic_regex(const basic_regex&); insert:

   basic_regex(basic_regex&&);

2. Just afterbasic_regex& operator=(const basic_regex&); insert:

   basic_regex& operator=(basic_regex&&);

3. Just afterbasic_regex& assign(const basic_regex& that); insert:

   basic_regex& assign(basic_regex&& that);

4. In 28.6.7.2[re.regex.construct], just after p.11 add the followingnew member definition:

   basic_regex(basic_regex&& e);

   Effects: Move-constructs abasic_regex instance frome.

   Postconditions:flags() andmark_count() returne.flags() ande.mark_count(), respectively,thate had before construction, leavinge in a valid state with an unspecified value.

   Throws: nothing.

5. Also in 28.6.7.2[re.regex.construct], just after p.18 add thefollowing new member definition:

   basic_regex& operator=(basic_regex&& e);

   Effects: Returns the result ofassign(std::move(e)).

6. In 28.6.7.3[re.regex.assign], just after p. 2 add the following newmember definition:

   basic_regex& assign(basic_regex&& rhs);

   Effects: Move-assigns abasic_regex instance fromrhs and returns*this.

   Postconditions:flags() andmark_count() returnrhs.flags()andrhs.mark_count(), respectively, thatrhs had before assignment, leavingrhsin a valid state with an unspecified value.

   Throws: nothing.