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2503. multiline option should be added to syntax_option_type

Section: 32.4.2 [re.synopt] Status: C++17 Submitter: Nozomu Katō Opened: 2015-05-22 Last modified: 2017-07-30

Priority: 2

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Discussion:

The specification of ECMAScript defines the Multiline property for its RegExp and the regular expressions ^ and $ behave differently according to the value of this property. Thus, this property should be available also in the ECMAScript compatible engine in std::regex.

[2015-05-22, Daniel comments]

This issue interacts somewhat with LWG 2343.

[Telecon 2015-07]

Set the priority to match LWG 2343.

[2016-08, Chicago]

Monday PM: Moved to Tentatively Ready. This also resolves 2343

Proposed resolution:

This wording is relative to N4431.

1. Change 32.4.2 [re.synopt] as indicated:

   namespace std::regex_constants {
     typedef T1 syntax_option_type;
     constexpr syntax_option_type icase = unspecified ;
     constexpr syntax_option_type nosubs = unspecified ;
     constexpr syntax_option_type optimize = unspecified ;
     constexpr syntax_option_type collate = unspecified ;
     constexpr syntax_option_type ECMAScript = unspecified ;
     constexpr syntax_option_type basic = unspecified ;
     constexpr syntax_option_type extended = unspecified ;
     constexpr syntax_option_type awk = unspecified ;
     constexpr syntax_option_type grep = unspecified ;
     constexpr syntax_option_type egrep = unspecified ;
     constexpr syntax_option_type multiline = unspecified ;
   }
   

2. Change 32.4.3 [re.matchflag], Table 138 — "syntax_option_type effects" as indicated:

   Table 138 — syntax_option_type effects

   Element	Effect(s) if set
   …
   multiline	Specifies that ^ shall match the beginning of a line and $ shall match the end of a line, if the ECMAScript engine is selected.
   …