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2761. directory_entry comparisons are members

Section: 31.12.10.4 [fs.dir.entry.obs] Status: NAD Submitter: Ville Voutilainen Opened: 2016-08-03 Last modified: 2017-03-19

Priority: 2

View all other issues in [fs.dir.entry.obs].

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Discussion:

The comparison operators for directory_entry are member functions (31.12.10.4 [fs.dir.entry.obs]).

That means that a directory_entry can be compared with a path, but a path cannot be compared with a directory_entry, because the left-hand side is not subject to conversions. This seems unfortunate.

Note that the comparisons for path are non-members (31.12.6.8 [fs.path.nonmember]).

The meta-p/r is to turn the directory_entry comparisons into non-member functions.

[2016-08 Chicago]

Wed PM: Priority 2

[2016-10-05 Ville provides concrete wording]

[2016-10 Telecon]

This (comparing a path with a directory_entry) works today w/o any changes. Closing as NAD.

Proposed resolution:

This wording is relative to N4606.

1. In [fs.class.directory_entry] synopsis, edit as follows:

   namespace std::filesystem {
   class directory_entry {
   public:
     […]
     bool operator< (const directory_entry& rhs) const noexcept;
     bool operator==(const directory_entry& rhs) const noexcept;
     bool operator!=(const directory_entry& rhs) const noexcept;
     bool operator<=(const directory_entry& rhs) const noexcept;
     bool operator> (const directory_entry& rhs) const noexcept;
     bool operator>=(const directory_entry& rhs) const noexcept;
   
   private:
     path pathobject; // exposition only
   };
   
   bool operator< (const directory_entry& lhs, const directory_entry& rhs) noexcept;
   bool operator==(const directory_entry& lhs, const directory_entry& rhs) noexcept;
   bool operator!=(const directory_entry& lhs, const directory_entry& rhs) noexcept;
   bool operator<=(const directory_entry& lhs, const directory_entry& rhs) noexcept;
   bool operator> (const directory_entry& lhs, const directory_entry& rhs) noexcept;
   bool operator>=(const directory_entry& lhs, const directory_entry& rhs) noexcept;
   
   }
   

2. In 31.12.10.4 [fs.dir.entry.obs]/6-11, edit as follows:

   bool operator==(const directory_entry& lhs, const directory_entry& rhs) const noexcept;
   

   -6- Returns: pathobjectlhs.path() == rhs.pathobjectpath().

   bool operator!=(const directory_entry& lhs, const directory_entry& rhs) const noexcept;
   

   -7- Returns:: pathobjectlhs.path() != rhs.pathobjectpath().

   bool operator< (const directory_entry& lhs, const directory_entry& rhs) const noexcept;
   

   -8- Returns:: pathobjectlhs.path() < rhs.pathobjectpath().

   bool operator<<=(const directory_entry& lhs, const directory_entry& rhs) const noexcept;
   

   -9- Returns:: pathobjectlhs.path() <= rhs.pathobjectpath().

   bool operator> (const directory_entry& lhs, const directory_entry& rhs) const noexcept;
   

   -10- Returns:: pathobjectlhs.path() > rhs.pathobjectpath().

   bool operator>=(const directory_entry& lhs, const directory_entry& rhs) const noexcept;
   

   -11- Returns:: pathobjectlhs.path() >= rhs.pathobjectpath().