Proposed resolution:

This wording is relative to N4606.

1. Edit [fs.path.append]/4-5 as indicated:

   template <class Source>
     path& operator/=(const Source& source);
   template <class Source>
     path& append(const Source& source);
   

   -?- Effects: Equivalent to return operator/=(path(source));.

   template <class InputIterator>
     path& append(InputIterator first, InputIterator last);
   

   -4- Effects: Equivalent to return operator/=(path(first, last));.Appends path::preferred_separator to pathname, converting format and encoding if required ([fs.path.cvt]), unless:

   1. — an added directory-separator would be redundant, or
   2. — an added directory-separator would change an relative path to an absolute path, or
   3. — source.empty() is true, or
   4. — *source.native().cbegin() is a directory-separator.

   Then appends the effective range of source ([fs.path.req]) or the range [first, last) to pathname, converting format and encoding if required ([fs.path.cvt]).

   -5- Returns: *this.

[ 2016-08 Chicago ]

Wed AM: Move to Tentatively Ready

Friday AM, in discussing 2664 a comment about missing "equivalent to" language was made, so PR updated.

Previous Resolution [SUPERSEDED]

This wording is relative to N4594.

1. Edit [fs.path.append]/4-5 as indicated:

   template <class Source>
     path& operator/=(const Source& source);
   template <class Source>
     path& append(const Source& source);
   

   -?- Effects: operator/=(path(source))

   -?- Returns: *this.

   template <class InputIterator>
     path& append(InputIterator first, InputIterator last);
   

   -4- Effects: Appends path::preferred_separator to pathname, converting format and encoding if required ([fs.path.cvt]), unless:

   • an added directory-separator would be redundant, or

   • an added directory-separator would change an relative path to an absolute path, or

   • source.empty() is true, or

   • *source.native().cbegin() is a directory-separator.

   Then appends the effective range of source ([fs.path.req]) or the range [first, last) to pathname, converting format and encoding if required ([fs.path.cvt])operator/=(path(first, last)).

   -5- Returns: *this.

[ 2016-07-03, Daniel comments ]

The same wording area is affected by LWG 2664.

The current specification of operator/= taking a const Source& parameter, and of path::append in [fs.path.append] appears to require Source to have a native() and an empty() member, and seemingly requires different behavior for append(empty_range) and append(first, last) when first == last (the last two bullet points being specified with source alone), which doesn't make any sense.

It appears that these overloads can just be specified using the operator/=(const path&) overload.