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cppdraft/fs/path/fmt/cvt.md

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+[fs.path.fmt.cvt]
+
+# 31 Input/output library [[input.output]](./#input.output)
+
+## 31.12 File systems [[filesystems]](filesystems#fs.path.fmt.cvt)
+
+### 31.12.6 Class path [[fs.class.path]](fs.class.path#fs.path.fmt.cvt)
+
+#### 31.12.6.3 Conversions [[fs.path.cvt]](fs.path.cvt#fs.path.fmt.cvt)
+
+#### 31.12.6.3.1 Argument format conversions [fs.path.fmt.cvt]
+
+[1](#1)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13935)
+
+[*Note [1](#note-1)*:
+
+The format conversions described in this subclause
+are not applied on POSIX-based operating systems
+because on these systems:
+
+- [(1.1)](#1.1)
+
+  The generic format is acceptable as a native path[.](#1.1.sentence-1)
+
+- [(1.2)](#1.2)
+
+  There is no need to distinguish between native format and generic format in function arguments[.](#1.2.sentence-1)
+
+- [(1.3)](#1.3)
+
+  Paths for regular files and paths for directories share the same syntax[.](#1.3.sentence-1)
+
+— *end note*]
+
+[2](#2)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13947)
+
+Several functions are defined to accept [*detected-format*](#def:detected-format) arguments,
+which are character sequences[.](#2.sentence-1)
+
+A detected-format argument represents a path
+using either a pathname in the generic format ([[fs.path.generic]](fs.path.generic "31.12.6.2 Generic pathname format"))
+or a pathname in the native format ([[fs.class.path]](fs.class.path "31.12.6 Class path"))[.](#2.sentence-2)
+
+Such an argument is taken to be in the generic format if and only if
+it matches the generic format and is not acceptable to the operating system
+as a native path[.](#2.sentence-3)
+
+[3](#3)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13956)
+
+[*Note [2](#note-2)*:
+
+Some operating systems have no unambiguous way to distinguish between native format and generic format arguments[.](#3.sentence-1)
+
+This is by design as it simplifies use for operating systems that do not require
+disambiguation[.](#3.sentence-2)
+
+It is possible that an implementation for an operating system
+where disambiguation is needed distinguishes between the formats[.](#3.sentence-3)
+
+— *end note*]
+
+[4](#4)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13964)
+
+Pathnames are converted as needed between the generic and native formats
+in an operating-system-dependent manner[.](#4.sentence-1)
+
+Let *G(n)* and *N(g)* in a mathematical sense
+be the implementation's functions that convert native-to-generic
+and generic-to-native formats respectively[.](#4.sentence-2)
+
+If *g=G(n)* for some *n*, then *G(N(g))=g*;
+if *n=N(g)* for some *g*, then *N(G(n))=n*[.](#4.sentence-3)
+
+[*Note [3](#note-3)*:
+
+Neither *G* nor *N* need be invertible[.](#4.sentence-4)
+
+— *end note*]
+
+[5](#5)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13976)
+
+If the native format requires paths for regular files to be formatted
+differently from paths for directories, the path shall be treated as a directory
+path if its last element is a [*directory-separator*](fs.path.generic#nt:directory-separator "31.12.6.2 Generic pathname format [fs.path.generic]"),
+otherwise it shall be treated as a path to a regular file[.](#5.sentence-1)
+
+[6](#6)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13982)
+
+[*Note [4](#note-4)*:
+
+A path stores a native format pathname ([[fs.path.native.obs]](fs.path.native.obs "31.12.6.5.6 Native format observers"))
+and acts as if it also stores a generic format pathname,
+related as given below[.](#6.sentence-1)
+
+The implementation can generate the generic format pathname
+based on the native format pathname (and possibly other information)
+when requested[.](#6.sentence-2)
+
+— *end note*]
+
+[7](#7)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13992)
+
+When a path is constructed from or is assigned a single representation
+separate from any path, the other representation is selected
+by the appropriate conversion function (*G* or *N*)[.](#7.sentence-1)
+
+[8](#8)
+
+[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L13997)
+
+When the (new) value *p* of one representation of a path
+is derived from the representation of that or another path,
+a value *q* is chosen for the other representation[.](#8.sentence-1)
+
+The value *q* converts to *p* (by *G* or *N* as appropriate)
+if any such value does so;*q* is otherwise unspecified[.](#8.sentence-2)
+
+[*Note [5](#note-5)*:
+
+If *q* is the result of converting any path at all,
+it is the result of converting *p*[.](#8.sentence-3)
+
+— *end note*]