24 Strings library [strings]

24.2 Character traits [char.traits]

24.2.1 Character traits requirements [char.traits.require]

In Table 54, X denotes a Traits class defining types and functions for the character container type CharT; c and d denote values of type CharT; p and q denote values of type const CharT*; s denotes a value of type CharT*; n, i and j denote values of type size_­t; e and f denote values of type X​::​int_­type; pos denotes a value of type X​::​pos_­type; state denotes a value of type X​::​state_­type; and r denotes an lvalue of type CharT.
Operations on Traits shall not throw exceptions.
Table 54 — Character traits requirements
Expression
Return type
Assertion/note
Complexity
pre-/post-condition
X​::​char_­type
charT
(described in [char.traits.typedefs])
compile-time
X​::​int_­type
(described in [char.traits.typedefs])
compile-time
X​::​off_­type
(described in [char.traits.typedefs])
compile-time
X​::​pos_­type
(described in [char.traits.typedefs])
compile-time
X​::​state_­type
(described in [char.traits.typedefs])
compile-time
X​::​eq(c,d)
bool
Returns: whether c is to be treated as equal to d.
constant
X​::​lt(c,d)
bool
Returns: whether c is to be treated as less than d.
constant
X​::​compare(p,q,n)
int
Returns: 0 if for each i in [0,n), X​::​eq(p[i],q[i]) is true; else, a negative value if, for some j in [0,n), X​::​lt(p[j],q[j]) is true and for each i in [0,j) X​::​eq(p[i],q[i]) is true; else a positive value.
linear
X​::​length(p)
size_­t
Returns: the smallest i such that X​::​eq(p[i],charT()) is true.
linear
X​::​find(p,n,c)
const X​::​char_­type*
Returns: the smallest q in [p,p+n) such that X​::​eq(*q,c) is true, zero otherwise.
linear
X​::​move(s,p,n)
X​::​char_­type*
for each i in [0,n), performs X​::​assign(s[i],p[i]).
Copies correctly even where the ranges [p,p+n) and [s,s+n) overlap.

Returns: s.
linear
X​::​copy(s,p,n)
X​::​char_­type*
Requires: p not in [s,s+n).
Returns: s.

for each i in [0,n), performs X​::​assign(s[i],p[i]).
linear
X​::​assign(r,d)
(not used)
assigns r=d.
constant
X​::​assign(s,n,c)
X​::​char_­type*
for each i in [0,n), performs X​::​assign(s[i],c).

Returns: s.
linear
X​::​not_­eof(e)
int_­type
Returns: e if X​::​eq_­int_­type(e,X​::​eof()) is false, otherwise a value f such that X​::​eq_­int_­type(f,X​::​eof()) is false.
constant
X​::​to_­char_­type(e)
X​::​char_­type
Returns: if for some c, X​::​eq_­int_­type(e,X​::​to_­int_­type(c)) is true, c; else some unspecified value.
constant
X​::​to_­int_­type(c)
X​::​int_­type
Returns: some value e, constrained by the definitions of to_­char_­type and eq_­int_­type.
constant
X​::​eq_­int_­type(e,f)
bool
Returns: for all c and d, X​::​eq(c,d) is equal to X​::​eq_­int_­type(X​::​to_­int_­type(c), X​::​to_­int_­type(d)); otherwise, yields true if e and f are both copies of X​::​eof(); otherwise, yields false if one of e and f is a copy of X​::​eof() and the other is not; otherwise the value is unspecified.
constant
X​::​eof()
X​::​int_­type
Returns: a value e such that X​::​eq_­int_­type(e,X​::​to_­int_­type(c)) is false for all values c.
constant
The class template
template<class charT> struct char_traits;
shall be provided in the header <string> as a basis for explicit specializations.