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
ExpressionReturn typeAssertion/noteComplexity
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.
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]).
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.
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.