[char.traits.require]

In Table 79, X denotes a traits class defining types and functions for the character container type C; c and d denote values of type C; p and q denote values of type const C*; s denotes a value of type C*; 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; and r denotes an lvalue of type C.

No expression which is part of the character traits requirements specified in this subclause [char.traits.require] shall exit via an exception.

Table 79: Character traits requirements [tab:char.traits.req]

🔗	Expression	Return type	Assertion/note	Complexity
🔗			pre-/post-condition
🔗	X::char_type	C		compile-time
🔗	X::int_type		(described in [char.traits.typedefs])	compile-time
🔗	X::off_type		(described in [iostreams.limits.pos] and [iostream.forward])	compile-time
🔗	X::pos_type		(described in [iostreams.limits.pos] and [iostream.forward])	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, nullptr 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*	Preconditions: The ranges [p, p+n) and [s, s+n) do not overlap. 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

23 Strings library [strings]

23.2 Character traits [char.traits]

23.2.2 Character traits requirements [char.traits.require]