std::char_traits<char>:: eq/lt, std::char_traits<wchar_t>:: eq/lt, std::char_traits<char8_t>:: eq/lt, std::char_traits<char16_t>:: eq/lt, std::char_traits<char32_t>:: eq/lt
From cppreference.com
<
cpp
|
string
|
char traits
|
static
bool
eq
(
char_type a, char_type b
)
;
|
(1) |
(constexpr since C++11)
(noexcept since C++11) |
|
static
bool
lt
(
char_type a, char_type b
)
;
|
(2) |
(constexpr since C++11)
(noexcept since C++11) |
Compares two characters.
1)
Compares
a
and
b
for equality, behaves identically to
-
static_cast
<
unsigned
char
>
(
a
)
==
static_cast
<
unsigned
char
>
(
b
)
, if
char_typeis char , - a == b otherwise.
2)
Compares
a
and
b
in such a way that they are totally ordered, behaves identically to
-
static_cast
<
unsigned
char
>
(
a
)
<
static_cast
<
unsigned
char
>
(
b
)
, if
char_typeis char , - a < b otherwise.
See
CharTraits
for the general requirements on character traits for
X::eq
and
X::lt
.
Parameters
| a, b | - | character values to compare |
Return value
1)
true
if
a
and
b
are equal,
false
otherwise.
2)
true
if
a
is less than
b
,
false
otherwise.
Complexity
Constant.
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 467 | C++98 |
for
std::
char_traits
<
char
>
, the semantics of
eq()
and
lt()
are the same as the built-in == and < on char respectively [1] |
changed to built-in
==
and
< on unsigned char |
- ↑ Most implementations call std::memcmp() for efficiency, which interprets the data as arrays of unsigned char . If char is signed on such implementations, std:: char_traits < char > fails to satisfy the requirements of CharTraits .