std::ranges:: less
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Defined in header
<functional>
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|
struct
less
;
|
(since C++20) | |
Function object for performing comparisons. Deduces the parameter types of the function call operator from the arguments (but not the return type).
Nested types
| Nested type | Definition |
is_transparent
|
unspecified |
Member functions
|
operator()
|
checks if the first argument is
less
than the second
(public member function) |
std::ranges::less:: operator()
|
template
<
class
T,
class
U
>
constexpr bool operator ( ) ( T && t, U && u ) const ; |
||
Given the expression std:: forward < T > ( t ) < std:: forward < U > ( u ) as expr :
-
If
expr
results in a call to
built-in
operator
<
comparing pointers, given the
composite pointer type
of
t
and
u
as
P:
-
-
If the converted
t
precedes the converted
u
(both are of type
P) in the implementation-defined strict total order over pointers , returns true , otherwise returns false . -
If the conversion sequence from
TtoPor the conversion sequence fromUtoPis not equality-preserving , the behavior is undefined.
-
If the converted
t
precedes the converted
u
(both are of type
- Otherwise:
-
- Returns the result of expr .
- If std:: totally_ordered_with < T, U > is not modeled, the behavior is undefined.
This overload participates in overload resolution only if std:: totally_ordered_with < T, U > is satisfied.
If there exists an expression
expr1
of type
T
and an expression
expr2
of
U
, such that the comparison results of
expr1
and
expr2
violate
strict total ordering
(rules are defined below), the behavior is undefined.
The comparison results of expr1 and expr2 follow strict total ordering only if exactly one of the following expressions is true :
- std :: ranges:: less { } ( expr1, expr2 )
- std :: ranges:: less { } ( expr2, expr1 )
- std :: ranges:: equal_to { } ( expr1, expr2 )
Notes
Unlike
std::less
,
std::ranges::less
requires all six comparison operators
<
,
<=
,
>
,
>=
,
==
and
!=
to be valid (via the
totally_ordered_with
constraint).
Example
|
This section is incomplete
Reason: no example |
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 3530 | C++20 | syntactic checks were relaxed while comparing pointers | only semantic requirements are relaxed |
See also
|
function object implementing
x
<
y
(class template) |