From cppreference.com
Defined in header
boolislessequal(floatx,floaty);boolislessequal(doublex,doubley);boolislessequal(longdoublex,longdoubley); (1)(since C++11)
(until C++23)constexprboolislessequal(/* floating-point-type */x,/* floating-point-type */y);(since C++23)
Defined in header
template<classArithmetic1,classArithmetic2>boolislessequal(Arithmetic1x,Arithmetic2y); (A) (since C++11)
(constexpr since C++23)1) Determines if the floating point number x is less than or equal to the floating-point number y, without setting floating-point exceptions. The library provides overloads for all cv-unqualified floating-point types as the type of the parameters x and y.(since C++23)
A) Additional overloads are provided for all other combinations of arithmetic types.
Parameters
x, y - floating-point or integer values Return value
true if x<=y, false otherwise.
Notes
The built-in operator<= for floating-point numbers may raise
if one or both of the arguments is NaN. This function is a "quiet" version of operator<=.
The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their first argument num1 and second argument num2:
If num1 or num2 has type longdouble, then std::islessequal(num1,num2) has the same effect as std::islessequal(static_cast<longdouble>(num1),
static_cast<longdouble>(num2)).
Otherwise, if num1 and/or num2 has type double or an integer type, then std::islessequal(num1,num2) has the same effect as std::islessequal(static_cast<double>(num1),
static_cast<double>(num2)).
Otherwise, if num1 or num2 has type float, then std::islessequal(num1,num2) has the same effect as std::islessequal(static_cast<float>(num1),
static_cast<float>(num2)).
(until C++23)If num1 and num2 have arithmetic types, then std::islessequal(num1,num2) has the same effect as std::islessequal(static_cast</*common-floating-point-type*/>(num1),
static_cast</*common-floating-point-type*/>(num2)), where /*common-floating-point-type*/ is the floating-point type with the greatest
floating-point conversion rank
and greatest
floating-point conversion subrank
between the types of num1 and num2, arguments of integer type are considered to have the same floating-point conversion rank as double.
If no such floating-point type with the greatest rank and subrank exists, then
does not result in a usable candidate from the overloads provided.
(since C++23)See also