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std::isless

Defined in header <cmath>
(1) 
bool isless( float x, float y );
bool isless( double x, double y );
bool isless( long double x, long double y );
 (since C++11)
(until C++23) 
constexpr bool isless( /* floating-point-type */ x,
                       /* floating-point-type */ y );
 (since C++23)
Additional overloads
Defined in header <cmath> 
template< class Arithmetic1, class Arithmetic2 >
bool isless( Arithmetic1 x, Arithmetic2 y );
 (A) (since C++11)
(constexpr since C++23)
1) Determines if the floating point number x is less than 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 FE_INVALID 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 long double, then std::isless(num1, num2) has the same effect as std::isless(static_cast<long double>(num1), static_cast<long double>(num2)).
  • Otherwise, if num1 and/or num2 has type double or an integer type, then std::isless(num1, num2) has the same effect as std::isless(static_cast<double>(num1), static_cast<double>(num2)).
  • Otherwise, if num1 or num2 has type float, then std::isless(num1, num2) has the same effect as std::isless(static_cast<float>(num1), static_cast<float>(num2)).
(until C++23)

If num1 and num2 have arithmetic types, then std::isless(num1, num2) has the same effect as std::isless(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 overload resolution does not result in a usable candidate from the overloads provided.

 (since C++23)

See also

function object implementing x < y
(class template)
(C++11)
 checks if the first floating-point argument is greater than the second
(function)
C documentation for isless

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