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    std::isless

    From cppreference.com
     
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    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)
    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

    See More

    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) [edit]
    (C++11)
    		 checks if the first floating-point argument is greater than the second
    (function) [edit]
    C documentation for isless