std::isless

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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

true if x < y, false

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

(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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