Function qt_core::q_float_distance_2_float

pub unsafe fn q_float_distance_2_float(a: c_float, b: c_float) -> u32

Returns the number of representable floating-point numbers between a and b.

Calls C++ function: quint32 qFloatDistance(float a, float b).

C++ documentation:

Returns the number of representable floating-point numbers between a and b.

This function provides an alternative way of doing approximated comparisons of floating-point numbers similar to qFuzzyCompare(). However, it returns the distance between two numbers, which gives the caller a possibility to choose the accepted error. Errors are relative, so for instance the distance between 1.0E-5 and 1.00001E-5 will give 110, while the distance between 1.0E36 and 1.00001E36 will give 127.

This function is useful if a floating point comparison requires a certain precision. Therefore, if a and b are equal it will return 0. The maximum value it will return for 32-bit floating point numbers is 4,278,190,078. This is the distance between -FLT_MAX and +FLT_MAX.

The function does not give meaningful results if any of the arguments are Infinite or NaN. You can check for this by calling qIsFinite().

The return value can be considered as the "error", so if you for instance want to compare two 32-bit floating point numbers and all you need is an approximated 24-bit precision, you can use this function like this:

if (qFloatDistance(a, b) < (1 << 7)) {   // The last 7 bits are not
                                          // significant
      // precise enough
}

This function was introduced in Qt 5.2.

See also qFuzzyCompare().