pow() works with real floating-point numbers and uses under the hood the formula pow(x,y) = e^(y log(x)) to calculate x^y. The int are converted to double before calling pow. (log is the natural logarithm, e-based) x^2 using pow() is therefore slower than x*x. Edit based on relevant comments Using pow even with integer exponents may … Read more
In C++, it’s always sufficient to use std::abs; it’s overloaded for all the numerical types. In C, abs only works on integers, and you need fabs for floating point values. These are available in C++ (along with all of the C library), but there’s no need to use them.
The function pow operates on two floating-point values, and can raise one to the other. This is done through approximating algorithm, as it is required to be able to handle values from the smallest to the largest. As this is an approximating algorithm, it sometimes gets the value a little bit wrong. In most cases, … Read more
Looks like libstdc++ is correct, this is not ill-formed, although we will see there are some doubts expressed over whether this is a defect in LWG active issue 2192. The draft C++11 standard section 26.8 [c.math] paragraph 11 says: Moreover, there shall be additional overloads sufficient to ensure: and includes the following item: Otherwise, if … Read more
std::ceil rounds up to the nearest integer std::floor rounds down to the nearest integer std::round performs the behavior you expect please give a use case with numbers if this does not provide you with what you need!
Implementations of the C++ standard library are permitted to declare C library functions in the global namespace as well as in std. Some would call this a mistake, since (as you’ve found) the namespace pollution can cause conflicts with your own names. However, that’s the way it is, so we must live with it. You’ll … Read more
Actually, because of old and annoying legacy, almost none of the math functions can be constexpr, since they all have the side-effect of setting errno on various error conditions, usually domain errors.
C/C++ provides sin(a), cos(a), tan(a), etc. functions that require a parameter with radian units rather than degrees. double DegreesToRadians(d) performs a conversion that is close but an approximate as the conversion results are rounded. Also machine M_PI is close, but not the same value as the the mathematical irrational π. OP’s code with 180 passed … Read more