Is multiplication always commutative in inexact floating point arithmetic?

Question

I\'m trying to understand some code in the D language runtime. It seems like there are separate functions for the following two things:

array1[] += scalar *         


        

Answer 1

I guess the difference is just in the function prototypes - one is (double, double[]) and the other is (double[], double). But the result should be the same either way.

Answer 2

I know nothing about the D language, but I'll happily answer the question in your title:

Is multiplication always commutative in inexact floating point arithmetic?

Up to the "payload" of NaN values, yes. IEEE-754 floating-point multiplication is commutative (and so is addition). If you don't know what the payload of a NaN is, don't worry about it.