Simplest way to calculate amount of even numbers in given range

Question

What is the simplest way to calculate the amount of even numbers in a range of unsigned integers?

An example: if range is [0...4] then the answer is 3 (0,2,4)

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Answer 1

In terms of start and length:

(length >> 1) + (1 & ~start & length)

half the length plus 1 if start is even and length is odd.

In terms of start and end:

((end - start + 1) >> 1) + (1 & ~start & ~end)

half the length plus 1 if start is even and end is even.