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

Oh well, why not:

#include 

int ecount( int begin, int end ) {
    assert( begin <= end );
    int size = (end - begin) + 1;
    if ( size % 2 == 0  || begin % 2 == 1 ) {
        return size / 2;
    }
    else {
        return size / 2 + 1;
    }
}

int main() {
    assert( ecount( 1, 5 ) == 2 );
    assert( ecount( 1, 6 ) == 3 );
    assert( ecount( 2, 6 ) == 3 );
    assert( ecount( 1, 1 ) == 0 );
    assert( ecount( 2, 2 ) == 1 );
}