Question

Can you please explain the order of operations for the following function that reverses a string?

//http://www.perlmonks.org/?node_id=589993 source of method
/* reverse a string in place, return str */
static char* reverse(char* str)
{
    char* left  = str;
    char* right = left + strlen(str) - 1;
    char  tmp;
    while (left < right)
    {
        tmp      = *left;
        *left++  = *right;//This part is real confusing...Does ++ happen after the assignment?
        *right-- = tmp;//This one is just as bad
    }
    return str;
}

I can follow the first 3 lines in the method pretty easily, but once it hits the while loop I am at a loss for how this works. Specifically the lines marked above. Thank you.

Answer 1

*left++  = *right

In this statement, *left is assigned *right, and then after all of that left (not *left) is incremented. The same logic goes for *right--

So rewritten, the pseudocode would be this:

while(not halfway)
{
    tmp = left value
    left value = right value
    left position += 1
    right value = tmp
    right position -= 1        
}