How to implement max/min without comparation operations(if,<,> and so on)?

Question

SHould be implemented in PHP.

Answer 1

Standard functions: max() and min()

Answer 2

The simplest way to implement max/min without comparison operators is to use the built-in PHP functions

$max = max($x, $y);

and

$min = min($x, $y);

Answer 3

I don't know how to do it in PHP, but this is more or less pseudo code:

function MAX(var a, var b)
{
    return a-b?a:b;
}
function MIN(var a, var b)
{
    return b-a?a:b;
}

Answer 4

bool equal(int a, int b){ // we have no comparison operators, so we make our own
    return !(a-b);
}

int abs(int a) {
    return sqrt(a*a); // I don't know whether this uses comparison operators
}

int max(int a, int b) {
    while(equal(abs(a-b), a-b)) // no if, but we must have some kind of control flow
        return a;
    return b;
}

int min(int a, int b) {
    while(equal(abs(a-b), a-b))
        return b;
    return a;
}

P.S. comparison functions could be implemented from abs(), too:

bool ispositive(int a) {
    return a + abs(a);
}

bool greaterthan(int a, int b){
    return ispositive(a-b);
}

Answer 5

From http://www.coranac.com/documents/bittrick/:

min = b + ((a-b) & (a-b)>>31);
max = a - ((a-b) & (a-b)>>31);

Caveat: works only with signed integers. (well, 32-bit integers in the above snippet, but that can be easily changed.) An explanation of how it works can be found at said link.