Question

i have one function but i am not getting what is it doing.

Below is my function

// My function gets two parameters lat and long

public function generate_peano1($lat, $lon)
{
    $lat = (($lat + 90.0)/180.0 * 32767) + 16384;
    $lon = ($lon + 180.0)/360.0 * 65535;

    $lat_16 = $lat&0x0000FFFF; // Not getting what is here.
    $lon_16 = $lon&0x0000FFFF; // Not getting what is here.

    $peano = self::derive_peano_32($lat_16, $lon_16);
    return $peano;

}

Thanks

Avinash

Answer 1

The & operator is the bitwise AND operator. 0x0000FFFF represents 16 unset bits (zeroes) followed by 16 set bits (ones) in hexadecimal.
$lat & 0x0000FFFF will then give you the 16 least significant bits (on a little endian machine, which is the most common architecture) of $lat.

As to why is that needed here it depends on what does self::derive_peano_32() do. I’d imagine it takes two 16 bit values and concatenate them somehow so they fit in a regular 32 bit integer.