How to know if a number belongs to a set in PHP?

I'll give an example, it's will be more straight to the point :

I'm working with coordinates and I want to filter the coordinates that do not belong to a set around the picked coordinate. Here for the latitude for instance :

$latitude = 4.3999291;

Basically, I have an array of latitudes, $array_latitudes, and I want to test each one to know if they belong to a ran开发者_如何学Goge around $latitude.

What I've done so far :

$set = range($latitude-0.2, $latitude+0.2, 0.0000001);
foreach ($array_latitudes as $lat){
    if (in_array($lat, $set)){
        echo $lat;
    }
}

So the issue is, you guessed it, about the performance... It takes a really long time to create an array of values of a 10^-7 range !

My question, then, is : "Is there a simpler and more efficient way to return the latitudes in $array_latitudes which belong to the set [$latitude-0.2, $latitude+0.2] with a precision of 10^-7 ?"

Thanks all :-)

---

Could you not just test

if (abs($lat - $latitude) <= 0.2) {
  echo $lat;
}

?

---

Unless I'm misunderstanding something terribly,

if ( ($lat >= $latitude - 0.2) && ($lat <= $latitude + 0.2) )
    echo $lat;

should work.

---

You could use array_filter to do the reduce the array down to values that you're looking for.

class RangeFilter {
    var $lowerBound = 0;
    var $upperBound = 0;
    function RangeFilter($lowerBound, $upperBound) {
        $this->lowerBound = $lowerBound;
        $this->upperBound = $upperBound;
    }
    function filter($value) {
        return ($value <= $this->upperBound && $value >= $this->lowerBound);
    }
}

$latitude = 4.3999291;
$filter = new RangeFilter($latitude - 0.2, $latitude + 0.2);

$filteredCoordinates = array_filter($coordinates, array($filter, 'filter'));

But really, if you want to be simple:

$latitude = 4.3999291;
$lowerBound = $latitude - 0.2;
$upperBound = $latitude + 0.2;

$filteredCoordinates = array();
foreach ($coordinates as $coordinate) {
    if ($coordinate <= $upperBound && $coordinate >= $lowerBound) {
        $filteredCoordinates[] = $coordinate;
    }
}