var other : Transform;
if (other) {
    var dist = Vector3.Distance(other.position, transform.position);
    print ("Distance to other: " + dist);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Transform other;
    void Example() {
        if (other) {
            float dist = Vector3.Distance(other.position, transform.position);
            print("Distance to other: " + dist);
        }
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public other as Transform

    def Example():
        if other:
            dist as single = Vector3.Distance(other.position, transform.position)
            print(('Distance to other: ' + dist))