var walkSpeed = 5.0;
var runSpeed = 10.0;
var speed = 8.0;

function Start() {
    // parameter is now 3 / 5
    var parameter : float = Mathf.InverseLerp(walkSpeed, runSpeed, speed);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public float walkSpeed = 5.0F;
    public float runSpeed = 10.0F;
    public float speed = 8.0F;
    void Start() {
        float parameter = Mathf.InverseLerp(walkSpeed, runSpeed, speed);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public walkSpeed as single = 5.0F

    public runSpeed as single = 10.0F

    public speed as single = 8.0F

    def Start():
        parameter as single = Mathf.InverseLerp(walkSpeed, runSpeed, speed)