(C# and Java)Unable to give the Damage from enemy bullet script to Player Health.

I want to give the Damage from enemy`s bullet script to Player Health, but it showed me this error :

Assets/Tactical Shooter AI/Tactical AI/Csharp/Damage Scripts/BulletScript.cs(15,3): error CS0246: The type or namespace name HealthingScript' could not be found. Are you missing an assembly reference? Here is my Enemys bullet script the problem is in IEnumertor ApplyDamage method :

 using UnityEngine;
 using System.Collections;
 
 /*
  * Moves an object until it hits a target, at which time it calls the Damage(float) method on all scripts on the hit object
  * Can also home in on targets and "detonate" when in close proximity.
  * */
 
 namespace TacticalAI
 {
     public class BulletScript : MonoBehaviour
     {
 
         public string damageMethodName = "Damage";
         HealthingScript hs;
 
         public float speed = 1000;
         public LayerMask layerMask;
         public float maxLifeTime = 3;
 
         //Bullet Stuff
         public float damage = 16;
 
         //use for shotguns
         public float bulletForce = 100;
         public int points = 12;
 
         //Hit Effects
         public GameObject hitEffect;
         public float hitEffectDestroyTime = 1;
         public string hitEffectTag = "HitBox";
         public GameObject missEffect;
         public float missEffectDestroyTime = 1;
         public float timeToDestroyAfterHitting = 0.5f;
         private RaycastHit hit;
         private Transform myTransform;
 
         //Rotation
         private Quaternion targetRotation;
 
         private Transform target = null;
         public float homingTrackingSpeed = 3;
 
         public float minDistToDetonate = 0.5f;
         private float minDistToDetonateSqr;
 
         public string friendlyTag;        
         
 
         void Awake()
         {
             myTransform = transform;
             Move();
             StartCoroutine(SetTimeToDestroy());
         }
 
         //Automatically destroy the bullet after a certain amount of time
         //Especially useful for missiles, which may end up flying endless circles around their target,
         //long after the appropriate sound effects have ended.
         IEnumerator SetTimeToDestroy()
         {
             yield return new WaitForSeconds(maxLifeTime);
 
             if (target)
             {
                 Instantiate(hitEffect, myTransform.position, myTransform.rotation);
             }
 
             Destroy(gameObject);
         }
 
         IEnumerator ApplyDamage()
         {
             //Reduce the enemy's health
             //Does NOT travel up the heirarchy.  
             if (hit.collider.tag == "Player") {
           
 
                 hit.collider.SendMessage ("PlayerDamage", damage, SendMessageOptions.DontRequireReceiver);
             }
            
 
             //Produce the appropriate special effect
             if (hit.transform.tag == hitEffectTag && hitEffect)
             {
                     GameObject currentHitEffect = (GameObject)(Instantiate(hitEffect, hit.point, myTransform.rotation));
                     GameObject.Destroy(currentHitEffect, hitEffectDestroyTime);
             }
             else if (missEffect)
             {
                 GameObject currentMissEffect = (GameObject)(Instantiate(missEffect, hit.point + hit.normal * 0.01f, Quaternion.LookRotation(hit.normal)));
                 GameObject.Destroy(currentMissEffect, missEffectDestroyTime);
             }
             this.enabled = false;
             yield return null;
 
             //Wait a fram to apply forces as we need to make sure the thing is dead
             if (hit.rigidbody)
                 hit.rigidbody.AddForceAtPosition(myTransform.forward * bulletForce, hit.point, ForceMode.Impulse);
 
             //Linger around for a while to let the trail renderer dissipate (if the bullet has one.)
             Destroy(gameObject, timeToDestroyAfterHitting);
         }
 
         // Update is called once per frame
         void Update()
         {
             Move();
         }
 
         //Move is a seperate method as the bullet must move IMMEDIATELY.
         //If it does not, the shooter may literally outrun the bullet-momentarily.
         //If the shooter passes the bullet, the bullet will then start moving and hit the shooter in the back.
         //That would not be good.
         void Move()
         {
             //Check to see if we're going to hit anything.  If so, move right to it and deal damage
             if (Physics.Raycast(myTransform.position, myTransform.forward, out hit, speed * Time.deltaTime, layerMask.value))
             {
                 myTransform.position = hit.point;
                 StartCoroutine(ApplyDamage());
             }
             else
             {
                 //Move the bullet forwards
                 transform.Translate(Vector3.forward * Time.deltaTime * speed);
             }
 
             //Home in on the target
             if (target != null)
             {
                 //Firgure out the rotation required to move directly towards the target
                 targetRotation = Quaternion.LookRotation(target.position - transform.position);
                 //Smoothly rotate to face the target over several frames.  The slower the rotation, the easier it is to dodg.
                 transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, homingTrackingSpeed * Time.deltaTime);
 
                 Debug.DrawRay(transform.position, (target.position - transform.position).normalized * minDistToDetonate,Color.red);
                 //Projectile will "detonate" upon getting close enough to the target..
                 if (Vector3.SqrMagnitude(target.position - transform.position) < minDistToDetonateSqr)
                 {
                     //The hitEffect should be your explosion.
                     Instantiate(hitEffect, myTransform.position, myTransform.rotation);
                     GameObject.Destroy(gameObject);
                 }
             }
         }
 
         //To avoid costly SqrRoot in Vector3.Distance
         public void SetDistToDetonate(float x)
         {
             minDistToDetonateSqr = x * x;
         }
 
         //Call this method upon instantating the bullet in order to make it home in on a target.
         public void SetAsHoming(Transform t)
         {
             target = t;
             SetDistToDetonate(minDistToDetonate);  
         }
     }
 }
 

Here is my PlayerHealth code the name of my player script is HealthingScript

COde is :

 #pragma strict

 
 var hitPoints : float;
 var maxHitPoints : int;
 var regeneration : boolean = false;
 var regenerationSpeed : float;
 var aSource : AudioSource;
 var painSound : AudioClip;
 var fallDamageSound : AudioClip;
 var deadReplacement : Transform;
 var mySkin : GUISkin;
 private var radar : GameObject;
 var damageTexture : Texture;
 private var t : float = 0.0;
 private var alpha : float;
 private var isDead : boolean = false;
 private var scoreManager : ScoreManager;
 var camShake : Transform;
 
 function Start(){
     if(regeneration)
          hitPoints = maxHitPoints;
     alpha = 0.0;
 }
 
 function Update(){
     if (t > 0.0){ 
         t -= Time.deltaTime;
         alpha = t;
     }
     
     if(regeneration){
         if( hitPoints < maxHitPoints)
             hitPoints += Time.deltaTime * regenerationSpeed;
     }        
 }
 
 public function PlayerDamage (damage : int) {
     if (hitPoints < 0.0) return;
     
     hitPoints -= damage;
     aSource.PlayOneShot(painSound, 1.0);
     t = 2.0;        
     
     if (hitPoints <= 0.0) Die();
 }
 
 //Picking up MedicKit
 function Medic (medic : int){
     
     hitPoints += medic;
     
     if( hitPoints > maxHitPoints){
         var convertToScore : float = hitPoints - maxHitPoints;
         scoreManager = gameObject.Find("ScoreManager").GetComponent(ScoreManager);
         scoreManager.addScore(convertToScore);
         hitPoints = maxHitPoints;
     }
 }
 
 function Die () {
     if(isDead) return;
     isDead = true;
     
     if(scoreManager == null)
         scoreManager = gameObject.Find("ScoreManager").GetComponent(ScoreManager);
     scoreManager.PlayerDead();
     
     Instantiate(deadReplacement, transform.position, transform.rotation);
     Destroy(gameObject);
 }
 
 
 function OnGUI () {
     GUI.skin = mySkin;
 
     GUI.Label (Rect(40, Screen.height - 50,60,60)," Health: ");
     GUI.Label (Rect(100, Screen.height - 50,60,60),"" +hitPoints.ToString("F0"), mySkin.customStyles[0]);
     
     
     GUI.color.a = alpha;
     GUI.DrawTexture(new Rect(0,0,Screen.width, Screen.height), damageTexture);
 }
 
 
 function PlayerFallDamage(dam : float){
     PlayerDamage(dam);
     if(fallDamageSound) aSource.PlayOneShot(fallDamageSound, 1.0);
 }
 
 function Shake(p : float) {
     var t : float = 1.0;
     var shakePower : float;
     while (t > 0.0) {
         t -= Time.deltaTime;
         shakePower = t/50;
         
         camShake.rotation.x += Random.Range(-shakePower, shakePower);
         camShake.rotation.y += Random.Range(-shakePower, shakePower);
         camShake.rotation.z += Random.Range(-shakePower, shakePower);
         
         yield;        
     }
 }

I am not a noob but I don`t know why I can`t able to do this

Any comment and solution is appreciated here! Thanks!