Environment class can now have a 'special' variable for the Program Counter defined (using the PCLabel property).

src/compiler/env.js

@@ -1,6 +1,7 @@
 
-// ALL Environments share the same program counter!
+// ALL Environments share the same program counter and label!
 var PC = 0;
+var PCL = "__PC__";
 
 
 class Environment{
@@ -14,10 +15,17 @@ class Environment{
     if (val < 0)
       throw new RangeError("Program Counter value is out of bounds.");
     PC = val;
-  } 
+  }
+
+  get PCLabel(){return PCL;}
+  set PCLabel(pcl){
+    if (typeof(pcl) !== 'string' || pcl === "")
+      throw new TypeError("Expected a non-zero-length string.");
+    PCL = pcl;
+  }
 
   hasVar(name){
-    if (name in Object.keys(this.__vars))
+    if (name === PCL || name in Object.keys(this.__vars))
       return true;
     if (this.__parent !== null)
       return this.__parent.hasVar(name);
@@ -25,6 +33,7 @@ class Environment{
   }
 
   getVarValue(name){
+    if (name === PCL){return PC;}
     if (name in Object.keys(this.__vars))
       return this.__vars[name];
     if (this.__parent !== null)
@@ -33,6 +42,12 @@ class Environment{
   }
 
   setVarValue(name, val){
+    if (name === PCL){
+      if (typeof(val) !== 'number' || val < 0)
+        throw new Error("Special Variable '" + name + "' expected to be a possitive integer.");
+      PC = Math.floor(val);
+      return this;
+    }
     if (!(name in Object.keys(this.__vars))){
       if (this.__parent.hasVar(name))
         return this.__parent.setVarVal(name, val);