Finished implementing Netscript. Not completely tested yet. Find out how to make it multithreaded (Web Workers is the best way according to internet

src/Netscript/Evaluator.js

@@ -0,0 +1,124 @@
+/* Evaluator
+ * 	Evaluates the Abstract Syntax Tree for Netscript
+ *  generated by the Parser class
+ */
+ 
+function evaluate(exp, env) {
+    switch (exp.type) {
+		case "num":
+		case "str":
+		case "bool":
+			return exp.value;
+
+		case "var":
+			return env.get(exp.value);
+
+		//Can currently only assign to "var"s
+		case "assign":
+			if (exp.left.type != "var")
+				throw new Error("Cannot assign to " + JSON.stringify(exp.left));
+			return env.set(exp.left.value, evaluate(exp.right, env));
+
+		case "binary":
+			return apply_op(exp.operator,
+							evaluate(exp.left, env),
+							evaluate(exp.right, env));
+
+
+		case "if":
+			var numConds = exp.cond.length;
+			var numThens = exp.then.length;
+			if (numConds == 0 || numThens == 0 || numConds != numThens) {
+				throw new Error ("Number of conds and thens in if structure don't match (or there are none)");
+			}
+			
+			for (var i = 0; i < numConds; i++) {
+				var cond = evaluate(exp.cond[i], env);
+				if (cond) return evaluate(exp.then, env);
+			}
+			
+			//Evaluate else if it exists, snce none of the conditionals
+			//were true
+			return exp.else ? evaluate(exp.else, env) : false;
+				
+		case "for":
+			evaluate(exp.init, env);
+			cond = evaluate(exp.cond, env);
+			console.log("Evaluated the conditional");
+			while (cond) {
+				evaluate(exp.code, env);
+				evaluate(exp.postloop, env);
+				cond = evaluate(exp.cond, env);
+			}
+		
+			//TODO Return somethin?
+			break;
+		case "while":
+			cond = evaluate(exp.cond, env);
+			
+			while (cond) {
+				evaluate(exp.code, env);
+				cond = evaluate(exp.cond, env);
+			}
+
+			//TODO DO i need to return anything?
+			break;
+		case "prog":
+			var val = false;
+			exp.prog.forEach(function(exp){ val = evaluate(exp, env) });
+			return val;
+
+		/* Currently supported function calls:
+		 * 		hack()
+		 *		sleep(N) - sleep N seconds
+		 *		print(x) - Prints a variable or constant
+		 *
+		 */
+		case "call":
+			//Define only valid function calls here, like hack() and stuff
+			//var func = evaluate(exp.func, env);
+			//return func.apply(null, exp.args.map(function(arg){
+			//	return evaluate(arg, env);
+			//}));
+			if (exp.func.value == "hack") {
+				console.log("Execute hack()");
+			} else if (exp.func.value == "sleep") {
+				console.log("Execute sleep()");
+			} else if (exp.func.value == "print") {
+				console.log(evaluate(exp.args[0], env));
+			}
+			break;
+
+		default:
+			throw new Error("I don't know how to evaluate " + exp.type);
+    }
+}
+
+function apply_op(op, a, b) {
+    function num(x) {
+        if (typeof x != "number")
+            throw new Error("Expected number but got " + x);
+        return x;
+    }
+    function div(x) {
+        if (num(x) == 0)
+            throw new Error("Divide by zero");
+        return x;
+    }
+    switch (op) {
+      case "+": return num(a) + num(b);
+      case "-": return num(a) - num(b);
+      case "*": return num(a) * num(b);
+      case "/": return num(a) / div(b);
+      case "%": return num(a) % div(b);
+      case "&&": return a !== false && b;
+      case "||": return a !== false ? a : b;
+      case "<": return num(a) < num(b);
+      case ">": return num(a) > num(b);
+      case "<=": return num(a) <= num(b);
+      case ">=": return num(a) >= num(b);
+      case "==": return a === b;
+      case "!=": return a !== b;
+    }
+    throw new Error("Can't apply operator " + op);
+}