Added basic class support.

examples/classes_demo.fun

@@ -0,0 +1,67 @@
+#!/usr/bin/env fun
+
+// Classes demo: fields, methods (with explicit 'this'), and usage.
+//
+// Notes:
+// - Define a class with `class Name`
+// - Fields are initialized with simple assignments inside the class body.
+// - Methods are written as `fun method(this, ...) { ... }` with 'this' required as the first parameter.
+// - Instantiation: p = Name()
+// - Method calls: load the method function from the instance into a variable, then call it with the instance as the first argument.
+//   Example:
+//     move_fn = p["move"]
+//     move_fn(p, dx, dy)
+
+class Point
+  x = 0
+  y = 0
+  fun move(this, dx, dy)
+    this.x = this.x + dx
+    this.y = this.y + dy
+    return 0
+  fun toString(this)
+    return "Point(" + to_string(this.x) + ", " + to_string(this.y) + ")"
+
+class Counter
+  value = 0
+  fun inc(this)
+    this.value = this.value + 1
+    return this.value
+  fun add(this, n)
+    this.value = this.value + n
+    return this.value
+
+// Instantiate a Point
+p = Point()
+
+// Types
+print("typeof(Point) = " + typeof(Point)) // Function (factory)
+print("typeof(p) = " + typeof(p))         // Map (instance)
+
+// Read/write fields
+print("p.x = " + to_string(p["x"]) + ", p.y = " + to_string(p["y"]))
+p["x"] = 10
+p["y"] = -2
+print("after set -> p.x = " + to_string(p["x"]) + ", p.y = " + to_string(p["y"]))
+
+// Call methods by first loading them into identifiers, then passing 'p' as first argument
+to_str = p["toString"]
+print("toString(p) => " + to_str(p))
+
+move_fn = p["move"]
+move_fn(p, 3, 5)
+print("after move(3,5) -> " + to_str(p)) // expect Point(13, 3)
+
+// Another instance with defaults
+q = Point()
+print("q initially -> " + to_str(q)) // Point(0, 0)
+
+// Counter demo
+c = Counter()
+inc = c["inc"]
+add = c["add"]
+
+print("counter inc -> " + to_string(inc(c)))     // 1
+print("counter inc -> " + to_string(inc(c)))     // 2
+print("counter add(5) -> " + to_string(add(c, 5))) // 7
+print("counter current value = " + to_string(c["value"]))