current memo and lazy impl

Lab6/cs2030s/fp/Lazy.java

@@ -1,5 +1,41 @@
 package cs2030s.fp;
 
-public class Lazy<T> /* implements Immutatorable<T> */ {
+public class Lazy<T> implements Immutatorable<T> {
   private Constant<? extends T> init;
-}
+
+  protected Lazy(Constant<? extends T> c) {
+    this.init = c;
+  }
+
+  public T get() {
+    return init.init();
+  }
+
+  public static <T> Lazy<T> from(T v) {
+    return new Lazy<>(() -> v);
+  }
+
+  public static <T> Lazy<T> from(Constant<? extends T> v) {
+    return new Lazy<T>(v);
+  }
+
+  @Override
+  public <R> Lazy<R> transform(Immutator<? extends R, ? super T> f) {
+    return Lazy.from(() -> f.invoke(this.init.init()));
+  }
+
+  public <R> Lazy<R> next(Immutator<? extends Lazy<? extends R>, ? super T> f) {
+
+    @SuppressWarnings("unchecked")
+    Lazy<R> result = (Lazy<R>) Lazy.from(() -> f.invoke(this.init.init()));
+
+    return result;
+
+  }
+
+  @Override
+  public String toString() {
+    return this.init.init().toString();
+  }
+
+}