finish

Lab5/cs2030s/fp/Transformer.java

@@ -0,0 +1,23 @@
+package cs2030s.fp;
+
+public abstract class Transformer<R, P> implements Immutator<R, P> {
+  public <N> Transformer<R, N> after(Transformer<P, N> g) {
+    Transformer<R, P> f = this;
+    return new Transformer<R, N>() {
+      @Override
+      public R invoke(N param) {
+        return f.invoke(g.invoke(param));
+      }
+    };
+  }
+
+  public <T> Transformer<T, P> before(Transformer<T, R> g) {
+    Transformer<R, P> f = this;
+    return new Transformer<T, P>() {
+      @Override
+      public T invoke(P param) {
+        return g.invoke(f.invoke(param));
+      }
+    };
+  }
+}