Added Abstraction.

generics/src/generics/Main.java

@@ -21,10 +21,10 @@ class Examples {
     }
     
     boolean testILoArmax(Tester t) {
-        return t.checkExpect(helloWorld.argmax(new IEvaluator<StrLen>()), "Hello, ")
-                        && t.checkExpect(helloAjcmsdj.argmax(new IEvaluator<StrLen>()), "Hello, ")
-                        && t.checkExpect(lint2.argmax(new IEvaluator<IntSize>()), 1)
-                        && t.checkExpect(lint.argmax(new IEvaluator<IntSize>()), 92);
+        return t.checkExpect(helloWorld.argmax(new StrLen()), "Hello, ")
+                        && t.checkExpect(helloAjcmsdj.argmax(new StrLen()), "Hello, ")
+                        && t.checkExpect(lint2.argmax(new IntSize()), 1)
+                        && t.checkExpect(lint.argmax(new IntSize()), 92);
     }
     
     
@@ -35,22 +35,25 @@ interface IFunc<X, Y> {
     Y apply(X input);
 }
 
+// Extracts the value of an input.
+interface IEvaluator<X> extends IFunc<X, Integer> {}
+
 // Calculate the length of a string.
-class StrLen implements IFunc<String, Integer> { public Integer apply(String input) {
+class StrLen implements IEvaluator<String> { public Integer apply(String input) {
     return input.length();
 }}
 
 // Calculate the size of an integer.
-class IntSize implements IFunc<Integer, Integer> { public Integer apply(Integer input) {
-    return input - 14;
+class IntSize implements IEvaluator<Integer> { public Integer apply(Integer input) {
+    return input;
 }}
 
-// Extracts the value of an input.
-interface IEvaluator<X> extends IFunc<X, Integer> {}
-
+// A list of A.
 interface ILo<A> { 
     ILo<A> append(ILo<A> a);
     A argmax(IEvaluator<A> eval);
+    A argmaxHelper(IEvaluator<A> eval, A prev, Integer prevVal);
+    ILo<A> skip();
 }
 
 class Cons<A> implements ILo<A> {
@@ -64,8 +67,21 @@ class Cons<A> implements ILo<A> {
     
     public ILo<A> append(ILo<A> a) { return new Cons<A>(this.first, this.rest.append(a)); }
     
-    public A argmax(IEvaluator<A> eval) {
-        return null;
+    public A argmax(IEvaluator<A> eval) {        
+        return argmaxHelper(eval, this.first, eval.apply(this.first));
+    }
+    
+    public A argmaxHelper(IEvaluator<A> eval, A prev, Integer prevVal) {
+        A now = this.first;
+        Integer nowVal = eval.apply(now);
+        
+        return prevVal >= nowVal ?
+            this.rest.argmaxHelper(eval, prev, prevVal) :
+            this.rest.skip().argmaxHelper(eval, now, nowVal);
+    };
+    
+    public ILo<A> skip() {
+        return this.rest;
     }
 }
 
@@ -74,4 +90,10 @@ class Mt<A> implements ILo<A> {
     public A argmax(IEvaluator<A> eval) {
         throw new UnsupportedOperationException("No max of empty list.");
     }
-}
+    
+    public A argmaxHelper(IEvaluator<A> eval, A prev, Integer prevVal) {
+        return prev;
+    }
+    
+    public ILo<A> skip() { return this; }
+}