java8
diff --git a/‎src/main/java/lambdasinaction/chap13/PatternMatching.java‎
Lines changed: 33 additions & 0 deletions b/‎src/main/java/lambdasinaction/chap13/PatternMatching.java‎
Lines changed: 33 additions & 0 deletions
diff --git a/‎src/main/java/lambdasinaction/chap13/PersistentDataStructures.java‎
Lines changed: 27 additions & 0 deletions b/‎src/main/java/lambdasinaction/chap13/PersistentDataStructures.java‎
Lines changed: 27 additions & 0 deletions
@@ -1,5 +1,38 @@
 package lambdasinaction.chap13;
 
 
+import java.util.function.Function;
+import java.util.function.Supplier;
+
 public class PatternMatching {
+
+
+    static class Expr {  }
+    static class Number extends Expr { int val;  }
+    static class BinOp extends Expr { String opname; Expr left, right; }
+
+
+
+    static <T> T MyIf(boolean b, Supplier<T> truecase, Supplier<T> falsecase) {
+        return b ? truecase.get() : falsecase.get();
+    }
+
+    static interface TriFunction<S, T, U, R>{
+        R apply(S s, T t, U u);
+    }
+    static <T> T PatternMatchExpr( Expr e,
+                                   TriFunction<String,Expr,Expr,T> binopcase, Function<Integer,T> numcase,
+                                   Supplier<T> defaultcase) {
+
+        if(e instanceof BinOp){
+                return binopcase.apply(((BinOp)e).opname, ((BinOp)e).left, ((BinOp)e).right);
+        }
+        else if(e instanceof Number){
+                return numcase.apply(((Number)e).val);
+        }
+        else{
+            return defaultcase.get();
+        }
+    }
+
 }
@@ -2,4 +2,31 @@
 
 
 public class PersistentDataStructures {
+
+
+    static class TrainJourney {
+        public int price;
+        public TrainJourney onward;
+        public TrainJourney(int p, TrainJourney t) {
+            price = p;
+            onward = t;
+        }
+    }
+
+    static TrainJourney link(TrainJourney a, TrainJourney b) {
+        if (a==null){
+            return b;
+        }
+        TrainJourney t = a;
+        while(t.onward != null){
+            t = t.onward;
+        }
+        t.onward = b;
+        return a;
+    }
+
+    static TrainJourney append(TrainJourney a, TrainJourney b)
+    {
+        return a==null ? b : new TrainJourney(a.price, append(a.onward, b));
+    }
 }