From 9ff78407129e7a1fbc96848ca09a5f28cf7080ed Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Thu, 31 Mar 2016 22:19:02 +0100
Subject: Improve generic support in the interpreter

---
 .../org/zwobble/couscous/util/ExtraIterables.java  | 54 ++++++++++++++++++++++
 1 file changed, 54 insertions(+)

(limited to 'src/main/java/org/zwobble/couscous/util/ExtraIterables.java')

diff --git a/src/main/java/org/zwobble/couscous/util/ExtraIterables.java b/src/main/java/org/zwobble/couscous/util/ExtraIterables.java
index 9cdb0f0..1fd9fca 100644
--- a/src/main/java/org/zwobble/couscous/util/ExtraIterables.java
+++ b/src/main/java/org/zwobble/couscous/util/ExtraIterables.java
@@ -1,6 +1,7 @@
 package org.zwobble.couscous.util;
 
 import java.util.Iterator;
+import java.util.function.BiFunction;
 
 public class ExtraIterables {
     private ExtraIterables() {}
@@ -15,4 +16,57 @@ public class ExtraIterables {
             throw new RuntimeException("Iterables not of same length");
         }
     }
+
+    public static <T1, T2, R> Iterable<R> map(Iterable<T1> iterable1, Iterable<T2> iterable2, BiFunction<T1, T2, R> function) {
+        return new Iterable<R>() {
+            @Override
+            public Iterator<R> iterator() {
+                Iterator<T1> iterator1 = iterable1.iterator();
+                Iterator<T2> iterator2 = iterable2.iterator();
+                return map(iterator1, iterator2, function);
+            }
+        };
+    }
+
+    private static <R, T1, T2> Iterator<R> map(Iterator<T1> iterator1, Iterator<T2> iterator2, BiFunction<T1, T2, R> function) {
+        return new Iterator<R>() {
+            @Override
+            public boolean hasNext() {
+                return iterator1.hasNext() && iterator2.hasNext();
+            }
+
+            @Override
+            public R next() {
+                return function.apply(iterator1.next(), iterator2.next());
+            }
+        };
+    }
+
+    public static <T> Iterable<T> cast(Class<T> type, Iterable<?> iterable) {
+        return new Iterable<T>() {
+            @Override
+            public Iterator<T> iterator() {
+                return cast(type, iterable.iterator());
+            }
+        };
+    }
+
+    private static <T> Iterator<T> cast(Class<T> type, Iterator<?> iterator) {
+        return new Iterator<T>() {
+            @Override
+            public boolean hasNext() {
+                return iterator.hasNext();
+            }
+
+            @Override
+            public T next() {
+                Object next = iterator.next();
+                if (type.isInstance(next)) {
+                    return (T) next;
+                } else {
+                    throw new ClassCastException();
+                }
+            }
+        };
+    }
 }
-- 
cgit v1.2.3