Add reduce to Collection.

corelib/src/implementation/collections.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * The [Collections] class implements static methods useful when
  * writing a class that implements [Collection] and the [iterator]
  * method.
  */
 class Collections {

[Lasse Reichstein Nielsen, 2012/08/08 07:19:14]

This class should die. Horribly.
Instead there should be:
  class Collection<T> {
    factory Collection.from(Iterable<T> iterable);
    ...
  }
so instad of:
 Collections.forEach(iterable, f)
you do:
 new Collection.from(iterable).forEach(f);
for the *rare* case where all you have is an iterable.

[Anders Johnsen, 2012/11/12 12:02:56]

Agreed. I'll gladly create a CL for this in a weeks time!

   static void forEach(Iterable iterable, void f(o)) {
     for (final e in iterable) {
       f(e);
     }
   }
 
   static bool some(Iterable iterable, bool f(o)) {
     for (final e in iterable) {
       if (f(e)) return true;
     }
     return false;
   }
 
   static bool every(Iterable iterable, bool f(o)) {
     for (final e in iterable) {
       if (!f(e)) return false;
     }
     return true;
   }
 
   static List map(Iterable source, List destination, f(o)) {
     for (final e in source) {
       destination.add(f(e));
     }
     return destination;
   }
 
+  static reduce(Iterable iterable, var init, f(prev, element)) {

[Lasse Reichstein Nielsen, 2012/08/08 07:19:14]

Add return value, even if it's just Object. It differentiates it from a "void"
return type.
Also add "var" in front of "prev" and "element" and don't abbreviate variables
nemes.

[Anders Johnsen, 2012/08/08 07:56:14]

Adding var does not provide any further information and is orthogonal to the
rest of the lib. The only reason to provide it in the Collection interface is to
show that prev and element is typed differently. We don't have that type
information here.

[Lasse Reichstein Nielsen, 2012/08/10 11:26:56]

Accepted, but not liked.
I prefer being explicit about what is expected. It differentiates a deliberate
choice from an accidental omission.

+    for (final e in iterable) {

[Lasse Reichstein Nielsen, 2012/08/08 07:19:14]

Yes, that means using 'element' instead of 'e'. It won't hurt.

[Anders Johnsen, 2012/08/08 07:56:14]

It's using the style from the rest of the file/lib. If we want to style it
differently, we should consider doing it to the hole file/lib.

[Lasse Reichstein Nielsen, 2012/08/10 11:26:56]

We do. We shoud. Please start here :)

[Anders Johnsen, 2012/11/12 12:02:56]

Done.

+      init = f(init, e);
+    }
+    return init;
+  }
+
   static List filter(Iterable source, List destination, bool f(o)) {
     for (final e in source) {
       if (f(e)) destination.add(e);
     }
     return destination;
   }
 
   static bool isEmpty(Iterable iterable) {
     return !iterable.iterator().hasNext();
   }
@@ skipping 89 matching lines @@
    * Returns true if the specified collection contains the specified object
    * reference.
    */
   static _containsRef(Collection c, Object ref) {
     for (var e in c) {
       if (e === ref) return true;
     }
     return false;
   }
 }