X-Git-Url: http://nitlanguage.org

diff --git a/lib/standard/collection/abstract_collection.nit b/lib/standard/collection/abstract_collection.nit
index d38e001..2f7e454 100644
--- a/lib/standard/collection/abstract_collection.nit
+++ b/lib/standard/collection/abstract_collection.nit
@@ -66,6 +66,14 @@ interface Collection[E]
 	#     assert [1..1[.is_empty   == true
 	fun is_empty: Bool do return length == 0
 
+	# Alias for `not is_empty`.
+	#
+	# Some people prefer to have conditions grammatically easier to read.
+	#
+	#     assert [1,2,3].not_empty  == true
+	#     assert [1..1[.not_empty   == false
+	fun not_empty: Bool do return not self.is_empty
+
 	# Number of items in the collection.
 	#
 	#     assert [10,20,30].length == 3
@@ -171,8 +179,9 @@ interface Collection[E]
 	end
 end
 
-# Instances of the Iterator class generates a series of elements, one at a time.
-# They are mainly used with collections.
+# Iterators generate a series of elements, one at a time.
+#
+# They are mainly used with collections and obtained from `Collection::iterator`.
 interface Iterator[E]
 	# The current item.
 	# Require `is_ok`.
@@ -203,7 +212,7 @@ end
 #
 # Used to pass arguments by reference.
 #
-# Also used when one want to give asingle element when a full
+# Also used when one want to give a single element when a full
 # collection is expected
 class Container[E]
 	super Collection[E]
@@ -497,6 +506,25 @@ interface MapRead[K, V]
 		end
 		return true
 	end
+
+	# A hashcode based on the hashcode of the keys and the values.
+	#
+	# ~~~
+	# var a = new HashMap[String, Int]
+	# var b = new ArrayMap[Object, Numeric]
+	# a["one"] = 1
+	# b["one"] = 1
+	# assert a.hash == b.hash
+	# ~~~
+	redef fun hash
+	do
+		var res = length
+		for k, v in self do
+			if k != null then res += k.hash * 7
+			if v != null then res += v.hash * 11
+		end
+		return res
+	end
 end
 
 # Maps are associative collections: `key` -> `item`.