Add Iterator(T).empty (#15039)

crystal-lang · Oct 10, 2024 · f237af0 · f237af0
1 parent 0606cf0
commit f237af0
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diff --git a/spec/std/iterator_spec.cr b/spec/std/iterator_spec.cr
@@ -33,6 +33,13 @@ private class MockIterator
 end
 
 describe Iterator do
+  describe "Iterator.empty" do
+    it "creates empty iterator" do
+      iter = Iterator(String).empty
+      iter.next.should be_a(Iterator::Stop)
+    end
+  end
+
   describe "Iterator.of" do
     it "creates singleton" do
       iter = Iterator.of(42)

diff --git a/src/iterator.cr b/src/iterator.cr
@@ -144,6 +144,19 @@ module Iterator(T)
     Stop::INSTANCE
   end
 
+  # Returns an empty iterator.
+  def self.empty
+    EmptyIterator(T).new
+  end
+
+  private struct EmptyIterator(T)
+    include Iterator(T)
+
+    def next
+      stop
+    end
+  end
+
   def self.of(element : T)
     SingletonIterator(T).new(element)
   end