Optimize Range#size for integers

crystal-lang · Jun 12, 2017 · 5370faf · 5370faf
1 parent c8ec408
commit 5370faf
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diff --git a/spec/std/range_spec.cr b/spec/std/range_spec.cr
@@ -368,6 +368,18 @@ describe "Range" do
     end
   end
 
+  describe "size" do
+    it "optimizes for int range" do
+      (5..12).size.should eq(8)
+      (5...12).size.should eq(7)
+      (5..4).size.should eq(0)
+    end
+
+    it "works for other types" do
+      ('a'..'c').size.should eq(3)
+    end
+  end
+
   it "clones" do
     range = [1]..[2]
     clone = range.clone

diff --git a/src/range.cr b/src/range.cr
@@ -292,6 +292,21 @@ struct Range(B, E)
     end
   end
 
+  # :nodoc:
+  def size
+    b = self.begin
+    e = self.end
+
+    # Optimized implementation for int range
+    if b.is_a?(Int) && e.is_a?(Int)
+      e -= 1 if @exclusive
+      n = e - b + 1
+      n < 0 ? 0 : n
+    else
+      super
+    end
+  end
+
   private class ItemIterator(B, E)
     include Iterator(B)