Out of range operations should return nil

lib/sorted_containers/sorted_array.rb

@@ -215,7 +215,7 @@ def slice!(*args)
     #
     # @return [Object] The last value in the array.
     def last
-      raise "Array is empty" if @size.zero?
+      return nil if @size.zero?
 
       @lists.last.last
     end
@@ -224,7 +224,7 @@ def last
     #
     # @return [Object] The first value in the array.
     def first
-      raise "Array is empty" if @size.zero?
+      return nil if @size.zero?
 
       @lists.first.first
     end
@@ -233,6 +233,7 @@ def first
     #
     # @param index [Integer] The index of the value to delete.
     def delete_at(index)
+      return nil if index.abs >= @size
       pos, idx = pos(index)
       internal_delete(pos, idx)
     end
@@ -241,7 +242,7 @@ def delete_at(index)
     #
     # @return [Object] The last value in the array.
     def pop
-      raise "Array is empty" if @size.zero?
+      return nil if @size.zero?
 
       value = @lists.last.pop
       if @lists.last.empty?

spec/sorted_array_spec.rb

@@ -47,11 +47,21 @@
     expect(array.first).to eq(1)
   end
 
+  it "should return nil if the array is empty" do
+    array = SortedContainers::SortedArray.new
+    expect(array.first).to be_nil
+  end
+
   it "should return the last value in the array" do
     array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
     expect(array.last).to eq(5)
   end
 
+  it "should return nil if the array is empty" do
+    array = SortedContainers::SortedArray.new
+    expect(array.last).to be_nil
+  end
+
   it "should return true if all elements meet a given criterion" do
     array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
     expect(array.all? { |i| i > 0 }).to be true
@@ -121,17 +131,31 @@
     expect(array[2]).to eq(3)
   end
 
-  it "should raise an error if the index is out of range" do
+  it "should handle negative indices" do
+    array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
+    expect(array[-1]).to eq(5)
+  end
+
+  it "should return nil if negative index is out of range" do
     array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
-    expect { array[5] }.to raise_error("Index out of range")
+    expect(array[-6]).to be_nil
+  end
+
+  it "should return nil if the index is out of range" do
+    array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
+    expect(array[5]).to be_nil
   end
 
-  # tests array[range] syntax
   it "should return the values in the given range" do
     array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
     expect(array[1..3]).to eq([2, 3, 4])
   end
 
+  it "should return empty array if the range is out of range" do
+    array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
+    expect(array[5..6]).to eq([])
+  end
+
   it "should return the values in the given range excluding the last value" do
     array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
     expect(array[1...3]).to eq([2, 3])
@@ -142,6 +166,11 @@
     expect(array[1, 3]).to eq([2, 3, 4])
   end
 
+  it "should return nil if the index is out of range" do
+    array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
+    expect(array[5, 1]).to be_nil
+  end
+
   it "should return values in the arithmetic sequence two dots" do
     array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
     expect(array[(1..).step(2)].to_a).to eq([2, 4])
@@ -222,15 +251,40 @@
     expect(array.to_a).to eq([1, 2])
   end
 
-  it "should delete the value at the given index" do
-    array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
-    array.delete_at(2)
-    expect(array.to_a).to eq([1, 2, 4, 5])
-  end
+  describe "delete_at" do
+    it "should delete the value at the given index" do
+      array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
+      array.delete_at(2)
+      expect(array.to_a).to eq([1, 2, 4, 5])
+    end
 
-  it "should raise an error if the index is out of range" do
-    array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
-    expect { array.delete_at(5) }.to raise_error(IndexError)
+    it "should return the value at the given index" do
+      array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
+      expect(array.delete_at(2)).to eq(3)
+    end
+
+    it "should return nil if the index is out of range" do
+      array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5])
+      expect(array.delete_at(5)).to be_nil
+    end
+
+    it "should work when array size is larger than load factor" do
+      array = SortedContainers::SortedArray.new((1..1000).to_a, load_factor: 3)
+      array.delete_at(500)
+      expect(array.size).to eq(999)
+    end
+
+    it "should update the index after deleting an element" do
+      array = SortedContainers::SortedArray.new((1..1000).to_a, load_factor: 3)
+      array.delete_at(50)
+      expect(array[50]).to eq(52)
+    end
+
+    it "should update the index after deleting an element from small array" do
+      array = SortedContainers::SortedArray.new([1, 2, 3, 4, 5], load_factor: 1)
+      array.delete_at(2)
+      expect(array[2]).to eq(4)
+    end
   end
 
   it "bisect_left should return the index where the value should be inserted" do
@@ -301,6 +355,11 @@
     expect(array.to_a).to eq([1, 2, 3, 4])
   end
 
+  it "should return nil if the array is empty" do
+    array = SortedContainers::SortedArray.new
+    expect(array.pop).to be_nil
+  end
+
   it "should sort hundreds of values" do
     array = SortedContainers::SortedArray.new
     (1..1000).to_a.shuffle.each do |i|