From 981cdc92b8d3bb1dbdc15240b379a0f7e7d7aa6e Mon Sep 17 00:00:00 2001
From: Philippe PITTOLI <karchnu@karchnu.fr>
Date: Sun, 26 May 2024 03:19:38 +0200
Subject: [PATCH] DoubleLinkedList#delete_at

---
 spec/test-lists.cr |  7 +++++++
 src/list.cr        | 18 ++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/spec/test-lists.cr b/spec/test-lists.cr
index 53e1fc2..5444f35 100644
--- a/spec/test-lists.cr
+++ b/spec/test-lists.cr
@@ -101,4 +101,11 @@ describe "DoubleLinkedList" do
 		list.pop
 		list.peek.value.should eq 3
 	end
+
+	it "delete_at" do
+		list = DoubleLinkedList(Int32).new
+		list << 1 << 2 << 3 << 4
+		list.delete_at(2).value.should eq 3
+		list.to_s.should eq "[ 1, 2, 4 ]"
+	end
 end
diff --git a/src/list.cr b/src/list.cr
index df94a1f..29980ac 100644
--- a/src/list.cr
+++ b/src/list.cr
@@ -88,6 +88,24 @@ class DoubleLinkedList(V)
 		new_node
 	end
 
+	# Removes an entry at an index.
+	def delete_at(index : Int32) : Node(V)
+		if index == 0
+			shift
+		elsif index == @size - 1
+			pop
+		else
+			v = self[index]
+			prev_node = v.previous.not_nil!
+			next_node = v.next.not_nil!
+
+			prev_node.next = next_node
+			next_node.previous = prev_node
+			@size -= 1
+			v
+		end
+	end
+
 	# Adds a *value* to the linked list at a specified index.
 	#
 	# ```