From f5d3c9762c02284a0ae07541d963aa733cad8a25 Mon Sep 17 00:00:00 2001
From: Edoardo La Greca
Date: Wed, 10 Sep 2025 21:29:24 +0200
Subject: implement dropJ from second exercise of lecture 7

---
 lec07/JoinList.hs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/lec07/JoinList.hs b/lec07/JoinList.hs
index 7ec30a9..61df8da 100644
--- a/lec07/JoinList.hs
+++ b/lec07/JoinList.hs
@@ -28,3 +28,14 @@ indexJ n (Append m jl1 jl2)
        | n >= tag1 = indexJ (n - tag1) jl2
        where tag1 = tag jl1
 
+dropJ :: (Sized b, Monoid b) => Int -> JoinList b a -> JoinList b a
+dropJ _ Empty = Empty
+dropJ n jl
+      | n <= 0 = jl
+dropJ n (Single _ _)
+      | n >= 1 = Empty
+dropJ n (Append m jl1 jl2)
+      | n >= m = Empty
+      | n >= tag1 = jl2
+      where tag1 = tag jl1
+
-- 
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