# HG changeset patch
# User Yasutaka Higa <e115763@ie.u-ryukyu.ac.jp>
# Date 1413607109 -32400
# Node ID 33b386de3f560c40003d5f28c765ffc9ab25bb96
# Parent  c2f40b6d4027b0e5fb0c960c1227d44146a0ac9e
Proof list-associative

diff -r c2f40b6d4027 -r 33b386de3f56 agda/list.agda
--- a/agda/list.agda	Tue Oct 07 15:32:11 2014 +0900
+++ b/agda/list.agda	Sat Oct 18 13:38:29 2014 +0900
@@ -24,4 +24,9 @@
     x :: (xs ++ [])
   ≡⟨ cong (_::_ x) (empty-append xs) ⟩
     x :: xs
-  ∎
\ No newline at end of file
+  ∎
+
+
+list-associative : {A : Set} -> (a b c : List A) -> (a ++ (b ++ c)) ≡ ((a ++ b) ++ c)
+list-associative [] b c = refl
+list-associative (x :: a) b c = cong (_::_ x) (list-associative a b c)
\ No newline at end of file