From c06d140c03020c669ce89bdb43c06fd27abc6e69 Mon Sep 17 00:00:00 2001
From: Ludovic Courtès <ludo@gnu.org>
Date: Sun, 11 Jan 2015 23:20:57 +0100
Subject: derivations: Use a set for 'substitution-oracle'.

* guix/derivations.scm (substitution-oracle): Use sets instead of lists.
---
 guix/derivations.scm | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/guix/derivations.scm b/guix/derivations.scm
index 2f015089a3..b48e7e604d 100644
--- a/guix/derivations.scm
+++ b/guix/derivations.scm
@@ -217,8 +217,8 @@ substituter many times."
                            (append self deps result)))
                        '()
                        drv)))
-         (subst (substitutable-paths store paths)))
-    (cut member <> subst)))
+         (subst (list->set (substitutable-paths store paths))))
+    (cut set-contains? subst <>)))
 
 (define* (derivation-prerequisites-to-build store drv
                                             #:key
-- 
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