From b0950cab8022b5bc8bbd2fdf25cf75867d197bf0 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Mon, 8 Jan 2007 22:49:26 +0000
Subject: [PATCH] * A function `elem' to check whether a list contains a
 specific   element.

svn path=/nixpkgs/trunk/; revision=7577
---
 pkgs/lib/default.nix | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/pkgs/lib/default.nix b/pkgs/lib/default.nix
index da279302306..0980a464704 100644
--- a/pkgs/lib/default.nix
+++ b/pkgs/lib/default.nix
@@ -61,6 +61,10 @@ rec {
     fold (x: y: if pred x then [x] ++ y else y) [] list;
 
 
+  # Return true if `list' has an element `x':
+  elem = x: list: fold (a: bs: x == a || bs) false list;
+
+
   # Find the sole element in the list matching the specified
   # predicate, or returns the default value.
   findSingle = pred: default: list: