From c0a483632c3e0193678dd58c994528d88d42ea00 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Mon, 13 Aug 2012 14:19:31 -0400
Subject: Eliminate some calls to ‘tail’
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---
 pkgs/lib/options.nix | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'pkgs/lib/options.nix')

diff --git a/pkgs/lib/options.nix b/pkgs/lib/options.nix
index cd60b8f3b88..05c9c5f9c0f 100644
--- a/pkgs/lib/options.nix
+++ b/pkgs/lib/options.nix
@@ -2,7 +2,7 @@
 
 let lib = import ./default.nix; in
 
-with { inherit (builtins) head tail; };
+with { inherit (builtins) head length; };
 with import ./trivial.nix;
 with import ./lists.nix;
 with import ./misc.nix;
@@ -133,7 +133,7 @@ rec {
   # separate the merge & apply fields from the interface.
   mergeOptionDecls = opts:
     if opts == [] then {}
-    else if tail opts == [] then
+    else if length opts == 1 then
       let opt = head opts; in
       if opt ? options then
         opt // { options = toList opt.options; }
@@ -189,7 +189,7 @@ rec {
     ) (attrNames defs));
 
   mergeDefaultOption = list:
-    if list != [] && tail list == [] then head list
+    if length list == 1 then head list
     else if all builtins.isFunction list then x: mergeDefaultOption (map (f: f x) list)
     else if all isList list then concatLists list
     else if all isAttrs list then fold lib.mergeAttrs {} list
@@ -214,7 +214,7 @@ rec {
 
   mergeOneOption = list:
     if list == [] then abort "This case should never happen."
-    else if tail list != [] then throw "Multiple definitions. Only one is allowed for this option."
+    else if length list != 1 then throw "Multiple definitions. Only one is allowed for this option."
     else head list;
 
 
-- 
cgit 1.4.1