From 1f68748a8bd6b03872f4d658d48a4a1acdd3f0ec Mon Sep 17 00:00:00 2001
From: Nicolas Pierron <nicolas.b.pierron@gmail.com>
Date: Tue, 6 Oct 2009 09:21:39 +0000
Subject: [PATCH] Add removePrefix function.

svn path=/nixpkgs/trunk/; revision=17667
---
 pkgs/lib/strings.nix | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/pkgs/lib/strings.nix b/pkgs/lib/strings.nix
index 415b53c6a136..dc1dbfd8de19 100644
--- a/pkgs/lib/strings.nix
+++ b/pkgs/lib/strings.nix
@@ -106,4 +106,18 @@ rec {
           cutUntil sLen;
     in
       recurse 0 0;
+
+  # return the suffix of the second argument if the first argument match its
+  # prefix. e.g.,
+  # `removePrefix "foo." "foo.bar.baz"' returns "bar.baz".
+  removePrefix = pre: s:
+    let
+      preLen = stringLength pre;
+      sLen = stringLength s;
+    in
+      if pre == substring 0 preLen s then
+        substring preLen (sub sLen preLen) s
+      else
+        s;
+
 }