How to check if a function exists on a SQL database

Question

I need to find out if a function exists on a database, so that I can drop it and create it again. It should basically be something like the following code that I use for stored procedures:

IF EXISTS (
     SELECT  *
     FROM    dbo.sysobjects
     WHERE   id = OBJECT_ID(N'[dbo].[SP_TEST]')
             AND OBJECTPROPERTY(id, N'IsProcedure') = 1 )