FullSimplify[Abs[Sign[x]],x>=0] equals 1?

*To*: mathgroup at smc.vnet.net*Subject*: [mg33691] FullSimplify[Abs[Sign[x]],x>=0] equals 1?*From*: Alain Cochard <al2 at noos.fr>*Date*: Tue, 9 Apr 2002 01:01:51 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Is the following behavior normal? In[1]:= Simplify[Abs[Sign[x]],x>=0] Out[1]= Abs[Sign[x]] In[2]:= FullSimplify[Abs[Sign[x]],x>=0] Out[2]= 1 In[3]:= $Version Out[3]= 4.1 for Sun Solaris (November 8, 2000) In this case I would have expected FullSimplify to give the save answer as Simplify, as I was (naively?) assuming Abs[Sign[0]] equals zero. What am I missing? (Note I get the same output for Version 4.0 for Linux (July 22, 1999).) AC