Re: Head logic
- To: mathgroup at smc.vnet.net
- Subject: [mg97058] Re: Head logic
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Wed, 4 Mar 2009 07:12:00 -0500 (EST)
- References: <goj2bk$2qu$1@smc.vnet.net>
Hi, may be there is a reason why there exist SameQ[] (===) and UnsameQ[] (=!=). The reason is that a==b is may be true if a and b have values but general this is an equation. If want to test something that must yield True or False use SameQ[] anf UnsameQ[] Regards Jens carlos at colorado.edu wrote: > Entering > > ClearAll[r]; > Head[r] > Head[r]!=Symbol > Head[r]==Symbol > > give Symbol, False and True as expected. But > > Head[r]==Integer > > evaluates to Symbol==Integer. Why not False? > Head[r] is certainly not Integer. Likewise > > r=4; > Head[r]==Integer > Head[r]!=Symbol > Head[r]==Symbol > > give True (correct) but Integer!=Symbol and Integer==Symbol. > Why not True and False? >