Re: Simplifying If expressions
- To: mathgroup at smc.vnet.net
- Subject: [mg102931] Re: Simplifying If expressions
- From: pfalloon <pfalloon at gmail.com>
- Date: Wed, 2 Sep 2009 04:05:20 -0400 (EDT)
- References: <h7ijt0$ial$1@smc.vnet.net>
On Sep 1, 5:53 pm, "beep.beep" <meph... at gmail.com> wrote: > Hi, > > When I try to Simplify[If[x==0,x,0]] Mathematica returns If[x==0,x,0] rather than 0. It seems that it does not take into account that left and right if-branches should be simplified using ($Assumptions)&&if-condition and ($Assumptions)&&!if-condition respectively. Is there a way to force that behaviour? > > Best regards, > Ilya It doesn't work because x==0 may be True, but that doesn't mean x is exactly zero. e.g. In[3]:= 0.==0 Out[3]= True You want to use SameQ (===) instead (and then you don't even need the Simplify): In[1]:= If[x===0,x,0] Out[1]= 0 Cheers, Peter.