Re: "Assuming"

*To*: mathgroup at smc.vnet.net*Subject*: [mg85622] Re: "Assuming"*From*: David Bailey <dave at Remove_Thisdbailey.co.uk>*Date*: Fri, 15 Feb 2008 06:52:58 -0500 (EST)*References*: <fp0m11$5u7$1@smc.vnet.net> <fp192b$gju$1@smc.vnet.net> <fp2khg$pka$1@smc.vnet.net>

> > Compare the following: > > In[8]:= Assuming[x == 0, {x/x^2, x/x, x^2/x}] > Out[8]= {1/x, 1, x} > > In[9]:= x = 0; {x/x^2, x/x, x^2/x} > Out[9]= {Indeterminate, Indeterminate, Indeterminate} > Assuming supplies conditions for use by a Simplify (or similar) operations within it. It does not initiate a Simplify operation itself. Compare for example: Assuming[x == 1, Simplify[x/x^2]] Assuming[x == 1, x/x^2] More generally, I think if Simplify[(a^2-1)(a-1)] returned a conditional expression (or did not evaluate at all, as in Simplify[Sqrt[x^2]] ), it would be practically useless in more complicated cases - A CAS is meant to be a practical tool. David Bailey http://www.dbaileyconsultancy.co.uk