       Re: Bug in Simplify?

• To: mathgroup at smc.vnet.net
• Subject: [mg33235] Re: Bug in Simplify?
• From: "Steve Durbin" <steved at vale.demon.co.uk>
• Date: Sat, 9 Mar 2002 18:05:21 -0500 (EST)
• References: <a61v7q\$gpt\$1@smc.vnet.net> <a64fu0\$n04\$1@smc.vnet.net> <a675en\$d0m\$1@smc.vnet.net> <a6chk6\$dr0\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```"David W. Cantrell" <DWCantrell at sigmaxi.org> wrote in message
news:a6chk6\$dr0\$1 at smc.vnet.net...
> If you really want some things to ruffle your feathers, try the following:
>
> Simplify[0/x, x==0]
> Simplify[x/y, x==0 && y==0]
> Simplify[x/x, x==0]
>
> The results are 0, 0, and 1, resp., which I consider as being closer to
> "crimes" than "misdemeanors".

It gets worse than that :-( Simplify doesn't agree with the rest of the
kernel:

In:=
a = Simplify[0/x, x == 0];
b = Simplify[x/y, x == 0 && y == 0];
c = Simplify[x/x, x == 0];
Print["0/x=", a, " x/y=", b, " x/x=", c]

Out:=
0/x=0 x/y=0 x/x=1

In:=
(* will give errors without Off[Power::infy]; *)
(* and Off[\[Infinity]::indet]; *)
x = 0; y = 0;
a = 0/x ;
b = x/y ;
c = x/x;
Print["0/x=", a, " x/y=", b, " x/x=", c]

Out:=
0/x=Indeterminate x/y=Indeterminate x/x=Indeterminate

So 0/0 is assumed to be either 0, 1 or indeterminate depending on which
input form is used. Also, the second form gives warnings about the problem,
whereas the first doesn't.

Cheers,
--
Steve Durbin | Look! Minimalism comes to ASCII art!
|                                           .

```

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