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Re: a problem applying Rule

• To: mathgroup@smc.vnet.net
• Subject: [mg10263] Re: a problem applying Rule
• From: Allan Hayes <hay@haystack.demon.co.uk>
• Date: Sat, 3 Jan 1998 05:07:16 -0500
• References: <68csbd$a8l@smc.vnet.net>

N Monomachoff wrote:

> Hi there,
> I'm using 3.0.
>
> g[f[f[],a]] /. (n:(f | g))[f[],x__] -> n[f[]] evaluates properly as
> g[f[f[]]].
> But after
> SetAttributes[f,Orderless]
> it no longer works. This doesn't make much sense to me. Is this a bug or
> a feature? And is there a way around this? Thanks for any help,
> nmonomachoff@msn.com

After

SetAttributes[f,Orderless]

The evaluation of

g[f[f[],a]] /. (n:(f | g))[f[],x__] -> n[f[]]

goes through

g[f[a,f[]]] /. (n:(f | g))[f[],x__] -> n[f[]]

hence the result.


Is

g[f[f[],a]] /. (n:(f | g))[u___,f[],x___] -> n[f[]]

g[f[f[]]]

of any use?

--
Allan Hayes
Training and Consulting
Leicester, UK
hay@haystack.demon.co.uk
http://www.haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44 (0)116 271 8642