Re: comparing rewite rules

• To: mathgroup at smc.vnet.net
• Subject: [mg78349] Re: comparing rewite rules
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Thu, 28 Jun 2007 06:36:08 -0400 (EDT)
• Organization: Uni Leipzig
• References: <f5vsg8\$l2f\$1@smc.vnet.net>

Hi,

Sort /@ ({yy -> 4, y -> 3} == {y -> 3, yy -> 4})

because you have to bring the rules into a unique order.
General {a,b} is different from {b,a}, but in for a list
of rules the order does not have a meaning.

Regards
Jens

dbsearch04 at yahoo.com wrote:
> Hello Mathematica UG:
>
> I input these 2 simple rewrite rule sets into Mathematica V5:
>
> - {yy -> 4, y -> 3}
>
> - {y -> 3, yy -> 4}
>
> I just want to compare these 2 simple rules for equality. I tried:
>
> - define each one and use % == %% (this just gives: {yy -> 4, y -> 3}
>  == {y -> 3, yy -> 4} )
> - making a symbol for each rule set and using ==, such as rul0 ==
> rul1,
>  it just echoes my input
>
> I also tried to replace the rules in an expression. If the replaced
> result evaluates to a simple expression, it is OK but, it still fails
> sometime when Mathematica reorders expressions, such as when x-1 becomes -1 +
> x
>
> Is it possible to determine in my code that 2 "rule lists" are the
> same?
>
> Of course, in the general case, I will have many more rules than just
> these 2 small lists (e.g. Solve[] output).
>