       Re: comparing rewite rules

• To: mathgroup at smc.vnet.net
• Subject: [mg78341] Re: comparing rewite rules
• From: dh <dh at metrohm.ch>
• Date: Thu, 28 Jun 2007 06:29:25 -0400 (EDT)
• References: <f5vsg8\$l2f\$1@smc.vnet.net>

```
Hi Roger,

you are trying to compare ordered list. Therefore, the order is

important. To circumvent this, define a new head e.g. myList and give it

the Orderless attribute:

SetAttributes[myList, Orderless]

myList[yy -> 4, y -> 3] == myList[y -> 3, yy -> 4]

this now reults in True.

hope this helps, Daniel

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).

>

>

> Regards..Roger

>

>

```

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