Re: TransformationFunctions

• To: mathgroup at smc.vnet.net
• Subject: [mg102288] Re: TransformationFunctions
• From: O <kakabomba at gmail.com>
• Date: Tue, 4 Aug 2009 04:27:57 -0400 (EDT)
• References: <h46p31\$e4g\$1@smc.vnet.net> <200907230754.DAA26659@smc.vnet.net>

```it works. i think it is good idea to report here what was wrong. I
used function with delayed assignment, and should use function with
delayed assignment and delayed rule. For now i can't fully understand
what is difference, but maybe this information will helpful for
somebody else.

In[1]:= WrongTransformation[l___ ** (a_ + b_) ** r___] := l ** a ** r
+ l ** b ** r
In[2]:= Simplify[a ** (b + c) ** d - a ** b ** d,
TransformationFunctions -> {Automatic, WrongTransformation}]
Out[2]:= -a ** b ** d + a ** (b + c) ** d

In[3]:= ProperTransformation[expr_] := expr /. l___ ** (a_ + b_) **
r___ :> l ** a ** r + l ** b ** r
In[4]:= Simplify[a ** (b + c) ** d - a ** b ** d,
TransformationFunctions -> {Automatic, ProperTransformation}]
Out[4]:= a ** c ** d

thanks

```

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