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Re: Replacement Rule with Sqrt in denominator

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114473] Re: Replacement Rule with Sqrt in denominator
  • From: Richard Fateman <fateman at cs.berkeley.edu>
  • Date: Sun, 5 Dec 2010 21:52:16 -0500 (EST)
  • References: <ic5igm$44p$1@smc.vnet.net> <ic8ad7$81f$1@smc.vnet.net> <id7t95$lh1$1@smc.vnet.net> <idagbn$js7$1@smc.vnet.net> <idd7s6$ngv$1@smc.vnet.net>

On 12/4/2010 3:15 AM, Roland Franzius wrote:

>>
>> and the pattern does not match.  Maybe you don't want it to match in
>> this case, but the problem persists even if you do. Like this pattern:
>>
>> ((1 + I x)^(a/2)/(1 - I x)^(a/2)) /. {HoldPattern[
>>        a_^(b_/c_) d_^(e_/c_)] :>   (a^b d^e)^(1/c)}
>>
>> which fails.
>
> It seems you have not yet recognized that pattern matching in
> Mathematica fails by construction if the symbol name of pattern, here a_
> concides  with a symbol in the expression.
Uh, no, I think you have it wrong.
Sin[a] + Sin[b] /. Sin[a_] -> h[a]
  is perfectly happy to return h[a]+h[b]
Sin[a] + Sin[a + b] /. Sin[a_] -> h[a]
  is perfectly happy to return h[a]+h[a+b].

...


>
> So the alternatives are to write an alternative language
... and  possibly implement it in Mathematica...
> or to learn
> mastering the of use it. The same alternative holds for all of
> mathematics.

Actually this is obviously not correct, since Mathematica can (and does)
change.  I don't know if "mathematics" changes, but certainly the
language of mathematics evolves.

RJF




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