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MathGroup Archive 2007

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Re: ReplaceRepeated info

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77697] Re: ReplaceRepeated info
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Fri, 15 Jun 2007 04:31:14 -0400 (EDT)
  • References: <f4r573$ber$1@smc.vnet.net>

Hi,

and

cnt = 0;
Log[d p q r] Log[a b c d] //. Log[x_ y_] :> (cnt++; Log[x] + Log[y])

will count in cnt the number of substitutions and asking for the value
of cnt will give you 6

Regards
   Jens

alexxx.magni at gmail.com wrote:
> Hi everybody,
> I need to use in my program ReplaceRepeated, and also to know, after
> it has been applied, how many times a replacement happened. Say, after
> this:
> 
>  Log[d p q r] Log[a b c d]//.Log[x_ y_] ->Log[x] + Log[y]
> 
> (Log[a] + Log[b] + Log[c] + Log[d]) (Log[d] + Log[p] + Log[q] +
> Log[r])
> 
> 
> ... I'd need to know that it performed 6 substitutions.
> There is a way with //. , or have I to resort to some loop around /. ,
> checking myself when no change happens anymore?
> 
> 
> Thank you!
> 
> Alessandro Magni
> 
> 


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