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MathGroup Archive 2000

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Re: Re: functional routine for {a, b, c, ...} -> {a - b, b - c, c - ...a}

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24930] Re: [mg24907] Re: [mg24892] functional routine for {a, b, c, ...} -> {a - b, b - c, c - ...a}
  • From: "Dr. Reinhard Simonovits" <Reinhard.Simonovits at kfunigraz.ac.at>
  • Date: Tue, 22 Aug 2000 16:22:41 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

>Dear Marteen

Probably you like that kind of programming style:

In[36]:=
#1-#2& @@ # & /@ Partition[{a, b, c, d, e, f, g, h},2,1]

Out[36]=
{a-b,b-c,c-d,d-e,e-f,f-g,g-h}

Partition produces {{a,b},{b,c},...} and #1-#2& generates the difference e.g.

In[37]:=
#1-#2& @@ {a,b}

Out[37]=
a-b



> >
> > lst = {a, b, c, d, e, f, g, h};
> >
> > Table[lst[[i]] - lst[[i + 1]], {i, 1, Length[lst] - 1}]
> > {a - b, b - c, c - d, d - e, e - f, f - g, g - h}
> >
> > ListCorrelate[{1, -1}, lst]
> > {a - b, b - c, c - d, d - e, e - f, f - g, g - h}
> >
> > The first method is rather clumsy and the 2nd one is quite short, but not
> > really obvious.
> > Initally I was looking for a functional programming style routine.
> > Something like: (#[[i]]-#[[i-1]])&/@lst.
> > Who can tell me how to do this in a functional programming style?
> >
> > Thanks
> >
> > Maarten van der Burgt
> > Leuven, Belgium
> >
> >
> >
> >

********************************************
              Dr. Reinhard Simonovits
Handelsakademie  |  Karl Franzens University
Math Department  |  Inst. of Th. Physics
Grazbachgasse 71 |  Universitaetsplatz 5
               A-8010 Graz, Austria

Email: Reinhard.Simonovits at kfunigraz.ac.at
*********************************************



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