Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2013

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Define function using lists or tables

  • To: mathgroup at smc.vnet.net
  • Subject: [mg131415] Re: Define function using lists or tables
  • From: "Louis Talman" <talmanl at gmail.com>
  • Date: Wed, 3 Jul 2013 22:00:41 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • Delivered-to: l-mathgroup@wolfram.com
  • Delivered-to: mathgroup-outx@smc.vnet.net
  • Delivered-to: mathgroup-newsendx@smc.vnet.net
  • References: <20130703085846.4E7676A7B@smc.vnet.net>

On Wed, 03 Jul 2013 02:58:46 -0600, Joaquim Nogueira <jen at fct.unl.pt>  
wrote:

> Hello. Possibly this is a very simple question.
>
> Is there a way to define a function over a (BIG) list of ordered pairs?  
> I mean, suppose that I have a list, created using a Table command or  
> something like that, of the form [{a,b},{c,d},etc.] such that, after  
> naming it f, say, f = [{a,b},{c,d},etc.], then, afterwards, whenever  
> there is a command such that one needs to compute f[a] (or f[c]), the  
> program immediately replaces f[a] by b,and f[c] by d?
>
> Thank you.
>

My previous post did almost exactly what you ask for here, with the  
difference that it reversed the order of the pairs---because that was what  
you asked for.

Call your original list of pairs, say, L, as in  L = {{a, b}, {c, d},...},  
and then do

L /. {x_,y_} :> Set[f[x], y];

--Louis A. Talman
   Department of Mathematical and Computer Sciences
   Metropolitan State University of Denver

   <http://rowdy.msudenver.edu/~talmanl>



  • Prev by Date: Re: Calculating derivate in Mathematica 9 giving wrong result
  • Next by Date: Re: Calculating derivate in Mathematica 9 giving wrong
  • Previous by thread: Define function using lists or tables
  • Next by thread: Re: Define function using lists or tables