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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)
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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>
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