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>

**References**:**Define function using lists or tables***From:*Joaquim Nogueira <jen@fct.unl.pt>