Re: Define function using lists or tables

*To*: mathgroup at smc.vnet.net*Subject*: [mg131427] Re: Define function using lists or tables*From*: "Nasser M. Abbasi" <nma at 12000.org>*Date*: Wed, 3 Jul 2013 22:04:42 -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*: <kr0oij$3dv$1@smc.vnet.net>*Reply-to*: nma at 12000.org

On 7/3/2013 3:49 AM, Joaquim Nogueira 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. > This looks like a hash table. In Mathematica, it is build in. All what you have to do is: -------------- f[a] = b; f[c] = d; ------------- Now --------------------- In[294]:= f[a] Out[294]= b -------------------- There are more advanced ways to do this for more complicated setups. google the subject of hash tables with mathematica for more information. --Nasser