Re: Can Mathematica evaluate step by step???

*To*: mathgroup at smc.vnet.net*Subject*: [mg29493] Re: Can Mathematica evaluate step by step???*From*: "Neri Kafkafi" <NKafkafi at intra.nida.nih.gov>*Date*: Fri, 22 Jun 2001 02:20:22 -0400 (EDT)*References*: <9gf03m$7m0$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Thanks David, I got several answers for this question, and the solution using DownValues worked best for me. I generaly appriciate very much the knowlage and resopnsiveness in this group. Since you were interested in my objective, it is simple: We use some complex algorithms for analysing a large database. Since most of these algorithms take some time to evaluate over the whole database, I wrote a function that store the results in files, and recall them whenever the same question is asked again. Since we sometimes improve our algorithms, I wanted to include in each file the symbolic definition of the algorithm that was used for generating it, and here I got into the problem... Thanks, Neri David Park <djmp at earthlink.net> wrote in message news:9gf03m$7m0$1 at smc.vnet.net... > Neri, > > It would be interesting to know what your larger objective is. A different > Mathematica approach is probably the answer to your problem. > > Once you set a value for a, you have to use rather round about methods to > keep it from being evaluated. So my first suggestion would be: don't set a > to a value if you intend to later use it as a variable. You could do > something like this (although I doubt that this is the answer you are > looking for) > > a = 4; > myfunction[a_] := 2a > > HoldForm @@ {myfunction[b]} > % /. b :> a > 2 b > 2 a > > But what use would that result be for you, since it is in a HoldForm? So I > think that you must avoid setting values for anything you want to use as a > symbolic variable. It is often better to use rules, a -> 4, to substitute > values for variables, or myfunction[4] to evaluate at a specific value. In > my work I follow my own rule of never setting a single character symbol > (a,b,x,y, etc.) to a value. The chances of getting tripped up by it are just > too high. > > David Park > djmp at earthlink.net > http://home.earthlink.net/~djmp/ > > > From: Neri Kafkafi [mailto:NKafkafi at intra.nida.nih.gov] To: mathgroup at smc.vnet.net > > > > Assume I define: > > myfunction:=2a > > > > and at some later time: > > a=4 > > > > Now if I evaluate myfunction I get 8. > > If I evaluate Hold[myfunction] I get myfunction. > > > > My question is, how do I get 2a ? > > > > In other words, I want to get the symbolic definition of > > myfunction, whether > > a is defined or not. > > > > In (yet) other words, I want to evaluate myfunction only one step further, > > up to 2a, but not all the way to 8. > > > > Is this possible in Mathematica? > > > > Thanks in advance, > > Neri > > > > > > > > > > > >

**Originality**

**Re: AMD vs. Intel Floating Point**

**RE: Can Mathematica evaluate step by step???**

**Odd behavior of InterpolationFunction derivative**