Re: Extracting a Function's Domain and Image
- To: mathgroup at smc.vnet.net
- Subject: [mg67995] Re: [mg67970] Extracting a Function's Domain and Image
- From: "Christoph Lhotka" <lhotka at astro.univie.ac.at>
- Date: Thu, 20 Jul 2006 06:04:38 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Try this: In[]:= #[[1, 1]] & /@ ReleaseHold[DownValues[f] /. f -> Unique[]] Out[]:= {"a","b",_} christoph On Wed, 19 Jul 2006 05:21:10 -0400 (EDT) Bruce Colletti <vze269bv at verizon.net> wrote: > Re Mathematica 5.2.2. > > Why does the last line of code return {x} and not {a,b,_}, while if the > f[_]=0 is struck, the answer is {a,b}? > > I want to extract the domain and image of a user-defined function, and tech > support recommended using DownValues (pretty handy). If you have an easier > approach, please share it. Thanks. > > Bruce > > Remove@f; > f[_]=0; > f["a"]=1; > f["b"]=2; > Clear@x; > h=DownValues@f > Cases[h,f[x_]->x,Infinity] > > Out[52]= > {HoldPattern[f[a]]:>1,HoldPattern[f[ > b]]:>2,HoldPattern[f[_]]:>0} > > Out[53]= > {x} > -- Mag. Christoph Lhotka -- University of Vienna / Institute for Astronomy fon. +43 (1) 4277 51841 mail. lhotka at astro.univie.ac.at