Re: Extracting a Function's Domain and Image
- To: mathgroup at smc.vnet.net
- Subject: [mg67996] Re: Extracting a Function's Domain and Image
- From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
- Date: Thu, 20 Jul 2006 06:04:39 -0400 (EDT)
- Organization: Uni Leipzig
- References: <e9ku8v$l1v$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi, because Cases[] handels Rules in a special way: Cases[expr, pattern -> rhs, levspec] gives the values of rhs which match the pattern. and you mean Cases[h, HoldPattern[f[a_]] -> a, Infinity] Regards Jens "Bruce Colletti" <vze269bv at verizon.net> schrieb im Newsbeitrag news:e9ku8v$l1v$1 at smc.vnet.net... | 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} |