Re: List-Operations on Heads other than List
- To: mathgroup at smc.vnet.net
- Subject: [mg29757] Re: List-Operations on Heads other than List
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Sat, 7 Jul 2001 02:26:02 -0400 (EDT)
- References: <9i068k$h0i$1@smc.vnet.net> <9i3pf2$lsh$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
"Orestis Vantzos" <atelesforos at hotmail.com> wrote in message news:9i3pf2$lsh$1 at smc.vnet.net... ..... > do keep in mind though, that Select searches in all the levels of your > expression and you might get weird results because of this. .... Orestis, Select only selects from level one, ignoring heads. You may be thinking of Cases: Select[h[a,b[c],d, e], MatchQ[#,_Symbol]&, 2] h[a,d] Cases[h[a,b[c],d, e], _Symbol,{1, 2}, 4,Heads\[Rule]True] {h,a,b,c} Note that Select uses the head h as a wrapper while Cases uses List. -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565