Re: Distance between to points in r^3
- To: mathgroup at smc.vnet.net
- Subject: [mg41660] Re: Distance between to points in r^3
- From: Olaf Rogalsky <Olaf.Rogalsky at physik.uni-erlangen.de>
- Date: Thu, 29 May 2003 08:15:41 -0400 (EDT)
- Organization: University of Erlangen, Germany
- References: <bauv0f$m7$1@smc.vnet.net> <bavavj$2bb$1@smc.vnet.net> <bb1uro$9ft$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Jeremy Foster wrote:
> Could you explain the syntax #.# and &[p1-p2]? I don't recognize this. Thanks.
<expr>& denotes an unnamed function. The formal parameters of that function are
available through "#1", "#2", ..., "#n" inside of <expr>. "#" is a synonym for
"#1". As usual, the actual parameters in a call to that function are denoted
by square brackets immediately following the function.
The following lines are (mostly) equivalent:
f[x_]:=Sqrt[x]; f[25]
f=Sqrt[#]&; f[25]
f=Sqrt[#1]&; f[25]
(Sqrt[#]&)[25]
Sqrt[25]
Unnamed functions are usefull in many contexts, e.g. in Map[]:
ListPlot[Map[{#,#^2}&,Range[-100,100]]]
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I Dr. Olaf Rogalsky Institut f. Theo. Physik I I
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