Re: evaluate f[{x,y,z}] when f[x,y,z] defined
- To: mathgroup at smc.vnet.net
- Subject: [mg103397] Re: evaluate f[{x,y,z}] when f[x,y,z] defined
- From: Peter Pein <petsie at dordos.net>
- Date: Sun, 20 Sep 2009 06:21:06 -0400 (EDT)
- References: <h9283i$lo6$1@smc.vnet.net>
Murray Eisenberg schrieb: > I ought to know how to do this (simply) but don't, or at least don't > recall how... > > Often I have a function of several variables defined, for example: > > f[x_, y_, z_] := Sqrt[x^2 + y^2 + z^2] > > And I have some list of numbers, e.g.: > > a = {4, 3, 2}; > > How can I evaluate the following... > > f[a] > > .... without having to make a separate definition such as > > f[{x_, y_, z_}] := f[x, y,z] > > ? > There are some methods but I prefer the first one (In[3]): In[1]:= f[x_, y_, z_] := Sqrt[x^2 + y^2 + z^2] In[2]:= a = {4, 3, 2}; In[3]:= f @@ a Out[3]= Sqrt[29] In[4]:= f[Sequence @@ a] Out[4]= Sqrt[29] In[5]:= a /. List -> f Out[5]= Sqrt[29]