Re: Controlled evaluation of functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg56800] Re: Controlled evaluation of functions*From*: Peter Pein <petsie at dordos.net>*Date*: Fri, 6 May 2005 03:00:19 -0400 (EDT)*References*: <d5ct4c$m5c$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Brett Patterson wrote: > Consider the following behaviour: > > In[1]:= f[i_, x_] := Sin[i x] > > In[2]:= g[x_] = Table[f[i, x], {i, 3}] > > Out[2]= {Sin[x], Sin[2 x], Sin[3 x]} > > In[3]:= {3, 0, 1} . g[y] > > Out[3]= 3 Sin[y] + Sin[3 y] > > This is what I want to do, but using my own function instead of Sin. > However, this is the result: > > In[4]:= k[x_] := x^2 (* This is my alternative to Sin *) > > In[5]:= f[i_, x_] := k[i x] > > In[6]:= g[x_] = Table[f[i, x], {i, 3}] > > Out[6]= {x^2, 4 x^2, 9 x^2} (* I want {k[x], k[2 x], k[3 x]} *) > > In[7]:= {3, 0, 1} . g[y] > > Out[7]= 12 y^2 (* I want 3 k[y] + k[3 y] *) > > How can I get the function k to behave like Sin, so that it is not > evaluated? > > Note that in my real application, k is a lot more complex and has > conditions on its arguments, etc. > > Thanks! > > Brett Patterson > Hi, there are at least 2 possibilities: a) leave k undefined b) k[x_?NumericQ]:=x^2 evaluate for numeric arguments only -- Peter Pein Berlin