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Re: Questions about functions.


  • To: mathgroup@smc.vnet.net
  • Subject: [mg11807] Re: Questions about functions.
  • From: dreissNOSPAM@nospam.earthlink.net (David Reiss)
  • Date: Tue, 31 Mar 1998 02:28:27 -0500
  • Organization: EarthLink Network, Inc.
  • References: <6esdkf$57j@smc.vnet.net> <6f1lvm$f9n@smc.vnet.net> <6fi7ca$4ri@smc.vnet.net>

In article <6fi7ca$4ri@smc.vnet.net>, El alchemista
<jaimeco@pecos.rc.arizona.edu> wrote:

> I will appreciate your input to these two questions.
> 
> 1 - How can I convert the sequence of all arguments of a function  into
> a list ?              In vain I tried      f[x__] := List @@ x 
> 
> 
> 2 - How can I make functions which use their own names , for instance so
> that   s[e,f]   for some symbol   s   and all expressions    e , f   
> becomes    (s+e)(s+f)  ?
> 
> 
> Many thanks
> 
> jaime Combariza
> jaimeco@arizona.edu


1 - How can I convert the sequence of all arguments of a function  into
a list ?              In vain I tried      f[x__] := List @@ x 


This does what you want:

In[14]:= Clear[f]

In[15]:=

Clear[f];
f[x__] := List@x

In[16]:= f[a,b,c,d]

Out[16]= {a,b,c,d}


Or equivalently,


In[17]:=

Clear[f];
f[x__] := {x}

In[18]:= f[a,b,c,d]

Out[18]= {a,b,c,d}

2 - How can I make functions which use their own names , for instance so
that   s[e,f]   for some symbol   s   and all expressions    e , f   
becomes    (s+e)(s+f)  ?


The following seems to work for the example that you give.  Perhaps you
want something more involved?


In[19]:=

Clear[s];
s[e_,f_] :=(s+e)(s+f) 

In[20]:= s[x,z] 

Out[20]= (s+x) (s+z)

-- 
David Reiss
dreissNOSPAM@nospam.earthlink.net
http://home.earthlink.net/~dreiss
To send personal email, remove the words  "nospam" and "NOSPAM" from the
email address



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