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Re: Recursion inspection technique : HoldForm but release variables

• To: mathgroup at smc.vnet.net
• Subject: [mg66425] Re: Recursion inspection technique : HoldForm but release variables
• From: Peter Pein <petsie at dordos.net>
• Date: Fri, 12 May 2006 02:03:00 -0400 (EDT)
• References: <e3um8v$hfr$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

flatmax schrieb:
> Hi,
> 
> If I define a recursion and hold its form to inspect it :
> Clear[test]
> test[j_Integer?Positive] :=
>                               test[j] = k[j] HoldForm[ test[j - 1] ]
> 
> then This is what happens :
> 
>    In[22]:= test[4]
> 
> Out[22]:= test[4 - 1] k[4]
> 
> But I would like it to be with the variable evaluated :
> 
> Out[22]:= test[3] k[4]
> 
> Whats the trick ???
> 
> thanks
> Matt
> 

Hi Matt,

  another possibility is to Hold just the function's name:

In[1]:=
Clear[test]
test[(j_Integer)?Positive] :=
   test[j] = k[j]*HoldForm[test][j - 1]
In[3]:=
test[4]
Out[3]=
k[4]*HoldForm[test][3] (* displays as k[4]*test[3] *)

hth,
   Peter