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A variable defaulting to a previous variable?

• To: mathgroup at smc.vnet.net
• Subject: [mg121920] A variable defaulting to a previous variable?
• From: Brentt <brenttnewman at gmail.com>
• Date: Thu, 6 Oct 2011 04:25:54 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

How would one go about making a variable default to a previous variable?

I would like results like this:

In[1]= f[x_, y_: x] := x+y;
> In[2]= f[2,3]
> Out[1]= 5
> In[3]= f[3]
> Out[1]= 6
>



But, of course, Mathematica won't let me use a previous argument for the
default of the next argument. Is there a way to do this?

• Follow-Ups:
  • Re: A variable defaulting to a previous variable?
    • From: Leonid Shifrin <lshifr@gmail.com>
  • Re: A variable defaulting to a previous variable?
    • From: DrMajorBob <btreat1@austin.rr.com>