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Re: Question on defaults in positional arguments

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112629] Re: Question on defaults in positional arguments
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 23 Sep 2010 04:23:57 -0400 (EDT)

Handle with two definitions

Clear[f]

f[y_: 2] := f[1, y, 3]
f[x_, y_, z_: 3] := {x, y, z}

{f[], f[y], f[x, y], f[x, y, z]}

{{1, 2, 3}, {1, y, 3}, {x, y, 3}, {x, y, z}}


Bob Hanlon

---- NP <nomplume69 at gmail.com> wrote: 

=============
Hi,

I was wondering if there was a way in selectively specifying some of
the arguments of a function (rest remaining default). For instance,
consider
Clear[f, x, y,z];
f[x_: 1, y_: 2,z_:3] := {x, y}
f[5]

{5,2,3}

Here the default values of y and z are automatically used. How can I
call f so that, for example,  the default value of x  and z are used
instead?

Thanks,

NP




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