Re: Holding Arguments in a Second Argument List
- To: mathgroup at smc.vnet.net
- Subject: [mg32259] Re: [mg32238] Holding Arguments in a Second Argument List
- From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
- Date: Wed, 9 Jan 2002 23:37:14 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
I can't see a way to do what you want in the first part of your message
(assign attributes for sub-arguments) but as for the second one way that
will work is:
In[1]:=
foo[mathgroup_] :=
Function[mat,
Module[{},
Do[If[Not[mathgroup === great], Return[$Failed]],{1}]
],
{HoldFirst}]
e.g.
In[2]:=
foo[x][mat]
Out[2]=
$Failed
Andrzej Kozlowski
Toyama International University
JAPAN
http://platon.c.u-tokyo.ac.jp/andrzej/
On Wednesday, January 9, 2002, at 05:17 PM, David Park wrote:
> Dear MathGroup,
>
> I have a series of procedures which manipulate a matrix. I like to
> define
> them in this fashion.
>
> function[args___][matrix_] := ... because then I can write lines like
>
> matrix // function[args...] etc.
>
> But I have to define the function so that matrix is held, and I don't
> want
> to write Unevaluated with every use. But Attributes = {HoldFirst} only
> applies to the first argument list. Is there a direct way to define the
> attributes of a second argument list?
>
> In any case, I write the routines this way.
>
> function[args___]:=
> Function[matrix,
> Module[{}, code],
> {HoldFirst}]
>
> and that works. The code usually changes the matrix and I display it
> separately. But sometimes the operation will fail and then I would like
>
> function[args...][matrix]
>
> to return $Failed. But I am unable to do that. The best I seem to be
> able to
> do is return Return[$Failed].
>
> Here is a sample routine which just tries to return $Failed.
>
> foo[mathgroup_] :=
> Function[mat,
> Module[{},
> If[Not[mathgroup === great], Return[$Failed]]],
> {HoldFirst}]
>
> foo[x][mat]
> Return[$Failed]
>
> Can anyone tell me how to get rid of the Return wrapper?
>
> Thanks
>
> David Park
> djmp at earthlink.net
> http://home.earthlink.net/~djmp/
>
>
>
>