Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2002
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2002

[Date Index] [Thread Index] [Author Index]

Search the Archive

Holding Arguments in a Second Argument List

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32238] Holding Arguments in a Second Argument List
  • From: "David Park" <djmp at earthlink.net>
  • Date: Wed, 9 Jan 2002 03:17:32 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

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/



  • Prev by Date: TeXForm and negative exponents
  • Next by Date: Re: System Ax=b!
  • Previous by thread: Re: TeXForm and negative exponents
  • Next by thread: Re: Holding Arguments in a Second Argument List