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MathGroup Archive 1999

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Re: MyPrependTo

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15988] Re: MyPrependTo
  • From: Dan Truong <dtruong at irisa.fr>
  • Date: Fri, 19 Feb 1999 03:27:06 -0500
  • Organization: Irisa, Rennes (FR)
  • References: <7ag26u$ag9@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

> In[2]:=
> push[someStack_, elt_] := (someStack = Prepend[someStack, elt];)

Is it legal in Mathematica to assign a function parameter?
I think not, because they are avaluated before going in the
function body (ie, parameters are passed by value, not by
reference or pointers)

The solution is to use a golbal stack parameter, or to use
Return[]

Push[...] := ( Return[Prepend[...]]);
e = Push[e,1];

BTW: does anyone know how to pass a pointer to an object
so it can be modified and returned? HoldFirst etc. do not
do that.

-- 
Dan N. Truong,  IRISA, Campus de Beaulieu, 35042 Rennes Cedex, FRANCE
tel:(+33)2 99 84 25 39            fax:(+33)2 99 84 25 28
mailto:dtruong at irisa.fr           http://www.irisa.fr/caps/PEOPLE/Dan
gsm:06 14 78 06 95 -> http://www.sfr.fr/html/annexes/sms/sendsms.html


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