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Re: pass by reference

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93732] Re: pass by reference
  • From: Raffy <raffy at mac.com>
  • Date: Mon, 24 Nov 2008 04:14:05 -0500 (EST)
  • References: <gg8p9s$jsp$1@smc.vnet.net>

On Nov 22, 3:09 am, juan flores <juan... at gmail.com> wrote:
> Dear all,
>
> How do you pass by reference in Mathematica?
>
> Let us say we want to program push and pop.
> --------
> Push[el_, stack_] := Prepend[stack, el]
> Pop[stack_] := {First[stack], Rest[stack]}
>
> stack = {1, 2, 3}; newel = 5;
>
> stack = Push[newel, stack]
> {5, 1, 2, 3}
>
> {lastel, stack} = Pop[stack]
> {5, {1, 2, 3}}
>
> stack
> {1, 2, 3}
> --------
>
> Code is working, but it is kind of awkward to have to use pure
> functional programming.  I have not been able to find the way to pass
> parameters by reference (or name - i.e. macros).
>
> Any pointers/ideas will be greatly appreciated.
>
> Have a good one,
>
> Juan Flores

push[ v_ , x__ ] := ( v = Join[ { x } // Reverse, v ] );
pop[ v_ ] /; Length[ v ] > 0 := { v // First, v = v // Rest; } //
First;
SetAttributes[ { push, pop }, HoldFirst ];



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