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Re: Making a stack.

  • To: mathgroup at
  • Subject: [mg128473] Re: Making a stack.
  • From: Bob Hanlon <hanlonr357 at>
  • Date: Tue, 23 Oct 2012 00:56:38 -0400 (EDT)
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SetAttributes[enqueue, HoldRest]

enqueue[x_, queue_Symbol] :=
  If[Head[queue] === List,
   AppendTo[queue, x], queue = {x}];

enqueue[3, q1]


x = 5;

enqueue[x, q1]

{3, 5}

Or if you want to require manual creation of queue

enqueue[x_, queue_Symbol] :=
  AppendTo[queue, x];

q2 = {};

enqueue[7, q2]


enqueue[x, q2]

{7, 5}

Bob Hanlon

On Mon, Oct 22, 2012 at 2:03 AM, Brentt <brenttnewman at> wrote:
> Hi, I'm trying to make stack functions like enqueue and dequeue to
> demonstrate algorithms. I know enqueue would do pretty much the same thing
> as AppendTo, but I want the arguments reversed and it to be called
> "enqueue". I figured this would work:
> enqueue[x_, queue_] := AppendTo[queue, x];
> But it spits out red. I tried to tinker with the evaluation order but to no
> avail. Is anyway to make this work? I want the functions to work like they
> would in a procedural language (I'm not using a procedural language because
> I want to accompany the algorithms with visualizations---i.e. it's for a
> demonstration project). I know I can just use Set when I want to que
> something, but I was hoping to figure out a way to make the code look like
> procedural code, and I'm guessing Mathematica is flexible enough to do
> that.
> Any ideas?

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