[Openmcl-devel] consing

[Taoufik Dachraoui]

I am not expecting the compiler to use consing, I want to do the same thing
as the compiler is doing, how to do it?

Taoufik


On Tue, May 14, 2013 at 6:01 PM, Tom Emerson <tremerson at gmail.com> wrote:

> If you disassemble your fact function you'll see that there is no consing
> going on: the machine stack is being used directly. I'm not sure why you
> would expect the compiler to use conses for this.
>
>
>
> On Tue, May 14, 2013 at 11:52 AM, Taoufik Dachraoui <
> dachraoui.taoufik at gmail.com> wrote:
>
>> What is not true? I am not saying that stacks are conses; we can push and
>> pop elements from a stack and macroexpanding (PUSH 1 X) gives (SETQ X (CONS
>> 1 X)); so the stack, used by pop/push, in CCL is implemented
>> using conses; we can implement stacks using arrays (no consing) if we
>> wish so.
>>
>> Now, the reason I am asking, is that I am implementing an interpreter for
>> a small language and I am using 3 stacks with a lot of consing. I wanted to
>> find a solution so that I can avoid consing; I recalled when we call a
>> function the passed parameters are pushed into a stack (implemented with
>> registers ESP/EBP), I am wondering if I can find a way to use the
>> processor's stack as for function calls to avoid consing.
>>
>> Or, how do you implement a VM using CCL for a new language? (any thing
>> offered by CCL even if it is not
>> standard would be acceptable).
>>
>> Taoufik
>>
>>
>>
>> On Tue, May 14, 2013 at 5:12 PM, Ron Garret <ron at flownet.com> wrote:
>>
>>> This kind of question is better posed to a general Lisp newsgroup.  This
>>> list is specific to CCL (f.k.a.  OpenMCL).
>>>
>>> But the answer is simple:
>>>
>>> > pushing an element on the stack, (PUSH 1 X) is equivalent
>>> > to (SETQ X (CONS 1 X)),
>>>
>>> That is not true.  Stacks and cons cells are fundamentally different
>>> data structures.  You can build a stack out of cons cells, but you can't
>>> build cons cells out of a stack.  A stack is *strictly* a last-in-first-out
>>> data structure, which is the reason it doesn't need to be garbage collected.
>>>
>>> rg
>>>
>>> On May 14, 2013, at 3:37 AM, Taoufik Dachraoui wrote:
>>>
>>> > Hi
>>> >
>>> > This is probably simple but I could not figure out the explanation, I
>>> hope that
>>> > someone could help me out
>>> >
>>> > CL-USER> (defun fac (n) (if (= n 0) 1 (* n (fac (- n 1)))))
>>> > FAC
>>> > CL-USER> (time (fac 3))
>>> > (FAC 3)
>>> > took 0 milliseconds (0.000 seconds) to run.
>>> > During that period, and with 1 available CPU core,
>>> >      0 milliseconds (0.000 seconds) were spent in user mode
>>> >      0 milliseconds (0.000 seconds) were spent in system mode
>>> > 6
>>> >
>>> > As you can see, there is no consing when FAC is called
>>> >
>>> > Now, knowing that pushing an element on the stack, (PUSH 1 X) is
>>> equivalent
>>> > to (SETQ X (CONS 1 X)), and since FAC is using a stack and thus pushing
>>> > values on the stack why there is no consing when (FAC 3) is called?
>>> >
>>> > I believe there is a simple explanation but I could not figure it out
>>> >
>>> > Kind regards
>>> > Taoufik
>>> >
>>> > _______________________________________________
>>> > Openmcl-devel mailing list
>>> > Openmcl-devel at clozure.com
>>> > http://clozure.com/mailman/listinfo/openmcl-devel
>>>
>>>
>>
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>>
>
>
> --
> Tom Emerson
> tremerson at gmail.com
> http://www.dreamersrealm.net/tree
>
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