tail call elimination

[gitfoxi]

It's interesting that this is valid syntax in Julia and Lua:

function rec()
    return rec()
end

The difference is that in Lua, when you call rec() it will stare at you and engage your motherboard's built-in space heater until you ctrl-C out. In Julia:

julia> rec()
ERROR: stack overflow
 in rec at none:2 (repeats 80000 times)

So the stack 80000 things deep. That's interesting.

Why does this matter? I'm not sure. But some people care a lot:

http://www.lua.org/pil/6.3.html

[ihnorton]

See: https://groups.google.com/d/msg/julia-dev/POP6YXCnP-k/_ibmsU0hTdIJ

[JeffBezanson]

I'm a schemehead and appreciate TCO as much as anybody, but we're not actually planning to implement this so I'm just going to close this. Apologies.

[gitfoxi]

There's a volcano of conversation coming from julia-dev. I'll definitely
search it as well is Issues in the future before bringing something up.
Clearly this topic has been discussed. I think the final word is:

Jeff Bezanson
Nov 24
No, no update. It's not a high priority, but eventually we will
probably do some of the optimizations, but not the semantic guarantee.

On Wed, Nov 27, 2013 at 6:24 PM, Isaiah notifications@github.com wrote:

See
https://groups.google.com/forum/#!searchin/julia-dev/tail-call/julia-dev/POP6YXCnP-k/qjEw2OiFVd8J

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Reply to this email directly or view it on GitHubhttps://github.com//issues/4964#issuecomment-29435198
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Michael

[gitfoxi]

Oh hey Jeff. I just quoted you from julia-dev but you had already responded
to me. How are you doing that?!? You actually showed up in person before I
finished reading the thread where you rejected the idea last year.

I want to figure out how this community is so engaged. A few hours before
thanksgiving and people are online. This is like the Reddit of ... I'm out
of metaphors. I need to go soak my head. What? Wow.

On Wed, Nov 27, 2013 at 7:14 PM, Jeff Bezanson notifications@github.comwrote:

I'm a schemehead and appreciate TCO as much as anybody, but we're not
actually planning to implement this so I'm just going to close this.
Apologies.

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Reply to this email directly or view it on GitHubhttps://github.com//issues/4964#issuecomment-29436759
.

Michael

[JeffBezanson]

I refuse to believe you're out of metaphors. We're all enjoying them :)

[ViralBShah]

Yes, we are enjoying all the metaphors. Please keep them coming. :-)

[staticfloat]

I must admit, I'm not sure why or even how I've gotten so involved with Julia. I think it has something to do with the other contributors, but the experiments proving this are still running.

[timholy]

I refuse to believe you're out of metaphors. We're all enjoying them :)

+1. I'm confident and hopeful that you can come up with something. I haven't yet seen one that involves both bicycle grease and wildebeests :-).

I must admit, I'm not sure why or even how I've gotten so involved with Julia. I think it has something to do with the other contributors, but the experiments proving this are still running.

I can't figure it out either, but it's extraordinarily addictive. Perhaps because it's so rewarding.

[StefanKarpinski]

I can't figure it out either, but it's extraordinarily addictive. Perhaps because it's so rewarding.

Julia specializes in having a very high result-to-effort ratio :-)

[StefanKarpinski]

Mentioning TCO and "tail call optimization" here so that we can avoid future duplicates of this issue.

[StefanKarpinski]

If someone wants to go ahead and implement tail call elimination, then feel free to go for it. I'll leave this open for that eventuality.

[gitfoxi]

+1

Also, language support for lazy evaluation is the other side of that coin.
LazySequences.jl demonstrates the power but not the performance that you
could have.

On Thu, Jan 9, 2014 at 5:51 AM, Stefan Karpinski
notifications@github.comwrote:

Reopened #4964 #4964.

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Reply to this email directly or view it on GitHubhttps://github.com//issues/4964
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Michael