<palomer>
what do you guys think about implicit constructors?
<palomer>
like we could have datatype a = int | float; and then foo(3) = 2 | foo(3.4) = 4
<Demitar>
async_, a couple of ways to do it are listed in the manual (bottom of the ocamlc section iirc). And yes, it's evil. :)
<Demitar>
palomer, err? What are you talking about?
<Demitar>
Some kind of overloading constructor inference thingie?
<async_>
ok, time to concat the files :)
<async_>
hehe
<mrvn>
palomer: How would you match against the type of a?
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<palomer>
mrvn, good point
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<mrvn>
It would be nice if ocaml would optimize out the variant type for simple variants.
<Demitar>
mrvn, how simple?
<mrvn>
'type foo = Foo of bla' as simplest case.
<Demitar>
What would be the point?
<mrvn>
'type foo = X of x | Y of y' when x and y are distinc types already, like int and object.
<Smerdyakov>
mrvn, how would you "optimize" that second case?
<Smerdyakov>
mrvn, do you mean to use the tag bit?
<mrvn>
yes.
<Smerdyakov>
Clearly that doesn't work just because x and y are "distinct types."
<mrvn>
There only are a very few distinct types. Most things end up as objects.
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<Smerdyakov>
You are using a different meaning of "distinct types" than I think most people would.
<mrvn>
distinct in memory. Looking at the tag bit would be the obvious choice.
<Demitar>
mrvn, just wanting to make sure. Are you actually having performance problems because of this? Or is it just a "nice to have" feature? :)
<mrvn>
nice to have.
<mrvn>
My cpu is too fast to have performance problems :)
<Smerdyakov>
Try SML if you want that sort of thing.
<Smerdyakov>
In MLton, there are no tag bits, so the second kind of optimization doesn't make sense.
<Smerdyakov>
But the first one is certainly implemented.
<Demitar>
Smerdyakov, what have we said about advocating other languages in here? ;-)
<mrvn>
I think there are only two common cases where the optimization could be used: type foo = Foo of ... and type foo = Empty | of Foo of ...; cases-
<Smerdyakov>
mrvn, MLton hits both of those.
<mrvn>
unfortunately the later is usualy a type 'a foo
* Demitar
usually relies on Smerdyakov to explain icky things to people wondering anyway. :)
<mrvn>
Smerdyakov: how does it catch "None" vs "Some None"?
<Smerdyakov>
mrvn, not sure, but it uses different representations for different instantiations of polymorphic types.
<mrvn>
So it might be using the tag bit for None and Some.
<Smerdyakov>
There is no tag bit with MLton.
<mrvn>
How does the GC work then?
<Smerdyakov>
Fancyness.
<mrvn>
You need the tag bit to differentiate between int and pointer.
<Smerdyakov>
Well, it might just be that values in registers are untagged.
<mrvn>
Without it you can only do conservative GC and that can leak memory.
<Smerdyakov>
It's quite easy to implement a completely tag-free runtime system, but it takes more work than people generally want to invest.
<mrvn>
Smerdyakov: well, yes. registers should be untaged and unboxed.
<Smerdyakov>
You just need to save shape information for use at GC-time.
<mrvn>
Smerdyakov: the shape information then is your tag bit.
<mrvn>
That would be like the array of float in ocaml I guess.
<Smerdyakov>
No, shape information need not be stored in values themselves.
<mrvn>
Obviously.
<Smerdyakov>
It need not even be stored per-value.
<Smerdyakov>
You only need per-program-point information.
<mrvn>
One thing ocaml is realy bad at is unboxing within code that does not call the GC. Like the inner loop for the Mandelbrot Fractal.
<mrvn>
defining that as extern C code gave a huge speedup.
<mrvn>
Does ocamlopt do unrolling of tail recursions?
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<Nutssh>
It does tail recursion (has to!), dead code elimination, and, pretty much nothing else. No redundancy elimination, no unrolling.
<mrvn>
It doesn't have to do tail recursion, it just wouldn't work very well.
<async__>
does anyone know of a function that converts a float value into the 32 bit IEEE representation?
<mrvn>
extern: float ieee_of_float(val f) { ... }
<mrvn>
But why convert 64bit to 32?
<async__>
float is 32 bits
<async__>
mrvn: so you're saying i have to make a c function to do it?
<mrvn>
async__: ocamls floats are doubles.
<mrvn>
I don't think ocaml has a 32 bit float type.
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<Nutssh>
It doesn't, except that you can create arrays of 32bit IEEE floats with BigArray.
<mrvn>
But afaik 32bit floats are slower on all modern cpus. So why bother?
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<mrmr>
so i was gonna take a look at ocaml and i was thinking my frist project might be a test engine for SMTP, IMAP and POP3, but I was reading a tutorial that said that Ocaml's UTF-8 support isn't that good. Is this till the case. I would really like support for many different charecter sets utf-7 and utf-8 being the most important
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<Nutssh>
google is a friend.
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<tyler>
Are there any major differences between O'Caml 2.04, and 3.08?
<tyler>
I'm reading the book linked from the homepahe
<tyler>
but it apparently is targetted at that older release
<tyler>
I mean, I'm sure there are lots of changes, but are there any that I, as a beginner, need to worry about?
<vincenz>
the o'reilly book on the website should be for ocaml 3.07 or 3.08
<tyler>
okay
<tyler>
heh, just found I think
<tyler>
using 3.08.1
<tyler>
let a = -1.0 /. 0.0;;
<tyler>
val a : float = neg infinity
<tyler>
a + 1.0;;
<tyler>
oh, doh
<tyler>
just realised
<tyler>
that's the one thing about o'caml I really, really don't likw
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<vincenz>
what?
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<malte>
hi. is there a native way to slice lists? (sort of like [2:4] in python)
<vincenz>
no because lists are implemented differently
<vincenz>
lists in python are more like arrays
<vincenz>
lists in ocaml are implemented in the cons-cell style
<vincenz>
however it shouldn't be too much work to make such a function
<vincenz>
if you want to work with lists a'la python. I'd look at arrays
<malte>
oh :)
<malte>
how does one slice an Array then?
<vincenz>
rtm?
<malte>
fair enough
<vincenz>
Array.sub
* vincenz
never uses the Array module much
<vincenz>
but python lists are more like resizable arrays than lists
<malte>
ah, thanks
<malte>
vincenz, yeah, i was trying to implement such a function myself. but i got stuck :)
<vincenz>
of course if you're planning on frequent inserts/appends, you'd better go for lists
<vincenz>
arrays are more for when the 'list' is fixed-size
<salo>
ocamlc.opt -c -w s -I +labltk -I ../../src togl.mli
<Demitar>
And what does locate widget.cmi tell you?
<salo>
no such file ... hmmm, that is the problem
<Demitar>
How did you install ocaml?
<salo>
binary package from inria
<salo>
so i bet the right thing to do is compile ocaml from source
<Demitar>
From the inria dl page (on OSX): "Note that this binary distribution is configured without the TCL/TK interface. If you want to use labltk, you will have to recompile OCaml yourself."
<Demitar>
I think it's possible to compile lablgl without tk support if that's what you want though.
* salo
is on the glide path
<salo>
thanks Demitar, esp for not calling attention to the fact that i am dumb
<Demitar>
Current knowledge is irrelevant. It's the willingness to learn which is valued.
<salo>
bonus q: what do people use to edit ocaml source? particularily revised syntax
<monochrom>
I use emacs currently. I have plans to use eclipse.
<Demitar>
Don't know about revised syntax. I use emacs and others use vim.
<Demitar>
With a bit of tweaking tuareg-mode is my very best friend. :)
<salo>
eclipse is great, but the ocaml mode is barely there. i found an emacs mode for revised syntax but it is slightly broken
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<malte>
vincenz, fine, thanks :) (i forgot to thank you for the help btw!)
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<pgas>
hello, let's start by saying that I know nothing about ocaml
<pgas>
I'm trying to compile ocaml for arm (zaurus), make world is ok but make bootstrap fails
<pgas>
Fatal error: unknown C primitive `int_xor'
<pgas>
Does this means something for someone?
<Smerdyakov>
Is OCaml known to compile on ARM?
<pgas>
Don't know ;)
<Smerdyakov>
I would be surprised if they had picked that platform for a port.
<Smerdyakov>
If no one has explicitly set things up to work there, it is very unlikely that someone who knows nothing about OCaml will be able to get it to work on that platform.
<Smerdyakov>
It includes native code generators, for example.
<pgas>
make world runs fine though
<Smerdyakov>
I'm not sure what that means, in terms of which hurdles have been surmounted.
<Smerdyakov>
But you could imagine that you might successfully compile a version of gcc that only targets x86, for example.
<Smerdyakov>
This wouldn't mean that you had "gotten gcc to work for ARM."
<pgas>
hmm I see
<Smerdyakov>
Though I would expect that the bytecode version of OCaml probably works on ARM w/ few changes, if any.
<pgas>
hmm I think this is the case, there is ocamlrun but no ocamlc in the boot dir thanks bye
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<vincenz>
hi
<vincenz>
re
<vincenz>
ARM tends to be an easy platform
<Smerdyakov>
Probably not easy enough for someone with no knowledge of the compiler's workings to target with a port.