Andrei Alexandrescu's talk just given at ACCU:

http://www.digitalmars.com/d/2.0/accu-functional.pdf

This is a great set of slides and I think it explains really clearly the "why" of D 2.0's const/invariant system. I wish there was a video of Andrei giving the presentation available.

I'm a systems/web programmer but I have a heavy background in FP, and I *love* where D 2.0 is going. To me the automatic multiprogramming, while awesome, is really just another side benefit. Even single-threaded code will see a huge benefit from the guarantees of purity that the compiler can give with this pure/invariant/const system in place. Reading through these slides has just make me even more excited.

Walter Bright:
> Andrei Alexandrescu's talk just given at ACCU: http://www.digitalmars.com/d/2.0/accu-functional.pdf

The pages of this talk are interesting, and simple enough.

Page 2: >As convenient as a scripting language<

This is a myth/lie. D seems more 'convenient' than C++ and C in some applications, but dynamic languages like Python are probably more 'productive' than D still.


P.6: >Ideal language—allow:<

I'm sure lot of people (like functional programming lovers) don't think that mix as the ideal situation :-)


P.14 >Defining a transitive const<

That's one possible D 2.x, the current one, but it may change. This talk presents such things like they are already finished and set in stone (FP programming in D 2.x too).


P. 31: >writeln(i);<

Can you put (temporary) debugging writeln/putr inside a pure function?


P. 35: >It all rests on an efficient machine model!<

I don't understand :-)

Bye,
bearophile

bearophile wrote:
> P. 31: >writeln(i);<
> 
> Can you put (temporary) debugging writeln/putr inside a pure function?

That's always bothered me about this stuff.  I don't want to lose debugging/logging ability!

On Sat, 05 Apr 2008 01:09:14 +0200, Jason House <jason.james.house@gmail.com> wrote:

> bearophile wrote:
>> P. 31: >writeln(i);<
>>
>> Can you put (temporary) debugging writeln/putr inside a pure function?
>
> That's always bothered me about this stuff.  I don't want to lose
> debugging/logging ability!


Just use multiple return types, and have the caller do the printing.

--Simen

Simen Kjaeraas wrote:
> On Sat, 05 Apr 2008 01:09:14 +0200, Jason House <jason.james.house@gmail.com> wrote:
> 
>> bearophile wrote:
>>> P. 31: >writeln(i);<
>>>
>>> Can you put (temporary) debugging writeln/putr inside a pure function?
>>
>> That's always bothered me about this stuff.  I don't want to lose
>> debugging/logging ability!
> 
> 
> Just use multiple return types, and have the caller do the printing.
> 
> --Simen


Monads!

Or at least I think that's what I read somewhere.  I can't understand the buggers for the life of me.  I think maybe it's just a fancy word for "loophole".  If someone here has a good explanation for what a monad is and how it allows mutable state in FP without making thing non-FP, I'd love to hear it.  Because I just don't get it.

--bb

== Quote from Walter Bright (newshound1@digitalmars.com)'s article
> Andrei Alexandrescu's talk just given at ACCU: http://www.digitalmars.com/d/2.0/accu-functional.pdf

It's unfortunate that he won't talk to any of us about this.


Sean

Surely there would be some sort of (detectable) cast or some such to "escape" a pure function for debugging?  Or maybe this just plain ol' relies on running a debugger (not so much fun.)

-[Unknown]


Jason House wrote:
> bearophile wrote:
>> P. 31: >writeln(i);<
>>
>> Can you put (temporary) debugging writeln/putr inside a pure function?
> 
> That's always bothered me about this stuff.  I don't want to lose
> debugging/logging ability!

Jason House, el  4 de abril a las 19:09 me escribiste:
> bearophile wrote:
> > P. 31: >writeln(i);<
> > 
> > Can you put (temporary) debugging writeln/putr inside a pure function?
> 
> That's always bothered me about this stuff.  I don't want to lose debugging/logging ability!

You can't have all. If you functions have side effects, you can't do a lot of things (like a rollback & retry with STM).

-- 
Leandro Lucarella (luca) | Blog colectivo: http://www.mazziblog.com.ar/blog/
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	-- Crónica TV

Sean Kelly:
> It's unfortunate that he won't talk to any of us about this.

Through that document he is talking to you. There are just less ways to push information the opposite direction :-)

Bye,
bearophile