Re: DDC compiler and effects; better than Haskell? (was Re: [Haskell-cafe] unsafeDestructiveAssign?)

On 12.08.2009, at 13:27, Peter Verswyvelen wrote:

Well, the point is that you still have monadic and pure programming styles. It's true that applicative style programming can help here, but then you have these <$> and <*> operators everywhere, which also feels like boilerplate code (as you mention, some extensions could help here)

And you have higher-order functions, you're right. My reply was a bit rushed ;) P.

Monadic style even has the do syntax, which really looks imperative, while of course, it isn't.

I know that for e.g. doing a DFS I can use the ST monad and still be pure, however, my code *looks* imperative when I use the do syntax, which mentally feels weird (maybe it's just me being mentally ill ;-)

It's even worse with the arrows syntax: without it I wouldn't be able to write complex Yampa stuff, but the syntax makes me feels that I'm drawing boxes and links using ASCII, and suddenly it *feels* different than when doing "nice" pure / applicative style programming. Again, maybe it's just my brain that is fucked up by 25 years of imperative programming :)

So to me, keeping the syntax in a pure style (a bit like ML and F#) plays nicer with my brain.

On Wed, Aug 12, 2009 at 11:13 AM, Pavel Perikov wrote:

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unless you have some insanely clever refactoring tool ready that can convert pure into monadic functions and vice versa.

Not trying to attack the idea, just some thoughts:

I don't see much problem converting pure function into an "effectfull" form :) Having pure function myPureFunction::a1->a2->a3->res .... myPureFunction a1 a2 a3 -- pure call myPureFunction <$> a1 <*> a2 <*> a3 -- call using Applicative

Probably, introducing some conventions and using some language extensions you can write a function taking pure function and converting it into monadic version (a-la SPJ' work on polyvariadic composition etc [1])

Have monadic function but needs to call it from pure code? use Control.Monad.Identity.

Not a big deal to me but maybe I'm missing the point

----- [1] http://okmij.org/ftp/Haskell/types.html#polyvar-comp

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