The Strange Loop conference

[Timon Gehr]

On 09/22/2011 02:29 PM, Christophe wrote:
> "Nick Sabalausky" , dans le message (digitalmars.D:145002), a écrit :
>>> For example, in Haskell, map (correctly) has the signature:
>>>
>>> map :: (a ->  b) ->  [a] ->  [b]
>>>
>>> but in D, std.map has the signature (expressed in some Haskell/D
>>> pseudocode)
>>>
>>> map :: (a ->  b) ->  [a] ->  Map!((a ->  b), [a])
>
> except that [a] should be a D Range, and that Map is a D Range too.
> So I'd go for:
>
> map :: (a ->  b) ->  Range!A ->  Range!B
>
> oh, that's quite close to Haskell's map...
>
>
> Let me try the other game: what is Haskell's signature ?
> I need to introduce Haskell's type to D, so:
>
> // all types are lazy pure:
> template Haskell(T)
> {
>      alias pure T function() Haskell;
> }
>
> // Haskell's list:
> template HaskellR(T)
> {
>      alias pure Tuple!(Haskell!A, HaskellR!T) function() HaskellR;
> }
>
> // Then the signature of map is:
> HaskellR!B map(A,B)(Haskell!B function(Haskell!A), HaskellR!A);
>
> Experienced Haskell's users may correct me.
>
> All functions must be pure, and those pure function, and a lot of
> optimization comes from the memoization of those functions.
> Haskell!T could be rewritten to take into account this memoization.
>
> I wonder what efficiency would we get compared to Haskell with a library
> based on this kind of stuff in D. We would probably miss many
> optimization opportunities that Haskell is tuned to find out, but it
> must be fun to try that out.
>

I did: http://pastebin.com/2rEdx0RD

port of some haskell code from RosettaCode (run it ~20 min to get 
results, haskell runs in less than 2s)
http://pastebin.com/Vx4hXvaT

Output of the second example is screwed up with the latest release 
though, I don't know why, but converting BigNums to string is a PITA 
anyways... Has there been a regression in the std.bigint.BigInt.toString 
code?


The main performance issue is the garbage collector. Turning it off will 
help performance a lot if you have enough RAM. Furthermore, DMD does not 
do any advanced optimizations