Haskell

[Timon Gehr]

On 08/25/2011 04:08 AM, bearophile wrote:
> Timon Gehr:
>
>> It is especially compact in that program,
>
> The coding style of that program is an unreadable mess, example:
>
> LList!T hamming(T)(){
>      LList!T merge(LList!T xs, LList!T ys){
>          return lz({
>                  auto x=xs.head, y=ys.head;
>                  if(x()<y()) return cons(x,merge(xs.tail,ys))();
>                  else if(x()>y()) return cons(y,merge(xs,ys.tail))();
>                  else return cons(x,merge(xs.tail,ys.tail))();
>              });
>      }
>
>      return lz({
>              LList!T r;
>              r=cons(st(1),lz({return merge(merge(map((Lazy!T a){return lz({return 2*a();});},r),map((Lazy!T a){return lz({return 3*a();});},r)),map((Lazy!T a){return lz({return 5*a();});},r))();}));
>              return r();
>          });
> }
>
>
> This is a bit better:
>
> LList!T hamming(T)() {
>      static LList!T merge(LList!T xs, LList!T ys) {
>          return lz({
>                  auto x = xs.head;
>                  auto y = ys.head;
>                  if (x()<  y())
>                      return cons(x, merge(xs.tail, ys))();
>                  else if (x()>  y())
>                      return cons(y, merge(xs, ys.tail))();
>                  else
>                      return cons(x, merge(xs.tail, ys.tail))();
>              });
>      }
>
>      return lz({
>                  LList!T r;
>                  r = cons(st(BigInt(1)), lz({
>                      return merge(merge(map((Lazy!T a){ return lz({ return 2 * a(); }); }, r),
>                                         map((Lazy!T a){ return lz({ return 3 * a(); }); }, r)),
>                                   map((Lazy!T a){ return lz({ return 5 * a(); }); }, r))();
>                  }));
>                  return r();
>              });
> }
>

Well, the main reason it is an unreadable mess is the bug with lazy and 
closures I reported, and I think inserting whitespace does not 
necessarily make the code better readable. (I like especially the first 
half of the code snippet better in the format I provided)

I usually do not spend much time to format my code, especially if like 
here the end result is not significantly better readable. Maybe code 
formatting should be automated completely via a dedicated tool.


>
>> I am starting to think this is not as intended.
>
> I think it's a DMD bug. Fit for Bugzilla.
>

See http://d.puremagic.com/issues/show_bug.cgi?id=6552

>
>> I cannot seem to find it, but I'd like to vote on it. Do you have a link?
>
> I have updated this:
> http://d.puremagic.com/issues/show_bug.cgi?id=5970
>

Thanks.