On Thursday 21 December 2006 21:27, Philippe Wang wrote:
> If you want to do that, use Lisp...

Lisp is too slow.

> Or use sum types...
> type t = Int of int | Float of float | ...

Manual boxing is too verbose.

> OCaml forgets types at runtime!

Some type related information is certainly retained, e.g. to unbox float 
arrays.

> This means that you can't know without a huge cost (cf. SafeUnmarshal
> costs), because what you can do in O(1) is to know whether a value is an
> int or a pointer...

I'd like to quantify this cost. I've read papers and heard work stating that 
carrying run-time type information can be cheap but I see evidence that might 
point to the contrary, e.g. F# is significantly slower than OCaml but it has 
concurrent GC that was designed for a non-FPL.

In F#, you have run-time type information. Amongst other things, this allows 
you to dispatch to more efficient type-specialised functions. For example, 
you can write functions over polymorphic arrays and dispatch to optimised 
BLAS versions for float arrays when the input happens to be a float array.

-- 
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
Objective CAML for Scientists
http://www.ffconsultancy.com/products/ocaml_for_scientists