[Caml-list] functor question

[Caml-list] functor question

[Brian Naylor]

Is there any efficiency difference between:

module Foo = Make (Bar) (Baz)

and

module Both = struct module Bar = Bar module Baz = Baz end
module Foo = Make (Both)

In other words, is it better to coalesce structures into a single functor
application rather than to apply multiple functors?  Do I pay more indirection
costs in the first case?  Thanks.


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Re: [Caml-list] functor question

[Xavier Leroy]

> Is there any efficiency difference between:
> module Foo = Make (Bar) (Baz)
> and
> module Both = struct module Bar = Bar module Baz = Baz end
> module Foo = Make (Both)
> In other words, is it better to coalesce structures into a single
> functor application rather than to apply multiple functors?  Do I
> pay more indirection costs in the first case?  Thanks.

Actually, you pay one more indirection in the second case (Make(Both)).

- Xavier Leroy
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[Caml-list] Functors, Modules and Indirections

[Thorsten Ohl]

Xavier Leroy <xavier.leroy@inria.fr> writes:

> [...] you pay one more indirection [...]

Is there a theoretical reason for the native compiler not to resolve
module indirections (including inlining) statically at compile time?
[I see that it would break independent compilation for the bytecode
compiler, but the native compiler requires recompilation of dependent
modules anyway.]

Or is there a technical reason other than potential code bloat?

Or are there plane to implement it?

In most cases, the performance penalty will be only a small constant
factor, but it would be nice not having to worry about it at all ---
even in hotspots.

Curious,
-Thorsten
-- 
Thorsten Ohl, Physics Dept., Wuerzburg Univ. -- ohl@physik.uni-wuerzburg.de
http://theorie.physik.uni-wuerzburg.de/~ohl/     [<=== PGP public key here]
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