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Improving OCaml's choice of type to display
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Date: -- (:)
From: Yaron Minsky <yminsky@g...>
Subject: Re: [Caml-list] Re: Improving OCaml's choice of type to display
Cool!  That was quick.

Does this patch also implement stephen's fewest-number-of-dots  
heuristic?  I was thinking one nice approach would be fewest-number-of- 
dots with ties broken by length of final identifier.

Y

Yaron Minsky

On Oct 11, 2009, at 10:57 AM, Jun Furuse <jun.furuse@gmail.com> wrote:

> I have quickly wrote a small patch against 3.11.1 for this feature, to
> see what it would be like.
>
> http://sites.google.com/a/furuse.info/jun/hacks/other-small-ocaml-patches
>
> With this patch, path names are printed without opened modules in the
> context. It also tries heuristic data type name simplification: if a
> variant/record data type is an alias of another data type whose name
> is shorter than the original, the printer uses the latter.
>
> For example:
>
> # open Hashtbl;;
> # let tbl = Hashtbl.create 10;;
> val tbl : ('_a, '_b) t = <abstr>      (* not Hashtbl.t, since  
> Hashtbl is open *)
>
> # type t = int;;
> type t = int
> # type long_name = int;;
> type long_name = int
> # (1 : t);;
> - : t = 1                     (* t is the shorter than its original  
> type int *)
> # (1 : long_name);;
> - : int = 1                   (* int is shorter name for long_name. t
> is even shorter but not aliased unfortunatelly. *)
>
> I warn you that the patch is very quickly written and not tested  
> well. Enjoy!
>
> Jun
>
> On Fri, Oct 9, 2009 at 10:53 AM, Yaron Minsky <yminsky@gmail.com>  
> wrote:
>> And you can compete to come up with the most innocuous code that  
>> comes up
>> with the longest type.  Here's my current favorite:
>>
>> # open Option.Monad_infix;;
>> # Map.find m 3 >>| fun x -> x + 1;;
>> - : int Core.Std.Option.Monad_infix.monad = Some 4
>>
>> Which of course could be rendered as:
>>
>> # open Option.Monad_infix;;
>> # Map.find m 3 >>| fun x -> x + 1;;
>> - : int option = Some 4
>>
>> y
>>
>> On Thu, Oct 8, 2009 at 9:40 PM, Yaron Minsky <yminsky@gmail.com>  
>> wrote:
>>>
>>> Anyone who plays around with the Core library that Jane Street just
>>> released can see showcased a rather ugly detail of how Core's design
>>> interacts with how OCaml displays types.  Witness:
>>>
>>> # Int.of_string;;
>>> - : string -> Core.Std.Int.stringable = <fun>
>>> # Float.of_string;;
>>> - : string -> Core_extended.Std.Float.stringable = <fun>
>>>
>>> I'd be much happier if this was rendered in the following equally  
>>> correct
>>> and more readable form:
>>>
>>> # Int.of_string;;
>>> - : string -> Int.t = <fun>
>>> # Float.of_string;;
>>> - : string -> Float.t = <fun>
>>>
>>> Or even:
>>>
>>> # Int.of_string;;
>>> - : string -> int = <fun>
>>> # Float.of_string;;
>>> - : string -> float = <fun>
>>>
>>> And this isn't just an issue in the top-level. The compiler also  
>>> displays
>>> types in the same difficult to read form.  I'm wondering if anyone  
>>> has some
>>> thoughts as to what we can do to make the compiler make better  
>>> choices
>>> here.  There are two issues to overcome:
>>>
>>> Dropping the module name.  I'd love to give the compiler the hint  
>>> that
>>> Core.Std. could be dropped from the prefix in a context where that  
>>> module is
>>> open.  This is what's done with the pervasives module already, I  
>>> believe, so
>>> it seems like it should be doable here.
>>> Choosing shorter names.  This one seems harder, but there are  
>>> various
>>> different possibilities for what type name to print out, and a  
>>> reasonable
>>> heuristic to use might be to pick the shortest one.  Part of the  
>>> reason
>>> these issues come up is our use of standardized interface  
>>> components (that's
>>> where the "stringable" type name comes from).  I suspect this one  
>>> will be
>>> hard to fix, sadly.
>>>
>>> Anyway, we'd be happy with any suggestions on how to improve  
>>> matters.
>>>
>>> y
>>
>>
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