[Caml-list] extend object type?

[Caml-list] extend object type?

[Steffen Smolka]

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Is there syntax to conveniently extend object types?
Concretely, for types

type t1 = < f : int >
type t2 = < f : int; g : bool >

I would like a syntax that allows me to define t2 in terms of t1.

Thanks!
-- Steffen

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Re: [Caml-list] extend object type?

[Kakadu]

AFAIK it is not possible

https://github.com/ocamllabs/compiler-hacking/wiki/Things-to-work-on#support-extending-existing-object-types

Happy hacking,
Kakadu

On Fri, Feb 10, 2017 at 7:15 AM, Steffen Smolka <smolka@cs.cornell.edu> wrote:
> Is there syntax to conveniently extend object types?
> Concretely, for types
>
> type t1 = < f : int >
> type t2 = < f : int; g : bool >
>
> I would like a syntax that allows me to define t2 in terms of t1.
>
> Thanks!
> -- Steffen

Re: [Caml-list] extend object type?

[Leo White]

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You can't do it for object types directly, but you can do it for
class types:


  class type t1 = object method f : int end



  class type t2 = object inherit t1 method g : bool end



Defining a class type also defines the corresponding object type, which
means the above results in types called t1 and t2 that are equal to the
ones you want.


This trick also lets you use #t2 to refer to the polymorphic type < f :
int; g : bool; .. >.


Regards,



Leo



On Thu, 9 Feb 2017, at 11:15 PM, Steffen Smolka wrote:

> Is there syntax to conveniently extend object types?

> Concretely, for types

> 

> type t1 = < f : int >

> type t2 = < f : int; g : bool >

> 

> I would like a syntax that allows me to define t2 in terms of t1.

> 

> Thanks!

> -- Steffen



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Re: [Caml-list] extend object type?

[Hongbo Zhang (BLOOMBERG/ 731 LEX)]

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The syntax is a bit too heavy.
Note that structual typing is a killer feature for FFI with JS libraries,
it would be awesome if we could add some sugar to make below happen
type t1 = < f : int > 
type t2 = < ..t1 ; g : bool>
Is it possible to make it happen? Thanks -- Hongbo

From: leo@lpw25.net At: 02/10/17 04:42:52
To: caml-list@inria.fr
Subject: Re: [Caml-list] extend object type?

    
You can't do it for object types directly, but you can do it for class types:
 

 
  class type t1 = object method f : int end
 

 
  class type t2 = object inherit t1 method g : bool end
 

 
Defining a class type also defines the corresponding object type, which means the above results in types called t1 and t2 that are equal to the ones you want.
 

 
This trick also lets you use #t2 to refer to the polymorphic type < f : int; g : bool; .. >. 

 
Regards,
 

 
Leo 

 
On Thu, 9 Feb 2017, at 11:15 PM, Steffen Smolka wrote:
 
Is there syntax to conveniently extend object types?
 
Concretely, for types
 

 
type t1 = < f : int >
 
type t2 = < f : int; g : bool >
 

 
I would like a syntax that allows me to define t2 in terms of t1.
 

 
Thanks!
 
-- Steffen


  

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Re: [Caml-list] extend object type?

[Steffen Smolka]

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Thanks, this will do! The #t1 syntax is something else I was looking for.

-- Steffen



> You can't do it for object types directly, but you can do it for class
> types:
>   class type t1 = object method f : int end
>   class type t2 = object inherit t1 method g : bool end
> Defining a class type also defines the corresponding object type, which
> means the above results in types called t1 and t2 that are equal to the
> ones you want.
> This trick also lets you use #t2 to refer to the polymorphic type < f :
> int; g : bool; .. >.
> Regards,
> Leo

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