Re: [Caml-list] Question about objects and method overriding

[Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>]

On 2014/02/02 20:55, Tom Ridge wrote:

> Dear caml-list,
> 
> With records, one can functionally update a field e.g. as
> 
> { r with some_field=new_value }
> 
> And new_value may, of course, be a function.
> 
> With objects, is there similar functionality? e.g. can I write something like
> 
> {{ myobj with method some_method=new_method }}
> 
> ?
> 
> Of course, I could copy the methods from myobj explicitly into a new
> object (and set some_method to new_method), but I might not know all
> the methods available on myobj, and even if I do this becomes
> textually extremely verbose.
> 
> Of course, new_method cannot directly refer to self etc. Basically I
> am using objects in a similar way to records, and would like to use
> this functional record update feature.
> 
> Thanks
> 
> Tom


You can copy an object updating a value field, not a method field:

class point (x:int) = object val x = x method get = x method bump dx = {< x = x+dx >} end

You can use this for methods too, by having them call a function value field.
However, this kind of update is only available inside methods, which requires some thinking
when designing your code.

I agree that what you suggest would be nice to have.
There is no majore technical difficulty, but there would be some overhead.

	Jacques Garrigue