re[Caml-list] cursive type definition camllight

re[Caml-list] cursive type definition camllight

[sieira]

I'm implementing a graphical interface in camllight on which there are forms.
I've defined a form as

type form == textbox list * (form,customer list -> customer list);;

This form displays some textboxes (using graphics library) on which the user
types the necessary data, after that, it is parsed and tailed to the
returned customer list. It is necessary that the function that does this
takes the form as a parameter. ¿Is this possible?

Otherwise, i could do:

type form == textbox list * (field_values list,customer list -> customer
list);;

but I would like to avoid it in order to keep a clean code.

Thanks in advance for your replies.


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[Caml-list] Re: recursive type definition camllight

[Damien Doligez]

On 2011-01-19, at 19:10, sieira wrote:

> type form == textbox list * (form,customer list -> customer list);;
> 
> This form displays some textboxes (using graphics library) on which the user
> types the necessary data, after that, it is parsed and tailed to the
> returned customer list. It is necessary that the function that does this
> takes the form as a parameter. ¿Is this possible?

You cannot define a recursive type abbreviation in Caml Light.  But you
can define a recursive concrete type:

type form = Form of textbox list * (form -> customer list -> customer list);;

This will make your code a bit more cumbersome (you'll have to add the
Form constructor in many places), but it should work.

-- Damien