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Constraining type parameters
f#

Hello.

Can I constrain type parameters of a class definition?

I want to do something like the following.

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type data = interface
 abstract get: unit -> int
end;;


// I want to constrain 'a to be a subtype of data 
type ('a :> data) c = class
  val d : 'a
  new (init) = { d = init } 
end;;

This is a syntax error :-(

Best regards,
Keiko

.

Hi,
This can be done using the "when" keyword - it works with both " 'a c " and " c<'a> " syntaxes, so you can use which one you prefer:

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type 'a c when 'a :> data = class  
  val d : 'a  
  new (init) = { d = init } 
end;;

type c<'a when 'a :> data> = class  
  val d : 'a  
  new (init) = { d = init } 
end;;
By on 12/17/2007 6:34 AM ()

Thank you.
I tried with the "when" keyword, but did not come up with the right syntax.

Best,
Keiko

By on 12/17/2007 7:13 AM ()

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