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DU with interface and member declaration not allowed ?
f#

The following is an illegal construct, but why ? I should be able to not using DU but static instance member value, just curious why. I can have either interface or simple with, but not both.

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type Identity<'a> = 
  |Id of 'a
  interface IMonad<'a> with
    member m.Bind f = match m with Id(a) -> f a
    member m.Unit x = Id(x):>IMonad<'a>
  with
    member m.foo() = match m with Id(a) -> a
.

You just need to get the order/indentation right. Check it out below.

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type IMonad<'a> =
    abstract Bind : ('a -> 'b) -> 'b
    abstract Unit : 'a -> IMonad<'a>

type Identity<'a> = 
  |Id of 'a
  with
    member m.foo() = match m with Id(a) -> a
    interface IMonad<'a> with
      member m.Bind f = match m with Id(a) -> f a
      member m.Unit x = Id(x):>IMonad<'a>
By on 2/12/2010 11:29 PM ()

ah, thanks. Though it is a bit confusing as the following seems to be ok. Or may be it is now what I think it is.

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type Identity<'a>(x) = 
  let v = x
  interface IMonad<'a> with
    member m.Bind f = f v
    member m.Unit x = Identity(x):>IMonad<'a>
  with
    member m.foo() = x
By on 2/12/2010 11:40 PM ()

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