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operator overload within an interface
f#

Hi,

can i write an interface class that expose an operator overload??

I know that a static abstract member is invalid, so how can i do? I would do something like this:

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let y:IFoo

let x = y + 7.3

let q = y + "string"

let u = y + H("another class")

Thanks

.

I believe this is not possible, due to the way the (+) operator is defined. It delegates to a static implementation of either of the operand's classes. This mechanism can't use abstract methods because it happens at compile time (uses statically resolved type parameters).

You could redefine operator (+), but I don't recommend that. You could however define a new operator like this:

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type IT =
   abstract Add : IT -> IT

let (+++) (lhs:IT) (rhs:IT) = lhs.Add rhs

And then implement the interface in a type:

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type T() =
   interface IT with
      override x.Add other = new T() :> IT

This implementation is quite nonsensical, of course. It is actually difficult to implement Add in a meaningfull way, because the method does't know anything about the "other" argument. But maybe this approach is useful in your application...

Example usage of the (+++) operator:

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let it = new T() :> IT
let t = new T()

let r = it +++ t
By on 6/4/2011 5:31 AM ()

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