Abstract Types & Self Type questions

Hello,   I am playing around with making some numeric types with varying operations, Eg. (possible to add shares but not multiply them) and have reach the limits of my understanding.   Here is one of my attempts:   trait Addition[T] {
    type N <: { def +(other: N) }
    val value: N       protected implicit def value2wrapper(v: N): T       def +(that: T): T = this.value + that.value
}   The compiler complains that N has a cyclic reference, I think it should be valid. It just means that the type should have a + method that takes a parameter with the same type ...   Another think that I think it may simplify the code would be to be able to use Self as a type:   trait Addition {
    type N <: { def +(other: N) }
    val value: N       protected implicit def value2wrapper(v: N): Self       def +(that: Self): Self = this.value + that.value
}   Is there any way to achieve something in that spirit? in that way it will be possible to do some mixins without type parameters reducing the noise :   class MyNumber extends Number with Addition   instead of   class MyNumber extends Number with Addition[MyNumber]   is just and small difference but it will read more nicely.   regards,   Oscar    

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