If I have code like 5 * 5.0
the result gets converted to the most accurate type, Double
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But this doesn't seem to work with code like
case class Value[T : Numeric](value: T) {
type This = Value[T]
def +(m: This) = Value[T](implicitly[Numeric[T]].plus(value, m.value))
...
}
implicit def numToValue[T : Numeric](v: T) = Value[T](v)
Is there a way to make things like someIntValue + double
work, where someIntValue
is Value[Int]
and double
is Double
?
PS: Sorry for the far less-than-perfect title. I'm thankful for suggestions for better wording ...
You can do this (with a lot of busywork) by creating implicit operators:
abstract class Arith[A,B,C] {
def +(a: A, b: B): C
def -(a: A, b: B): C
def *(a: A, b: B): C
def /(a: A, b: B): C
}
implicit object ArithIntLong extends Arith[Int,Long,Long] {
def +(a: Int, b: Long) = a+b
def -(a: Int, b: Long) = a-b
def *(a: Int, b: Long) = a*b
def /(a: Int, b: Long) = a/b
}
...
def f[A,B,C](a: A, b: B)(implicit arith: Arith[A,B,C]) = arith.*(a,b)
scala> f(5,10L)
res46: Long = 50
but you really have to do more than that, since you need a Numeric equivalent for A and B alone, and the asymmetric operations need to be defined both ways. And it's not really practical to specialize given that there are three types involved.
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