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POHow to write a function with a generic AnyVal
 

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  1. POHow to write a function with a generic AnyVal
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    <p>I'm trying to get the following Scala code to compile:</p> <pre><code>// Something that Scala is very bad at: don't try and figure out if every type I *could* possibly use supports it, // just let me use it until I try a type that doesn't. Or at least have AnyValue provide an abstraction for all // Numeric Types (Interface) trait NumericValue[T] { def +(rhs : T, lhs : T) : T } implicit object ByteNumericValue extends NumericValue[Byte] { def +(rhs : Byte, lhs : Byte) : Byte = (rhs + lhs).toByte } implicit object ShortNumericValue extends NumericValue[Short] { def +(rhs : Short, lhs : Short) : Short = (rhs + lhs).toShort } implicit object IntNumericValue extends NumericValue[Int] { def +(rhs : Int, lhs : Int) : Int = rhs + lhs } implicit object LongNumericValue extends NumericValue[Long] { def +(rhs : Long, lhs : Long) : Long = rhs + lhs } implicit object BigIntNumericValue extends NumericValue[BigInt] { def +(rhs : BigInt, lhs : BigInt) : BigInt = rhs + lhs } def doMath[T &lt;: AnyVal](initializer : Long)(implicit Num : NumericValue[T]) : T = { Num.+(initializer.asInstanceOf[T], initializer.asInstanceOf[T]) } lazy val math = doMath[Short](0) </code></pre> <p>The idea here is that I need a way to make doMath operate on any Integer and thus a type with an addition operator. I want it to be agnostic of large number like BigInt or a very small number like Byte.</p> <p>When I try to compile this I get an error:</p> <pre><code>error: could not find implicit value for parameter Num: NumericValue[Short] lazy val math = doMath[Short](0) </code></pre> <p>Any ideas?</p>
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    1. USTimeHorse
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    1. COWhat version of Scala are you using? It compiles fine for me (but gives a cast error since you can't cast a `Long` to a `Short`--if you change `initializer` to type `T` it all works fine).
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      1. USRex Kerr
    2. COyou are doing exactly what scala Numeric is all about
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      1. USArjan
    3. COSeems like you need to somehow implement widening of the numeric types when doing something else than combining two values of the same type.
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      1. USziggystar
 

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