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    <p>I think the reason Scala requires the type annotation on the parameters of a newly defined function comes from the fact that Scala uses a more local type inference analysis than that used in Haskell.</p> <p>If all your classes mixed in a trait, say <code>Addable[T]</code>, that declared the <code>+</code> operator, you could write your generic add function as:</p> <pre><code>def add[T &lt;: Addable[T]](x : T, y : T) = x + y </code></pre> <p>This restricts the add function to types T that implement the Addable trait.</p> <p>Unfortunately, there is not such trait in the current Scala libraries. But you can see how it would be done by looking at a similar case, the <code>Ordered[T]</code> trait. This trait declares comparison operators and is mixed in by the <code>RichInt</code>, <code>RichFloat</code>, etc. classes. Then you can write a sort function that can take, for example, a <code>List[T]</code> where <code>[T &lt;: Ordered[T]]</code> to sort a list of elements that mix in the ordered trait. Because of implicit type conversions like <code>Float</code> to <code>RichFloat</code>, you can even use your sort function on lists of <code>Int</code>, or <code>Float</code> or <code>Double</code>.</p> <p>As I said, unfortunately, there is no corresponding trait for the <code>+</code> operator. So, you would have to write out everything yourself. You would do the Addable[T] trait, create <code>AddableInt</code>, <code>AddableFloat</code>, etc., classes that extend Int, Float, etc. and mix in the Addable trait, and finally add implicit conversion functions to turn, for example, and Int into an <code>AddableInt</code>, so that the compiler can instantiate and use your add function with it.</p>
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    1. POScala: How to define "generic" function parameters?
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    1. USRam Ghadiyaram
    1. USfxt
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      1. VTUpMod
    1. COThis is certainly doable, but not as nice.
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      1. USairportyh
 

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