Averages/Arithmetic mean: Difference between revisions

=={{header|Scala}}==

Using Scala 2.7, this has to be defined for each numeric type:

<lang scala>def mean(s: Seq[Int]) = s.foldLeft(0)(_+_) / s.size</lang>

However, Scala 2.8 gives much more flexibility, but you still have to opt

between integral types and fractional types. For example:

<lang scala>def mean[T](s: Seq[T])(implicit n: Integral[T]) = {

import n._

s.foldLeft(zero)(_+_) / fromInt(s.size)

}</lang>

This can be used with any subclass of <tt>Sequence</tt> on integral types, up

to and including BigInt. One can also create singletons extending <tt>Integral</tt>

for user-defined numeric classes. Likewise, <tt>Integral</tt> can be replaced by

<tt>Fractional</tt> in the code to support fractional types, such as <tt>Float</tt>

and <tt>Double</tt>.

Alas, Scala 2.8 also simplifies the task in another way:

<lang scala>def mean[T](s: Seq[T])(implicit n: Fractional[T]) = n.div(s.sum, n.fromInt(s.size))</lang>

Here we show a function that supports fractional types. Instead of importing the definitions

from <tt>n</tt>, we are calling them on <tt>n</tt> itself. And because we did not import them,

the implicit definitions that would allow us to use <tt>/</tt> were not imported as well.

Finally, we use <tt>sum</tt> instead of <tt>foldLeft</tt>.