# Scala Extractors Infix Sample with Rational Numbers

# Scala Extractors Infix Sample with Rational Numbers

### The author demonstrates the use of Scala Extractors through a short exercise involving rational numbers.

Join the DZone community and get the full member experience.

Join For FreeMicroservices! They are everywhere, or at least, the term is. When should you use a microservice architecture? What factors should be considered when making that decision? Do the benefits outweigh the costs? Why is everyone so excited about them, anyway? Brought to you in partnership with IBM.

I keep coming back to the awesome introductory material on Scala put together by Daniel Westheide. One of the examples that he provides for extractors using an infix operation pattern is the Streams API -

```
val xs = 58 #:: 43 #:: 93 #:: Stream.empty
xs match {
case first #:: second #:: _ => first - second
case _ => -1
}
```

Where the extractor is defined this way:

```
object #:: {
def unapply[A](xs: Stream[A]): Option[(A, Stream[A])] =
if (xs.isEmpty) None
else Some((xs.head, xs.tail))
}
```

Given this I wanted to try an extractor on the Rational number samples from the Scala by Example book, this is how the Rational number looks:

```
class Rational(n: Int, d: Int) {
private def gcd(x: Int, y: Int): Int = {
if (x == 0) y
else if (x < 0) gcd(-x,y)
else if (y < 0) -gcd(x, -y)
else gcd(y % x, x)
}
private val g = gcd(n, d)
val numer: Int = n/g
val denom: Int = d/g
def +(that: Rational) =
new Rational(numer * that.denom + that.numer * denom,
denom * that.denom)
def -(that: Rational) =
new Rational(numer * that.denom - that.numer * denom,
denom * that.denom)
def *(that: Rational) =
new Rational(numer * that.numer, denom * that.denom)
def /(that: Rational) =
new Rational(numer * that.denom, denom * that.numer)
override def toString = "" + numer + "/" + denom + ""
def square = new Rational(numer*numer, denom*denom)
}
```

And I wanted an extractor which would behave the following way:

```
val r = new Rational(2, 3)
r match {
case num / denom => num + "/" + denom
}
```

This is absolutely feasible in Scala given the flexibility in the names of identifiers. Given this an extractor called "/" can be defined the following way:

```
object / {
def unapply(r: Rational): Option[(Int, Int)] = Some(r.numer, r.denom)
}
```

And used for extracting the numerator and denominator of the rational number!

Discover how the Watson team is further developing SDKs in Java, Node.js, Python, iOS, and Android to access these services and make programming easy. Brought to you in partnership with IBM.

Published at DZone with permission of Biju Kunjummen. See the original article here.

Opinions expressed by DZone contributors are their own.

## {{ parent.title || parent.header.title}}

## {{ parent.tldr }}

## {{ parent.linkDescription }}

{{ parent.urlSource.name }}