I have a match statement like this:
i match {
case x if x == 0 ⇒
romanNumeral
case x if x >= 1000 ⇒
this.roman(i - 1000, s"${romanNumeral}M")
case x if x >= 900 ⇒
this.roman(i - 900, s"${romanNumeral}CM")
// etc.
Depending on how this is formatted, it could be about 30 lines of redundant code. So I'm wondering whether it is possible to make this code more dry.
So I created a partial function:
private def toRoman(upperGuard: Int, token: String, romanNumeral: String): String = {
case value: Int if value >= upperGuard ⇒
this.roman(upperGuard - 1, s"$romanNumeral$token")
}
which I then tried to include into the above matcher like:
i match {
case x if x == 0 ⇒
romanNumeral
toRoman(1000, "M", romanNumeral)
toRoman(900, "CM", romanNumeral)
// etc.
... But this won't work because Scala's compiler doesn't recognize these functions are the case statements it is looking for.
Is there any way to make this work?
You could create your cases as partial functions:
private def toRoman(upperGuard: Int, token: String, romanNumeral: String): PartialFunction[Int, String] = {
case value if value >= upperGuard =>
this.roman(upperGuard - 1, s"$romanNumeral$token")
}
val firstCase: PartialFunction[Int, String] = {
case x if x == 0 => romanNumeral
}
And then compose it like this:
val toRomanPartialFunction = firstCase
.orElse(toRoman(1000, "M", romanNumeral))
.orElse(toRoman(900, "CM", romanNumeral))
After that you could use it like regular function:
toRomanPartialFunction.apply(443)
toRomanPartialFunction(443)