Pattern Match against Function

Question

While playing around in Scala, I came up against something that I think should be possible, but I don't know how to do.

I'm returning a value that's bounded by a given min/max. With an if-else statement, the function would look like this:

def set(n: Int, min: Int, max: Int): Int = 
{
  if (n < min) return min
  if (n > max) return max
  return n
}

I was wondering if it was possible to do this (elegantly) with pattern matching. I tried the following, but it was syntactically incorrect:

def set(n: Int, min: Int, max: Int): Int = n match 
{
  case (n < min) => min
  case (n > max) => max
  case _ => n
}

I think there's a way to do it by mixing case and if statements, but by the time I've done that I might as well just be using a standard if/else chain. Is there a correct syntax to do what I'm attempting?

def set(...) is declared type Unit, but returns a value. I guess you want it to be set(...):Int ? — maasg
@maasg Oops, wasn't thinking there. Fixed. Question still stands, though. — KChaloux

Rex Kerr Rex Kerr · Accepted Answer · 2012-11-15T18:57:11

Pattern matching works but is less elegant:

def set(n: Int, min: Int, max: Int) = n match {
  case _ if n < min => min
  case _ if n > max => max
  case _ => n
}

because:

def set(n: Int, min: Int, max: Int) = if (n < min) min else if (n > max) max else n

(or if you like line breaks:

def set(n: Int, min: Int, max: Int) = {
  if (n < min) min
  else if (n > max) max
  else n
}

)

Return not needed.

(Don't forget math.min(max,math.max(min,n)), either.)

Pattern Match against Function

2 Answers