match basics in Scala

Matching on plain values, with alternatives, guards, and a catch-all.

// match is an expression: every case produces a value.
def dayKind(day: Int): String = day match
  case 6 | 7 => "weekend" // | matches any of several values
  case 1     => "restock"
  case _     => "workday" // _ catches everything left over

// A guard puts a condition on a case.
def cellarNote(celsius: Int): String = celsius match
  case c if c < 4  => "too cold for the barrels"
  case c if c < 13 => "ideal"
  case c if c < 20 => "watch it"
  case _           => "move the casks"

def matchDemo(): Unit =
  val today = dayKind(6)
  println(today + ": " + cellarNote(11))
  println(dayKind(3) + ": " + cellarNote(22))

How it works

1. case 6 | 7 => "weekend" matches either value, and the final case _ picks up everything left over.
2. cellarNote puts a condition on each case, as in case c if c < 4 and case c if c < 13.
3. def dayKind(day: Int): String = day match uses match as an expression, so the matched result is the return value.

Keywords and builtins used here

• Int
• String
• Unit
• case
• cellarNote
• dayKind
• def
• if
• match
• matchDemo
• val

The run, in numbers

Lines

17

Characters to type

605

Tokens

109

Three-star pace

75 tpm

At the three-star pace of 75 tokens a minute, this run takes about 87 seconds.

Type this snippet

Step 2 of 3 in Expressions, step 5 of 27 in Language basics.

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