Switch Statement

Flow-Wing supports the switch keyword to handle multiple cases.

Example (value match; first matching case wins)

Pattern from the test suite (SwitchTests fixtures): the switched expression is evaluated once; each case is compared in order.

var a: int = 1
switch a {
case 1: {
  println("first")
}
case 1: {
  println("second")
}
default: {
  println("default")
}
}

warning

Duplicate case values are not errors, but only the first matching case executes. The second case 1: above is dead code.

Output: first (the second case 1 never runs).

var a: int = 5
switch true {
  case a > 0 && a < 10: {
      print("a is between 0 and 10")
  }
  case a > 10 && a < 20: {
      print("a is between 10 and 20")
  }
  default: {
      print("default")
  }
}

Output:

a is between 0 and 10

This pattern replaces long if/else if chains when each case tests a different expression. It reads cleaner than nested ternaries.

Break in Switch

Unlike some languages, Flow-Wing switch cases do not fall through. Each case block is self-contained — no break needed between cases:

var x: int = 1
switch x {
  case 1: {
      print("one")
  }
  case 2: {
      print("two")
  }
}

Both cases are independent. The break keyword exits the entire switch early, useful inside nested loops:

fun getInput() -> str {
  return "quit"
}

while (true) {
  switch getInput() {
      case "quit": {
          break  /; exits the switch, not the while
      }
  }
}

Example (discriminant switch a with default)

var a: int = 5
switch a {
  case 0: {
      print("a is 0")
  }
  case 1: {
      print("a is 1")
  }
  case 2: {
      print("a is 2")
  }
  case 3: {
      print("a is 3")
  }
  case 4: {
      print("a is 4")
  }
  default: {
      print("default")
  }
}

Output:

default

Here, the switch keyword is used to handle multiple cases.