Standard Library: Panic

Terminate the program upon an unexpected program state

In constrast with errors (which signal anticipated error states), panics are used to indicate an unexpected program state from which recovery is not possible. Raising a panic terminates the program.

Module Contents

  1. raise
  2. unimplemented
  3. unreachable

Panic.raise(message)

Raise a panic with the given message string.

score = -10

if score < 0 then
  Panic.raise("score should never be negative")
end
panic: score should never be negative

  Panic.raise("score should never be negative")
             ^
At Panic:embedded:4:14

Panic.unimplemented()

Raise a panic indicating an unfinished implementation.

score = 101

if score > 100 then
  Panic.unimplemented()
end
panic: not implemented

  Panic.unimplemented()
                     ^
At Panic:embedded:4:22

Panic.unreachable()

Raise a panic indicating an unexpected program state.

score = -10

if score >= 0 then
  score /= 2
else
  Panic.unreachable()
end
panic: encountered unreachable code

  Panic.unreachable()
                   ^
At Panic:embedded:6:20