Control Flow

Ozark has three control-flow constructs:

  • if/with/else
  • all
  • repeat

This is an intentionally small set; each allows predictable patterns for accomplishing specific things.

If / With / Else

The if statement evaluates a Boolean value and, if that value is true, executes the body.

The if statement body is executed, or not, based on the result of the conditional. For more complex if statements that involve pattern matching, the powerful ... notation can be used to match a value or tuple with a value description. The with keyword unpacks an optional variable. with is mandatory shorthand for if «someOptional» is not nil.

Conditions following an else execute only if none of the previously chained statements have executed.

Conditions can omit trailing any flags.

inheritance Example

method branch object: Object, condition1: Boolean, condition2: Boolean
	if condition1, condition2 is
	...	true, 3
		object doSomething

	...	false
		object doSomethingElse

	...	else any, in [1, 2, 5]
		object doAnotherThing

	...	else
		object reset
inheritance Example

method testAndContinue object: ExampleObject?
	with object
		object doSomething

		print "Success"

	...	else
		print "Cannot continue - no object."


The all keyword indicates that an array is being used in place of an object, and that the statement will be executed once for every element in the array.

This can be used with multi-dimensional arrays.

inheritance Example

method printRange count: Integer
	print all [1~count]

method printNames attendees: [Attendee]
	all attendees name -> names
	print all names


The repeat clause is appended to a statement after a pipe |. It indicates that the statement should repeat based on the type and parameters of the following clause. Valid repeat clauses follow one of these formats:

  • repeat X times
  • repeat while someCondition
  • repeat until someCondition

In the above examples, someCondition indicates an output of the statement, and X can represent any Integer or Integer variable.

inheritance Example

method listenForInput io: StandardIO
	io getInputFromUser -> input | repeat until input is not nil

method growTo2KB file: implied File
	@fileManager appendToFile file chunk: 1000 -> size | repeat until size is 2000000