Null object: Difference between revisions

=={{header|Lingo}}==

Null/nil is called "<Void>" in Lingo. Lingo doesn't distinguish undefined variables from <Void> objects, and by using the constant VOID you can even assign <Void> to variables. Functions that don't return anything, return <Void>. Checking for <Void> (e.g. by using built-in function voidP) can also be used to implement optional function arguments: if voidP() returns TRUE (1) for some argument, a default value can be assigned in the function body.

<lang lingo>put _global.doesNotExist

-- <Void>

put voidP(_global.doesNotExist)

-- 1

x = VOID

put x

-- <Void>

put voidP(x)

-- 1</lang>