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Null object: Difference between revisions
Lingo added
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#y->type == 'null'
//true</lang>
=={{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>
=={{header|Lily}}==
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