Null object: Difference between revisions
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=={{header|Lingo}}== |
=={{header|Lingo}}== |
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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 |
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 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. |
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<lang lingo>put _global.doesNotExist |
<lang lingo>put _global.doesNotExist |
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-- <Void> |
-- <Void> |