Null object: Difference between revisions
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Drkameleon (talk | contribs) No edit summary |
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{.experimental: "notnil".} |
{.experimental: "notnil".} |
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let ns: pointer not nil = nil # Compile time error</lang> |
let ns: pointer not nil = nil # Compile time error</lang> |
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The value "nil" can be used for pointers, references (i.e. pointers managed by the garbage collector) and procedures. It was also used for strings and sequences, but this is no longer the case (option <code>--nilseqs:on</code> allows to retrieve the old behavior). |
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Testing if a pointer āpā is <code>nil</code> can be done either by using <code>==</code> or using the procedure <code>isNil</code>. |
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<lang Nim>var p: ptr int |
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if p == nil: echo "it is nil" |
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if p != nil: echo "it is not nil" |
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if p.isNil: echo "it is nil"</lang> |
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=={{header|Oberon-2}}== |
=={{header|Oberon-2}}== |