Null object: Difference between revisions

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 =={{header|Erlang}}==
-Erlang does not have an undefined value.  As an alternative, many applications tend to pick a convention for return values and use that.
+Erlang does not have an null object.  As an alternative, many applications tend to pick a convention for returning an empty condition and use that.
 Example alternatives:
-# Something like <pre>{ok, 3}</pre> or <pre>{err, no_more}</pre> on error.
+# Something like <pre>{ok, 3} % normal case</pre> or <pre>{err, no_more} % error case</pre> on error.
 # Don't ever allow an undefined return value, and throw an exception instead.
 # Return an atom:
-## <pre>undefined</pre>*
+## '''undefined'''*
-## <pre>undef</pre>
+## '''undef'''
-## <pre>null</pre>
+## '''null'''
-## <pre>nil</pre>
+## '''nil'''
-## <pre>none</pre>
+## '''none'''
-<pre>undefined</pre> is often used by records as an initial value and the stdlib module.
+'''undefined''' is often used by records as an initial value and the stdlib module.
 Atoms are erlang's user-defined constants that always evaluates to is itself.  It is also equal to no other value else but itself.