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Undefined values: Difference between revisions

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Undefined values (view source)

Revision as of 12:17, 13 July 2018

344 bytes added ,  5 years ago
Scala contribution added.
m (→‎{{header|Perl 6}}: Remove nyi, speculative type smiley example)
(Scala contribution added.)
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=={{header|Scala}}==
Learned from [http://catless.ncl.ac.uk/Risks/25.51.html#subj9.1 Tony Hoare's "Null References: The Billion Dollar Mistake"], Scala discourages the use of ''null'' values. For Java compatibility the value could be used, but this a bad practice.
 
Notices that ''.isEmpty'' methods (on e.g. String) usually test for nullable.
=={{header|Seed7}}==
Seed7 variables are initialized, when they are defined. This way a variable can never have an undefined value. There is also no general NULL value. When there is a need for a NULL value, an interface type can define its own NULL value. E.g.: The interface type [http://seed7.sourceforge.net/libraries/file.htm file] defines [http://seed7.sourceforge.net/libraries/null_file.htm#STD_NULL STD_NULL], which is used to initialize file variables and as result of [http://seed7.sourceforge.net/libraries/external_file.htm#open%28in_string,in_string%29 open], when a file cannot be opened.
Seed7 variables are initialized, when they are defined.
This way a variable can never have an undefined value.
There is also no general NULL value.
When there is a need for a NULL value, an interface type can define its own NULL value.
E.g.: The interface type [http://seed7.sourceforge.net/libraries/file.htm file] defines
[http://seed7.sourceforge.net/libraries/null_file.htm#STD_NULL STD_NULL],
which is used to initialize file variables and as result of
[http://seed7.sourceforge.net/libraries/external_file.htm#open%28in_string,in_string%29 open],
when a file cannot be opened.
 
=={{header|Sidef}}==
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