Undefined values: Difference between revisions
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=={{header|Seed7}}== |
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Seed7 variables are initialized, when they are defined. |
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This way a variable can never have an undefined value. |
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There is also no general NULL value. |
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When there is a need for a NULL value, an interface type can define its own NULL value. |
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E.g.: The interface type [http://seed7.sourceforge.net/libraries/file.htm file] defines |
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[http://seed7.sourceforge.net/libraries/null_file.htm#STD_NULL STD_NULL], |
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which is used to initialize file variables and as result of |
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[http://seed7.sourceforge.net/libraries/external_file.htm#open%28in_string,in_string%29 open], |
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when a file cannot be opened. |
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=={{header|Tcl}}== |
=={{header|Tcl}}== |