Null object: Difference between revisions
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(Pari/GP) |
(→{{header|Tcl}}: Remove someone's ignorant and untested blunder; wrong is wrong!) |
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if ![info exists arr(nullval)] ... |
if ![info exists arr(nullval)] ... |
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if ![dict exists $dic nullval] ...</lang> |
if ![dict exists $dic nullval] ...</lang> |
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You can also use this condition inside an if statement to check if the variable $value is set or not: |
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<lang Tcl>[expr {([string compare "$value[puts \"\"]" ""]==1)}]</lang> |
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I think this is the better way to achieve it. In this case, if $value is set, returns true, or else returns false. |
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{{omit from|TI-83 BASIC}} {{omit from|TI-89 BASIC}} <!-- Does not have a null value. --> |
{{omit from|TI-83 BASIC}} {{omit from|TI-89 BASIC}} <!-- Does not have a null value. --> |
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