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47 lines
1.1 KiB
Markdown
47 lines
1.1 KiB
Markdown
The [_ASSERT](_ASSERT) statement can be used to perform tests in code that's in development, for debugging purposes.
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## Syntax
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> [_ASSERT](_ASSERT) condition[, errorMessage$]
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## Description
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* condition is the condition that must be met in order to consider the _ASSERT valid.
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* Optional errorMessage$ is the message to be displayed in the console window if [$ASSERTS]($ASSERTS) is used.
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* If the condition is not met (that is, if it evaluates to 0), an error occurs ("_ASSERT failed on line #") and program execution stops.
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## Availability
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* Version 1.4 and up.
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## Example(s)
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Adding test checks for parameter inputs in a function.
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```vb
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$ASSERTS:CONSOLE
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DO
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a = INT(RND * 10)
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b$ = myFunc$(a)
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PRINT a, , b$
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_LIMIT 3
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LOOP UNTIL _KEYHIT
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FUNCTION myFunc$ (value AS SINGLE)
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_ASSERT value > 0, "Value cannot be zero"
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_ASSERT value <= 10, "Value cannot exceed 10"
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IF value > 1 THEN plural$ = "s"
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myFunc$ = STRING$(value, "*") + STR$(value) + " star" + plural$ + " :-)"
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END FUNCTION
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```
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## See Also
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* [$ASSERTS]($ASSERTS)
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* [$CHECKING]($CHECKING)
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* [Relational Operations](Relational-Operations)
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