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Relational Operations
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| Operation
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Description
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Example usage
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| A = B
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Tests if A is equal to B.
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IF A = B THEN
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| A <> B
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Tests if A is not equal to B.
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IF A <> B THEN
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| A < B
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Tests if A is less than B.
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IF A < B THEN
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| A > B
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Tests if A is greater than B.
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IF A > B THEN
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| A <= B
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Tests if A is less than or equal to B.
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IF A <= B THEN
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| A >= B
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Tests if A is greater than or equal to B.
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IF A >= B THEN
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Table 3: The relational operations for condition checking.
In this table, A and B are the Expressions to compare. Both must represent
the same general type, i.e. they must result into either numerical values
or STRING values. If a test succeeds, then true (-1) is returned, false (0)
if it fails, which both can be used in further Boolean evaluations.
┌─────────────────────────────────────────────────────────────────────────┐
│ Relational Operations │
├────────────┬───────────────────────────────────────────┬────────────────┤
│ Operation │ Description │ Example usage │
├────────────┼───────────────────────────────────────────┼────────────────┤
│ A = B │ Tests if A is equal to B. │ IF A = B THEN │
├────────────┼───────────────────────────────────────────┼────────────────┤
│ A <> B │ Tests if A is not equal to B. │ IF A <> B THEN │
├────────────┼───────────────────────────────────────────┼────────────────┤
│ A < B │ Tests if A is less than B. │ IF A < B THEN │
├────────────┼───────────────────────────────────────────┼────────────────┤
│ A > B │ Tests if A is greater than B. │ IF A > B THEN │
├────────────┼───────────────────────────────────────────┼────────────────┤
│ A <= B │ Tests if A is less than or equal to B. │ IF A <= B THEN │
├────────────┼───────────────────────────────────────────┼────────────────┤
│ A >= B │ Tests if A is greater than or equal to B. │ IF A >= B THEN │
└────────────┴───────────────────────────────────────────┴────────────────┘
The operations should be very obvious for numerical values. For strings
be aware that all checks are done case sensitive (i.e. "Foo" <> "foo").
The equal/not equal check is pretty much straight forward, but for the
less/greater checks the ASCII value of the first different character is
used for decision making:
E.g. "abc" is less than "abd", because in the first difference (the 3rd
character) the "c" has a lower ASCII value than the "d".
This behavior may give you some subtle results, if you are not aware of
the ASCII values and the written case:
E.g. "abc" is greater than "abD", because the small letters have higher
ASCII values than the capital letters, hence "c" > "D". You may use
LCASE$ or UCASE$ to make sure both strings have the same case.
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