Vlad Shalnev wrote:
* from the manual: >> Logical OR. Evaluates to 1 if any operand is non-zero, to NULL if any >> operand is NULL, otherwise 0 is returned.
* Roger Baklund:
This definition (from the manual) is self-contradicting: 1 OR NULL should evaluate to 1 because "any operand is non-zero", but it should also evaluate to NULL because "any operand is NULL".
Why self-contradicting ?
It is self-contradicting because one part of the definition contradicts another part of the same definition.
> If you apply this rule as described ( from left
to right ) you will get correct result.
Definitions are usually not implemented left to right. Consider this definition: "The day can be devided into two parts: at night it is dark, in the day you can breathe." Implemented from left to right, it gives the "correct" answer, but that does not make it a good definition, mostly because the second part does not only fit the "day", it also fits the "night". A good definition is clear and unambiguous.
While we're at it: the term "non-zero"... what does it mean? As we all know, NULL != 0, and 0 == zero, consequently NULL must be non-zero.
I guess "non-false" or simply "true" would be more correct, as NULL evaluates to false in a boolean expression.
> And it isn't work in 4.1.7 :((
I don't know why the behaviour has changed. I suggest it is because the definition is unclear, but I don't know.
-- Roger
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