why this is true:
(true | false & false)
and this is false:
(true | false && false)
in my mind should be the oposite..
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6`|` and `&` are bitwise operators (that happen to be defined for bools as well) - use `||` and `&&` for logical operations including short-curcuiting. – Feb 11 '11 at 11:38
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That's the reason why I always explicitly add braces in such situations ;-) – Lucero Feb 11 '11 at 11:39
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@delnan: Terminology nitpick: `|` and `&` are defined for integral types and for bool. For integral types they are bitwise operators; for bool they are logical operators without short-circuiting. – R. Martinho Fernandes Feb 11 '11 at 11:47
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@Martinho: Well, assuming the definition `true = 1` and `false = 0`, both work ;) But point taken. – Feb 11 '11 at 11:50
3 Answers
15
They bind as:
true | (false & false) // true
and
(true | false) && false // false
I would avoid writing code which relies on these rules though - it's obviously unclear to the reader :)
For reference, see section 7.3.1 of the C# 4 language specification, which shows & having higher precedence than | (hence the first result) and | having higher precedence than && (hence the second result).
Jon Skeet
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8Also: my rule of thumb: **never learn the precedence table**; use brackets instead. Save your brain for stuff that matters. – Marc Gravell Feb 11 '11 at 11:39
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1Yes, it's advisable to use brackets to make your code easier to read. – DaeMoohn Feb 11 '11 at 11:41
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3
& has priority to | which has priority to &&, so your expressions are evaluated as
(true | (false & false)) = (true | false) = true
and
((true | false) && false) = (true && false) = false
See the reference of C# operators containing there precedence for more information.
Sören
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