问题
We have equivalent assignment operators for all Logical operators, Shift operators, Additive operators and all Multiplicative operators.
Why did the logical operators get left out? Is there a good technical reason why it is hard?
回答1:
Why did the logical operators get left out? Is there a good technical reason why it is hard?
They didn't. You can do &=
or |=
or ^=
if you want.
bool b1 = false;
bool b2 = true;
b1 |= b2; // means b1 = b1 | b2
The ||
and &&
operators do not have a compound form because frankly, they're a bit silly. Under what circumstances would you want to say
b1 ||= b2;
b1 &&= b2;
such that the right hand side is not evaluated if the left hand side does not change? It seems like only a few people would actually use this feature, so why put it in?
For more information about the compound operators see my serious article here:
http://blogs.msdn.com/b/ericlippert/archive/2011/03/29/compound-assignment-part-one.aspx
and the follow-up April-Fools article here:
http://blogs.msdn.com/b/ericlippert/archive/2011/04/01/compound-assignment-part-two.aspx
回答2:
maybe just use
isAdmin = isAdmin || IsGroupAdmin()
I guess it is partially because a ||= b
is kind of confusing because there might be two versions of the implementation: a = a || b
, or a = b || a
. And they act differently because the right-hand side of the expression is sometimes not evaluated.
来源:https://stackoverflow.com/questions/6346001/why-are-there-no-or-operators-in-c