问题
[It seems odd this doesn't exist, so apologies in advance if it's a duplicate]
I want to test for logical equality in C. In other words, I want to know whether two values would be equal if both were converted in the normal way associated with logical expressions.
In C99, I think that
(bool)a == (bool)b
gives what I want. Is that correct? What is the normal way of writing this in traditional C?
回答1:
You typically see this:
if ((a == 0) == (b == 0))
Or
if (!!a == !!b)
Since !!a evaluates to 1 if a is nonzero and 0 otherwise.
Hope this helps!
回答2:
In C, zero is false. If you want to convert any value to its boolean equivalent, the standard way (well, except that there's almost never a need for it) is to prefix an expression with !! , as in !!a. In the case of your expression,
!!a == !!b
may be simplified to
!a == !b
回答3:
In pre-C99 C, the tradiitional, idiomatic way to "cast to bool" is with !!.
回答4:
There is no (bool) in traditional c. True/False is handled using ints. You can check for boolean equality with
a ? b : !b
来源：https://stackoverflow.com/questions/10952759/logical-equality-in-c