问题
Can I compare three variables like the following, instead of doing if((x==y)&&(y==z)&&(z=x))? [The if statement should execute if all three variables have the same value. These are booleans.]
if(debounceATnow == debounceATlast == debounceATlastlast)
{
debounceANew = debounceATnow;
}
else
{
debounceANew = debounceAOld;
}
回答1:
No, it does not.
x == y is converted to int, yields 0 or 1, and the result is compared to z. So x==y==z will yield true if and only if (x is equal to y and z is 1) or (x is not equal to y and z is 0)
What you want to do is
if(x == y && x == z)
回答2:
No. The equality check associates from the left and the logical result is compared as a number, so that the expression 2 == 2 == 1 parses as (2 == 2) == 1, which in turn gives 1 == 1 and results in 1, which is probably not what you want.
回答3:
You can actually type something like this:
int main()
{
const int first = 27,
second = first,
third = second,
fourth = third;
if (!((first & second & third) ^ fourth))
return 1;
return 0;
}
来源：https://stackoverflow.com/questions/4378131/in-c-does-x-y-z-behave-as-id-expect