Logical equality in C

Question

[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 tw

Answer 1

There is no (bool) in traditional c. True/False is handled using ints. You can check for boolean equality with

a ? b : !b

Answer 2

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!

Answer 3

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

Answer 4

In pre-C99 C, the tradiitional, idiomatic way to "cast to bool" is with !!.