Why ~(true^true) is not true? Boolean operators (negation) works for `unsigned char`s, but not for bools? (C++)

boolean, boolean-expression, boolean-operations, c++

Solution

I heard that often "everything" besides 0 is true

It is valid for conditions as for example in the if statement (here and below I am citing the C++Standard)

The value of a condition that is an expression is the value of the expression, contextually converted to bool for statements other than switch

For example if you would write as

if (~(true^true) )
    cout << "true";
else
    cout << "false";

instead of your code snippet

if (~(true^true) == true)
    cout << "true";
else
    cout << "false";

or when the logical negation operator `!` is used

9 The operand of the logical negation operator ! is contextually converted to bool (Clause 4); its value is true if the converted operand is false and false otherwise. The type of the result is bool

As for operator `==` then

6 If both operands are of arithmetic or enumeration type, the usual arithmetic conversions are performed on both operands; each of the operators shall yield true if the specified relationship is true and false if it is false.

That is in case of

if (~(true^true) == true)

the usual arithmetic conversion is applied that is boolean value true is converted to integer value 1 and it is not equal to the expression of the left operanf because internal binary representation of the left operand differs from 1 as showed the output of your first code snippet..

Problem

I heard that often "everything" besides 0 is true. But now very strange things are happening to me... or I just think that I do it in correct way while I don't. Here's what is happening: When I want to check if a is equivalent b, I can use `NOT(a XOR b)`. When I checked it for `unsigned char`'s, everything was ok, for example ``` unsigned char a = 5; unsigned char b = 3; unsigned char c = ~(a^b); ``` gave me `c == 249`: a is: `00000101`, which is 5. b is: `00000011`, which is 3. ~(a^b) is: `11111001`, which is 249. Now, let's try this with `bool`'s. ``` cout << ~(true^true) << ~(true^false) << ~(false^true) << ~(false^false) << endl; cout << ~(~(true^true)) << ~(~(true^false)) << ~(~(false^true)) << ~(~(false^false)) << endl; if (~(true^true) == true) cout << "true"; else cout << "false"; ``` This gives me in console: ``` -1-2-2-1 0110 false ``` while I expected the first line to be: ``` 1001 ``` After asking a friend, he advised me to try `!` instead of `~` and see if it will work correctly. And (I think) it works correctly now. But I don't understand why. Shouldn't boolean negation work for bools?

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