Implementing Tribool with int8_t

For digital electronic circuit simulation, i wanted to implement Three states. i.e High, Low and Undefined in C++.

I saw Boost::tribool, and they implement it using enum

Now for conserving some memory i have implemented it using 1 Byte Int

#ifdef _WINDOWS
typedef __int8 State;
#elif
typedef int8_t State;
#endif

const State kLow = 0;
const State kHigh = 1;
const State kUndefined = 2;

• Do you see any potential problem with it?

• And why would one waste 4 bytes instead of a single byte for 3 values only

• Do you have a still better way?

The main reason there is no accidental conversion (type safety is one of the keys to using C++ correctly).

enum Tri { Yes, No, Maybe };

int main()
{
    Tri     y   = Yes;
    y= 1;   // Fails to compile.
}

Secondly you are using three bytes to hold the different states here

const State kLow = 0;
const State kHigh = 1;
const State kUndefined = 2;

With an enum there is no space taken up (though potentially the above may be optimized out).

C++11 also allows you to specify the size of an enum:

enum class Tri : char { Yes, No, Maybe };
//               ^^^^  Uses a char sized object

Do you see any potential problem with it?

Yes. Not type safe


And why would one waste 4 bytes instead of a single byte for 3 values only

Why not. Does it really matter in any modern PC.

OK for embedded systems maybe (but you obviously are using WINDOWS)


Do you have a still better way?

Yes. Use enum in C++11

StackExchange Code Review Q#7262, answer score: 5