Question

I am learning C++. I come from a background of: .NET and VB6.

I am intrigued about what the following webpage says about booleans: http://msdn.microsoft.com/en-us/library/ff381404(v=vs.85).aspx i.e.

“Despite this definition of TRUE, however, most functions that return a BOOL type can return any non-zero value to indicate Boolean truth. Therefore, you should always write this:

// Right way.
BOOL result = SomeFunctionThatReturnsBoolean();
if (result) 
{ 
    ...
}

“

Does this apply to VB6 as well i.e. is there a problem saying: If BooleanValue = True Then?

Answer 1

The Windows API was designed to be used from C programs. Which until C99 didn’t have a bool type. And still doesn’t completely, C99 was never implemented by the Microsoft compiler for example. So they had to come up with a workaround, one that’s highly compatible with the way C compilers deal with logical values. An int where 0 is false and anything else is true. Thus the advice.

VB6 has a dedicated Boolean type and keywords for the literal values True and False so doesn’t quite have the same problem. You can however still get into trouble with poorly written COM servers. The underlying integral value for True is -1, highly incompatible with many other languages’ implementation of a logical boolean type. Including C. There’s a good reason for VB6 being the oddball, its And and Or operators don’t distinguish between a logical and a arithmetic and/or. By making True equal to -1 and False equal to 0 there is no difference. Trouble can arise when a COM server returns a 1 to indicate true instead of VARIANT_TRUE.

But most of all, writing If booleanVariable = True Then is just ugly and nails on the blackboard for many programmers. Just write If booleanVariable Then and be done with it.