Bool Functions

Functions can return bool values just like any other type, which is often convenient for hiding complicated tests inside functions. For example:

bool IsSingleDigit ( int iX )

{

if ( iX >= 0 && iX < 10)

{

return true;

}

else

{

return false;

}

}

The name of this function is IsSingleDigit. It is common to give boolean functions names that sound like yes/no questions. The return type is bool, which means that every return statement has to provide a bool expression.

The code itself is straightforward, although it is a bit longer than it needs to be. Remember that the expression x >= 0 && x < 10 has type bool, so there is nothing wrong with returning it directly and avoiding the if statement altogether:

bool IsSingleDigit ( int iX )

{

return ( iX >= 0 && iX < 10);

}

Y ou can call this function in the usual ways:

void Scene1 ()

{

…

ShowText ( IsSingleDigit ( 2 ) );

bool bBigFlag = ! IsSingleDigit ( 17 );

…

}

The first line outputs the value true because 2 is a single-digit number. The second line assigns the value true to bBigFlag because 17 is not a single-digit number.

The most common use of bool functions is inside conditional statements:

if ( IsSingleDigit ( iX ) )

{

ShowText ( "iX is little" );

}

else

{

ShowText ( "iX is big" );

}