How do i write a C plus plus program to output to determine the truth of a statement in a single statement?

Answer 1

You cannot determine the truth of a statement, you can only determine the truth of an expression. However, a statement is merely an expression followed by a semi-colon, so it amounts to the same thing.

Only a Boolean expression can evaluate true or false. Numeric expressions implicitly convert to Boolean; they evaluate true when the result is non-zero. However, any class of object that overloads operator bool() implicitly converts to Boolean. E.g., containers are true when they contain one or more objects while streams are true when their state is good.

The following statement will determine the truth about any Boolean expression:

std::cout << "The expression is " << (expression ? "true" : "false") << "\n";

Example:

int a=0;

int b=42;

std::cout << "The expression " << a << "==" << b << " is " << ((a==b) ? "true" : "false") << "\n";

// false

int c = 0;

double d = 0.0;

std::cout << "The expression " << c << "==" << d << " is " << ((c==d) ? "true" : "false") << "\n";

// true

std::string s {}; // an empty string

std::cout << "The expression "" << s << "" is " << (s ? "true" : "false") << "\n";

// false