returning multiple boolean functions

[E3h7X9L8]

Can someone explain me this piece of code , the function isSafe is supposed to check the other three functions if they are false or true , if one is false isSafe must return false, I dont really understand whats happening if 2 functions are true and false and whats the purpose of "!" operator.

bool isSafe()
{
    return !checkRow() &&
           !checkCol() &&
           !checkBox();          
}

[MiiNiPaa]

whats the purpose of "!" operator.

It's logical not, your code is absolutely equivalent to this one:

bool isSafe()
{
    return not checkRow() &&
           not checkCol() &&
           not checkBox();          
}

I dont really understand whats happening if 2 functions are true and false

Maybe you need to learn more about logic operators?
http://www.learncpp.com/cpp-tutorial/36-logical-operators/

[Bdanielz]

your code...

bool isSafe()
{
    return !checkRow() && !checkCol() && !checkBox();          
}

The truth table for your function is

a | b | c | ¬a&&¬b&&¬c
T | T | T | F
T | T | F | F
T | F | T | F
T | F | F | F
F | T | T | F
F | T | F | F
F | F | T | F
F | F | F | T

and the above table should show how your function evaluates on each condtion being true or false.

in English...

bool isSafe()
{
    return not (checkrow) and not (checkcol) and not (checkbox)

[E3h7X9L8]

thanks for help guys , i understand now