This is giving me a headache...can someone please tell me why these statements ARE NOT equivalent?
Statement 1.)
if(running_result && shell[8 * (x - 1) + (y - 1)].input_val)
running_result = true;
else
running_result = false;
Statement 2.)
running_result &= shell[8 * (x - 1) + (y - 1)].input_val;
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The first statement works; the second does NOT. The second always evaluates to false. Why? Both of these vars are bools.
This is giving me a headache...can someone please tell me why these statements ARE NOT equivalent?
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The first statement works; the second does NOT. The second always evaluates to false. Why? Both of these vars are bools.
Maybe the problem is elsewhere.
#include <iostream>
int main()
{
bool a, b;
//Statement 1.)
a = false; b = false; std::cout << "a = " << a << ", b = " << b;
if ( a && b )
a = true;
else
a = false;
std::cout << ": a = " << a << std::endl;
a = false; b = true; std::cout << "a = " << a << ", b = " << b;
if ( a && b )
a = true;
else
a = false;
std::cout << ": a = " << a << std::endl;
a = true; b = false; std::cout << "a = " << a << ", b = " << b;
if ( a && b )
a = true;
else
a = false;
std::cout << ": a = " << a << std::endl;
a = true; b = true; std::cout << "a = " << a << ", b = " << b;
if ( a && b )
a = true;
else
a = false;
std::cout << ": a = " << a << std::endl;
std::cout << std::endl;
//Statement 2.)
a = false; b = false; std::cout << "a = " << a << ", b = " << b;
a &= b;
std::cout << ": a = " << a << std::endl;
a = false; b = true; std::cout << "a = " << a << ", b = " << b;
a &= b;
std::cout << ": a = " << a << std::endl;
a = true; b = false; std::cout << "a = " << a << ", b = " << b;
a &= b;
std::cout << ": a = " << a << std::endl;
a = true; b = true; std::cout << "a = " << a << ", b = " << b;
a &= b;
std::cout << ": a = " << a << std::endl;
std::cout << std::endl;
return 0;
}
/* my output
a = 0, b = 0: a = 0
a = 0, b = 1: a = 0
a = 1, b = 0: a = 0
a = 1, b = 1: a = 1
a = 0, b = 0: a = 0
a = 0, b = 1: a = 0
a = 1, b = 0: a = 0
a = 1, b = 1: a = 1
*/the first statements uses logical and (&&) the second uses bitwise and (&), so you might try using '&&=' in the second statement.
The difference might be subtle; say the input_val was '2'. In the first statement the running result would be true and in the second statement it would be 0 because TRUE (1) & 2 == 0, but (1 && 2) is true.
the first statements uses logical and (&&) the second uses bitwise and (&), so you might try using '&&=' in the second statement.
There is no such critter: '&&='.
Hee hee - well there SHOULD be! In any case, & and && are not the same.
In any case, & and && are not the same.
But for bools, the results should be the same, shoudn't they?
Why? Both of these vars are bools.
I am so excited because I finished my program.
Chainsaw is right, any nonzero value is true in a bool, so a bitwise AND wouldn't necessarily evaluate to true... and I shouldn't have tried using a bitwise op for boolean algebra.
(Incidentally I settled on):
running_result = running_result && shell[8 * (x - 1) + (y - 1)].input_val;
Not too stylish, but it served its purpose.
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