Hello, why Matlab does not check for second condition and give an answer without checking second condition after AND short circuit operator?

Hello everyone!

Kindly ask help in if statement. If I want to write..

if plane00 ==plane1 OR plane00==plane3 AND plane01==plane1 OR plane01==plane3, then print ('Planes are parallel1')

when I test the code below it only check for one condition isequal(plane00, plane1) || isequal(plane00, plane3)) and then supposed is true if it is true, but did not check second condition after && operator

(isequal(plane01,plane1))||isequal(plane01,plane3)

Thnak you in advance for your time and consideration. Apreciate any help

if (isequal(plane00, plane1) || isequal(plane00, plane3)) && ((isequal(plane01,plane1))||isequal(plane01,plane3))
    
    fprintf('Planes are parallel1:');
    ThetaBar = -(Theta0);
    PhiBar =  -(Phi0);
    fprintf('ThetaBar: %f\n',ThetaBar);
    fprintf('PhiBar: %f\n',PhiBar);
    % I also tried to do smth like this
    %(plane01 == 1 || 3 && plane00 == 1 || 3)

[Walter Roberson]

Despite your "supposed is true", (isequal(plane00, plane1) || isequal(plane00, plane3)) is probably false.

For debugging, break it into two pieces:

part1 = isequal(plane00, plane1) || isequal(plane00, plane3);
disp(part1)
if part1 && ((isequal(plane01,plane1))||isequal(plane01,plane3))

Answer 1

[Askic V]

Hi Aknur,

in the example below, the part after && is evaluated.

BTW, operators || and && are so called short-circuit operators.

https://www.mathworks.com/help/matlab/ref/shortcircuitand.html

plane00 = 1;
plane1 = 1;
plane01 = 3;
plane3 = 3;
if (isequal(plane00, plane1) || isequal(plane00, plane3)) &&...
        (isequal(plane01,plane1) || isequal(plane01, plane3))
    
    fprintf('True');
    
end

True

[Aknur]

Hi, Dear @Askic V thank you for your answer and clarification.

Yes it works perfect. I change my code and it works as a separate script. But it does not work especially for my code inside of function. Plane00 and plane01 are variables. In some case it give me True answer but in some False( but shoud be true)

Appreciate any advice what can be wrong with my statement or shoudl I try to do it using normal

plane00 = 4

plane01 = 3

parallel_planes =

1 3

2 4

5 6

plane1 = parallel_planes(1,1)

plane2 = parallel_planes(1,2)

plane3 = parallel_planes(2,1)

plane4 = parallel_planes(2,2)

plane5 = parallel_planes(3,1)

plane6 = parallel_planes(3,2)

if (isequal(plane01,plane1)||isequal(plane01,plane3)) && (isequal(plane00, plane1) || isequal(plane00, plane3))

fprintf('Planes are parallel5:');

ThetaBar = -(Theta0);

PhiBar = -(Phi0);

fprintf('ThetaBar: %f\n',ThetaBar);

fprintf('PhiBar: %f\n',PhiBar);

elseif (isequal(plane00,plane2)||isequal(plane00,plane4)) && (isequal(plane01, plane2) || isequal(plane01, plane4))

fprintf('Planes are parallel2:');

ThetaBar = -(Theta0);

PhiBar = -(Phi0);

fprintf('ThetaBar: %f\n',ThetaBar);

fprintf('PhiBar: %f\n',PhiBar);

elseif (isequal(plane00,plane5)||isequal(plane00,plane6)) && (isequal(plane01, plane5) || isequal(plane01, plane6))

fprintf('Planes are parallel3:');

ThetaBar = -(Theta0);

PhiBar = -(Phi0);

fprintf('ThetaBar: %f\n',ThetaBar);

fprintf('PhiBar: %f\n',PhiBar);

else

ThetaBar = -(Theta0);

PhiBar = (180 - Phi0);

fprintf('Planes are not parallel:');

fprintf('ThetaBar: %f\n',ThetaBar);

fprintf('PhiBar: %f\n',PhiBar);

end

Thank you in advance

[Stephen23]

This is your code run here on the forum. So far it seems that && and || are working as expected.

plane00 = 4;
plane01 = 3;
parallel_planes = [1,3;2,4;5,6];    
plane1 = parallel_planes(1,1)

plane1 = 1

plane2 = parallel_planes(1,2)

plane2 = 3

plane3 = parallel_planes(2,1)

plane3 = 2

plane4 = parallel_planes(2,2)

plane4 = 4

plane5 = parallel_planes(3,1)

plane5 = 5

plane6 = parallel_planes(3,2)

plane6 = 6

if (isequal(plane01,plane1)||isequal(plane01,plane3)) && (isequal(plane00, plane1) || isequal(plane00, plane3))
    fprintf('Planes are parallel5:');
    % ThetaBar = -(Theta0);
    % PhiBar =  -(Phi0);
    % fprintf('ThetaBar: %f\n',ThetaBar);
    % fprintf('PhiBar: %f\n',PhiBar);
elseif (isequal(plane00,plane2)||isequal(plane00,plane4)) && (isequal(plane01, plane2) || isequal(plane01, plane4))
    fprintf('Planes are parallel2:');
    % ThetaBar = -(Theta0);
    % PhiBar = -(Phi0);
    % fprintf('ThetaBar: %f\n',ThetaBar);
    % fprintf('PhiBar: %f\n',PhiBar);
elseif (isequal(plane00,plane5)||isequal(plane00,plane6)) && (isequal(plane01, plane5) || isequal(plane01, plane6))
    fprintf('Planes are parallel3:');
    % ThetaBar = -(Theta0);
    % PhiBar =  -(Phi0);
    % fprintf('ThetaBar: %f\n',ThetaBar);
    % fprintf('PhiBar: %f\n',PhiBar); 
else
    % ThetaBar = -(Theta0);
    % PhiBar = (180 - Phi0);
    fprintf('Planes are not parallel:');
    % fprintf('ThetaBar: %f\n',ThetaBar);
    % fprintf('PhiBar: %f\n',PhiBar);
end

Planes are parallel2: