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

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Aknur 2023-4-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1944404-hello-why-matlab-does-not-check-for-second-condition-and-give-an-answer-without-checking-second-con

评论： Walter Roberson 2023-4-11

采纳的回答： Askic V

在 MATLAB Online 中打开

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)

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Walter Roberson 2023-4-11

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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))

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Answer 1

Askic V 2023-4-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1944404-hello-why-matlab-does-not-check-for-second-condition-and-give-an-answer-without-checking-second-con#answer_1212759

在 MATLAB Online 中打开

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

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Aknur 2023-4-11

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 2023-4-11

在 MATLAB Online 中打开

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:

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

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

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