about easy logic operators

A=[2 4 10 9 24;3 5 56 -1 7];
for i = 1: 5
     if A(1,i) && A(2,i) < 0  % if 9 && -1 < 0 
     fprintf('Invalid dimension.The area cannot be computed.\n')
    else
       fprintf('The area of rectangle %d is %d.\n',i,(A(1,i)*A(2,i)));
    end
end

if A(1,i) && A(2,i) < 0 % if 9 && -1 < 0 i think the left one and the right one is the same but the outputs they give are different . Why are they different? Thanks.

Answer 1

[David Hill]

Need <0 for both conditions

A=[2 4 10 9 24;3 5 56 -1 7];
for i = 1: 5
     if A(1,i)<0 && A(2,i)< 0  % if 9 && -1 < 0 
     fprintf('Invalid dimension.The area cannot be computed.\n')
    else
       fprintf('The area of rectangle %d is %d.\n',i,(A(1,i)*A(2,i)));
    end
end

[Umut Oskay]

A=[2 4 10 9 24;3 5 56 -1 7];
for i = 1: 5
     if (A(1,i)< 0) || (A(2,i)< 0)  
     fprintf('Invalid dimension.The area cannot be computed.\n')
    else
       fprintf('The area of rectangle %d is %d.\n',i,(A(1,i)*A(2,i)));
    end
end

% i got the point and i should write like this thank you but i want to know why  [A(1,i) && A(2,i) < 0  %  9 && -1 < 0] are different?

[David Hill]

Matlab syntax for logicals. Any number other than zero is a logical true value.

9 && -1<0; %true && true = true
A(1,1) && A(2,1)<0;%true && false = false