hi i want to ask,why matlab cannot process the condition for the while loop ? Thank you!

Question

NUR AIN ATIKAH ABDUL LATIF 2022-1-10

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1626055-hi-i-want-to-ask-why-matlab-cannot-process-the-condition-for-the-while-loop-thank-you

评论： NUR AIN ATIKAH ABDUL LATIF 2022-1-11

clc
clear
close all
%Input data
w=input('Enter the load,w: ');
L=input('Enter the beam length: ');
x=input('Enter specific point: ');
%While loop if false
while (w<1||L<1||x<0||isempty(w)||isempty(L)||isempty(x))
    fprintf("\nPlease recheck input data\n")
    w=input('Enter the load,w: ');
    L=input('Enter the beam length: ');
    x=input('Enter specific point: '); 
    
end
%true input data          
Ra=w*L;
Ma=-w*L.^2/2;
Mx=-w*(L-x).^2/2;
Sx=w*(L-x);
fprintf("\nThe reaction at A is %.2f\n",Ra)
fprintf("The moment at A is %.2f\n",Ma)
fprintf("The bending moment at point %.f is %.2f\n",x,Mx)
fprintf("The shear force at point %.f is %.2f\n",x,Sx)

2 个评论
显示无隐藏无

Image Analyst 2022-1-10

Works fine for me. What are your initial inputs before the loop and then what are you entering in the loop?

NUR AIN ATIKAH ABDUL LATIF 2022-1-11

i want to make the process re-input the data if user key-in wrong input like negative value and no input from user

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Steven Lord 2022-1-10

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1626055-hi-i-want-to-ask-why-matlab-cannot-process-the-condition-for-the-while-loop-thank-you#answer_871920

在 MATLAB Online 中打开

Since you're using the short-circuiting or operator you should check the size of the inputs first. Rather than asking if they're empty, ask if they're not a scalar.

%{
while ~isscalar(w) || ~isscalar(L) || ~isscalar(x) || w < 1 || L < 1 || x < 0
%}

That way if (for example) w was not a scalar the ~isscalar(w) check would make the while condition return false before it gets to the w < 1 part (and throws an error.)

w = 0:5;
~isscalar(w) || w < 1 % false, MATLAB doesn't get to the w < 1 check
ans = logical
   1
w < 1 || ~isscalar(w) % error, w < 1 is logical but not scalar
Operands to the logical and (&&) and or (||) operators must be convertible to logical scalar values.