How can I do dynamic calculation?
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How can I update the following variable?
a = 1; b = a + 2;
then I changed a = 2, but b is still 3.
How can I change or update b without executing b = a + 2?
If Matlab supports pointer in C, I guess the above problem is solved easily.
1 个评论
John D'Errico
2017-6-13
But you are using MATLAB, not C. No pointers available.
回答（2 个）
Even in C, I think a re-calculation would have to occur somewhere in the code to get a revised value. However, the kind of auto-updating I believe you're looking for is something a dependent class property can do:
classdef myclass
properties
a
end
properties (Dependent)
b
end
methods
function val=get.b(obj)
val=obj.a+2;
end
end
end
Now you can do things like this,
>> obj=myclass;
>> obj.a=1; obj.b
ans =
3
>> obj.a=3; obj.b
ans =
5
Walter Roberson
2017-6-13
syms a
b = a + 2
a = 1
subs(b)
a = 2
subs(b)
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2017-6-13
2017-6-13
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