Why is this code not working whilst the other is?

Question

Michael Vaughan 2020-9-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/599173-why-is-this-code-not-working-whilst-the-other-is

评论： Steven Lord 2020-9-24

采纳的回答： Ameer Hamza

I have written this script:

function sum = Sum2(x,y,z)

s = 0;

for i=0:min(x,y)

for k=0:y-i

s = s + (-1)^k * QuantumDimension(2*x+k-2*i, 2*y-2*k-2*i) * Twist(2*x+k-2*i, 2*y-2*k-2*i)^(z/2);

end

s

When I type Sum2(5,3,2) it gives me an appropriate output

but then I have the script

function sum = Sum3(x,y,z)

s = 0;

for i=0:min(x,y)

s = s + (-1)^k * QuantumDimension(2*x-2*i, 2*y-2*i) * Twist(2*x-2*i,2*y-2*i)^(z/2);

end

s

And when I type Sum3(5,2,1) I get:

Error: File: Sum3.m Line: 8 Column: 1

This statement is not inside any function.

(It follows the END that terminates the definition of the function "Sum3".)

What the heck?!?!? The placement of s in the script is completly similar to the function Sum2... What is going on here!! Thanks

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Answer 1

Ameer Hamza 2020-9-24

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https://ww2.mathworks.cn/matlabcentral/answers/599173-why-is-this-code-not-working-whilst-the-other-is#answer_499792

编辑：Ameer Hamza 2020-9-24

在 MATLAB Online 中打开

You have written an 's' after end of the function. Nothing should come after the end keyword

function sum = Sum3(x,y,z)
s = 0;
    for i=0:min(x,y)
        s = s + (-1)^k * QuantumDimension(2*x-2*i, 2*y-2*i) * Twist(2*x-2*i,2*y-2*i)^(z/2);
    end
end
s % remove this

Also note that 'k' is not defined.

In the case of Sum2, you don't have an end keyword corresponding to the function. Remember the end keyword is optional. The two end keyword you have are related to for loops.

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Steven Lord 2020-9-24

More to the point, it looks like Sum3 is a copy of Sum2 but with (almost) all references to k edited away. If that's the case Michael Vaughan erased the for k = ... line from the copy but forgot to erase the corresponding end statement (rather than typing s after the second end.)

If you make this copy by copying and pasting in the MATLAB Editor you'll receive one red Code Analyzer error and two orange Code Analyzer warnings in the copy. The second of those warnings states that for is not aligned with its corresponding end, which may lead the developer to take a closer look at their end statements.

The first Code Analyzer warning is due to the fact that these functions are defined to return a variable named sum (which should not be used as a variable name as it already has a meaning in MATLAB) but the functions never define that variable.

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