Matlab Grader - Determining if a variable is a function handle.

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Justin Wyss-Gallifent 2020-6-15

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编辑： Cris LaPierre 2020-6-15

I'm writing a Matlab Grader assignment in which I'd like the students to define a function, say f, as a function handle. I'd then like an assessment test which verifies this. I figured an assessment test in Matlab code which simply said:

isa(f,'function_handle')

would do the job but this registers as true (in Matlab Grader) even when f is not a function handle.

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Adam Danz 2020-6-15

编辑：Adam Danz 2020-6-15

Hmmmm..... that's fishy. So, the assert(isa(f,'function_handle')) line does throw an error when f is f=5? Why would the isa() function work when it's inside of assert() but not outside of assert()? Unfortunately I haven't used the grader and can't fiddle with it right now.

Justin Wyss-Gallifent 2020-6-15

Weird, huh? I have no idea why it would behave this way. I'll nudge tech support. Thanks.

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采纳的回答

Cris LaPierre 2020-6-15

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https://ww2.mathworks.cn/matlabcentral/answers/548631-matlab-grader-determining-if-a-variable-is-a-function-handle#answer_451644

编辑：Cris LaPierre 2020-6-15

Assessment tests must assert the result. They do not recognize logical results as answers to the test. So the issue is not that false is being marked as correct. The isa(f,'function_handle') is returning false. It is that no assert has told Grader the result is incorrect.

Put another way, assessment tests are correct unless the code returns an error. Assert throws an error if the condition is false. So does the built-in assessVariableEqual function.