the @ symbol within handles

Question

William 2011-9-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/15782-the-symbol-within-handles

采纳的回答： Walter Roberson

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hello,

I cannot seem to figure out what the "@" means in handles

Here is the example code

set(handles.axisGroup, 'SelectionChangeFcn', @axisGroup_SelectionChangeFcn);

is that a pass by reference notation as in C++?

Thanks

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Answer 1

Walter Roberson 2011-9-13

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https://ww2.mathworks.cn/matlabcentral/answers/15782-the-symbol-within-handles#answer_21387

No, it is not a pass-by-reference notation. It creates a function pointer object, with the function pointer object then being passed by value. The function pointer object may contain a lot more information than just a reference to the code: it may contain a complete p-coded version of the code and it may contain references to local variables.

Technically speaking, the @ notation creates a "closure" -- though it will be a near trivial closure if it is not being used as an anonymous function or if the routine being referenced does not have an 'end' statement matching the 'function' statement (which is interpreted as a signal to create a complete closure rather than to use the older style plain "reference to a routine")

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David Young 2011-9-13

I had no idea that including the final 'end' in a single-function m-file had any effect on the compiler. I'm delighted to learn that my obsessive inclusion of it in all my new functions and any old functions that I revisit has a purpose!

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