how to pass keyword arguments to a function via a struct
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Stephen Vavasis
on 16 Jan 2023
Moved: Walter Roberson
on 16 Jan 2023
In recent versions of Matlab, functions can declare optional arguments with default values that get automatically packed into a struct e.g.,
function examplefn(x)
arguments
x.a (1,1) double = 12
x.b (1,1) double = 7
end
With such a declaration, the function is called via examplefn('a', 8, 'b', 9) (or just examplefn('a',8)), and the examplefn function body can now use x.a and x.b as variables. Suppose I have written such a function, and its caller (rather than the function) has the arguments in a struct:
y = struct('a', 8, ,'b', 9);
What is the way to pass y as an input argument to examplefn? I'd like to be able to say something like: examplefn(unpack(y)). Obviously, I could spell it out: examplefn('a', y.a, 'b', y.b) but expanding in this way partly defeats the purpose of having optional and keyword arguments in the first place and makes it fragile to chain a sequence of functions that share keyword/optional arguments. Thanks.
2 Comments
dpb
on 16 Jan 2023
At this time there is no syntax to do anything other than pass the name-value parameter pairs explicitly.
I didn't 'spearmint; you might be able to write an anonymous function that would do the unwrapping to the string to pass, but then you would have to revert to eval to execute the result; MATLAB wouldn't know what to do with the string as an argument list.
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