Function to create struct with parameters

Currently I have a function with settings/parameters for my program, where all parameters are written into a struct like "inp.month = 7;" so that I can pass the struct "inp" to functions afterwards. Is it possible to have all the assignments in the function without the struct, eg "month = 7;" and at the end somehow get 'all variables in this function' into the struct "inp". Something like "inp = <gather all variables assigned in this function>", and then have the struct be the output. It would add readability in my opinion and also I thought this to be easy, but didn't find a good solution yet and thought I'd ask here.

Cheers

Felix

[Matt J]

A better alternative is to automate the coding of the assignments with this:

https://www.mathworks.com/matlabcentral/fileexchange/26216-structure-fields-to-variables

[Felix Müller]

Thanks! That is a good solution for when there are loads of variables. But also it only generates the code and does not automate the assignment itself. Also I already have it coded and just wanted to make it more concise.

[Stephen23]

"I thought this to be easy"

Nope. While there are a few approaches to achieve this, they will all add complexity and make your code slower.

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

[Bruno Luong]

This request is interesting only for lazy programmers who wants to make a quick and dirty code.

Just create a struct with the list of variables that you control explicitly.

[Felix Müller]

Well, that might not be so obvious before thinking about it, eh?

Answer 1

[Jeff Miller]

Maybe you would like something like this?

month = 1;
year = 1951;
day = 11;
inp = CreateStruct(month,day,year)

function outstruc = CreateStruct(varargin)
    % Create a structure with the input variables as fields.
    outstruc = struct;
    for iField=1:numel(varargin)
        sfName = inputname(iField);
        outstruc.(sfName) = varargin{iField};
    end
end

[Felix Müller]

Thanks, that does look interesting. Do you think there are any drawbacks or weird errors that could pop up while using this?

[Stephen23]

"Do you think there are any drawbacks...?"

Slower code: "Avoid functions that query the state of MATLAB such as inputname, which, whos, exist(var), and dbstack. Run-time introspection is computationally expensive."

source: https://www.mathworks.com/help/matlab/matlab_prog/techniques-for-improving-performance.html

Answer 2

[Walter Roberson]

The following code is not recommended.. but it should work.

ZZ_filename = [tempname '.mat'];
save(ZZ_filename, '-struct', '-regexp', '^[^Z]', '^Z[^Z]');
inp = load(ZZ_filename);
delete(ZZ_filename);

If you already have variable names that begin with 'ZZ' then this code would have to be modified.

The purpose of the -regexp is to allow saving all of the variables except the over-head variable ZZ_filename .

[Felix Müller]

True, good point, that would work. I'd very much like to avoid saving the workspace to a file and reopening it.

[Walter Roberson]

Then you will need to write code that uses dynamic variable naming, which is not at all recommended.

http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Hint: who() returns names of variables.

[Felix Müller]

Okay, thanks! I thought it might work without fiddling with the assignment of variables myself (eg with a function written exactly for this), but it might not.

Answer 3

[Bruno Luong]

s = buildparams()

s = struct with fields:
    a: 1
    b: 2

function s = buildparams()
a = 1;
b = 2;
s = gathervars();
end

function s = gathervars()
vars = evalin('caller', 'whos');
for k=1:length(vars)
    name = vars(k).name;
    s.(name) =  evalin('caller', name);
end
end