a demo of closure with Matlab (R2023b)

counter.m

% https://www.mathworks.com/matlabcentral/answers/439671-why-i-cannot-define-a-function-in-live-script
[inc, get] = createCounter();
inc();
inc();

disp(get());

% https://www.mathworks.com/help/matlab/function-handles.html
obj = createCounterMap();
disp(obj);
inc = obj("inc");
get = obj("get");
inc();
inc();

disp(feval(obj("get")));
functions(obj("get"))
functions(@(x) x+1)

obj = createCounterStruct()
obj.inc();
obj.inc(123);
disp(obj.get());
% https://www.mathworks.com/help/matlab/matlab_prog/fundamental-matlab-classes.html

function [inc, getter] = createCounter()
    count = 0;
    function increment()
        count = count + 1;
    end
    function c = get_count()
        c=count;
    end
    inc = @increment;
    getter = @get_count;
end

% https://www.mathworks.com/help/matlab/ref/dictionary.html
function m = createCounterMap()
    count = 0;
    function increment()
        count = count + 1;
    end
    function c = get_count()
        c=count;
    end
    m = dictionary("inc", @increment, "get", @get_count);
end

% https://www.mathworks.com/help/matlab/ref/struct.html
% https://www.mathworks.com/help/matlab/ref/arguments.html
% https://www.mathworks.com/help/matlab/matlab_prog/customize-code-suggestions-and-completions.html
% https://www.mathworks.com/help/matlab/input-and-output-arguments.html
function s = createCounterStruct()
    count = 0;
    function increment(varargin)
        % Argument blocks are not supported in nested functions, 
        % abstract methods, or handle class destructor methods.
        % https://www.mathworks.com/help/matlab/matlab_prog/parse-function-inputs.html
        p = inputParser;
        % mustBeFinite
        % isnumeric
        addOptional(p, "val", 1, @isfinite);
        parse(p, varargin{:});
        count = count + p.Results.val;
    end
    function c = get_count()
        c=count;
    end
    s = struct("inc", @increment, "get", @get_count);
end