How do I retrieve the names of function parameters in matlab?

Question

Aside from parsing the function file, is there a way to get the names of the input and output arguments to a function in matlab?

For example, given the following fun

Answer 1

MATLAB offers a way to get information about class metadata (using the meta package), however this is only available for OOP classes not regular functions.

One trick is to write a class definition on the fly, which contain the source of the function you would like to process, and let MATLAB deal with the parsing of the source code (which can be tricky as you'd imagine: function definition line spans multiple lines, comments before the actual definition, etc...)

So the temporary file created in your case would look like:

classdef SomeTempClassName
    methods
        function [value, remain] = divide(left, right)
            %# ...
        end
    end
end

which can be then passed to meta.class.fromName to parse for metadata...

---

Here is a quick-and-dirty implementation of this hack:

function [inputNames,outputNames] = getArgNames(functionFile)
    %# get some random file name
    fname = tempname;
    [~,fname] = fileparts(fname);

    %# read input function content as string
    str = fileread(which(functionFile));

    %# build a class containing that function source, and write it to file
    fid = fopen([fname '.m'], 'w');
    fprintf(fid, 'classdef %s; methods;\n %s\n end; end', fname, str);
    fclose(fid);

    %# terminating function definition with an end statement is not
    %# always required, but now becomes required with classdef
    missingEndErrMsg = 'An END might be missing, possibly matching CLASSDEF.';
    c = checkcode([fname '.m']);     %# run mlint code analyzer on file
    if ismember(missingEndErrMsg,{c.message})
        % append "end" keyword to class file
        str = fileread([fname '.m']);
        fid = fopen([fname '.m'], 'w');
        fprintf(fid, '%s \n end', str);
        fclose(fid);
    end

    %# refresh path to force MATLAB to detect new class
    rehash

    %# introspection (deal with cases of nested/sub-function)
    m = meta.class.fromName(fname);
    idx = find(ismember({m.MethodList.Name},functionFile));
    inputNames = m.MethodList(idx).InputNames;
    outputNames = m.MethodList(idx).OutputNames;

    %# delete temp file when done
    delete([fname '.m'])
end

and simply run as:

>> [in,out] = getArgNames('divide')
in = 
    'left'
    'right'
out = 
    'value'
    'remain'