MATLAB: How to change all variable names in a Matlab function

replace variable namessearch and replacevariables

I would like to have a method for duplicating a function and at the same time rename all variables in the file so that they have a specific prefix, for example:

function c = main(m)
a = m*2
b = m*3
c = a+b+m;

should be duplicated and the prefix 'main_' should be added. The new function becomes:

function main_c = main(main_m)
main_a = main_m*2
main_b = main_m*3
main_c = main_a+main_b+main_m;

It can be done in the Matlab editor ( see here ) but I would like to do it via code.

Thanks for any inputs 🙂

Best Answer

You need a powerful parser, which can distinguish names of variables from (shadowed) functions, strings and longer names, which contains the string as a part only.

Most likely somebody has written such a thing already and published it in the FEX. What about < http://www.mathworks.com/matlabcentral/fileexchange/15924-farg--a-pedestrian-m-file-parser-showing-all-used-functions--syntax> It should contain all you need. But the modification of the code to replace the strings is not trivial.

I guess that solving the problem in the editor is much faster than creating a powerful parser as a program. Using an automatic tool is only useful, if the codes are large and complicated. And especially in this case, finding potential bugs of the parsing+replacing procedure is very hard. I expect, that the required time for validating and debugging will exceed the advantage in runtime massively.

The efficiency of a program is determined by the time required to solve the problem, not by the runtime only.

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MATLAB: List Built in Commands used by .m function

One possible way, use the undocumented mtree function to get the parse tree of the code, identify the function calls in that tree (the hard bit!), then use exist to identify the built in ones

For example (works on R2014b):

parsetree = mtree('array2table.m', '-file');
treeids = parsetree.mtfind('Kind', 'ID');
idstrings = unique(treeids.strings);
isbuiltin = cellfun(@(id) exist(id, 'builtin') == 5, idstrings);
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builtinid = idstrings(isbuiltin)

MATLAB: Dynamic comments on variables

This sounds like a magic meta programming. I recommend to avoid such smart tricks and keep comments in the source code as usual. Bot of course it is possible:

obj.pmExpo.iter_comment = ['this is a comment indicating the use of this variable, ', ...
                           'so I do not need to go back to the code to know what it does'];

And now the function to display a field:

function MagicDisp(S, Field)
sprintf('Field: %s\n', Field);
disp(S.(Field));
Magic = [Field, '_comment'];
if isfield(S, Magic)
   fprintf('%s\n', S.(Magic));
end
end

Now call it as:

MagicDisp(obj.pmExpo, 'iter')

Well, the name "MagicDisp" implies, that I would not use it for productive code. The function could be enhanced, but I would not do it, because variable which do explain their meaning actively are too tricky to be useful. What would happen if you run a larger code, which uses 200 of such variables and process them in a loop?

If a variable should do anything actively, that it would be starting the daily backup. This is more important, forgotten too often, and the explanations can appear in the code instead.

Best Answer

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