Clear variables from workspace with exceptions by use of regular expressions

Question

I'd like to clear all variables from workspace, but with some exceptions defined by regular expressions.

The function clear has an additional option -regexp

clear -regexp expr1 ... exprN clears all variables that match any of the regular expressions listed. This option only clears variables.

So I'm looking for the opposite.

Also there is

clearvars -regexp p1 p2 ... clears all variables that match regular expression patterns p1, p2, and so on.

clearvars -except v1 v2 ... clears all variables except for those specified following the -except flag.

Which is already quite nice for complete variable names, but not working for regexp like the first option.

There are solutions on FEX, but I don't want to use additional custom functions.

But As there are such convenient solutions for the just slightly different cases above, I wonder if there is also a simple way to do:

keep -regexp expr1 ... exprN

with inbuilt functions.

Answer 1

Take a look at this for inverse regexp matching. In this context:

clear -regexp ^((?!expr1|expr2|...).)*$

clearvars is not built-in, but an m-function, which has its own disadvantages. With the inverse regexp matching, you can do everything with clear (a built-in).