Is there a way to push a MATLAB workspace onto a stack?

Question

Does anyone know if it's possible to have a stack of workspaces in MATLAB? It would be very convenient, to say the least.

I need this for research. We have several scripts which interact in interesting ways. Functions have local variables, but not scripts...

Answer 1

It sounds like you'd like to switch back and forth between workspaces of variables. The best way I can think to do this is to use the SAVE, CLEAR, and LOAD commands to move sets of variables back and forth between MAT-files and the workspace:

save workspace_1.mat   %# Save all variables in the current workspace
                       %#   to a .mat file
clear                  %# Clear all variables in the current workspace
load workspace_2.mat   %# Load all variables from a .mat file into the
                       %#   current workspace

Answer 2

The regular Matlab function call stack is itself a stack of workspaces. Just using functions is the easiest way to use one, and Matlab's copy-on-write makes this reasonably efficient. But that's probably not what you're asking.

There's a natural correspondence between workspaces and structs, since the same identifiers are valid for variable names and struct fields. They're both essentially identifier => Mxarray mappings.

You can use whos and evalin to capture workspace state to a struct. Use a cell vector to implement a stack of them. (A struct array won't work because it requires homogeneous field names.) The stack could be stored in appdata to prevent it from appearing in a workspace itself.

Here are push and pop functions for this technique.

function push_workspace()

c = getappdata(0, 'WORKSPACE_STACK');
if isempty(c)
    c = {};
end

% Grab workspace
w = evalin('caller', 'whos');
names = {w.name};
s = struct;
for i = 1:numel(w)
    s.(names{i}) = evalin('caller', names{i});
end

% Push it on the stack
c{end+1} = s;
setappdata(0, 'WORKSPACE_STACK', c);


function pop_workspace()

% Pop last workspace off stack
c = getappdata(0, 'WORKSPACE_STACK');
if isempty(c)
    warning('Nothing on workspace stack');
    return;
end
s = c{end};
c(end) = [];
setappdata(0, 'WORKSPACE_STACK', c);

% Do this if you want a blank slate for your workspace
evalin('caller', 'clear');

% Stick vars back in caller's workspace
names = fieldnames(s);
for i = 1:numel(names)
    assignin('caller', names{i}, s.(names{i}));
end