Verified that this problem has been fixed somewhere in the past.  Marking as Fixed and closing report.

I've been working on improving function handles.  See this mailing list thread:

https://lists.gnu.org/archive/html/octave-maintainers/2020-05/msg00066.html

Saving and loading handles to functions is kind of a weird thing to do, especially so for functions that are private in some way (subfunctions, local functions, private functions) or that carry additional info with them (nested functions) or that depend class data to work (class methods).  In any case, maybe we can make some of these features work.

In my recent changes, Octave now creates a proper scopedfunction function handle object that contains a reference to the scoped fucntion, the name of the file where the function is found, and parent function info.  This should allow us to correctly save and load handles to subfunctions, local functions, and private functions and make them available on loading even after "clear functions" or in a new Octave session.

If I understand correctly, we need to do something like the following after loading the function handle from the file:

• check the currently loaded functions to see whether the referenced function is already loaded.

• If it is, add a reference to it to the newly loaded handle object.

• If not, attempt to load the primary parent function, then search for the appropriate subfunction.

Determining whether the function is already loaded is a bit tricky because of possible changes in the load path.  It's not entirely clear how to do this in a 100% reliable way.  It seem there could be many ways to end up referencing the wrong function.

I think the problem is still present.  Unlike Harmut, I did not create a file gas_phase_ODE.m, which creates a primary function of that name.  When I load the structure back in and query it I get

 model
model =

  scalar structure containing the fields:

    odefun = @gas_phase_ODE

Octave knows that it is a function handle to gas_phase_ODE, but it doesn't know where to fnd that function since there is no m-file of that name.  It seems that in this case it really should store something like

odefun = @create_func>gas_phase_ODE

That is the syntax that dbstop uses for subfunctions.

dbstop create_func>gas_phase_ODE
ans =  10

Maybe I'm missing the point here, but when I call the main script from comment #0, (just skipping the clc command for clarity here), I always get the following result with Octave 4.2.0:

>> main
ans =

  -1.28000
   0.64000

ans =

  -1.28000
   0.64000

>> main
ans =

  -1.28000
   0.64000

ans =

  -1.28000
   0.64000

>> model.odefun([2 3],0)
ans =

  -1.28000
   0.64000

>>

I have created two separate m-files in the current directory, called create_func.m and gas_phase_ODE.m, one for each function defintion. Maybe that's what I did different?

@Rik: Or did you define those two functions as subfunctions in your main.m? In this case you migh only see Octave's "clear all bug", bug #35881. (Currently "clear all" in Octave also clears subfunction definitions, Matlab doesn't.)

So if I think this isssue is either solved as fixed, or might just be a duplicate of bug #35881.

I think this is now FIXED in Octave 4.2.0.

When running the demo script from comment #0 (including the two function definitions in separate files) than I get twice the same result.

I found a strange behavior using function handles in Octave.

Here is what I'm trying to do:

1) Create a function handle in a structure like:

    model.odefun = @plant_ODE

2) Save the handle

    save stored_model.mat model

3) when I try to call the function:

    load stored_model.mat;
    model.odefun(0,[2 4]);

octave does not recognize "model.odefun" as an handle anymore.

Actually the problem is a little bit more complex. Attached is a small example. It works in Matlab but it doesnt in Octave.

clear all
close all
clc

model = create_func;
model.odefun([2 3],0)

save -binary handle_saved.dat model
clear all

load handle_saved.dat
model.odefun([2 3],0)

function [model] = create_func

 model.odefun = @gas_phase_ODE;

end


function dxdt = gas_phase_ODE(x,t)
  k_ = 0.16;
  v = [-2 1];
  r = k_*x(1)^2;
  dxdt = v'*r;
end