How to clear workspace from a function?

Hi,

I want to create a function that will perform some maintenance operations at the beginning of the script. For example, this function takes a few arguments that will lead to specific initialisations of paths and variables, and above all, clear the workspace from the previous run.

I want to put it in a specific function as the job requires dozens of lines which are quite irrelevant in the work. And I want my "main' script to be as short, readible and high-level as possible.

Below only the first lines of the function.

function init_step(varargin)

    clearvars -except varargin
    close all
    clc    

However if I do 2 consecutive runs, it does not clear the workspace. If I want to, I need to explicitely write the "clear" command in the main script, which I try to avoid.

Is there any way to do it?

Thanks in advance.

[Stephen23]

The simple solution would be to make the "specific function" a script, then when you run it, it will clear the worksapce of your main script. But.... using scripts and needing to clear workspaces is a strong indication that you should to refactor your code:

https://en.wikipedia.org/wiki/Code_smell

[Louis Tomczyk]

@Stephen23, I didn't think about it, thanks.

By the way I didn't know about the "code smell", thanks again.

Answer 1

[Bora Eryilmaz]

Functions do not keep their variables across calls to them unless a variable is specifically defined in the function using the "persistent" keyword. So, you do not need to try to clear variables in a function workspace in this scenario. Each call to the function has its own variable scope (i.e., workspace), which is already clear when the function starts executing, except of course for the variables that you pass to the function as input arguments.

If the function accesses the variables in the base workspace (using evalin, etc.), that is a different question, in which case you can use the clear command.

Answer 2

[Hiro Yoshino]

You should understand Base and Function Workspaces. Note that they are different.

One way you can delete variables from the Function Workspace is that you make your variables "global" so you can have access from anywhere.

Here is how to make variables "global".

Answer 3

[Louis Tomczyk]

@Bora Eryilmaz@Hiro Yoshino,

Thanks to both of you.

However let me be more precise. Let's call WS1 : the workspace of the script, the main.

I would like to clear WS1 by a command I call in a function I created ()

So that each time I run the script, it runs first my function, that will clear all the variables used in the script:

% my script
init_step("my argument")
a=10;

When I run it for the first time, in WS1 there will be "a" in it.

When I run it again, I expect the "clear" command in to clear the "a", but it does not.

I hope it is more understandable. Thx again

[Bora Eryilmaz]

You cannot clear the variables in the main function by calling clear inside another function (init_step).

You can probably describe why you are trying to do something like this as this is a highly unusual thing to try to do. Then someone can probably offer a better workflow/solution. For example, you can make init_step return the initial values of the variables that you are trying to clear. Something like this:

[a, b, c] = init_step(...)

[Louis Tomczyk]

Actually I am not doing anything really special, it was more curiosity. It was almost a yes or no question.

I would like to accept your answer but it seems I cannot accept a comment as an answer.

Thanks a lot.

Best,