find all anonymous function in a workspace

There surely has to be a way of doing this: finding all anonymous functions in a specified workspace.

Presumably the solution involves using `whos` but I can't find it on web.

For a specific example suppose my workspace has the following variables

f = @x) x^2 ;

g = @(z,y) x^3 + z;

a = rand(5,3);

b = a^3 + 5;

I want a command that will identify (and return) f and g. A bonus would be for the command to list the arguments of f and g, but I can live without that.

Thanks for any suggestions.

[Steven Lord]

What's your application? Why are you trying to do this / how would you use this information?

If you're trying to generate a list of possible objective functions to pass into an optimization function, an ODE solver, an integration function, etc. know that some of those functions may accept objects that have an feval method as their "function" input. So you may not be generating all the possible values available for use in that function.

[Leo Simon]

In poorly written code, I have many anonymous functions; in some, the only arguments are endogenous variables; in others the arguments include parameters in addition. E.g.,

f = @(x,y) a*x + b*y
g = @(x,y,a,b) a*x +b*y

I obviously don't want two functions that are intended to do the same thing, so I'm going to rewrite f as below, but first I need to find all the duplicates. Applying func2str to the elements of @Benjamin 's and @Walter Roberson answer should do the trick!

f = @(x,y) g(x,y,a,b)

Answer 1

[Walter Roberson]

Borrowing heavily from @Benjamin

f = @(x) x^2 ;
g = @(z,y) y^3  + z;
h = @sin; % This is NOT an anonymous function!!!!
a = rand(5,3);
b  = a.^3 + 5;
S = whos();
names = {S.name};
classes = {S.class};
function_handle_names = names(strcmp(classes,'function_handle'))
info = cellfun(@(S) functions(evalin('caller', S)), function_handle_names, 'uniform', 0);
issimple = strcmp(cellfun(@(S)S.type, info, 'uniform', 0), 'simple');
anonymous_functions = function_handle_names(~issimple)

[Walter Roberson]

func2str() can return the text of an anonymous function, and from there you can parse out the @(...) part to get the parameter list

[Stephen23]

@Walter Roberson: isn't that text is already available in info.function ?

[Leo Simon]

Thanks to all for this combined effort. This works great except for one thing. At least on my machine, I'm seeing

>> anonymous_functions
anonymous_functions =
1x3 cell array
{'curly'}    {'f'}    {'g'}

where curly is generated by one of Walter's lines.

So I've added at the bottom:

anonymous_functions = anonymous_functions(find(~strcmp(anonymous_functions,'curly')))

@Walter Roberson, could you add this to your answer, or something more elegant.

[Walter Roberson]

I do not see it?

f = @(x) x^2 ;
g = @(z,y) y^3  + z;
h = @sin; % This is NOT an anonymous function!!!!
a = rand(5,3);
b  = a.^3 + 5;
S = whos();
names = {S.name};
classes = {S.class};
function_handle_names = names(strcmp(classes,'function_handle'))

function_handle_names = 1×3 cell array
    {'f'}    {'g'}    {'h'}

info = cellfun(@(S) functions(evalin('caller', S)), function_handle_names, 'uniform', 0);
issimple = strcmp(cellfun(@(S)S.type, info, 'uniform', 0), 'simple');
anonymous_functions = function_handle_names(~issimple)

anonymous_functions = 1×2 cell array
    {'f'}    {'g'}

Not here, and not on my desktop machine.

Remember that it is extracting information from whos() and the anonymous functions I create for info and issimple are not done until after whos() is run, so curly would have had to have been in your workspace already for it to show up.

[Walter Roberson]

I do not see it?

f = @(x) x^2 ;
g = @(z,y) y^3  + z;
h = @sin; % This is NOT an anonymous function!!!!
a = rand(5,3);
b  = a.^3 + 5;
S = whos();
names = {S.name};
classes = {S.class};
function_handle_names = names(strcmp(classes,'function_handle'))

function_handle_names = 1×3 cell array
    {'f'}    {'g'}    {'h'}

info = cellfun(@(S) functions(evalin('caller', S)), function_handle_names, 'uniform', 0);
issimple = strcmp(cellfun(@(S)S.type, info, 'uniform', 0), 'simple');
anonymous_functions = function_handle_names(~issimple)

anonymous_functions = 1×2 cell array
    {'f'}    {'g'}

Not here, and not on my desktop machine.

Remember that it is extracting information from whos() and the anonymous functions I create for info and issimple are not done until after whos() is run, so curly would have had to have been in your workspace already for it to show up.

[Leo Simon]

Ugh, sorry, it was in my startup script, shouidl have checked that. It's instructive though. I guess the pure way to be sure would be to run the info command before and after running the program, then do a setdiff to find the added anon functions.

Answer 2

[Voss]

% set up some variables in the workspace:
f = @(x) x^2 ;
g = @(z,y) y^3  + z; 
a = rand(5,3);
b  = a.^3 + 5;

S = whos();
names = {S.name};
classes = {S.class};
function_handle_names = names(strcmp(classes,'function_handle'));
display(function_handle_names);

function_handle_names = 1×2 cell array
    {'f'}    {'g'}

[Stephen23]

This finds all function handles, not anonymous functions as the question requests.

f = @(x) x^2 ;
g = @(z,y) y^3  + z;
h = @sin; % This is NOT an anonymous function!!!!
a = rand(5,3);
b  = a.^3 + 5;
S = whos();
names = {S.name};
classes = {S.class};
function_handle_names = names(strcmp(classes,'function_handle'));
display(function_handle_names);

function_handle_names = 1×3 cell array
    {'f'}    {'g'}    {'h'}

[Voss]

That's a good point.