Passing multiple outputs inside a function

I have been trying to program a function that will evaluate another function:

function [result]=evaluate(second_function,x,y,z)
.
.
.

the problem arises when the second_function has multiple outputs:

function [a,b,c]=second_function(x,yz)

I am clueless as to how to pass each output to the calling function ("evaluate"), so that it can use them for further purposes. I am aware of the nargout function but then I am lost as to how to dynamically assign each output to, say, a vector containing each output in a different row:

function [result]=evaluate(second_function,x,y,z)
v(:)=second_function(x,y,z);

Of course, I could program second_function in a way that the multiple outputs would be compressed in a vector:

function [a]=second_function(x,y,z)

a(1)=...;
a(2)=...;
a(3)=...;

But that adds further complications to the rest of my code.

I have to clarify that second_function is different each time (user defined) and I want the program to dynamically evaluate it.

Answer 1

[Walter Roberson]

You cannot do this unless you are willing to restrict the user functions to not using varargout .

If you are willing to restrict to not using varargout, then you can use

clear out
[out{1:nargout(second_function)}] = second_function(x,y,z);

and then pass out{:} down the line.

However, if the user is allowed to use varargout, then they could easily write a function that returns as many outputs as there were output slots provided. Such a function already exists, by the way: deal() will return as many outputs as you give output locations.

[Victor]

Spot on!

[out{1:nargout(second_function)}] = second_function(x,y,z)

it really worked!

I would like to avoid varargout since I believe that it is easier for the user, who I assume doesn't necessarily know how it works. Also, I believe that having several separate outputs makes my work easier as I can analyze the input function with nargin and nargout (nargout yields -nargout when used with a varargout function and is "blind" to how many variables are nested in varargout: I need to have a full understanding of the target, user-defined, function).

I digress, thanks for the help!

Answer 2

[Paulo Silva]

doc varargin

[Victor]

Sorry if I am being thick, but *varargin* is for "flexible" inputs, right?

Maybe I didn't formulate my question clearly enough. What I'm trying to do is to pass the *outputs* from any given function to a variable in my function.

The number of outputs could be anything. They are user defined. My function needs each and every output in order to perform further calculations.

Thanks anyway!

[Oleg Komarov]

You can use varargout and store several outputs in a cell array and pass it to the second functions as out{:}, i.e. "unpacking" the content of the cell array.