How to avoid writing a script function ?

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Patrick Mboma
Patrick Mboma il 15 Feb 2012
Modificato: ebi il 14 Ott 2013
Dear all, I have the following problem: I would like to avoid writing a function as an m-file. Instead (and ideally) I would like to have it created as an anonymous function handle. The m-file equivalent of the function could look as complicated as the following:
function [a,b,c]=myfunc(d,e,f,g)
a=myfunc2(d,e,f);
if a>0
b=[];
c=[];
return
end
[b,c]=myfunc3(a,d,e,f,g);
Originally I thought a shortcut would be to simply create the m-file, create a handle to it and then delete the m-file. But I quiclkly realized it would not work. Is there any way to do to it, even using objects in some way or another?
Thanks, Patrick
  2 Commenti
Friedrich
Friedrich il 15 Feb 2012
Why do you need such a thing?
per isakson
per isakson il 15 Feb 2012
"Warum soll man es einfach machen, wenn man es so schön komplizieren kann". Seriously, I need a better description to understand what you may gain by such a construct.

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Risposta accettata

Daniel Shub
Daniel Shub il 15 Feb 2012
Maybe another person chiming in will convince you this is a bad idea. That said, if I had to go down this road I would probably approach it something like I suggested here: http://www.mathworks.com/matlabcentral/answers/14512-cellfun-for-objects
  3 Commenti
Daniel Shub
Daniel Shub il 15 Feb 2012
I would guess that it could "work" with "if" statements. There is very little that cannot be accomplished with eval statements. That said, they make understanding and maintaining the code much more difficult and often eval makes writing the code more difficult too.
Patrick Mboma
Patrick Mboma il 16 Feb 2012
Daniel, I totally agree with you on this. The problem is that I am facing this tradeoff between writing a massive amount of files to disk and finding a way to have anonymous functions. I see a two-step implementation here. In the first, I could write the functions to disk and thoroughly test that I get the results that I want and in the second step, try the anonymous implementation. I will also have to see what difference it makes in terms of speed of execution.

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Più risposte (2)

Jan
Jan il 15 Feb 2012
The M-file is fine and runs fast. Are you sure that you need an anonymous function?
  4 Commenti
Patrick Mboma
Patrick Mboma il 15 Feb 2012
Hi Jan, thanks for you answers. I understand your concerns about the possible bugs. In my case, I am 99.9999 percent sure there won't be any bug there.
On the other hand, besides the huge amount of m-files generated, another problem with creating m-files and creating handles to them is that if you change something in the input and you run the same program again, the handles may not be properly updated even after you first delete the existing files from the first run.
As an example, in one my runs I had a 3x7 matrix. Then I changed something that makes the matrix 3x9. When I ran the same program again, I kept having a 3x7 matrix.
Rather than having multiple functions created, if at least I could have one function that evaluates expressions (strings), I think I would prefer such a solution.
Jan
Jan il 16 Feb 2012
I still do not see the drawback of the M-files. Of course you have to remove a loaded file from the memory using CLEAR FILENAME, after the file has been modified.
But I agree that even creating a large number of M-files dynamically means a very high complexity and slow execution speed. Loading and parsing an M-file the first time needs a lot of resources.
Anyhow, I'm sure you will remember our warnings when they will get important in the future. And if they are not getting important, this is even better! Good luck.

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Walter Roberson
Walter Roberson il 15 Feb 2012
It is not possible to construct an anonymous function that specifies returning multiple outputs.
  3 Commenti
Patrick Mboma
Patrick Mboma il 15 Feb 2012
Sean is right that one could always return a cell array.
Teja Muppirala
Teja Muppirala il 16 Feb 2012
You can return multiple outputs from an anonymous function by using DEAL, for example:
F = @(x) deal( x, 2*x, 3*x )
[a,b,c] = F(10)

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