# The extrinsic function 'perms' is not available for standalone code generation.

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nirwana on 28 Jun 2024
Commented: Umar on 7 Jul 2024
I am trying generate mex file using matlab coder, where in my function i use function perms, but I get this problem
The extrinsic function 'perms' is not available for standalone code generation. It must be eliminated for stand-alone code to be generated. It could not be eliminated because its outputs appear to influence the calling function. Fix this error by not using 'perms' or by ensuring that its outputs are unused.
I already using coder.extrinsic('perms'); but the problem still appear.
Anyone knows how to solve this, or Is there other function that I can use to replace perms?
David Goodmanson on 2 Jul 2024
Edited: David Goodmanson on 2 Jul 2024
yes, for n = 5, perms produces a result that is only 120x5 and you could do a lot of things to produce that, including the inelegant but probably effective way of just saving the matrix directly in lines of code.
nirwana on 2 Jul 2024
Thanks @David Goodmanson !! It works perfectly.

Raghu Boggavarapu on 4 Jul 2024
Moved: Matt J on 7 Jul 2024
Hi Nirwana,
Starting MATLAB R2024b we have enabled perms for code generation: perms . So using the later version will solve the issue.

Matt J on 7 Jul 2024
Edited: Matt J on 7 Jul 2024
Here's an alternative implementation of perms(), suitable for small vectors. Maybe pre-2024b Coder will find it more pallatable...
permsBasic(4)
ans = 24x4
1 2 3 4 1 2 4 3 1 3 2 4 1 3 4 2 1 4 2 3 1 4 3 2 2 1 3 4 2 1 4 3 2 3 1 4 2 3 4 1
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function out = permsBasic(N,sub)
%permsBasic(N) gives permutations of integers 1:N.
%
%Use V(permsBasic(numel(V)) for permutations of an arbitrary vector, V.
if nargin<2
out=permsBasic(N,(1:N)'); return;
end
[H,W]=size(sub);
w=N-W;
if w==0, out=sub; return; end
e=1:N;
P=permsBasic(w);
p=height(P);
out=cell(H,1);
for i=1:H
S=sub(i,:);
subc=setdiff(e,S);
tmp=[repmat(S,p,1), subc(P)];
out{i}=tmp;
end
out=cell2mat(out);
end
Paul on 7 Jul 2024
I was wondering whether or not recursion is supported for code generation. Apparently it is, with various options and constraints. I came across a strange restriction at Recursive Function Limitations for Code Generation: "Inputs and outputs of run-time recursive functions cannot be classes." Isn't every Matlab object in the workspace an instance of class? Maybe the doc means "... cannot be instances of user-defined classes." ?
Umar on 7 Jul 2024
Hi Paul,
The restriction you mentioned states that "Inputs and outputs of run-time recursive functions cannot be classes." This can indeed be a bit confusing, as Matlab objects in the workspace are typically instances of classes. However, the key distinction here lies in the type of classes being referred to. In this context, the limitation is specifically targeting user-defined classes. While Matlab objects are indeed instances of classes, they are instances of built-in or predefined classes provided by Matlab itself. User-defined classes, on the other hand, are classes created by the user through custom definitions. The restriction is likely in place due to the complexities involved in handling user-defined classes within recursive functions during code generation. User-defined classes can introduce additional complexities and dependencies that may not be easily resolved in the context of code generation for recursive functions. Also, could you please let me know how can you fix level 3 status to level 4 status, for instance my level status is shown level 3.

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