When I create a recursive code and have the desired output, after following it with 'return' the next line - it continues running and outputting unwanted results - can someone help me avoid this please.

Return function in a recursive function code

Ameer Hamza 2018-4-25

Can you show us your friends function code, along with data you are using to call that function?

Rdmn Raja 2018-4-25

编辑：Rdmn Raja 2018-4-25

[C]=Function(A,P,K)
%A is adjacency matrix of a Graph say
%P, K are vectors
if (terminating condition)
   C=P;
   return
else 
    ......
    P=.....%redefined
    K=.....%redefined
    Function(A,P,K)
end
end

The code is of this type.

Ameer Hamza 2018-4-25

I think in the first condition you meant K=P. The only reason it can be happening is C never becomes equal to P.

Rdmn Raja 2018-4-25

No, the termination condition could be that all(P)==1 for instance and this is reached, I've debugged it and seen every step. I can use disp(P) but this doesn't output the result I want as a matrix.

Walter Roberson 2018-4-25

编辑：Walter Roberson 2018-4-25

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The line

    Function(A,P,K)

does not change C, so there is no point running the call.

Rdmn Raja 2018-4-25

true, C is only determined right at the end, can I display the output as a matrix using disp(..)

Ameer Hamza 2018-4-25

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If you want to return P from the last termination call to recursive function than you will need to assign it to the output of Function in else condition like this

[C]=Function(A,P,K)
%A is adjacency matrix of a Graph say
%P, K are vectors
if (terminating condition)
   C=P;
   return
else 
    ......
    P=.....%redefined
    K=.....%redefined
    C = Function(A,P,K);
end
end

No point of using disp if you want the output in a matrix.

Rdmn Raja 2018-4-25

i see my mistake, thanks

Rdmn Raja 2018-4-26

在 MATLAB Online 中打开

I'm actually facing a similar problem today again

[]=function(A,b,c,i,j,f,G)
if termination condition
   disp(G) %as G is a matrix containing matrices, I'm sending it to my workspace as a variable at the moment 
   return
else 
    if some condition
       G{i,j}= some matrix
    else 
    ....
end
end
        if true
          % code
        end

The issue is this function runs even after I've sent that big G I'm building up I presume because of the recursive nature. I can't really use the idea above as I'm using my function to find an entry via several steps. Any help will be appreciated as after debugging I see the out of memory error is coming after when I would like the algo to stop - despite the use of return.

Ameer Hamza 2018-4-26

There is no recursion in above code. It is hard to spot an error if we cannot see where the recursion is happening.

Rdmn Raja 2018-4-26

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function[]=HELP(A,R,P,X,i,j,n,D,C)
%A is a fixed matrix, R is something I'm building up then assigning it as an try of C, P, X are matrices for the algo, i and j are indices for the entry in C, n and D are used for the algo
if i>length(A)
   assignin('base','x',C); *<<<I just want C as output*
   return
else
if isempty(P)==1
   if isempty(X)==1
   C{i,j}=R;
   %R,P,X are changed
          if isempty(P)==1
          HELP(A,[],1:length(A),[],i+1,1,0,[],C);
          else
          HELP(A,R,P,X,i,j+1,n-1,D,C);
         end
   end
else
   if n==0 
      some algo stuff
      .
      .
      .
   HELP(A,R,P,X,i,j,n+1,D,C);
   else
   algo stuff
   .
   .
   .
   .
   .
   .
   HELP(A,R,P,X,i,j,n+1,D,C); 
   end
end
end
end

This is the framework of the code, I have debugged and I see it works, just some bad coding in the process.

Ameer Hamza 2018-4-26

Are you sure that termination condition is met? Apparently, the above code is logically correct and it should fall out of recursion once termination condition is met.

Rdmn Raja 2018-4-26

yes logically it's good, and yes the output falls out....but when I debugged it and ran it step by step it carries out further steps after it creates the variable 'x' in my workspace...

Ameer Hamza 2018-4-26

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What do you mean by "further steps". The only statement after that is return. What exactly it is doing after

assignin('base','x',C);

Rdmn Raja 2018-4-26

haha exactly, after return it goes to HELP(....) below and starts editing my matrices, it's not an issue as I have my output but I would love to know what I'm doing wrong from a programming point of view ( if any).

Ameer Hamza 2018-4-26

在 MATLAB Online 中打开

From the code you gave, all calls to HELP function are followed by end. There are no statements after that. How can the function start editing matrices? Or are there any other statements which you haven't included in the given code?

One possible solution can be adding a return after every call to HELP. For example

if isempty(P)==1
  HELP(A,[],1:length(A),[],i+1,1,0,[],C);
  return;
else
  HELP(A,R,P,X,i,j+1,n-1,D,C);
  return;
end

Similar for other two calls to HELP.

Rdmn Raja 2018-4-27

thanks, added it in but didn't check in the debugger mode if it runs after as I get the desired output I need.

Return function in a recursive function code

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