MATLAB: Matlab Coder, C-function return type

c functioncode generationmatlab coderreturn parameter

What determines the return of a parameter when generating C-code from a function? In which case is the parameter returned by value (as the c-function's value) and in which case is it returned in the parameter list? How can I ensure that the generated c-function is alwasy of type void()? Thanks for helping

Best Answer

Hi Christian

Functions in programming languages like 'c' and 'c++' are of a certain type, whether it be int, double, string etc. And when called using the main program, these functions return a value of that type. That is not the case in MATLAB, here we don't define return type also the function can return many values.

The coder is designed in such a way that when the matlab function returns more than one value the value to be returned is passed as parameters in the function.

If you have only one return and want is passed as parameter in the function, you could do this:

..............................................

function res = doit(a, b, res)

res= a+b;

end

................................................

>>codegen doit -args {0, 0, 0} -config:lib -report

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MATLAB: Does LIBFUNCTIONS not display more than 8 return arguments in MATLAB 7.6 (R2008a)

This is a limitation of the METHODS, METHODSVIEW, LIBFUNCTIONS, and LIBFUNCTIONVIEW functions in MATLAB release version up to and including MATLAB 7.6 (R2008a). METHODS -full does not list more then 8 output arguments and displays only the first output. Note that the function can still be called correctly and all outputs are returned.

A workaround to view the full function signature is to use the following:

libpkg=findpackage('lib'); 
class=findclass(libpkg,'fifteenArgDLL'); 
methods=class.methods;

The "method" variable would then contain information about the library:

%Sample invocation:
>> get(methods(1))
                  Name: 'myfun'
           Description: 'myfun'
             Signature: [1x1 schema.signature]
                Static: 'on'
      FirstArgDispatch: 'on'
>> get(methods(1).Signature)
       InputTypes: {16x1 cell}
      OutputTypes: {17x1 cell}
        Varargout: 'off'
         Varargin: 'off'
>> methods(1).Signature.OutputTypes
ans = 
      'double'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'
      'doublePtr'

MATLAB: Changing matrices form, echelon the matrices

A=[0  1  0  0
  0  0  1  1
  0  0  0  1
  0  0  0  0]

%For the first case

n=size(A,1)
out=[A(1,:)';cell2mat(arrayfun(@(x) A(x,x+1:n)',(2:n-1)','un',0))]

% Forthe second case

B=A';
B=B(:)

Best Answer

Related Solutions

MATLAB: Does LIBFUNCTIONS not display more than 8 return arguments in MATLAB 7.6 (R2008a)

MATLAB: Changing matrices form, echelon the matrices

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