print mxArray type.

Hi,

I want to know how to print mxArray data type. I have a program below

int main(int ac, const char *av[]) {

int param1 = atoi(av[1]); int param2 = atoi(av[2]);

mxArray *in1 = NULL, *in2= NULL;

printf(" input param1 = %d\n", param1); printf(" input param2 = %d\n", param2);

in1 = mxCreateDoubleScalar(param1); in2 = mxCreateDoubleScalar(param2);

}

I want to know how to print in1 & in2

I also want to know how to print mxArray type, if mxArray was string , array , matrix or struct.

If a I have to use any function for this which header file should I include in my .c file

Thansk in advance

Answer 1

[Friedrich]

Okay, ML Compiler DLL. There is no print function available in C for the mxArray data type. One thing I use quite often in such a case is that I add a specific function to my generated DLL:

function chararray = mlprint(input)
  chararray = evalc('disp(input)');
end

In that way you use the MATLAB display functionality, capture this in a char array and return it back to the C side. Once you have that char array in C, you can apply the normal printf on it.

I created a DLL with the name printtest which contains the function above. On the C side I do:

#include <stdio.h>
#include "printtest.h"

int main()
{
    mxArray *test;
    mxArray *out = NULL;

      double data[] = {1,2,3,4,5,6,7,8,9};

      if( !mclInitializeApplication(NULL,0) )
      {
          fprintf(stderr, "Could not initialize the application.\n");
          return -1;
      }

      test = mxCreateDoubleMatrix(3,3,mxREAL);
      memcpy(mxGetPr(test), data, 9*sizeof(double));

      if (!printtestInitialize()){
          fprintf(stderr,"Could not initialize the library.\n");
          return -2;
      }
      else
      {
          int i = 0;
          mlfMlprint(1, &out, test);
          printf("%s\n",mxArrayToString(out));
          mxDestroyArray(out);
          out = NULL;
          mxDestroyArray(test);
          test = NULL;
          printtestTerminate();
      }
      mclTerminateApplication();
      return 0;
  }

[Mohammed Samdani]

Wanted to know if any body has tried below functions to pass and collect data from dll using varargin & varargout.

// Outputs

mxArray** plhs[] = { ..., };

//Inputs

mxArray* prhs[] = { };

[Friedrich]

Yes and it works fine. This is also documented here:

http://www.mathworks.com/help/toolbox/compiler/f2-998954.html#f2-1008549

E.g. a function like that

function varargout = foo(varargin)

get this C/C++ interface (this is one of multiple interfaces which are generated):

void foo(int nargout, mwArray& varargout,

const mwArray& varargin)

Answer 2

[Kaustubha Govind]

The easiest way is to just have the MATLAB "disp" function do the job for you:

   mexCallMATLAB(0,NULL,1, &in1, "disp");
   mexCallMATLAB(0,NULL,1, &in2, "disp");

(The required header is still "mex.h", which all MEX-files need)

However, if you want to do it the old school way in C, you'll need to get the pointer to the built-in representation of the mxArrays using mxGetPr (and mxGetPi if you are dealing with a complex variable).

   #include "matrix.h"
   ...
   double *in1pr = mxGetPr(in1);
   mexPrintf("in1=%f\n", in1pr[0]);
   double *in2pr = mxGetPr(in2);
   mexPrintf("in2=%f\n", in2pr[0]);

[Mohammed Samdani]

Thanks for quick reply kaustubha,

I get this error when i try the both the soloution above.

Operations_C.obj : error LNK2019: unresolved external symbol _mexCallMATLAB refe

renced in function _main

Operations_C.obj : error LNK2019: unresolved external symbol _mexPrintf referenc

ed in function _main

Operations_C.exe : fatal error LNK1120: 2 unresolved externals

Any suggestios.

[James Tursa]

Did you #include "mex.h" ? What command are you using to compile the code?

[Mohammed Samdani]

Yes I did, have also included #include "matrix.h"

mbuild Operations_C.c lib_Operations_C.lib I had also tried

mbuild -g -v Operations_C.c lib_Operations_C.lib. same error message.

[Gauraang Khurana]

Thanks Kaustubha, I was struck on this problem for almost 5hours now. I have finally printed the elements. Thanks alot.

Answer 3

[Friedrich]

Hi,

first of all, mexcallmatlab can be called from a mex file only. Since Mohammed writes an exe, this won't work.

Why are you writing an exe which uses the mxArray API? Do you use the MATLAB Engine? Or do you try to use a MATLAB Compiler generated DLL?

[Mohammed Samdani]

Hi,

Yes, I am using MATLAB comiler generated DLL.

I create a DLL of m file using

mcc -B csharedlib:lib_Operations_C Operations_C.m

Then I do an

mbuild Operations_C.c lib_Operations_C.lib

Operations_C 5 2.

But cannot print the value of mxArray.