MATLAB: Do I have difficulty in using the << operator with the ramp function with mwArray

cMATLAB C/C++ Math Library

Why do I have difficulty in using the << operator with the RAMP function with the mwArray interface?

The following code segment produces an error when compiled to a stand-alone and executed using MBUILD:

1. Create test.cpp from the following C++ code:

 #include "matlab.hpp"
 void main()
 {
   mwArray x;
   x=ramp(-10,0.1,9);
   cout<<x<<endl;
 }

2. Compile it using mbuild:

mbuild -setup  %select VC++
mbuild -v test.cpp

3. Execute the code:

!test

from the MATLAB prompt.

I should receive the following error message:

 abnormal program termination 
   [

However, if I replace the code in test.cpp with the following:

 #include "matlab.hpp"
 void main()
 {
   mwArray x;
   x=ramp(-10,0.1,11);
   cout<<x<<endl;
 }

and run steps 2 and 3 again, I receive a listing of the contents of 'x' rather than the error message.

The problem occurs when the last argument to RAMP is less than 10 (the absolute value of the first variable).

Best Answer

This is a bug in the MATLAB C/C++ Math Library 2.2 (R12.1) that is being investigated by our development staff.

The current work around is to explicitly print the variables out in a FOR loop.

 #include "matlab.hpp"
 void main()
 {
   mwArray x;
   x=ramp(-10,0.1,9);
   for(int i = 0; i<190; i++)
        cout<<x(i)<<endl;
 }

Related Solutions

MATLAB: Can I create a dynamic array with the mwArray class of the MATLAB Compiler 4.1 (R14SP1) C++ Utility Library

It is possible to create dynamic arrays with the mwArray class in MATLAB Compiler 4.1 (R14SP1). Below is an example (testme.cpp) that will let the user define the size of 2 arrays:

#include "mclcppclass.h"
int main(){
      if (!mclInitializeApplication(NULL,0))
      {   std::cerr << "could not initialize the library properly"<<std::endl;
           return -1;
      }  
      try
      {   int x,y;
          int* a = NULL;
          int* b = NULL;              
          std::cout << "Enter length of array 1:" <<std::endl;
          std::cin >> x;          // Create input data
          std::cout << "Enter length of array 2:" <<std::endl;
          std::cin >> y;
          a = new int[x]; // Allocate x ints and save ptr in a.
          b = new int[y]; // Allocate y ints and save ptr in b.     
          for (int i=0; i<x; i++) {
              a[i] = i;    // Initialize all elements in increments of 1.
          }    
          for (int j=0; j<y; j++) {
              b[j] = 1;    // Initialize all elements to one.
          }    
          mwArray in1(1, x, mxDOUBLE_CLASS, mxREAL);
          mwArray in2(1, y, mxDOUBLE_CLASS, mxREAL);         
          in1.SetData(a, x);
          in2.SetData(b, y);        
          std::cout << "The 1st array is:" << std::endl;
          std::cout << in1 << std::endl;      
          std::cout << "The 2nd array is:" << std::endl;
          std::cout << in2 << std::endl;        
          delete [] a;  //When done free memory pointed to by a.
          a = NULL; 
          delete [] b;
          b = NULL;     //When done, free memory pointed to by b.
      }
      catch (const mwException& e)
      {   std::cerr << e.what() << std::endl;
          return -1;        
      }
      catch (...)
      {  std::cerr << "Unexpected error thrown" << std::endl;
          return -1;
      }   
      mclTerminateApplication();
      return 0;
   }

You can compile this example using the following command:

mbuild -v testme.cpp

MATLAB: How to pass a function handle to the MATLAB C++ Math Library functions

In order to pass a function handle into your function, you must first register your function in the function look-up table. This is discussed in the C++ Math Library Users Guide.

Here is a simple example code that illustrates how to add the function "func" to the function table look-up.

 #include "matlab.hpp"
 mwArray func(mwArray x)    /*Function that will be passed as a handle to another function*/
 {
     return sin(x);
 }
 DECLARE_FEVAL_TABLE /*Macro that adds the function func into the FEVAL table*/
 FEVAL_ENTRY(func)
 END_FEVAL_TABLE
 int main(void)
 {
     mwArray x;
     mwArray x0(2);
     cout<<x0<<"\n"<<"\n"<<endl;
     x = fzero("func",x0);      /*func is passed to the function FZERO as a function handle*/
     cout<<x<<endl;
     return 0; 
 }

Best Answer

Related Solutions

MATLAB: Can I create a dynamic array with the mwArray class of the MATLAB Compiler 4.1 (R14SP1) C++ Utility Library

MATLAB: How to pass a function handle to the MATLAB C++ Math Library functions

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