External Interfaces

Using Data Types

You can write MEX-files, MAT-file applications, and engine applications in C that accept any data type supported by MATLAB. In Fortran, only the creation of double-precision n-by-m arrays and strings are supported. You can treat C and Fortran MEX-files, once compiled, exactly like M-functions.

Caution    MATLAB does not check the validity of MATLAB data structures created in C or Fortran using one of the mx functions (e.g., mxCreateStructArray). Using invalid syntax to create a MATLAB data structure can result in unexpected behavior in your C or Fortran program.

The explore Example

There is an example MEX-file included with MATLAB, called explore, that identifies the data type of an input variable. The source file for this example is in the <matlab>/extern/examples/mex directory, where <matlab> represents the top-level directory where MATLAB is installed on your system.

Note    In platform independent discussions that refer to directory paths, this book uses the UNIX convention. For example, a general reference to the mex directory is <matlab>/extern/examples/mex.

For example, typing

• cd([matlabroot '/extern/examples/mex']);
  x = 2;
  explore(x);
  

produces this result

• ------------------------------------------------
  Name: prhs[0]
  Dimensions: 1x1 
  Class Name: double
  ------------------------------------------------
      (1,1) = 2
  

explore accepts any data type. Try using explore with these examples.

• explore([1 2 3 4 5])
  explore 1 2 3 4 5
  explore({1 2 3 4 5})
  explore(int8([1 2 3 4 5]))
  explore {1 2 3 4 5}
  explore(sparse(eye(5)))
  explore(struct('name', 'Joe Jones', 'ext', 7332))
  explore(1, 2, 3, 4, 5)
  

Data Types in MATLAB

Building MEX-Files

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