Prime 3.0 Custom Functions (string arguments)

Hi guys,

just to develop a little more this subject, this is what works for me:

// -----------------------------------------------

// File: test_string_return.cpp

// test for a function that returns a string

#include "stdafx.h"

#include "mcadincl.h"

#include <string>

using namespace std;

LRESULT test_string_return_Function( LPMCSTRING ParamValue, LPCMCSTRING ParamName );

LRESULT test_string_return_Function( LPMCSTRING ParamValue, LPCMCSTRING ParamName )

{

// see: http://stackoverflow.com/questions/347949/convert-stdstring-to-const-char-or-char

string str_val = "foox";

char *cstr_val = MathcadAllocate(str_val.size() + 1);

std::copy(str_val.begin(), str_val.end(), cstr_val);

cstr_val[str_val.size()] = '\0';

ParamValue->str = cstr_val;

// normal return

return 0;

}

// fill out a FUNCTIONINFO structure with

// the information needed for registering the

// function with Mathcad

FUNCTIONINFO test_string_return =

{

// Name by which mathcad will recognize the function

"test_string_return",

// description of "test_string_return_Function" parameters to be used

// by the Insert Function dialog box

"string-value",

// description of the function for the Insert Function dialog box

"test: pass a string and receive a string as output",

// pointer to the executible code

(LPCFUNCTION)test_string_return_Function,

// type of returned object

STRING,

// number of input parameters (not including the returned object)

// test_string_return_Function( value )

1,

// types of input parameters

{STRING}

};

// -----------------------------------------------

This is needed, for example, when one wants to read the attribute of a dataset in an HDF file. In that case the string, which is the attribute value, has to be returned to Mathcad.

Agostino