How?

Example
-------

Ok, here's a little C++ example, as it would appear in VisualC.

First, we write the DLL:

//demo.dll
//
#include <math.h>
#include <string.h>
#include <stdlib.h>

#define BBDECL extern "C" _declspec(dllexport)
#define BBCALL _stdcall

//returns a float and has 6 float parameters
BBDECL float BBCALL VecDistance( float x1,float y1,float z1,float x2,float y2,float z2 ){
	float dx=x1-x2,dy=y1-y2,dz=z1-z2;
	return sqrtf( dx*dx+dy*dy+dz*dz );
}

//returns a string and has one string parameter
BBDECL const char * BBCALL ShuffleString( const char *str ){
	static char *_buf;

	int sz=strlen(str);

	delete[] _buf;
	_buf=new char[ sz+1 ];
	strcpy( _buf,str );
	
	for( int k=0;k<sz;++k ){
		int n=rand()%sz;
		int t=_buf[k];_buf[k]=_buf[n];_buf[n]=t;
	}

	return _buf;
}
After building this, the resultant 'demo.dll' should be placed in the userlibs directory.

Now, we also need to create a 'demo.decls' file, describing the functions in our dll. This file
is also placed in the userlibs directory:

.lib "demo.dll"
VecDistance#( x1#,y1#,z1#,x2#,y2#,z2# ):"_VecDistance@24"
ShuffleString$( str$ ):"_ShuffleString@4"

...Voila! The next time Blitz is started up, the new commands appear within the IDE and can be used.