Mixed Mode Windows Programming using C#/C++ -Part 6

I know a developer ( Binny VA ) who has written a series of programs in various programing languages (which he calls "Hello World" method of learning ) to demonstrate it's constructs . His method seems to be a very effective method to learn a new programming language. I will attempt a "Hello World method" program for C++/CLI ( i have not covered classes , interfaces , struct etc )

The program computes the average of series of numbers from the command line.

////////////////////////////////
// average_Cmd.cpp
// A mixed mode  C++/CLI Program to demonstrate 
// various language features...
// 
//
// Written By           Praseed Pai K.T.
//                      http://praseedp.blogspot.com
//
// @ the Visual studio command prompt..
//
// cl /clr average_cmd.cpp      
//
//


using namespace System;

///////////////////////////////////
//
// A Function which takes a double array
// as an argument (interior_ptr array)
//
//
double Average( interior_ptr<double> r , int len ) ;

///////////////////////////////////
//
// A Function which takes a ANSI C++ double array
// as an argument (to demonstrate pinning)
//
//

double Ptr_Average(double * r , int len ) ;

//////////////////////////////////////////////////
//
// User Entry Point ( Ask yourself ! - who calls main ?)
//
//
//

int main(array<String^>^ args )
{

    if ( args->Length == 0 ) {
        Console::WriteLine("No Command line parameters");
        return 1;  
    }

    int rs = args->Length;

    array<double>^ dbl_array =gcnew array<double>(rs);

    /////////////////////////////////////////////
    //
    // Collect all the command line arguments by converting 
    // into IEEE 754 floating point...

    for(int i=0; i<rs; ++i ) {

    try {
    
        dbl_array [i] = Convert::ToDouble(args[i]);
    }
    catch(Exception^ e ) {

        Console::WriteLine("Non numeric character at the cmd line");
        return -1;                 

        }    
        }
    //////////////////////////////
    // Accumulate 
    //
    
    double sum = 0.0;
    for each(double t in dbl_array ) {
        sum +=t;
    }    

    Console::WriteLine("Sum is {0}",sum );

    //////////////////////////////////////////////
    //
    // interior_pointer....
    //

    interior_ptr<double> s = &dbl_array[0];
    double r = Average(s,rs);
    Console::WriteLine("Average is {0}",r );

    /////////////////////////////////////////////////////
    //
    //
    //
    pin_ptr<double>st = &dbl_array[0];        
    r = Average(st,rs);
    Console::WriteLine("Average is {0}",r );
 

}
/////////////////////////////////
// interior_pointer version of the average...
//
//
//

double Average(interior_ptr<double> r , int len ) 
{
         if (len == 0 )
                return 0;
         double sum = 0;  
         int tlen = len;  
         while (tlen-- )
            sum += *r++;

         Console::WriteLine("{0}",sum);  

         return sum/len;
      
}   

/////////////////////////////
//
// Native array version...
//
//
double Ptr_Average(double * r , int len ) 
{
         if (len == 0 )
                return 0;
         double sum = 0;  
         int tlen = len;  
         while (tlen-- )
            sum += *r++;

         Console::WriteLine("{0}",sum);  

         return sum/len;
      
}