Linking errors

when I compile this I get no errors. When I go to debug/run I get these 2 errors, I'm using MS Visual Studio .NET for compiler

#include <iostream>
using namespace std;

double sum (double);
main()
{

double ctr=1;
double x;
double total;
total = sum(ctr);
cout << total;
}

double sum (double &x)
{
      double temp;

      if (x<10)
            temp = sum(x+1)+1/(x*x);
      else
            temp = 1/x;
      return temp;
}


error LNK2001: unresolved external symbol "double __cdecl sum(double)" (?sum@@$$FYANN@Z)
fatal error LNK1120: 1 unresolved externals

thanks for the help with this.....
LVL 1
Orlando15767Asked:
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tinchosCommented:
Hi Orlando15767,

First of all

the declaration of the sum function does not match the definition (one receives a reference to a double and the other just a double).
Also the parameter can be passed as a const reference


Try with

#include <iostream>
using namespace std;

double sum (const double &);
main()
{

double ctr=1;
double x;
double total;
total = sum(ctr);
cout << total;
}

double sum (const double &x)
{
     double temp;

     if (x<10)
          temp = sum(x+1)+1/(x*x);
     else
          temp = 1/x;
     return temp;
}

Hope this helps

Tincho

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Orlando15767Author Commented:
works good

if you don't mind, could you elaborate a little bit about const regerence how it works..... thanks for the help
tinchosCommented:
Ok

When you pass an object to a function you pass the whole object

void function( MyClass object )

but when you pass a reference to an object you pass just the address of that object (generally smaller than the object itself), so it is often recommended that you pass objects as references.....

void function( MyClass & object )

When you pass a const referente to an object

void function( const MyClass & object )

it means that you'll pass the address of the object, but the object can't be changed.
you can only call const functions to that object or get the member variables, but you cannot modify it.

I guess that's almost everything

If you need any more help let me know

Tincho
Orlando15767Author Commented:
thanks for the help and the added explaination....... helped me understands what the code was actually doing....

thanks again
tinchosCommented:
Glad it helped Orlando

:D

Tincho
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