Pointer Trouble (GCC complains)

[Ghiofish]

When trying to compile this:

#include <iostream>

using namespace std;

void DoubleIt(int *pointer);

int main ()
{
  int a = 0;
  int b = 0;
  
  //int *ptr_a = &a;
  //int *ptr_b = &b;
  
  cout << "Enter a value for a: ";
  cin >> a;
  
  cout << "Enter a value for b: ";
  cin >> b;
  
  cout << "Double a is " << DoubleIt(&a) << ".\n";
  cout << "Double b is " << DoubleIt(&b) << ".\n";
  
  return 0;
}

void DoubleIt(int *pointer)
{
  *pointer *= 2;
}

GCC says this:

$ g++ doubleit.cpp -o doubleit                                                      
doubleit.cpp: In function ‘int main()’:                                                                  
doubleit.cpp:22: error: no match for ‘operator<<’ in ‘std::operator<< [with _Traits = std::char_traits<char>](((std::basic_ostream<char, std::char_traits<char> >&)(& std::cout)), ((const char*)"Double a is ")) << DoubleIt(ptr_a)’

(and a WHOLE lot more (looks like mostly the same message though)).

This strikes me as strange, because it seems to be complaining about I/O, but as far as I can tell there aren't any syntax errors. I've been looking at this for about an hour and can't figure out what's wrong.

Any ideas?

[cyberfish]

DoubleIt returns void (doesn't return anything).

You are using its return values

  cout << "Double a is " << DoubleIt(&a) << ".\n";
  cout << "Double b is " << DoubleIt(&b) << ".\n";

[Ghiofish]

.... Oh man... *FACEPALM* I think it's time for bed. lol. Thanks for the help.