Adding headlights to the buggy tutorial - Half-Life 2

[page=The Tutorial]
This tutorial explains how to add headlights to the Jeep. It requires basic understanding of C++
The actual code is very simple

First open vehicle_jeep.h. Find:

bool HeadlightIsOn( void ) { return m_bHeadlightIsOn; }
void HeadlightTurnOn( void ) { m_bHeadlightIsOn = true; }
void HeadlightTurnOff( void ) { m_bHeadlightIsOn = false; }

and replace them with

bool HeadlightIsOn( void ) { return m_bHeadlightIsOn; }
void HeadlightTurnOn( void );
void HeadlightTurnOff( void );

Now for vehicle_jeep.cpp. Go to void CPropJeep::Precache( void ) and add these

PrecachescriptSound( "Airboat_headlight_on" );
PrecachescriptSound( "Airboat_headlight_off" );

Then in void CPropJeep::DriveVehicle( ... ) uncomment

/* if ( ucmd->impulse == 100 )
 {
  if (HeadlightIsOn())
  {
   HeadlightTurnOff();
  }
        else 
  {
   HeadlightTurnOn();
  }
 }*/

At the end of the file add:

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
void CPropJeep::HeadlightTurnOn( void )
{
 EmitSound( "Airboat_headlight_on" );
 m_bHeadlightIsOn = true;
}

//-----------------------------------------------------------------------------
// Purpose: 
//-----------------------------------------------------------------------------
void CPropJeep::HeadlightTurnOff( void )
{
 EmitSound( "Airboat_headlight_off" );
 m_bHeadlightIsOn = false;
}

Next in void CPropJeep::ExitVehicle( int nRole ) replace

HeadlightTurnOff();

with

if (HeadlightIsOn())
  {
   HeadlightTurnOff();
  }

And we're done! All we needed to do was uncomment some code and add a sound to play.