// Dick.	cs201/lab/04
// Date Sun Apr 23 11:31:41 PDT 1995
// Teaching how functions work

/* 
This program shows you how a functions with reference arguments work.
To do this it has special tracing commands that report
what it is doing to the special diagnostic output channel "cerr".

It also shows that you don't have to store a value before printing it.

The calculation is not very exciting.... 

This is not a very good style,   

Experiment by removing '&' characters and see what changes!
But put them back afterwards!
*/

#include <iostream>

using namespace std;

void odd(int& p) //Puts 1 into p, if p is odd and zero otherwise
{
	cerr<<"\n\tEntering 'odd' with argument p equal to "<<p<<endl;
	p = p%2;
	cerr<<"\n\tLeaving 'odd' with argument p equal to "<<p<<endl;
}

//-------------------------------------------------------------------


void half(int& p)//Divides p by 2 (rounded down)
{
	cerr<<"\n\tEntering 'half' with argument p equal to "<<p<<endl;
	p = p/2;
	cerr<<"\n\tLeaving 'half' with argument p equal to "<<p<<endl;
}

//-------------------------------------------------------------------


void dubl(int& p)//Experiment a:  Delete the & here and the prototype
		// for dubl() above
{
	cerr<<"\n\tEntering 'dubl' with argument p equal to "<<p<<endl;
	p = p+p;
	cerr<<"\n\tLeaving 'dubl' with argument p equal to "<<p<<endl;
		//Experiment c: What happens if you add the following
		// return p*p;
			// the star above is not a typo!
		/// Remove it when you have found out.
}

//-------------------------------------------------------------------


void trbl(int& p)
{
	cerr<<"\n\tEntering 'trbl' with argument p equal to "<<p<<endl;
	p = p + p + p;
	cerr<<"\n\tLeaving 'trbl' with argument p equal to "<<p<<endl;
}

//-------------------------------------------------------------------


void next(int& p)
{
	cerr<<"\n\tEntering 'next' with argument p equal to "<<p<<endl;
	p = p+1;
	cerr<<"\n\tLeaving 'next' with argument p equal to "<<p<<endl;
}

//-------------------------------------------------------------------

int main( ) 
{ 
  // Main's local variable is
	int n=0,m=1;

	//Experiment: is this valid here
	//		next(0);

	cout <<"In main,  n is now "<<n<<" and m is "<<m<<endl;
	next(n);
	cout <<"In main,  n is now "<<n<<" and m is "<<m<<endl;
	dubl(m);
	cout <<"In main,  n is now "<<n<<" and m is "<<m<<endl;
	half(n);
	cout <<"In main,  n is now "<<n<<" and m is "<<m<<endl;
	odd(n);
	cout <<"In main,  n is now "<<n<<" and m is "<<m<<endl;
	trbl(m);
	cout <<"In main,  n is now "<<n<<" and m is "<<m<<endl;

	return 0;
}