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

/* 
This program shows you how a functions work in expressions.
To do this it has special tracing commands that report
what it is doing.  These command use 
the special diagnostic output channel "cerr".

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

*/

#include <iostream.h>

void main( ) 
{ 
  //Use the following functions
	int odd(int);//returns true if argument is odd
	int half(int);//returns half of the aargument
	int dubl(int);//returns twice the argument
	int trbl(int);//return three times the argument
	int next(int);//returns the next whole number after the argument

	cout<<"4 * 2 ="<<dubl(dubl(2))<<endl;

	cout<<"6 * 2 ="<<trbl(dubl(2))<<endl;

	cout<< "odd(half(dubl(next(0)))) is " <<odd(half(dubl(next(0)))) <<endl;
}


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

int odd(int n) //returns 1 if n is odd and 0 otherwise
{
	cerr<<"\n\tEntering 'odd' with n equal to "<<n<<endl;

	cerr<<"\n\tReturning "<< n%2<<" to caller."<<endl;
	return n%2;
}

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

int half(int n)//returns half of n (rounded down)
{
	cerr<<"\n\tEntering 'half' with n equal to "<<n<<endl;
	cerr<<"\n\tReturning "<< n/2<<" to caller."<<endl;
	return n/2;
}

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

int dubl(int n)
{
	cerr<<"\n\tEntering 'dubl' with n equal to "<<n<<endl;
	cerr<<"\n\tReturning "<< n+n<<" to caller."<<endl;
	return n+n;
}

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

int trbl(int n)
{
	cerr<<"\n\tEntering 'trbl' with n equal to "<<n<<endl;
	cerr<<"\n\tReturning "<< dubl(n)+n<<" to caller."<<endl;
	return dubl(n)+n;
}

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

int next(int n)
{
	cerr<<"\n\tEntering 'next' with n equal to "<<n<<endl;
	cerr<<"\n\tReturning "<< n+1<<" to caller."<<endl;
	return n+1;
}

//Exercise  Put the comment symbol '//' infront 
//			of  all the 'cerr<<' statements
//	What happens when you compile and run the result?
//	Why do you add cerr<< statements and then comment them out?