//MyAccumulators2.h
//   tom bailey   25 sep 06

// Declare and Define accumulator classes Counter, Summer,
//   and Averager.

#ifndef MY_ACCUMULATORS_H_
#define MY_ACCUMULATORS_H_

// A Counter is a Simple Accumulator that tracks the size of 
//   its sequence.
class Counter {
public:
	// post: The sequence is empty.
	Counter();

	// pre:  The sequence is S.
	// post: The sequence is S, then x.
	void append( double x );

	// pre:  The sequence is S.
	// post: The size of S has been returned.
	double operator()();

private:
	double count;
};

Counter::Counter() 
: count( 0.0 ) {
}

void Counter::append( double x ) {
	count += 1.0;
}

double Counter::operator ()() {
	return count;
}


// A Summer is a Simple Accumulator that tracks the sum of 
//   values in its sequence.
class Summer {
public:
	// post: The sequence is empty.
	Summer();

	// pre:  The sequence is S.
	// post: The sequence is S, then x.
	void append( double x );

	// pre:  The sequence is S.
	// post: The sum for S has been returned.
	double operator()();

private:
	double sum;
};

Summer::Summer() 
: sum( 0.0 ) {
}

void Summer::append( double x ) {
	sum += x;
}

double Summer::operator ()() {
	return sum;
}


// An Averager is a Simple Accumulator that tracks the
//   average of the values in its sequence.
class Averager {
public:
	// post: The sequence is empty.
	Averager();

	// pre:  The sequence is S.
	// post: The sequence is S, then x.
	void append( double x );

	// pre:  The sequence is S.  S is not empty.
	// post: The mean of S has been returned.
	double operator()();

private:
	Counter count;
	Summer sum;
};

Averager::Averager() {
}

void Averager::append( double x ) {
	count.append( x );
	sum.append( x );
}

// pre:  At least one entry has been added to this Averager.
double Averager::operator ()() {
	return sum() / count();
}
#endif