// FILE: charstack.cpp
// CLASS IMPLEMENTED: CharStack (see charstack.h for documentation)
// INVARIANT for the stack class:
//   1. The number of chars in the stack is in the member variable used.
//   2. The actual chars of the stack are stored in a partially-filled
//      array data[0]..data[used-1]. The stack elements appear from the
//      bottom (at data[0]) to the top (at data[used-1]).

#include <cassert>  // Provides assert
#include "charstack.h"

void CharStack::push(const char& entry)
// Library facilities used: cassert
{
	assert(size( ) < CAPACITY);
	data[used] = entry;
	++used;
}

void CharStack::pop( )
// Library facilities used: cassert
{
	assert(!empty( ));
	--used;
}

char CharStack::top( ) const
// Library facilities used: cassert
{
	assert(!empty( ));
	return data[used-1];
}