#include "expression_parts.h"
#include "expr_stack.h"

// Part printer.
std::ostream & operator<<(std::ostream &strm, const Expression_Part &p)
{
	p.print(strm);
	return strm;
}

// Action for reading an integer.
void Operand::action(expr_stack &s) { s.push(shared_from_this()); }

// Action on reading (
void Left::action(expr_stack &s) { s.push(shared_from_this()); }

// Action on reading an operator.
void Operator::action(expr_stack &s)
{
	// Perform pending operations of equal or greater precedence,
	// then push ourself onto the stack.
	s.reduce(m_precedence);
	s.push(shared_from_this());
}

/*
 * When a right paren is input, use reduce to replace the contents of
 * the parenthetical with its value.  Then remove the paren itself, and
 * discard it, along with the one read.  Throws if something goes wrong.
 */
void Right::action(expr_stack &s)
{
	// Perform all operations to the matching left paren.
	s.reduce();

	// Remove the value, remove and discard the left paren, then
	// return the value.
	auto paren_value = s.pop();
	if(!s.pop()->is_left())
		throw bad_expression("Unbalanced right paren.");
	s.push(paren_value);
}