#include "evaluator.h"

int evaluate(const expression_t *expression)
{
	if (expression->is_number)
		return expression->number;
	const int x = evaluate(expression->application.operands[0]);
	const int y = evaluate(expression->application.operands[1]);
	switch (expression->application.operator) {
	case OPERATOR_ADD:
		return x + y;
	case OPERATOR_SUBTRACT:
		return x - y;
	case OPERATOR_MULTIPLY:
		return x * y;
	case OPERATOR_DIVIDE:
		return x / y;
	default:
		return -1;
	}
}