/**
* Flatten an expression with respect to an associative operator: for example the expression (a+b)
* + (c+d) becomes list(a,b,c,d), with the list in canonical order (sorted by hashCode)
*
* @param list a list provided by the caller to contain the result
* @return the list of expressions
*/
private List flattenExpression(List list) {
if (operand0 instanceof BinaryExpression
&& ((BinaryExpression) operand0).operator == operator) {
((BinaryExpression) operand0).flattenExpression(list);
} else {
int h = operand0.hashCode();
list.add(operand0);
int i = list.size() - 1;
while (i > 0 && h > list.get(i - 1).hashCode()) {
list.set(i, list.get(i - 1));
list.set(i - 1, operand0);
i--;
}
}
if (operand1 instanceof BinaryExpression
&& ((BinaryExpression) operand1).operator == operator) {
((BinaryExpression) operand1).flattenExpression(list);
} else {
int h = operand1.hashCode();
list.add(operand1);
int i = list.size() - 1;
while (i > 0 && h > list.get(i - 1).hashCode()) {
list.set(i, list.get(i - 1));
list.set(i - 1, operand1);
i--;
}
}
return list;
}
/** Is this expression the same as another expression? */
public boolean equals(Object other) {
if (other instanceof BinaryExpression) {
BinaryExpression b = (BinaryExpression) other;
if (operator == b.operator) {
if (operand0.equals(b.operand0) && operand1.equals(b.operand1)) {
return true;
}
if (isCommutative(operator) && operand0.equals(b.operand1) && operand1.equals(b.operand0)) {
return true;
}
if (isAssociative(operator)
&& pairwiseEqual(
flattenExpression(new ArrayList(4)), b.flattenExpression(new ArrayList(4)))) {
return true;
}
}
if (isInverse(operator, b.operator)
&& operand0.equals(b.operand1)
&& operand1.equals(b.operand0)) {
return true;
}
}
return false;
}