/**
* calculate the number of permutations
*
* @param operand[0] = the order of the equation
* @return the coefficients as a vector
*/
public OperandToken evaluate(Token[] operands) {
OperandToken result = new DoubleNumberToken(0);
if (operands.length >= 1 && operands[0] instanceof DoubleNumberToken) {
double val = ((DoubleNumberToken) operands[0]).getValueRe();
int order = (new Double(val)).intValue();
double[][] results = new double[1][order + 1];
DoubleNumberToken total = ((DoubleNumberToken) operands[0]);
for (int count = 0; count <= order; count++) {
// comb(x y) = y!/(x! * (y-x)!)
DoubleNumberToken objects = new DoubleNumberToken(count);
// result = x!
OperandToken temp = objects.factorial();
// temp2 = y-x
OperandToken temp2 = ((OperandToken) total.clone());
temp2 = temp2.subtract(objects);
// temp2 = (y-x)!
temp2 = temp2.factorial();
// temp = x! * (y-x)!
temp = temp.multiply(temp2);
// temp2 = y! / (x! * (y-x)!)
temp2 = total.factorial();
temp2 = temp2.divide(temp);
results[0][count] = ((DoubleNumberToken) temp2).getValueRe();
}
result = new DoubleNumberToken(results);
}
return result;
}
