public Expr evaluate(Expr[] args) throws ExprException {
assertArgCount(args, 1);
Expr a = evalArg(args[0]);
String s = null;
if (a instanceof ExprString) {
s = ((ExprString) a).str;
} else if (a instanceof ExprNumber) {
s = a.toString();
}
if (s != null && s.length() > 0) return new ExprInteger(s.charAt(0));
return ExprError.VALUE;
}
private double findChange(Expr old, Expr nu) {
if (old == null || nu == null) return 0;
if (old.type != nu.type) return 0;
if (nu instanceof ExprNumber) {
return Math.abs(((ExprNumber) old).doubleValue() - ((ExprNumber) nu).doubleValue());
}
if (nu instanceof ExprArray) {
Expr[] oldA = old.getArgs();
Expr[] nuA = nu.getArgs();
double change = 0;
for (int i = 0; i < oldA.length && i < nuA.length; i++) {
double c = findChange(oldA[i], nuA[i]);
if (c > change) change = c;
}
return change;
}
return 0;
}