simplify method

@override Expression simplify()

Possible simplifications:

1. e^0 = 1
2. e^1 = e
3. e^(x*ln(y)) = y^x (usually easier to read for humans)

Implementation

@override
Expression simplify() {
  final Expression expSimpl = exp.simplify();

  if (_isNumber(expSimpl, 0)) {
    return Number(1); // e^0 = 1
  }

  if (_isNumber(expSimpl, 1)) {
    return Number(math.e); // e^1 = e
  }

  if (expSimpl is Times && expSimpl.second is Ln) {
    final ln = expSimpl.second as Ln;
    return Power(ln.arg, expSimpl.first); // e^(x*ln(y)) = y^x
  }

  return Exponential(expSimpl);
}