public int lookupDouble( final double n ) {

        final long bits = Double.doubleToLongBits(n);

        for (int i = 1; i < index; i++) {

            if (constants[i] instanceof ConstantDouble) {

                final ConstantDouble c = (ConstantDouble) constants[i];

                if (Double.doubleToLongBits(c.getBytes()) == bits) {

                    return i;

                }

            }

        }

        return -1;

    }