I got a bug about scientific notation. Numeral variables sometimes output in the 'E' notation which conflicts 'e' constant since the variable name and its index are case-insensitive.
For example, a variable has value 1.234567E-15. When piping the variable into expression, the class evaluates it as (1.234567 x exp(1)) - 15 instead of 1.234567 x (10^-15).
I solve this by modifying your 'e' constant into 'ee' that works for me.