Emacs Calculator with high precision will get you what you need (`M-x calc RET P 20 RET 9999999999999999.0 RET 9999999999999998.0 RET -` gives you `1.`) Defini

Emacs Calculator with high precision will get you what you need (`M-x calc RET P 20 RET 9999999999999999.0 RET 9999999999999998.0 RET -` gives you `1.`) Definitely keeping this example in my back pocket for explaining to people why floating point is not what you think it is.