Oh, there must be a Common Lisp predicate that addresses this. prettymuchequalsp? More seriously, I remember APL\360 SETFUZZ from long before many of you whip

Oh, there must be a Common Lisp predicate that addresses this. prettymuchequalsp? More seriously, I remember APL\360 SETFUZZ from long before many of you whippersnappers were born, which told the system to disregard so-many bits in an 'equals' evaluation. FP implementations are generally evil, and errors cascade in irritating fashion. 50% of a numerical analysis class I took once was dedicated to error estimation. Stick to rationals if you can - it'll save your hairline.