[jameshart]

> assuming the float is completely accurate (i.e. every decimal digit after the last internally-represented one is assumed to be 0)

Careful though - the float is probably not actually a set of decimal digits but most likely binary ones, so it would be assuming that every binary digit after the last one is zero.

Just because you wrote ‘0.1’ in your source code that doesn’t mean you only have a single significant figure in the float in memory. It’s going to be 0.0001100110011… (repeating 0011 to the extent of your float representation’s precision).

Although the Common Lisp language doesn’t actually appear to require that the internal float radix be 2 - a floating point decimal type would be valid implementation.