[jlgustafson]

Exactly. Floating-point numbers cannot represent such numbers without error, yet we still see people asserting that floats represent "the entire real number line." The first format to represent such numbers honestly was the original unum format, where the last bit of the fraction indicates if the number is exact or represents the open interval between exact numbers. Like saying pi is 3.14... means pi is between 3.14 and 3.15, a mathematically honest statement. The presence or absence of "..." as a bit in the number was the main idea behind unum arithmetic.