On: 0.30000000000000004

[YeGoblynQueenne]

Swi-Prolog (listed int he article) also supports rationals:

  ?- A is rationalize(0.1 + 0.2), format('~50f~n', [A]).
  0.30000000000000000000000000000000000000000000000000
  A = 3 rdiv 10.