[gioele]

That is just a coincidence (decimal ending in "5"), plus the fact that `.to_d` does some cleanup preprocessing.

Counterexample:

  BigDecimal("1.5999999999999996") == 1.5999999999999996.to_d
  => false

The most ergonomic way to initialize decimal numbers is IMO

  "123.45".to_d

(Note the quotes around the number. `.to_d` is being called on a string.)

BigDecimal's only lossless API is through strings. It would be nice to have native support for decimals at the parser level:

  0d123.45 => BigDecimal("123.45")