floor

        # Float.floor

(from ruby core)
---
    floor(ndigits = 0) -> float or integer

---

Returns the largest number less than or equal to `self` with a precision
of `ndigits` decimal digits.

When `ndigits` is positive, returns a float with `ndigits` digits after
the decimal point (as available):

    f = 12345.6789
    f.floor(1) # => 12345.6
    f.floor(3) # => 12345.678
    f = -12345.6789
    f.floor(1) # => -12345.7
    f.floor(3) # => -12345.679

When `ndigits` is non-positive, returns an integer with at least
`ndigits.abs` trailing zeros:

    f = 12345.6789
    f.floor(0)  # => 12345
    f.floor(-3) # => 12000
    f = -12345.6789
    f.floor(0)  # => -12346
    f.floor(-3) # => -13000

Note that the limited precision of floating-point arithmetic may lead to
surprising results:

    (0.3 / 0.1).floor  #=> 2 (!)

Related: Float#ceil.