
  -spec round(Number) -> integer() when Number :: number().

  Returns an integer by rounding Number, for example:

    round(42.1).
    42

    round(5.5).
    6

    round(-5.5).
    -6

    round(36028797018963969.0).
    36028797018963968

  In the last example, round(36028797018963969.0) evaluates to 
  36028797018963968. The reason for this is that the number 
  36028797018963969.0 cannot be represented exactly as a float
  value. Instead, the float literal is represented as 
  36028797018963968.0, which is the closest number that can be
  represented exactly as a float value. See Representation of
  Floating Point Numbers for additional information.

  Allowed in guard tests.
