
  -spec float(Number) -> float() when Number :: number().

  Returns a float by converting Number to a float, for example:

    > float(55).
    55.0

  Allowed in guard tests.

  Note:
    If used on the top level in a guard, it tests whether the
    argument is a floating point number; for clarity, use 
    is_float/1 instead.

    When float/1 is used in an expression in a guard, such as '
    float(A) == 4.0', it converts a number as described earlier.
