<=>

        # Float.<=>

(from ruby core)
---
    self <=> other ->  -1, 0, +1, or nil

---

Returns a value that depends on the numeric relation between `self` and
`other`:

*   -1, if `self` is less than `other`.
*   0, if `self` is equal to `other`.
*   1, if `self` is greater than `other`.
*   `nil`, if the two values are incommensurate.


Examples:

    2.0 <=> 2              # => 0
    2.0 <=> 2.0            # => 0
    2.0 <=> Rational(2, 1) # => 0
    2.0 <=> Complex(2, 0)  # => 0
    2.0 <=> 1.9            # => 1
    2.0 <=> 2.1            # => -1
    2.0 <=> 'foo'          # => nil

This is the basis for the tests in the Comparable module.

`Float::NAN <=> Float::NAN` returns an implementation-dependent value.