#### 12.1.4.2 Examples of Rule of Float and Rational Contagion ¶

     ;;;; Combining rationals with floats.
     ;;; This example assumes an implementation in which
     ;;; (float-radix 0.5) is 2 (as in IEEE) or 16 (as in IBM/360),
     ;;; or else some other implementation in which 1/2 has an exact
     ;;;  representation in floating point.
     (+ 1/2 0.5) ⇒  1.0
     (- 1/2 0.5d0) ⇒  0.0d0
     (+ 0.5 -0.5 1/2) ⇒  0.5

     ;;;; Comparing rationals with floats.
     ;;; This example assumes an implementation in which the default float
     ;;; format is IEEE single-float, IEEE double-float, or some other format
     ;;; in which 5/7 is rounded upwards by FLOAT.
     (< 5/7 (float 5/7)) ⇒  true
     (< 5/7 (rational (float 5/7))) ⇒  true
     (< (float 5/7) (float 5/7)) ⇒  false