(var K->C (+ -273.15))
(var K->R (* 1.8))
(var K->F (comp K->R (+ -459.67)))

(function kelvin-conversions K
  (let [C R F] ((juxt K->C K->R K->F) K)
       [C R F] (map @(round 2) [C R F]))
  (print "{K} K / {C} °C / {R} °R / {F} °F"))

(kelvin-conversions 21.0)
;prints "21 K / -252.15 °C / 37.8 °R / -421.87 °F"