Fix logic of updating output

[MityaDementiy]

Hi, @kendru! I have noticed logical issue while working with Section 4 code, Writing pure functions section. Now I see there this code:

(defn target-label-for-input-unit [unit]
  (case unit
    :fahrenheit "F"
    :celsius "C"))

(defn convert [unit temp] 
  (if (= :celsius unit)
    (c->f temp)
    (f->c temp)))

(defn update-output [_]  
  (let [unit (get-input-unit)
        input-temp (get-input-temp)
        output-temp (convert unit input-temp)
        output-label (target-label-for-input-unit unit)]
    (set-output-temp output-temp)
    (gdom/setTextContent output-unit-target output-label)))

When I run this code, I get C output label when use Celsius input and F when use Fahrenheit input. But I expect to see F output label when using Celsius input. I assume code should be fixed that way:

(defn target-label-for-output-unit [unit]
  (case unit
    :fahrenheit "C"
    :celsius "F"))

(defn convert [unit temp]
  (if (= unit :celsius)
    (c->f temp)
    (f->c temp)))

(defn update-output [_]
  (let [unit (get-input-unit)
        input-temp (get-input-temp)
        output-temp (convert unit input-temp)
        output-label (target-label-for-output-unit unit)]
    (set-output-temp output-temp)
    (gdom/setTextContent output-unit-target output-label)))

Thank you for your tremendous work on this book!