4Clojure 166

http://www.4clojure.com/problem/166

Comparisons

 

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Difficulty:	Elementary
Topics:

For any orderable data type it's possible to derive all of the basic comparison operations (<, ≤, =, ≠, ≥, and >) from a single operation (any operator but = or ≠ will work). Write a function that takes three arguments, a less than operator for the data and two items to compare. The function should return a keyword describing the relationship between the two items. The keywords for the relationship between x and y are as follows:

• x = y → :eq
• x > y → :gt
• x < y → :lt

	(= :gt (__ < 5 1))
	(= :eq (__ (fn [x y] (< (count x) (count y))) "pear" "plum"))
	(= :lt (__ (fn [x y] (< (mod x 5) (mod y 5))) 21 3))
	(= :gt (__ > 0 2))

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(fn [lt a b] 
    (cond (lt a b) :lt
          (lt b a) :gt
          :else :eq))