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Task/Arithmetic-Rational/EchoLisp/arithmetic-rational-1.echolisp

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+;; Finding perfect numbers
+(define (sum/inv n) ;; look for div's in [2..sqrt(n)] and add 1/n
+	(for/fold (acc (/ n)) [(i (in-range 2 (sqrt n)))]
+		#:break (> acc 1) ; no hope
+		(when (zero? (modulo n i ))
+			(set! acc (+ acc (/ i) (/ i n))))))

Task/Arithmetic-Rational/EchoLisp/arithmetic-rational-2.echolisp

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+;; rational operations
+(+ 1/42 1/666) → 59/2331
+42/666 → 7/111
+(expt 3/4 7) → 2187/16384 ; 3/4 ^7
+(/ 6 8) → 3/4   ;; / operator → rational
+(// 6 8) → 0.75 ;; // operator → float
+(* 6/7 14/12) → 1
+
+;; even perfect numbers (up to 100000)
+(for [(i (in-range 4 100000 2))] ;; 8 seconds
+	(when (= (sum/inv i) 1)
+		(printf "🍏 🍒 🍓 %d is perfect." i)))
+
+🍏 🍒 🍓 6 is perfect.
+🍏 🍒 🍓 28 is perfect.
+🍏 🍒 🍓 496 is perfect.
+🍏 🍒 🍓 8128 is perfect.