Interesting!
Based upon
http://mathforum.org/library/drmath/view/52343.html
mod might be modified to look like this
(defn mod1
"modulus of num and div."
[num div]
(cond
(or (not (integer? num)) (not (integer? div)))
(throw (IllegalArgumentException.
"mod requires two integers"))
(< num 0 div) (- (rem num div))
(< div 0 num) (rem num (- div))
:else (rem num div)))
user=> (map #(mod1 % 3) (range -9 9))
(0 2 1 0 2 1 0 2 1 0 1 2 0 1 2 0 1 2)
> [0, 1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 2, 0, 1, 2]
Notably that is still not the same as those other languages! However I
believe it is 'correct' due to Java and Clojure's definition of div.
Ruby and Python define integer division of or by a negative number
differently that C and Java do. Consider the quotient -7/3. Java gives
-2. Ruby gives -3.
Regards,
Tim.
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