At least I believe so: it would allow client code to set the desired
precision once and then be able to invoke functions that take an
optional precision parameter (or none at all) without having to
specify precision every time.
For example:
(set! *default-precision* (. java.math.MathContext/DECIMAL128
getPrecision))
(defn harmonic-number
([]
((fn more [sum n] (let [new-sum (+ sum (with-precision *default-
precision* :rounding HALF_EVEN (/ 1 (bigdec n))))]
(lazy-seq (cons (bigdec new-sum) (more new-sum (inc n))))))
0 1))
([n] (harmonic-number n *default-precision*))
([n #^Integer precision]
(reduce + (map #(with-precision precision :rounding HALF_EVEN (/
1 (bigdec %))) (range 1 (inc n)))))
)
user=> (harmonic-number 5)
2.2833333333333333333333333333333333M
user=> (take 10 (harmonic-number))
(1M 1.5M 1.8333333333333333333333333333333333M
2.0833333333333333333333333333333333M
2.2833333333333333333333333333333333M
2.4500000000000000000000000000000000M
2.5928571428571428571428571428571429M
2.7178571428571428571428571428571429M
2.8289682539682539682539682539682540M
2.9289682539682539682539682539682540M)
Any thoughts? Is there another way to accomplish this that I have
overlooked?
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