求对数

下面是求以 1.12 为底，2.7 的对数。本方法极其低效，仅仅标记一下以备以后参考。

(ns t
  (:require [clojure.contrib.generic.math-functions :as math]))

(defn abs [x]
  (if (< x 0) (* -1 x) x))

(defn close-enough? [delta]
  #(< (abs (- %1 %2)) delta))

(defn calc-log [lg lg-level acc-stack]
  (let [acc (math/pow 1.12 lg)
        close? (close-enough? 0.00000000000000000001M)
        lg-inc (/ 1 (math/pow 10 lg-level))
        finer-lg-inc (/ 1 (math/pow 10 (inc lg-level)))]
    (if (close? acc 2.7)
      lg
      (if (> acc 2.7)
        (recur (+ (- lg lg-inc) finer-lg-inc) (inc lg-level) acc-stack)
        (recur (+ lg lg-inc) lg-level (conj acc-stack acc))))))

(println (calc-log 1 0 []))