3629dbe4d8ff

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author Steve Losh <steve@stevelosh.com>
date Mon, 25 Sep 2017 20:14:29 -0400
parents c81a4bca6e78
children 072186c1d12e
branches/tags (none)
files src/problems.lisp

Changes

diff -r c81a4bca6e78 -r 3629dbe4d8ff src/problems.lisp
--- a/src/problems.lisp	Mon Sep 25 20:11:11 2017 -0400
+++ b/src/problems.lisp	Mon Sep 25 20:14:29 2017 -0400
@@ -1718,6 +1718,13 @@
   ;; given above.
   (iterate
     (for line-number :from 1)
+    ;; Lisp can compute the exponents, but it takes a really long time.  We can
+    ;; avoid having to compute the full values using:
+    ;;
+    ;;   log(base^expt) = expt * log(base)
+    ;;
+    ;; Taking the log of each number preserves their ordering, so we can compare
+    ;; the results and still be correct.
     (for (base exponent) :in-csv-file "data/099-exponents.txt"
          :key #'parse-integer)
     (finding line-number :maximizing (* exponent (log base)))))