project-euler: Rewrap, update links, add copyrights, tests

[factor.git] / extra / project-euler / 063 / 063.factor

diff --git a/extra/project-euler/063/063.factor b/extra/project-euler/063/063.factor
index 2bca4467b2e02b8daca3050657d749f5c502779e..a64c4d428bcb7206ace244a1708f3d8af1d90861 100644 (file)
--- a/extra/project-euler/063/063.factor
+++ b/extra/project-euler/063/063.factor
@@ -1,32 +1,37 @@
 ! Copyright (c) 2009 Aaron Schaefer.
 ! See https://factorcode.org/license.txt for BSD license.
-USING: kernel math math.functions ranges project-euler.common sequences ;
+USING: kernel math math.functions ranges project-euler.common
+sequences ;
 IN: project-euler.063
 
-! https://projecteuler.net/index.php?section=problems&id=63
+! https://projecteuler.net/problem=63
 
 ! DESCRIPTION
 ! -----------
 
-! The 5-digit number, 16807 = 7^5, is also a fifth power. Similarly, the
-! 9-digit number, 134217728 = 8^9, is a ninth power.
+! The 5-digit number, 16807 = 7^5, is also a fifth power.
+! Similarly, the 9-digit number, 134217728 = 8^9, is a ninth
+! power.
 
-! How many n-digit positive integers exist which are also an nth power?
+! How many n-digit positive integers exist which are also an nth
+! power?
 
 
 ! SOLUTION
 ! --------
 
-! Only have to check from 1 to 9 because 10^n already has too many digits.
-! In general, x^n has n digits when:
+! Only have to check from 1 to 9 because 10^n already has too
+! many digits. In general, x^n has n digits when:
 
 !     10^(n-1) <= x^n < 10^n
 
-! ...take the left side of that equation, solve for n to see where they meet:
+! ...take the left side of that equation, solve for n to see
+! where they meet:
 
 !     n = log(10) / [ log(10) - log(x) ]
 
-! Round down since we already know that particular value of n is no good.
+! Round down since we already know that particular value of n is
+! no good.
 
 : euler063 ( -- answer )
     9 [1..b] [ log [ 10 log dup ] dip - /i ] map-sum ;