ERROR: roman-range-error n ;
: roman-range-check ( n -- n )
- dup 1 3999 between? [ roman-range-error ] unless ;
+ dup 1 10000 between? [ roman-range-error ] unless ;
: roman-digit-index ( ch -- n )
1string roman-digits index ; inline
--- /dev/null
+! Copyright (c) 2009 Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
+USING: io.encodings.ascii io.files kernel math
+project-euler.common roman sequences ;
+IN: project-euler.089
+
+! http://projecteuler.net/index.php?section=problems&id=089
+
+! DESCRIPTION
+! -----------
+
+! The rules for writing Roman numerals allow for many ways of writing
+! each number (see FAQ: Roman Numerals). However, there is always a
+! "best" way of writing a particular number.
+
+! For example, the following represent all of the legitimate ways of
+! writing the number sixteen:
+
+! IIIIIIIIIIIIIIII
+! VIIIIIIIIIII
+! VVIIIIII
+! XIIIIII
+! VVVI
+! XVI
+
+! The last example being considered the most efficient, as it uses
+! the least number of numerals.
+
+! The 11K text file, roman.txt (right click and 'Save Link/Target As...'),
+! contains one thousand numbers written in valid, but not necessarily
+! minimal, Roman numerals; that is, they are arranged in descending units
+! and obey the subtractive pair rule (see FAQ for the definitive rules
+! for this problem).
+
+! Find the number of characters saved by writing each of these in their minimal form.
+
+! SOLUTION
+! --------
+
+: euler089 ( -- n )
+ "resource:extra/project-euler/089/roman.txt" ascii file-lines
+ [ ] [ [ roman> >roman ] map ] bi
+ [ [ length ] map-sum ] bi@ - ;
+
+! [ euler089 ] 100 ave-time
+! 14 ms ave run time - 0.27 SD (100 trials)
+
+SOLUTION: euler089