From fbab5f7a7a5e7eab10b40847bdd8aa6283f2f4ef Mon Sep 17 00:00:00 2001 From: Dimitri Sokolyuk Date: Fri, 17 Jun 2016 16:30:56 +0200 Subject: Roman numerals --- roman.go | 25 +++++++++++++++++++++++++ roman_test.go | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 57 insertions(+) create mode 100644 roman.go create mode 100644 roman_test.go diff --git a/roman.go b/roman.go new file mode 100644 index 0000000..8b99242 --- /dev/null +++ b/roman.go @@ -0,0 +1,25 @@ +package roman + +// https://www.rosettacode.org/wiki/Roman_numerals/Encode#Go + +var ( + m0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"} + m1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"} + m2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"} + m3 = []string{"", "M", "MM", "MMM", "I̅V̅", "V̅", "V̅I̅", "V̅I̅I̅", "V̅I̅I̅I̅", "I̅X̅"} + m4 = []string{"", "X̅", "X̅X̅", "X̅X̅X̅", "X̅L̅", "L̅", "L̅X̅", "L̅X̅X̅", "L̅X̅X̅X̅", "X̅C̅"} + m5 = []string{"", "C̅", "C̅C̅", "C̅C̅C̅", "C̅D̅", "D̅", "D̅C̅", "D̅C̅C̅", "D̅C̅C̅C̅", "C̅M̅"} + m6 = []string{"", "M̅", "M̅M̅", "M̅M̅M̅"} +) + +type Roman int + +func (n Roman) String() string { + if n < 1 || n >= 4e6 { + return "" + } + // this is efficient in Go. the seven operands are evaluated, + // then a single allocation is made of the exact size needed for the result. + return m6[n/1e6] + m5[n%1e6/1e5] + m4[n%1e5/1e4] + m3[n%1e4/1e3] + + m2[n%1e3/1e2] + m1[n%100/10] + m0[n%10] +} diff --git a/roman_test.go b/roman_test.go new file mode 100644 index 0000000..081460f --- /dev/null +++ b/roman_test.go @@ -0,0 +1,32 @@ +package roman + +import "fmt" + +func ExampleRoman() { + for i := 0; i <= 21; i++ { + fmt.Println(Roman(1 << uint(i))) + } + // Output: + // I + // II + // IV + // VIII + // XVI + // XXXII + // LXIV + // CXXVIII + // CCLVI + // DXII + // MXXIV + // MMXLVIII + // I̅V̅XCVI + // V̅I̅I̅I̅CXCII + // X̅V̅I̅CCCLXXXIV + // X̅X̅X̅MMDCCLXVIII + // L̅X̅V̅DXXXVI + // C̅X̅X̅X̅MLXXII + // C̅C̅L̅X̅MMCXLIV + // D̅X̅X̅I̅V̅CCLXXXVIII + // M̅X̅L̅V̅I̅I̅I̅DLXXVI + // M̅M̅X̅C̅V̅I̅I̅CLII +} -- cgit v1.2.3