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authorDimitri Sokolyuk <demon@dim13.org>2016-06-17 16:30:56 +0200
committerDimitri Sokolyuk <demon@dim13.org>2016-06-17 16:30:56 +0200
commitfbab5f7a7a5e7eab10b40847bdd8aa6283f2f4ef (patch)
treebbafbfc3a3a21844865c759a0bcd5a830249838d
Roman numerals
-rw-r--r--roman.go25
-rw-r--r--roman_test.go32
2 files changed, 57 insertions, 0 deletions
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
+}