Add exercise: roman-numerals (JuliaLang#29)

* Add exercise: roman-numerals

* Fix config.json add missing comma

* Fix roman-numerals example

* Fix roman-numerals test sets as suggested

* Fix roman-numerals test set cycle as suggested

* Remove hint from roman-numerals example

* Fix roman-numerals test set

Added more samples, added negative number test

config.json

@@ -75,6 +75,15 @@
         "strings"
       ]
     },
+    {
+        "slug": "roman-numerals",
+        "difficulty": 1,
+        "topics": [
+          "control-flow (loops)",
+          "strings",
+          "mathematics"
+        ]
+    },
     {
       "slug": "anagram",
       "difficulty": 2,

exercises/roman-numerals/example.jl

@@ -0,0 +1,21 @@
+# Aliases: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000.
+function to_roman(number::Integer)
+    number < 1 && error("Invalid number")
+    alias = [
+        ["I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"],
+        ["X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"],
+        ["C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"],
+        ["M", "MM", "MMM"],
+    ]
+    i = 1
+    result = []
+    while number > 0
+        j = rem(number, 10)
+        if j > 0
+            push!(result, alias[i][j])
+        end
+        i += 1
+        number = div(number, 10)
+    end
+    join(reverse(result))
+end

exercises/roman-numerals/roman-numerals.jl

@@ -0,0 +1,3 @@
+function to_roman(number::Integer)
+
+end

exercises/roman-numerals/runtests.jl

@@ -0,0 +1,37 @@
+using Base.Test
+
+include("roman-numerals.jl")
+
+# HINT: There is no need to be able to convert numbers larger than about 3000.
+samples = Dict(
+    1 => "I",
+    2 => "II",
+    3 => "III",
+    4 => "IV",
+    5 => "V",
+    6 => "VI",
+    9 => "IX",
+    27 => "XXVII",
+    48 => "XLVIII",
+    59 => "LIX",
+    93 => "XCIII",
+    141 => "CXLI",
+    163 => "CLXIII",
+    402 => "CDII",
+    575 => "DLXXV",
+    911 => "CMXI",
+    1024 => "MXXIV",
+    1703 => "MDCCIII",
+    1991 => "MCMXCI",
+    2017 => "MMXVII",
+    3000 => "MMM"
+)
+
+@testset "convert $sample[1] to roman numeral" for sample in samples
+    @test to_roman(sample[1]) == sample[2]
+end
+
+@testset "error handling" begin
+    @test_throws ErrorException to_roman(0)
+    @test_throws ErrorException to_roman(-2017)
+end