tasks a-s

Task/Roman-numerals-Decode/CoffeeScript/roman-numerals-decode.coffeescript

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+roman_to_demical = (s) ->
+  # s is well-formed Roman Numeral >= I
+  numbers =
+    M: 1000
+    D: 500
+    C: 100
+    L: 50
+    X: 10
+    V: 5
+    I: 1
+
+  result = 0
+  for c in s
+    num = numbers[c]
+    result += num
+    if old_num < num
+      # If old_num exists and is less than num, then
+      # we need to subtract it twice, once because we
+      # have already added it on the last pass, and twice
+      # to conform to the Roman convention that XC = 90,
+      # not 110.
+      result -= 2 * old_num
+    old_num = num
+  result
+
+tests =
+  IV: 4
+  XLII: 42
+  MCMXC: 1990
+  MMVIII: 2008
+  MDCLXVI: 1666
+
+for roman, expected of tests
+  dec = roman_to_demical(roman)
+  console.log "error" if dec != expected
+  console.log "#{roman} = #{dec}"