Utils fix and test, add decode roman numbers

seminar/tests.py

@@ -11,6 +11,7 @@ from django.core.management import call_command
 from seminar.models import Skola, Resitel, Rocnik, Cislo, Problem, Reseni, PrilohaReseni, Soustredeni, Nastaveni
 from seminar.testutils import create_test_data
 from seminar import ovvpfile
+from seminar import utils
 
 class SeminarBasicTests(TestCase):
     def setUp(self):
@@ -72,4 +73,9 @@ class SeminarBasicTests(TestCase):
         t = o.to_string()
         assert t == filetext
 
+    def test_roman(self):
+        for i in [0, 1, 23, 2015, 1999, 42, 4, 400, 78, 4321, 8765, 999]:
+            r = utils.roman(i)
+            fr = utils.from_roman(r)
+            assert fr == i
 

seminar/utils.py

@@ -1,12 +1,20 @@
 # -*- coding: utf-8 -*-
 
+roman_numerals = zip((1000, 900,  500, 400, 100,  90, 50,  40, 10,  9,   5,  4,   1),
+                     ('M',  'CM', 'D', 'CD','C', 'XC','L','XL','X','IX','V','IV','I'))
+
 def roman(num):
-    ints = (1000, 900,  500, 400, 100,  90, 50,  40, 10,  9,   5,  4,   1)
-    nums = ('M',  'CM', 'D', 'CD','C', 'XC','L','XL','X','IX','V','IV','I')
     res = ""
-    for i, n in zip(ints, nums):
+    for i, n in roman_numerals:
         res += n * (num // i)
         num %= i
     return res
 
+def from_roman(rom):
+    if not rom:
+        return 0
+    for i, n in roman_numerals:
+        if rom.upper().startswith(n):
+            return i + from_roman(rom[len(n):])
+    raise Exception('Invalid roman numeral: "%s"', rom)