Data commit

Task/Roman-numerals-Decode/Python/roman-numerals-decode-1.py

@@ -0,0 +1,12 @@
+_rdecode = dict(zip('MDCLXVI', (1000, 500, 100, 50, 10, 5, 1)))
+
+def decode( roman ):
+    result = 0
+    for r, r1 in zip(roman, roman[1:]):
+        rd, rd1 = _rdecode[r], _rdecode[r1]
+        result += -rd if rd < rd1 else rd
+    return result + _rdecode[roman[-1]]
+
+if __name__ == '__main__':
+    for r in 'MCMXC MMVIII MDCLXVI'.split():
+        print( r, decode(r) )

Task/Roman-numerals-Decode/Python/roman-numerals-decode-2.py

@@ -0,0 +1,14 @@
+roman_values = (('I',1), ('IV',4), ('V',5), ('IX',9),('X',10),('XL',40),('L',50),('XC',90),('C',100),
+                    ('CD', 400), ('D', 500), ('CM', 900), ('M',1000))
+
+def roman_value(roman):
+    total=0
+    for symbol,value in reversed(roman_values):
+        while roman.startswith(symbol):
+            total += value
+            roman = roman[len(symbol):]
+    return total
+
+if __name__=='__main__':
+    for value in "MCMXC", "MMVIII", "MDCLXVI":
+        print('%s = %i' % (value, roman_value(value)))

Task/Roman-numerals-Decode/Python/roman-numerals-decode-3.py

@@ -0,0 +1,3 @@
+numerals = { 'M' : 1000, 'D' : 500, 'C' : 100, 'L' : 50, 'X' : 10, 'V' : 5, 'I' : 1 }
+def romannumeral2number(s):
+        return reduce(lambda x, y: -x + y if x < y else x + y, map(lambda x: numerals.get(x, 0), s.upper()))

Task/Roman-numerals-Decode/Python/roman-numerals-decode-4.py

@@ -0,0 +1,111 @@
+'''Roman numerals decoded'''
+
+from operator import mul
+from functools import reduce
+from collections import defaultdict
+from itertools import accumulate, chain, cycle
+
+
+# intFromRoman :: String -> Maybe Int
+def intFromRoman(s):
+    '''Just the integer represented by a Roman
+       numeral string, or Nothing if any
+       characters are unrecognised.
+    '''
+    dct = defaultdict(
+        lambda: None,
+        zip(
+            'IVXLCDM',
+            accumulate(chain([1], cycle([5, 2])), mul)
+        )
+    )
+
+    def go(mb, x):
+        '''Just a letter value added to or
+           subtracted from a total, or Nothing
+           if no letter value is defined.
+        '''
+        if None in (mb, x):
+            return None
+        else:
+            r, total = mb
+            return x, total + (-x if x < r else x)
+
+    return bindMay(reduce(
+        go,
+        [dct[k.upper()] for k in reversed(list(s))],
+        (0, 0)
+    ))(snd)
+
+
+# ------------------------- TEST -------------------------
+def main():
+    '''Testing a sample of dates.'''
+
+    print(
+        fTable(__doc__ + ':\n')(str)(
+            maybe('(Contains unknown character)')(str)
+        )(
+            intFromRoman
+        )([
+            "MDCLXVI", "MCMXC", "MMVIII",
+            "MMXVI", "MMXVIII", "MMZZIII"
+        ])
+    )
+
+
+# ----------------------- GENERIC ------------------------
+
+# bindMay (>>=) :: Maybe a -> (a -> Maybe b) -> Maybe b
+def bindMay(m):
+    '''Injection operator for the Maybe monad.
+       If m is Nothing, it is passed straight through.
+       If m is Just(x), the result is an application
+       of the (a -> Maybe b) function (mf) to x.'''
+    return lambda mf: (
+        m if None is m else mf(m)
+    )
+
+
+# maybe :: b -> (a -> b) -> Maybe a -> b
+def maybe(v):
+    '''Either the default value v, if m is Nothing,
+       or the application of f to x,
+       where m is Just(x).
+    '''
+    return lambda f: lambda m: v if None is m else (
+        f(m)
+    )
+
+
+# snd :: (a, b) -> b
+def snd(ab):
+    '''Second member of a pair.'''
+    return ab[1]
+
+
+# ---------------------- FORMATTING ----------------------
+
+# fTable :: String -> (a -> String) ->
+# (b -> String) -> (a -> b) -> [a] -> String
+def fTable(s):
+    '''Heading -> x display function ->
+       fx display function -> f -> xs -> tabular string.
+    '''
+    def go(xShow, fxShow, f, xs):
+        ys = [xShow(x) for x in xs]
+        w = max(map(len, ys))
+        return s + '\n' + '\n'.join(map(
+            lambda x, y: (
+                f'{y.rjust(w, " ")} -> {fxShow(f(x))}'
+            ),
+            xs, ys
+        ))
+    return lambda xShow: lambda fxShow: lambda f: (
+        lambda xs: go(xShow, fxShow, f, xs)
+    )
+
+
+# MAIN ---
+if __name__ == '__main__':
+    main()