Data commit

Task/SEDOLs/Mercury/sedols.mercury

@@ -0,0 +1,53 @@
+:- module sedol.
+:- interface.
+
+:- import_module io.
+:- pred main(io::di, io::uo) is det.
+
+:- implementation.
+:- import_module char, int, list, require, string.
+
+main(!IO) :-
+    Input = [
+        "710889",
+        "B0YBKJ",
+        "406566",
+        "B0YBLH",
+        "228276",
+        "B0YBKL",
+        "557910",
+        "B0YBKR",
+        "585284",
+        "B0YBKT",
+        "B00030"
+     ],
+     list.foldl(print_with_checksum, Input, !IO).
+
+:- pred print_with_checksum(string::in, io::di, io::uo) is det.
+
+print_with_checksum(S, !IO) :-
+   io.format("%s%d\n", [s(S), i(sedol_checksum(S))], !IO).
+
+:- func sedol_checksum(string) = int.
+
+sedol_checksum(Sedol) = CheckSum :-
+   Digits = string.foldr((func(C, A) = [to_sedol_code(C) | A]), Sedol, []),
+   WeightedDigits = list.map_corresponding(int.times, Digits, [1, 3, 1, 7, 3, 9]),
+   WeightedSum = list.foldl(int.plus, WeightedDigits, 0),
+   CheckSum = (10 - (WeightedSum mod 10)) mod 10.
+
+:- func to_sedol_code(char) = int.
+
+to_sedol_code(Char) =
+    ( if char.digit_to_int(Char, Code), not is_vowel(to_upper(Char))
+    then Code
+    else func_error("invalid SEDOL")
+    ).
+
+:- pred is_vowel(char::in) is semidet.
+
+is_vowel('A').
+is_vowel('E').
+is_vowel('I').
+is_vowel('O').
+is_vowel('U').