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Ingy döt Net 2013-04-10 23:57:08 -07:00
parent 47bf37c096
commit b83f433714
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Task/Roman-numerals-Decode/Prolog/roman-numerals-decode.pro Normal file
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decode_digit(i, 1).
decode_digit(v, 5).
decode_digit(x, 10).
decode_digit(l, 50).
decode_digit(c, 100).
decode_digit(d, 500).
decode_digit(m, 1000).
decode_string(Sum, _, [], Sum).
decode_string(LastSum, LastValue, [Digit|Rest], NextSum) :-
decode_digit(Digit, Value),
Value < LastValue,
Sum is LastSum - Value,
decode_string(Sum, Value, Rest, NextSum).
decode_string(LastSum, LastValue, [Digit|Rest], NextSum) :-
decode_digit(Digit, Value),
Value >= LastValue,
Sum is LastSum + Value,
decode_string(Sum, Value, Rest, NextSum).
decode_string(Atom, Value) :-
atom_chars(Atom, String),
reverse(String, [Last|Rest]),
decode_digit(Last, Start),
decode_string(Start, Start, Rest, Value).
test :-
decode_string(mcmxc, 1990),
decode_string(mmviii, 2008),
decode_string(mdclxvi, 1666).