blob: f4a793bcd140411cc26e579ff5a9e79c4a9b3786 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
|
module Fractran.Parser (
FractranProgram(..),
parseFractran
) where
import Control.Applicative( some )
import Text.ParserCombinators.Parsec
data FractranProgram = FractranProgram { fractions :: [(Int,Int)]
, initialValue :: Int }
deriving (Show)
parseFractran :: String -> Either ParseError FractranProgram
parseFractran = parse fractran "error"
fractran = do
value <- initVal
fractionList <- many intPair
whiteSpace
eof
return (FractranProgram fractionList value)
intPair = do
whiteSpace
numerator <- wholeNumber
slash
denominator <- positiveNumber
return (numerator,denominator)
slash = char '/'
initVal = do
whiteSpace
value <- wholeNumber
return value
wholeNumber = do
value <- some digit
return (read value)
positiveNumber = do
firstDigit <- nonZeroDigit
rest <- many digit
return (read (firstDigit:rest))
nonZeroDigit = oneOf "123456789"
whiteSpace = many (oneOf "\t\n\r ")
|