Telwoorden.hs

module Language.Dutch.Telwoorden where

telwoord :: Integer -> String
telwoord 0 = "nul"
telwoord 1 = "een"
telwoord 2 = "twee"
telwoord 3 = "drie"
telwoord 4 = "vier"
telwoord 5 = "vijf"
telwoord 6 = "zes"
telwoord 7 = "zeven"
telwoord 8 = "acht"
telwoord 9 = "negen"
telwoord 10 = "tien"
telwoord 11 = "elf"
telwoord 12 = "twaalf"
telwoord 13 = "dertien"
telwoord 14 = "veertien"
telwoord n | n < 20 = concat [ telwoord (n `mod` 10), "tien" ]

telwoord n | n < 100 = decade (n `div` 10) (n `mod` 10)
    where
        decade d 0 = concat [ prefix d, "tig" ]
            where
                prefix 2 = "twin"
                prefix 3 = "der"
                prefix 4 = "veer"
                prefix 8 = "tach"
                prefix n = telwoord n

        decade d r = concat [ telwoord r, "en", decade d 0 ]

telwoord n | n < 1000 = hundred (n `div` 100) (n `mod` 100)
    where
        hundred 1 0 = "honderd"
        hundred h 0 = concat [ telwoord h, "honderd" ]
        hundred h r = concat [ hundred h 0, telwoord r ]

telwoord n | n < 10000 = thousand (n `div` 1000) (n `div` 100 `mod` 10) (n `mod` 100)
    where
        -- t h d r  -- thousands, hundreds, rest
        thousand 1 0 0 = "duizend"
        thousand t 0 0 = concat [ telwoord t, "duizend" ]

        -- 2500 -> "vijventwintighonderd"
        thousand t h 0 | t < 10 = concat [ telwoord (h + t * 10), "honderd" ]

        -- 3001 -> "drieduizend-een"
        thousand t d r | r < 10 = concat [ thousand t 0 0, "-", telwoord r]

        thousand t h r = concat [ thousand t h 0 , "-", telwoord r ]

telwoord n = show n