SVG.hs

data XMLItem = XMLElem String [(String, String)] [XMLItem]
             | Text String

attrsShow as = concat [" " ++ k ++ "=\"" ++ v ++ "\"" | (k, v) <- as]

instance Show XMLItem where
    show (Text s) = s
    show (XMLElem tag as []) = "<" ++ tag ++ attrsShow as ++ " />"
    show (XMLElem tag as cs) = "<" ++ tag ++ attrsShow as ++ ">" ++
                               concatMap show cs ++
                               "</" ++ tag ++ ">"

arrowHead = XMLElem "defs" [] [
             XMLElem "marker" [("id","Triangle"),
                               ("viewBox","0 0 10 10"),
                               ("refX","0"),
                               ("refX","5"),
                               ("markerUnits","strokeWidth"),
                               ("markerWidth","4"),
                               ("markerHeight","3"),
                               ("orient","auto")] [
                          XMLElem "path" [("d", "M 0 0 L 10 5 L 0 10 z")] []
                         ]
            ]