regex.curry

-- Maps input string to leftover string
type Reg = String -> String

-- Literal match
lit :: String -> Reg
lit s (s ++ s') = s'

-- Optional; regex EXPR?
opt :: Reg -> Reg
opt r s = s ? r s

-- Plus; regex EXPR+
plus :: Reg -> Reg
plus r s
    | s /= "" = r s ? plus r (r s)

-- Star; regex EXPR*
star :: Reg -> Reg
star r s = opt (plus r) s

-- Adjacency; regex EXPR0 EXPR1
(%&) :: Reg -> Reg -> Reg
(%&) r0 r1 s = r1 (r0 s)

-- Choice; regex EXPR0 | EXPR1
(%|) :: Reg -> Reg -> Reg
(%|) r0 r1 s = r0 s ? r1 s

-- Define the javascript-function-decl-ish syntax:
-- function\((NAME(,NAME)*)?\)

-- regex [abcdefghijklmnopqrstuvwxyz1234567890]
alph :: Reg
alph = foldl (%|) (lit "a") $ map (lit.(:[])) "abcdefghijklmnopqrstuvwxyz1234567890"

name :: Reg
name = plus alph

-- whitespace
ws :: Reg
ws = star (lit " " %| lit "\n")
-- matches javascript function declarartion-type strings
jsfdecl :: Reg
jsfdecl =
  lit "function(" %& ws %& opt (name %& star (lit "," %& ws %& name)) %& lit ")"