--
--
-- String
--
--

def string :=
  matcher
    | regexCg #$regexpr $ $ $ as (string, list string, string) with
      | $tgt -> regexCg regexpr tgt
    | regex #$regexpr $ $ $ as (string, string, string) with
      | $tgt -> regex regexpr tgt
    | [] as () with
      | $tgt -> if "" = tgt then [()] else []
    | $ :: $ as (char, string) with
      | $tgt -> if "" = tgt then [] else [unconsString tgt]
    | $ ++ #$px :: $ as (string, string) with
      | $tgt ->
        matchAll S.split (pack [px]) tgt as list string with
          | (![] & $xs) ++ ![] & $ys ->
            (S.intercalate (pack [px]) xs, S.intercalate (pack [px]) ys)
    | $ ++ #$pxs ++ $ as (string, string) with
      | $tgt ->
        matchAll S.split pxs tgt as list string with
          | (![] & $xs) ++ ![] & $ys ->
            (S.intercalate pxs xs, S.intercalate pxs ys)
    | $ ++ $ as (string, string) with
      | $tgt ->
        matchAll tgt as string with
          | loop $i (1, $n)
              ($xa_i :: ...)
              $rs -> (pack (map (\i -> xa_i) (between 1 n)), rs)
    | #$val as () with
      | $tgt -> if val = tgt then [()] else []
    | $ as (something) with
      | $tgt -> [tgt]

--
-- String as collection
--
def S.isEmpty xs := xs = ""

def S.cons x xs := appendString (pack [x]) xs

def S.head xs :=
  match xs as string with
    | $x :: _ -> x

def S.tail xs :=
  match xs as string with
    | _ :: $r -> r

def S.last str :=
  match str as string with
    | _ ++ [$c] -> c

def S.map f xs := pack (map f (unpack xs))

def S.length := lengthString
def S.split  := splitString
def S.append := appendString

def S.concat xss := foldr (\xs rs -> S.append xs rs) "" xss

def S.intercalate sep ss := S.concat (intersperse sep ss)

def S.replace before after str := S.intercalate after (S.split before str)

--
-- Alphabet
--
def C.between c1 c2 := map itoc (between (ctoi c1) (ctoi c2))

def C.isBetween c1 c2 c := ctoi c >= ctoi c1 && ctoi c <= ctoi c2

def isAlphabet c := C.isBetween 'a' 'z' c || C.isBetween 'A' 'Z' c

def isAlphabetString s := all isAlphabet (unpack s)

def upperCase c := if C.isBetween 'a' 'z' c then itoc (ctoi c - 32) else c

def lowerCase c := if C.isBetween 'A' 'Z' c then itoc (ctoi c + 32) else c