053string.wart

defcall string (s idx ... ends)
  withs (idx (range_start idx len.s)
         end (if no.ends
                   (idx + 1)
                 ~car.ends
                   len.s
                 :else
                   (range_bounce car.ends len.s)))
    (string_range s idx end)

defset string ((s idx ... ends) val)
  `(withs ($idx (range_start ,idx (len ,s))
           $end ,(if no.ends
                   `($idx + 1)
                   `(if (not ,car.ends)
                      (len ,s)
                      (range_bounce ,car.ends (len ,s)))))
      (string_splice ,s $idx $end (or ,val "")))

defcoerce string symbol
  string_to_sym

def (string ... args)
  making stdout (outstring)
    each arg args
      if arg
        pr.arg
    outstring_buffer.stdout

defcoerce symbol string
  string

def (join head ... tail) :case (or string?.head sym?.head)
  (string head @tail)

def (+ head ... tail) :case (or string?.head sym?.head)
  (string head @tail)

def (pos fragment str n) :case string?.str
  default n :to 0
  if (len.str - n >= len.fragment)
    if (fragment = (str n (n + len.fragment)))
      n
      (pos fragment str n+1)

def (empty? s) :case string?.s
  (s = "")

defcoerce string list
  string_to_list

defcoerce list string
  (fn(_)
    (string @_))

def (rev s) :case string?.s
  (as string (rev (as list s)))

defcoerce nil string
  (fn() "")

def (< a b ... rest) :case (and string?.a no.rest)
  (string_lesser a b)

def (digit? c)
  (and string?.c
       (len.c = 1)
       ("0" <= c <= "9"))

def (letter? c)
  (and string?.c
       (len.c = 1)
       (or ("A" <= c <= "Z")
           ("a" <= c <= "z")))