/-
Copyright (c) 2020 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Author: Leonardo de Moura
-/
prelude
import Init.Control.Except
import Init.Data.ByteArray
import Init.Util

namespace String

def toNat! (s : String) : Nat :=
  if s.isNat then
    s.foldl (fun n c => n*10 + (c.toNat - '0'.toNat)) 0
  else
    panic! "Nat expected"

/--
  Convert a UTF-8 encoded `ByteArray` string to `String`.
  The result is unspecified if `a` is not properly UTF-8 encoded. -/
@[extern "lean_string_from_utf8_unchecked"]
constant fromUTF8Unchecked (a : @& ByteArray) : String

@[extern "lean_string_to_utf8"]
constant toUTF8 (a : @& String) : ByteArray

end String