--         __________   __________   __________   __________   ________
--        /  _______/  /  ____   /  /  _______/  /  _______/  /  ____  \
--       /  / _____   /  /   /  /  /  /______   /  /______   /  /___/  /
--      /  / /_   /  /  /   /  /  /  _______/  /  _______/  /  __   __/
--     /  /___/  /  /  /___/  /  /  /         /  /______   /  /  \  \ 
--    /_________/  /_________/  /__/         /_________/  /__/    \__\
--
--    Functional programming environment, Version 2.21
--    Copyright Mark P Jones 1991.
--
--    Minimal Gofer prelude for experimentation with different approaches
--    to standard operations.
--
--    Any Gofer prelude file should typically include at least the following
--    definitions:

infixr 5 :
infixr 3 &&
infixr 2 ||

(&&), (||)     :: Bool -> Bool -> Bool
False && _      = False     -- (&&) and (||) names predefined in Gofer
True  && x      = x
False || x      = x
True  || _      = True

flip           :: (a -> b -> c) -> b -> a -> c
flip  f x y     =  f y x

error          :: String -> a
error s | False = error s

-- I/O functions and definitions:
-- This is the minimum required for bootstrapping and execution of
-- interactive programs.

data Request  =  -- file system requests:
                ReadFile      String         
              | WriteFile     String String
              | AppendFile    String String
                 -- channel system requests:
              | ReadChan      String 
              | AppendChan    String String
                 -- environment requests:
              | Echo          Bool

data Response = Success
              | Str String 
              | Failure IOError

data IOError  = WriteError   String
              | ReadError    String
              | SearchError  String
              | FormatError  String
              | OtherError   String

type Dialogue = [Response] -> [Request]