module EnvSimple(Env, empty_env, lookup_variable, maybe_lookup_variable, bind_variable,
  variable_table, merge_declarations) where

import qualified Table

type Symbol = String

data Env val = Env (Table.T Symbol val)

instance Eq val => Eq(Env val) where
  (Env t1) == (Env t2) = t1 == t2

empty_env :: Env val
empty_env = Env Table.empty

lookup_variable :: Env val -> Symbol -> val
lookup_variable (Env t) name = Table.lookup t name

maybe_lookup_variable :: Env val -> Symbol -> Maybe val
maybe_lookup_variable (Env t) name = Table.maybe_lookup t name

bind_variable :: Env val -> Symbol -> val -> Env val
bind_variable (Env t) name loc = Env (Table.bind t name loc)

variable_table :: Env val -> Table.T Symbol val
variable_table (Env t) = t

merge_declarations :: Env val -> Table.T Symbol val -> Env val
merge_declarations (Env t) decls = Env (Table.merge t decls)