module Base
(
    interpreter
)
where

import Isomorphism
import MonadF
import Package

-- Figure 4: The base interpreter prepackage

data TermZ  = Bogon
data ValueZ = Wrong

interpreter :: (MonadF mt, MonadF mv)
    => Prepackage TermZ ValueZ
                  (mt (FixF mt TermZ) TermZ) (mv (FixF mv ValueZ) ValueZ)
                  ve (FixF mt TermZ) (FixF mv ValueZ)

interpreter = Prepackage my_isom_t'' my_isom_v'' my_finalize
  where
    my_isom_t'' = wisom
    my_isom_v'' = wisom
    my_finalize realTop = Package { parser    = parseZ
                                  , interpr   = interpZ
                                  , complainr = complainZ
                                  , showvalr  = showvalZ
                                  , namer     = nameZ
                                  , makenumr  = error "undefined makenumr"
                                  , makefunr  = error "undefined makefunr"
                                  , applyr    = error "undefined applyr"
                                  }
      where
        top = lowerTop my_isom_t'' my_isom_v'' realTop

        parseZ s = [(unit Bogon, s)]

        interpZ Bogon _ = complainr top "invalid expression"

        complainZ s = unit Wrong

        showvalZ Wrong = "<wrong>"

        nameZ = "interpreter"