%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[PrelInfo]{The @PrelInfo@ interface to the compiler's prelude knowledge}

\begin{code}
{-# LANGUAGE CPP #-}
module PrelInfo (
        wiredInIds, ghcPrimIds,
        primOpRules, builtinRules,

        ghcPrimExports,
        wiredInThings, basicKnownKeyNames,
        primOpId,

        -- Random other things
        maybeCharLikeCon, maybeIntLikeCon,

        -- Class categories
        isNumericClass, isStandardClass

    ) where

#include "HsVersions.h"

import PrelNames
import PrelRules
import Avail
import PrimOp
import DataCon
import Id
import MkId
import TysPrim
import TysWiredIn
import HscTypes
import Class
import TyCon
import Util
import {-# SOURCE #-} TcTypeNats ( typeNatTyCons )

import Data.Array
\end{code}

%************************************************************************
%*                                                                      *
\subsection[builtinNameInfo]{Lookup built-in names}
%*                                                                      *
%************************************************************************

Notes about wired in things
~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Wired-in things are Ids\/TyCons that are completely known to the compiler.
  They are global values in GHC, (e.g.  listTyCon :: TyCon).

* A wired in Name contains the thing itself inside the Name:
        see Name.wiredInNameTyThing_maybe
  (E.g. listTyConName contains listTyCon.

* The name cache is initialised with (the names of) all wired-in things

* The type checker sees if the Name is wired in before looking up
  the name in the type environment.  So the type envt itself contains
  no wired in things.

* MkIface prunes out wired-in things before putting them in an interface file.
  So interface files never contain wired-in things.


\begin{code}
wiredInThings :: [TyThing]
-- This list is used only to initialise HscMain.knownKeyNames
-- to ensure that when you say "Prelude.map" in your source code, you
-- get a Name with the correct known key (See Note [Known-key names])
wiredInThings
  = concat
    [           -- Wired in TyCons and their implicit Ids
          tycon_things
        , concatMap implicitTyThings tycon_things

                -- Wired in Ids
        , map AnId wiredInIds

                -- PrimOps
        , map (AnId . primOpId) allThePrimOps
    ]
  where
    tycon_things = map ATyCon ([funTyCon] ++ primTyCons ++ wiredInTyCons
                                    ++ typeNatTyCons)
\end{code}

We let a lot of "non-standard" values be visible, so that we can make
sense of them in interface pragmas. It's cool, though they all have
"non-standard" names, so they won't get past the parser in user code.

%************************************************************************
%*                                                                      *
                PrimOpIds
%*                                                                      *
%************************************************************************

\begin{code}
primOpIds :: Array Int Id
-- A cache of the PrimOp Ids, indexed by PrimOp tag
primOpIds = array (1,maxPrimOpTag) [ (primOpTag op, mkPrimOpId op)
                                   | op <- allThePrimOps ]

primOpId :: PrimOp -> Id
primOpId op = primOpIds ! primOpTag op
\end{code}


%************************************************************************
%*                                                                      *
\subsection{Export lists for pseudo-modules (GHC.Prim)}
%*                                                                      *
%************************************************************************

GHC.Prim "exports" all the primops and primitive types, some
wired-in Ids.

\begin{code}
ghcPrimExports :: [IfaceExport]
ghcPrimExports
 = map (Avail . idName) ghcPrimIds ++
   map (Avail . idName . primOpId) allThePrimOps ++
   [ AvailTC n [n]
   | tc <- funTyCon : primTyCons, let n = tyConName tc  ]
\end{code}



%************************************************************************
%*                                                                      *
\subsection{Built-in keys}
%*                                                                      *
%************************************************************************

ToDo: make it do the ``like'' part properly (as in 0.26 and before).

\begin{code}
maybeCharLikeCon, maybeIntLikeCon :: DataCon -> Bool
maybeCharLikeCon con = con `hasKey` charDataConKey
maybeIntLikeCon  con = con `hasKey` intDataConKey
\end{code}


%************************************************************************
%*                                                                      *
\subsection{Class predicates}
%*                                                                      *
%************************************************************************

\begin{code}
isNumericClass, isStandardClass :: Class -> Bool

isNumericClass     clas = classKey clas `is_elem` numericClassKeys
isStandardClass    clas = classKey clas `is_elem` standardClassKeys

is_elem :: Eq a => a -> [a] -> Bool
is_elem = isIn "is_X_Class"
\end{code}