ghc/compiler/basicTypes/BasicTypes.lhs

   1 %
   2 % (c) The GRASP/AQUA Project, Glasgow University, 1997-1998
   3 %
   4 \section[BasicTypes]{Miscellanous types}
   5
   6 This module defines a miscellaneously collection of very simple
   7 types that
   8
   9 \begin{itemize}
  10 \item have no other obvious home
  11 \item don't depend on any other complicated types
  12 \item are used in more than one "part" of the compiler
  13 \end{itemize}
  14
  15 \begin{code}
  16 module BasicTypes(
  17         Version, Arity,
  18         Unused, unused,
  19         Fixity(..), FixityDirection(..), StrictnessMark(..),
  20         NewOrData(..), TopLevelFlag(..), RecFlag(..)
  21    ) where
  22
  23 #include "HsVersions.h"
  24
  25 import {-# SOURCE #-} DataCon ( DataCon )
  26 import {-# SOURCE #-} Type    ( Type )
  27 import Outputable
  28 \end{code}
  29
  30 %************************************************************************
  31 %*                                                                      *
  32 \subsection[Unused]{Unused}
  33 %*                                                                      *
  34 %************************************************************************
  35
  36 Used as a placeholder in types.
  37
  38 \begin{code}
  39 type Unused = ()
  40
  41 unused :: Unused
  42 unused = error "Unused is used!"
  43 \end{code}
  44
  45
  46 %************************************************************************
  47 %*                                                                      *
  48 \subsection[Arity]{Arity}
  49 %*                                                                      *
  50 %************************************************************************
  51
  52 \begin{code}
  53 type Arity = Int
  54 \end{code}
  55
  56
  57 %************************************************************************
  58 %*                                                                      *
  59 \subsection[Version]{Module and identifier version numbers}
  60 %*                                                                      *
  61 %************************************************************************
  62
  63 \begin{code}
  64 type Version = Int
  65 \end{code}
  66
  67
  68 %************************************************************************
  69 %*                                                                      *
  70 \subsection[Fixity]{Fixity info}
  71 %*                                                                      *
  72 %************************************************************************
  73
  74 \begin{code}
  75 data Fixity = Fixity Int FixityDirection
  76 data FixityDirection = InfixL | InfixR | InfixN
  77                      deriving(Eq)
  78
  79 instance Outputable Fixity where
  80     ppr (Fixity prec dir) = hcat [ppr dir, space, int prec]
  81
  82 instance Outputable FixityDirection where
  83     ppr InfixL = ptext SLIT("infixl")
  84     ppr InfixR = ptext SLIT("infixr")
  85     ppr InfixN = ptext SLIT("infix")
  86
  87 instance Eq Fixity where                -- Used to determine if two fixities conflict
  88   (Fixity p1 dir1) == (Fixity p2 dir2) = p1==p2 && dir1 == dir2
  89 \end{code}
  90
  91
  92 %************************************************************************
  93 %*                                                                      *
  94 \subsection[NewType/DataType]{NewType/DataType flag}
  95 %*                                                                      *
  96 %************************************************************************
  97
  98 \begin{code}
  99 data NewOrData
 100   = NewType     -- "newtype Blah ..."
 101   | DataType    -- "data Blah ..."
 102   | EnumType    -- Enumeration; all constructors are nullary
 103   deriving( Eq )        -- Needed because Demand derives Eq
 104 \end{code}
 105
 106 %************************************************************************
 107 %*                                                                      *
 108 \subsection[Top-level/local]{Top-level/not-top level flag}
 109 %*                                                                      *
 110 %************************************************************************
 111
 112 \begin{code}
 113 data TopLevelFlag
 114   = TopLevel
 115   | NotTopLevel
 116 \end{code}
 117
 118 %************************************************************************
 119 %*                                                                      *
 120 \subsection[Recursive/Non-Recursive]{Recursive/Non-Recursive flag}
 121 %*                                                                      *
 122 %************************************************************************
 123
 124 \begin{code}
 125 data RecFlag = Recursive
 126              | NonRecursive
 127 \end{code}
 128
 129 %************************************************************************
 130 %*                                                                      *
 131 \subsection{Strictness indication}
 132 %*                                                                      *
 133 %************************************************************************
 134
 135 \begin{code}
 136 data StrictnessMark = MarkedStrict
 137                     | MarkedUnboxed DataCon [Type]
 138                     | NotMarkedStrict
 139 \end{code}