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 Outputable
  26 \end{code}
  27
  28 %************************************************************************
  29 %*                                                                      *
  30 \subsection[Unused]{Unused}
  31 %*                                                                      *
  32 %************************************************************************
  33
  34 Used as a placeholder in types.
  35
  36 \begin{code}
  37 type Unused = ()
  38
  39 unused :: Unused
  40 unused = error "Unused is used!"
  41 \end{code}
  42
  43
  44 %************************************************************************
  45 %*                                                                      *
  46 \subsection[Arity]{Arity}
  47 %*                                                                      *
  48 %************************************************************************
  49
  50 \begin{code}
  51 type Arity = Int
  52 \end{code}
  53
  54
  55 %************************************************************************
  56 %*                                                                      *
  57 \subsection[Version]{Module and identifier version numbers}
  58 %*                                                                      *
  59 %************************************************************************
  60
  61 \begin{code}
  62 type Version = Int
  63 \end{code}
  64
  65
  66 %************************************************************************
  67 %*                                                                      *
  68 \subsection[Fixity]{Fixity info}
  69 %*                                                                      *
  70 %************************************************************************
  71
  72 \begin{code}
  73 data Fixity = Fixity Int FixityDirection
  74 data FixityDirection = InfixL | InfixR | InfixN
  75                      deriving(Eq)
  76
  77 instance Outputable Fixity where
  78     ppr (Fixity prec dir) = hcat [ppr dir, space, int prec]
  79
  80 instance Outputable FixityDirection where
  81     ppr InfixL = ptext SLIT("infixl")
  82     ppr InfixR = ptext SLIT("infixr")
  83     ppr InfixN = ptext SLIT("infix")
  84
  85 instance Eq Fixity where                -- Used to determine if two fixities conflict
  86   (Fixity p1 dir1) == (Fixity p2 dir2) = p1==p2 && dir1 == dir2
  87 \end{code}
  88
  89
  90 %************************************************************************
  91 %*                                                                      *
  92 \subsection[NewType/DataType]{NewType/DataType flag}
  93 %*                                                                      *
  94 %************************************************************************
  95
  96 \begin{code}
  97 data NewOrData
  98   = NewType     -- "newtype Blah ..."
  99   | DataType    -- "data Blah ..."
 100   | EnumType    -- Enumeration; all constructors are nullary
 101   deriving( Eq )        -- Needed because Demand derives Eq
 102 \end{code}
 103
 104 The @RecFlag@ tells whether the thing is part of a recursive group or not.
 105
 106
 107 %************************************************************************
 108 %*                                                                      *
 109 \subsection[Top-level/local]{Top-level/not-top level flag}
 110 %*                                                                      *
 111 %************************************************************************
 112
 113 \begin{code}
 114 data TopLevelFlag
 115   = TopLevel
 116   | NotTopLevel
 117 \end{code}
 118
 119
 120 %************************************************************************
 121 %*                                                                      *
 122 \subsection[Top-level/local]{Top-level/not-top level flag}
 123 %*                                                                      *
 124 %************************************************************************
 125
 126 \begin{code}
 127 data RecFlag = Recursive
 128              | NonRecursive
 129 \end{code}
 130
 131 %************************************************************************
 132 %*                                                                      *
 133 \subsection{Strictness indication}
 134 %*                                                                      *
 135 %************************************************************************
 136
 137 \begin{code}
 138 data StrictnessMark = MarkedStrict
 139                     | NotMarkedStrict
 140 \end{code}