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(..), defaultFixity,
  20         NewOrData(..),
  21         RecFlag(..), isRec, isNonRec,
  22         TopLevelFlag(..), isTopLevel, isNotTopLevel
  23    ) where
  24
  25 #include "HsVersions.h"
  26
  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
  90
  91 defaultFixity = Fixity 9 InfixL
  92 \end{code}
  93
  94
  95 %************************************************************************
  96 %*                                                                      *
  97 \subsection[NewType/DataType]{NewType/DataType flag}
  98 %*                                                                      *
  99 %************************************************************************
 100
 101 \begin{code}
 102 data NewOrData
 103   = NewType     -- "newtype Blah ..."
 104   | DataType    -- "data Blah ..."
 105   | EnumType    -- Enumeration; all constructors are nullary
 106   deriving( Eq )        -- Needed because Demand derives Eq
 107 \end{code}
 108
 109 %************************************************************************
 110 %*                                                                      *
 111 \subsection[Top-level/local]{Top-level/not-top level flag}
 112 %*                                                                      *
 113 %************************************************************************
 114
 115 \begin{code}
 116 data TopLevelFlag
 117   = TopLevel
 118   | NotTopLevel
 119
 120 isTopLevel, isNotTopLevel :: TopLevelFlag -> Bool
 121
 122 isNotTopLevel NotTopLevel = True
 123 isNotTopLevel TopLevel    = False
 124
 125 isTopLevel TopLevel     = True
 126 isTopLevel NotTopLevel  = False
 127 \end{code}
 128
 129 %************************************************************************
 130 %*                                                                      *
 131 \subsection[Recursive/Non-Recursive]{Recursive/Non-Recursive flag}
 132 %*                                                                      *
 133 %************************************************************************
 134
 135 \begin{code}
 136 data RecFlag = Recursive
 137              | NonRecursive
 138
 139 isRec :: RecFlag -> Bool
 140 isRec Recursive    = True
 141 isRec NonRecursive = False
 142
 143 isNonRec :: RecFlag -> Bool
 144 isNonRec Recursive    = False
 145 isNonRec NonRecursive = True
 146 \end{code}