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(..),
  20         defaultFixity, maxPrecedence,
  21         NewOrData(..),
  22         RecFlag(..), isRec, isNonRec,
  23         TopLevelFlag(..), isTopLevel, isNotTopLevel
  24    ) where
  25
  26 #include "HsVersions.h"
  27
  28 import Outputable
  29 \end{code}
  30
  31 %************************************************************************
  32 %*                                                                      *
  33 \subsection[Unused]{Unused}
  34 %*                                                                      *
  35 %************************************************************************
  36
  37 Used as a placeholder in types.
  38
  39 \begin{code}
  40 type Unused = ()
  41
  42 unused :: Unused
  43 unused = error "Unused is used!"
  44 \end{code}
  45
  46
  47 %************************************************************************
  48 %*                                                                      *
  49 \subsection[Arity]{Arity}
  50 %*                                                                      *
  51 %************************************************************************
  52
  53 \begin{code}
  54 type Arity = Int
  55 \end{code}
  56
  57
  58 %************************************************************************
  59 %*                                                                      *
  60 \subsection[Version]{Module and identifier version numbers}
  61 %*                                                                      *
  62 %************************************************************************
  63
  64 \begin{code}
  65 type Version = Int
  66 \end{code}
  67
  68
  69 %************************************************************************
  70 %*                                                                      *
  71 \subsection[Fixity]{Fixity info}
  72 %*                                                                      *
  73 %************************************************************************
  74
  75 \begin{code}
  76 data Fixity = Fixity Int FixityDirection
  77 data FixityDirection = InfixL | InfixR | InfixN
  78                      deriving(Eq)
  79
  80 instance Outputable Fixity where
  81     ppr (Fixity prec dir) = hcat [ppr dir, space, int prec]
  82
  83 instance Outputable FixityDirection where
  84     ppr InfixL = ptext SLIT("infixl")
  85     ppr InfixR = ptext SLIT("infixr")
  86     ppr InfixN = ptext SLIT("infix")
  87
  88 instance Eq Fixity where                -- Used to determine if two fixities conflict
  89   (Fixity p1 dir1) == (Fixity p2 dir2) = p1==p2 && dir1 == dir2
  90
  91 maxPrecedence = (9::Int)
  92 defaultFixity = Fixity maxPrecedence InfixL
  93 \end{code}
  94
  95
  96 %************************************************************************
  97 %*                                                                      *
  98 \subsection[NewType/DataType]{NewType/DataType flag}
  99 %*                                                                      *
 100 %************************************************************************
 101
 102 \begin{code}
 103 data NewOrData
 104   = NewType     -- "newtype Blah ..."
 105   | DataType    -- "data Blah ..."
 106   | EnumType    -- Enumeration; all constructors are nullary
 107   deriving( Eq )        -- Needed because Demand derives Eq
 108 \end{code}
 109
 110 %************************************************************************
 111 %*                                                                      *
 112 \subsection[Top-level/local]{Top-level/not-top level flag}
 113 %*                                                                      *
 114 %************************************************************************
 115
 116 \begin{code}
 117 data TopLevelFlag
 118   = TopLevel
 119   | NotTopLevel
 120
 121 isTopLevel, isNotTopLevel :: TopLevelFlag -> Bool
 122
 123 isNotTopLevel NotTopLevel = True
 124 isNotTopLevel TopLevel    = False
 125
 126 isTopLevel TopLevel     = True
 127 isTopLevel NotTopLevel  = False
 128 \end{code}
 129
 130 %************************************************************************
 131 %*                                                                      *
 132 \subsection[Recursive/Non-Recursive]{Recursive/Non-Recursive flag}
 133 %*                                                                      *
 134 %************************************************************************
 135
 136 \begin{code}
 137 data RecFlag = Recursive
 138              | NonRecursive
 139
 140 isRec :: RecFlag -> Bool
 141 isRec Recursive    = True
 142 isRec NonRecursive = False
 143
 144 isNonRec :: RecFlag -> Bool
 145 isNonRec Recursive    = False
 146 isNonRec NonRecursive = True
 147 \end{code}