1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
------------------------------------------------------------------------------
--- This library supports meta-programming, i.e., the manipulation of
--- Curry programs in Curry. For this purpose, the library contains
--- definitions of data types for the representation of Curry programs
--- in the FlatCurry format where all function definitions are
--- at the top-level and pattern matching is replaced by case expressions
--- and disjunctions.
---
--- @author Michael Hanus
--- @version July 2016
------------------------------------------------------------------------------

module FlatCurry.Types where

--- Data type for representing a Curry module in the intermediate form.
--- A value of this data type has the form
---
---     (Prog modname imports typedecls functions opdecls)
---
--- where
--- `modname` is the name of this module,
--- `imports` is the list of modules names that are imported, and
--- `typedecls`, `functions`, and `opdecls` are the list of
--- data type, function, and operator declarations
--- contained in this module, respectively.
data Prog = Prog String [String] [TypeDecl] [FuncDecl] [OpDecl]
  deriving (Eq, Ord, Read, Show)

--- The data type for representing qualified names.
--- In FlatCurry all names are qualified to avoid name clashes.
--- The first component is the module name and the second component the
--- unqualified name as it occurs in the source program.
type QName = (String, String)

--- Data type to specify the visibility of various entities.
data Visibility
  = Public    -- public (exported) entity
  | Private   -- private entity
 deriving (Eq, Ord, Read, Show)

--- The data type for representing type variables.
--- They are represented by `(TVar i)` where `i` is a type variable index.
type TVarIndex = Int

--- Kinded type variables are represented by a tuple of type variable
--- index and kind.
type TVarWithKind = (TVarIndex, Kind)

--- Data type for representing definitions of algebraic data types
--- and type synonyms.
---
--- A data type definition of the form
---
---     data t x1...xn = ...| c t1....tkc |...
---
--- is represented by the FlatCurry term
---
---     (Type t [i1,...,in] [...(Cons c kc [t1,...,tkc])...])
---
--- where each `ij` is the index of the type variable `xj`.
---
--- Note: the type variable indices are unique inside each type declaration
---       and are usually numbered from 0
---
--- Thus, a data type declaration consists of the name of the data type,
--- a list of type parameters and a list of constructor declarations.
data TypeDecl
  = Type    QName Visibility [TVarWithKind] [ConsDecl]
  | TypeSyn QName Visibility [TVarWithKind] TypeExpr
  | TypeNew QName Visibility [TVarWithKind] NewConsDecl
  deriving (Eq, Ord, Read, Show)

--- A constructor declaration consists of the name and arity of the
--- constructor and a list of the argument types of the constructor.
data ConsDecl = Cons QName Int Visibility [TypeExpr]
  deriving (Eq, Ord, Read, Show)

--- A constructor declaration for a newtype consists
--- of the name of the constructor
--- and the argument type of the constructor.
data NewConsDecl = NewCons QName Visibility TypeExpr
    deriving (Eq, Ord, Read, Show)

--- Data type for type expressions.
--- A type expression is either a type variable, a function type,
--- or a type constructor application.
---
--- Note: the names of the predefined type constructors are
--- "Int", "Float", "Bool", "Char", "IO",
--- "()" (unit type), "(,...,)" (tuple types), "[]" (list type)
data TypeExpr
  = TVar TVarIndex                      -- type variable
  | FuncType TypeExpr TypeExpr          -- function type t1->t2
  | TCons QName [TypeExpr]              -- type constructor application
                                        -- TCons module name typeargs
  | ForallType  [TVarWithKind] TypeExpr -- forall type
 deriving (Eq, Ord, Read, Show)

data Kind
  = KStar
  | KArrow Kind Kind
  deriving (Eq, Ord, Read, Show)

--- Data type for operator declarations.
--- An operator declaration `fix p n` in Curry corresponds to the
--- FlatCurry term `(Op n fix p)`.
data OpDecl = Op QName Fixity Int
  deriving (Eq, Ord, Read, Show)

--- Data types for the different choices for the fixity of an operator.
data Fixity = InfixOp | InfixlOp | InfixrOp
 deriving (Eq, Ord, Read, Show)

--- Data type for representing object variables.
--- Object variables occurring in expressions are represented by `(Var i)`
--- where `i` is a variable index.
type VarIndex = Int

--- Arity of a function.
type Arity = Int

--- Data type for representing function declarations.
---
--- A function declaration in FlatCurry is a term of the form
---
---     (Func name k type (Rule [i1,...,ik] e))
---
--- and represents the function `name` with definition
---
---     name :: type
---     name x1...xk = e
---
--- where each `ij` is the index of the variable `xj`.
---
--- Note: the variable indices are unique inside each function declaration
---       and are usually numbered from 0
---
--- External functions are represented as
---
---     (Func name arity type (External s))
---
--- where s is the external name associated to this function.
---
--- Thus, a function declaration consists of the name, arity, type, and rule.
data FuncDecl = Func QName Arity Visibility TypeExpr Rule
 deriving (Eq, Ord, Read, Show)

--- A rule is either a list of formal parameters together with an expression
--- or an "External" tag.
data Rule
  = Rule [VarIndex] Expr
  | External String
 deriving (Eq, Ord, Read, Show)

--- Data type for classifying case expressions.
--- Case expressions can be either flexible or rigid in Curry.
data CaseType = Rigid | Flex       -- type of a case expression
 deriving (Eq, Ord, Read, Show)

--- Data type for classifying combinations
--- (i.e., a function/constructor applied to some arguments).
--- @cons FuncCall     - a call to a function where all arguments are provided
--- @cons ConsCall     - a call with a constructor at the top, all arguments are provided
--- @cons FuncPartCall - a partial call to a function (i.e., not all arguments
---                      are provided) where the parameter is the number of
---                      missing arguments
--- @cons ConsPartCall - a partial call to a constructor (i.e., not all arguments
---                      are provided) where the parameter is the number of
---                      missing arguments
data CombType = FuncCall | ConsCall | FuncPartCall Arity | ConsPartCall Arity
 deriving (Eq, Ord, Read, Show)

--- Data type for representing expressions.
---
--- Remarks:
---
--- if-then-else expressions are represented as rigid case expressions:
---
---     (if e1 then e2 else e3)
---
--- is represented as
---
---     (case e1 of { True -> e2; False -> e3})
---
--- Higher-order applications are represented as calls to the (external)
--- function `apply`. For instance, the rule
---
---     app f x = f x
---
--- is represented as
---
---     (Rule  [0,1] (Comb FuncCall ("Prelude","apply") [Var 0, Var 1]))
---
--- A conditional rule is represented as a call to an external function
--- `cond` where the first argument is the condition (a constraint).
--- For instance, the rule
---
---     equal2 x | x=:=2 = True
---
--- is represented as
---
---     (Rule [0]
---           (Comb FuncCall ("Prelude","cond")
---                 [Comb FuncCall ("Prelude","=:=") [Var 0, Lit (Intc 2)],
---                  Comb FuncCall ("Prelude","True") []]))
---
--- @cons Var - variable (represented by unique index)
--- @cons Lit - literal (Int/Float/Char constant)
--- @cons Comb - application `(f e1 ... en)` of function/constructor `f`
---              with `n`<=arity(`f`)
--- @cons Let - introduction of local variables via (recursive) let declarations
--- @cons Free - introduction of free local variables
--- @cons Or - disjunction of two expressions (used to translate rules
---            with overlapping left-hand sides)
--- @cons Case - case distinction (rigid or flex)
--- @cons Typed - typed expression to represent an expression with a
---               type declaration
data Expr
  = Var VarIndex
  | Lit Literal
  | Comb CombType QName [Expr]
  | Let [(VarIndex, Expr)] Expr
  | Free [VarIndex] Expr
  | Or Expr Expr
  | Case CaseType Expr [BranchExpr]
  | Typed Expr TypeExpr
 deriving (Eq, Ord, Read, Show)

--- Data type for representing branches in a case expression.
---
--- Branches "(m.c x1...xn) -> e" in case expressions are represented as
---
---     (Branch (Pattern (m,c) [i1,...,in]) e)
---
--- where each `ij` is the index of the pattern variable `xj`, or as
---
---     (Branch (LPattern (Intc i)) e)
---
--- for integers as branch patterns (similarly for other literals
--- like float or character constants).
data BranchExpr = Branch Pattern Expr
 deriving (Eq, Ord, Read, Show)

--- Data type for representing patterns in case expressions.
data Pattern
  = Pattern QName [VarIndex]
  | LPattern Literal
 deriving (Eq, Ord, Read, Show)

--- Data type for representing literals occurring in an expression
--- or case branch. It is either an integer, a float, or a character constant.
data Literal
  = Intc   Int
  | Floatc Float
  | Charc  Char
 deriving (Eq, Ord, Read, Show)

-----------------------------------------------------------------------
--- Shows a qualified type name as a name relative to a module
--- (first argument). Thus, names not defined in this module (except for names
--- defined in the prelude) are prefixed with their module name.
showQNameInModule :: String -> QName -> String
showQNameInModule mod qn@(qmod, name)
  | qmod == mod || qmod == "Prelude" = name
  | otherwise                        = showQName qn

--- Shows a qualified name.
showQName :: QName -> String
showQName (qmod, name) = qmod ++ '.' : name

-----------------------------------------------------------------------