2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsExpr]{Abstract Haskell syntax: expressions}
9 #include "HsVersions.h"
12 import {-# SOURCE #-} HsMatches ( pprMatches, pprMatch, Match )
14 import HsBinds ( HsBinds )
15 import HsBasic ( HsLit )
16 import BasicTypes ( Fixity(..), FixityDirection(..) )
17 import HsTypes ( HsType )
20 import Name ( Name, isLexId )
22 import PprType ( pprType, pprParendType )
24 import Var ( TyVar, Id )
25 import DataCon ( DataCon )
26 import SrcLoc ( SrcLoc )
29 %************************************************************************
31 \subsection{Expressions proper}
33 %************************************************************************
37 = HsVar id -- variable
38 | HsLit HsLit -- literal
39 | HsLitOut HsLit -- TRANSLATION
40 Type -- (with its type)
42 | HsLam (Match id pat) -- lambda
43 | HsApp (HsExpr id pat) -- application
46 -- Operator applications:
47 -- NB Bracketed ops such as (+) come out as Vars.
49 -- NB We need an expr for the operator in an OpApp/Section since
50 -- the typechecker may need to apply the operator to a few types.
52 | OpApp (HsExpr id pat) -- left operand
53 (HsExpr id pat) -- operator
54 Fixity -- Renamer adds fixity; bottom until then
55 (HsExpr id pat) -- right operand
57 -- We preserve prefix negation and parenthesis for the precedence parser.
58 -- They are eventually removed by the type checker.
60 | NegApp (HsExpr id pat) -- negated expr
61 (HsExpr id pat) -- the negate id (in a HsVar)
63 | HsPar (HsExpr id pat) -- parenthesised expr
65 | SectionL (HsExpr id pat) -- operand
66 (HsExpr id pat) -- operator
67 | SectionR (HsExpr id pat) -- operator
68 (HsExpr id pat) -- operand
70 | HsCase (HsExpr id pat)
74 | HsIf (HsExpr id pat) -- predicate
75 (HsExpr id pat) -- then part
76 (HsExpr id pat) -- else part
79 | HsLet (HsBinds id pat) -- let(rec)
83 [Stmt id pat] -- "do":one or more stmts
87 [Stmt id pat] -- "do":one or more stmts
91 Type -- Type of the whole expression
94 | ExplicitList -- syntactic list
96 | ExplicitListOut -- TRANSLATION
97 Type -- Gives type of components of list
100 | ExplicitTuple -- tuple
102 -- NB: Unit is ExplicitTuple []
103 -- for tuples, we can get the types
104 -- direct from the components
107 | HsCon DataCon -- TRANSLATION; a saturated constructor application
111 -- Record construction
112 | RecordCon id -- The constructor
113 (HsRecordBinds id pat)
115 | RecordConOut DataCon
116 (HsExpr id pat) -- Data con Id applied to type args
117 (HsRecordBinds id pat)
121 | RecordUpd (HsExpr id pat)
122 (HsRecordBinds id pat)
124 | RecordUpdOut (HsExpr id pat) -- TRANSLATION
125 Type -- Type of *result* record (may differ from
126 -- type of input record)
127 [id] -- Dicts needed for construction
128 (HsRecordBinds id pat)
130 | ExprWithTySig -- signature binding
133 | ArithSeqIn -- arithmetic sequence
134 (ArithSeqInfo id pat)
136 (HsExpr id pat) -- (typechecked, of course)
137 (ArithSeqInfo id pat)
139 | CCall FAST_STRING -- call into the C world; string is
140 [HsExpr id pat] -- the C function; exprs are the
141 -- arguments to pass.
142 Bool -- True <=> might cause Haskell
143 -- garbage-collection (must generate
144 -- more paranoid code)
145 Bool -- True <=> it's really a "casm"
146 -- NOTE: this CCall is the *boxed*
147 -- version; the desugarer will convert
148 -- it into the unboxed "ccall#".
149 Type -- The result type; will be *bottom*
150 -- until the typechecker gets ahold of it
152 | HsSCC FAST_STRING -- "set cost centre" (_scc_) annotation
153 (HsExpr id pat) -- expr whose cost is to be measured
156 Everything from here on appears only in typechecker output.
159 | TyLam -- TRANSLATION
162 | TyApp -- TRANSLATION
163 (HsExpr id pat) -- generated by Spec
166 -- DictLam and DictApp are "inverses"
174 type HsRecordBinds id pat
175 = [(id, HsExpr id pat, Bool)]
176 -- True <=> source code used "punning",
177 -- i.e. {op1, op2} rather than {op1=e1, op2=e2}
180 A @Dictionary@, unless of length 0 or 1, becomes a tuple. A
181 @ClassDictLam dictvars methods expr@ is, therefore:
183 \ x -> case x of ( dictvars-and-methods-tuple ) -> expr
187 instance (Outputable id, Outputable pat) =>
188 Outputable (HsExpr id pat) where
189 ppr expr = pprExpr expr
193 pprExpr :: (Outputable id, Outputable pat)
194 => HsExpr id pat -> SDoc
196 pprExpr e = pprDeeper (ppr_expr e)
197 pprBinds b = pprDeeper (ppr b)
199 ppr_expr (HsVar v) = ppr v
201 ppr_expr (HsLit lit) = ppr lit
202 ppr_expr (HsLitOut lit _) = ppr lit
204 ppr_expr (HsLam match)
205 = hsep [char '\\', nest 2 (pprMatch (True,empty) match)]
207 ppr_expr expr@(HsApp e1 e2)
208 = let (fun, args) = collect_args expr [] in
209 (ppr_expr fun) <+> (sep (map ppr_expr args))
211 collect_args (HsApp fun arg) args = collect_args fun (arg:args)
212 collect_args fun args = (fun, args)
214 ppr_expr (OpApp e1 op fixity e2)
216 HsVar v -> pp_infixly v
219 pp_e1 = pprParendExpr e1 -- Add parens to make precedence clear
220 pp_e2 = pprParendExpr e2
223 = hang (pprExpr op) 4 (sep [pp_e1, pp_e2])
226 = sep [pp_e1, hsep [pp_v_op, pp_e2]]
229 pp_v_op | isLexId (_PK_ (showSDoc pp_v)) = char '`' <> pp_v <> char '`'
231 -- Put it in backquotes if it's not an operator already
232 -- We use (showSDoc pp_v), rather than isSymOcc (getOccName v) simply so
233 -- that we don't need NamedThing in the context of all these funcions.
234 -- Gruesome, but simple.
236 ppr_expr (NegApp e _)
237 = char '-' <+> pprParendExpr e
239 ppr_expr (HsPar e) = parens (ppr_expr e)
241 ppr_expr (SectionL expr op)
243 HsVar v -> pp_infixly v
246 pp_expr = pprParendExpr expr
248 pp_prefixly = hang (hsep [text " \\ x_ ->", ppr op])
249 4 (hsep [pp_expr, ptext SLIT("x_ )")])
250 pp_infixly v = parens (sep [pp_expr, ppr v])
252 ppr_expr (SectionR op expr)
254 HsVar v -> pp_infixly v
257 pp_expr = pprParendExpr expr
259 pp_prefixly = hang (hsep [text "( \\ x_ ->", ppr op, ptext SLIT("x_")])
260 4 ((<>) pp_expr rparen)
262 = parens (sep [ppr v, pp_expr])
264 ppr_expr (HsCase expr matches _)
265 = sep [ sep [ptext SLIT("case"), nest 4 (pprExpr expr), ptext SLIT("of")],
266 nest 2 (pprMatches (True, empty) matches) ]
268 ppr_expr (HsIf e1 e2 e3 _)
269 = sep [hsep [ptext SLIT("if"), nest 2 (pprExpr e1), ptext SLIT("then")],
274 -- special case: let ... in let ...
275 ppr_expr (HsLet binds expr@(HsLet _ _))
276 = sep [hang (ptext SLIT("let")) 2 (hsep [pprBinds binds, ptext SLIT("in")]),
279 ppr_expr (HsLet binds expr)
280 = sep [hang (ptext SLIT("let")) 2 (pprBinds binds),
281 hang (ptext SLIT("in")) 2 (ppr expr)]
283 ppr_expr (HsDo do_or_list_comp stmts _) = pprDo do_or_list_comp stmts
284 ppr_expr (HsDoOut do_or_list_comp stmts _ _ _ _ _) = pprDo do_or_list_comp stmts
286 ppr_expr (ExplicitList exprs)
287 = brackets (fsep (punctuate comma (map ppr_expr exprs)))
288 ppr_expr (ExplicitListOut ty exprs)
289 = hcat [ brackets (fsep (punctuate comma (map ppr_expr exprs))),
290 ifNotPprForUser ((<>) space (parens (pprType ty))) ]
292 ppr_expr (ExplicitTuple exprs True)
293 = parens (sep (punctuate comma (map ppr_expr exprs)))
295 ppr_expr (ExplicitTuple exprs False)
296 = ptext SLIT("(#") <> sep (punctuate comma (map ppr_expr exprs)) <> ptext SLIT("#)")
298 ppr_expr (HsCon con_id tys args)
299 = ppr con_id <+> sep (map pprParendType tys ++
300 map pprParendExpr args)
302 ppr_expr (RecordCon con_id rbinds)
303 = pp_rbinds (ppr con_id) rbinds
304 ppr_expr (RecordConOut data_con con rbinds)
305 = pp_rbinds (ppr con) rbinds
307 ppr_expr (RecordUpd aexp rbinds)
308 = pp_rbinds (pprParendExpr aexp) rbinds
309 ppr_expr (RecordUpdOut aexp _ _ rbinds)
310 = pp_rbinds (pprParendExpr aexp) rbinds
312 ppr_expr (ExprWithTySig expr sig)
313 = hang (nest 2 (ppr_expr expr) <+> dcolon)
316 ppr_expr (ArithSeqIn info)
317 = brackets (ppr info)
318 ppr_expr (ArithSeqOut expr info)
319 = brackets (ppr info)
321 ppr_expr (CCall fun args _ is_asm result_ty)
323 then ptext SLIT("_casm_ ``") <> ptext fun <> ptext SLIT("''")
324 else ptext SLIT("_ccall_") <+> ptext fun)
325 4 (sep (map pprParendExpr args))
327 ppr_expr (HsSCC label expr)
328 = sep [ ptext SLIT("_scc_") <+> doubleQuotes (ptext label), pprParendExpr expr ]
330 ppr_expr (TyLam tyvars expr)
331 = hang (hsep [ptext SLIT("/\\"), interppSP tyvars, ptext SLIT("->")])
334 ppr_expr (TyApp expr [ty])
335 = hang (ppr_expr expr) 4 (pprParendType ty)
337 ppr_expr (TyApp expr tys)
338 = hang (ppr_expr expr)
339 4 (brackets (interpp'SP tys))
341 ppr_expr (DictLam dictvars expr)
342 = hang (hsep [ptext SLIT("\\{-dict-}"), interppSP dictvars, ptext SLIT("->")])
345 ppr_expr (DictApp expr [dname])
346 = hang (ppr_expr expr) 4 (ppr dname)
348 ppr_expr (DictApp expr dnames)
349 = hang (ppr_expr expr)
350 4 (brackets (interpp'SP dnames))
354 Parenthesize unless very simple:
356 pprParendExpr :: (Outputable id, Outputable pat)
357 => HsExpr id pat -> SDoc
361 pp_as_was = pprExpr expr
365 HsLitOut l _ -> ppr l
368 ExplicitList _ -> pp_as_was
369 ExplicitListOut _ _ -> pp_as_was
370 ExplicitTuple _ _ -> pp_as_was
373 _ -> parens pp_as_was
376 %************************************************************************
378 \subsection{Record binds}
380 %************************************************************************
383 pp_rbinds :: (Outputable id, Outputable pat)
385 -> HsRecordBinds id pat -> SDoc
387 pp_rbinds thing rbinds
389 4 (braces (hsep (punctuate comma (map (pp_rbind) rbinds))))
391 pp_rbind (v, e, pun_flag)
392 = getPprStyle $ \ sty ->
393 if pun_flag && userStyle sty then
396 hsep [ppr v, char '=', ppr e]
399 %************************************************************************
401 \subsection{Do stmts and list comprehensions}
403 %************************************************************************
406 data StmtCtxt -- Context of a Stmt
407 = DoStmt -- Do Statment
408 | ListComp -- List comprehension
409 | CaseAlt -- Guard on a case alternative
410 | PatBindRhs -- Guard on a pattern binding
411 | FunRhs Name -- Guard on a function defn for f
412 | LambdaBody -- Body of a lambda abstraction
415 = hang (ptext SLIT("do")) 2 (vcat (map ppr stmts))
418 hang (pprExpr expr <+> char '|')
421 ReturnStmt expr = last stmts -- Last stmt should be a ReturnStmt for list comps
431 | LetStmt (HsBinds id pat)
433 | GuardStmt (HsExpr id pat) -- List comps only
436 | ExprStmt (HsExpr id pat) -- Do stmts; and guarded things at the end
439 | ReturnStmt (HsExpr id pat) -- List comps only, at the end
443 instance (Outputable id, Outputable pat) =>
444 Outputable (Stmt id pat) where
445 ppr stmt = pprStmt stmt
447 pprStmt (BindStmt pat expr _)
448 = hsep [ppr pat, ptext SLIT("<-"), ppr expr]
449 pprStmt (LetStmt binds)
450 = hsep [ptext SLIT("let"), pprBinds binds]
451 pprStmt (ExprStmt expr _)
453 pprStmt (GuardStmt expr _)
455 pprStmt (ReturnStmt expr)
456 = hsep [ptext SLIT("return"), ppr expr]
459 %************************************************************************
461 \subsection{Enumerations and list comprehensions}
463 %************************************************************************
466 data ArithSeqInfo id pat
467 = From (HsExpr id pat)
468 | FromThen (HsExpr id pat)
470 | FromTo (HsExpr id pat)
472 | FromThenTo (HsExpr id pat)
478 instance (Outputable id, Outputable pat) =>
479 Outputable (ArithSeqInfo id pat) where
480 ppr (From e1) = hcat [ppr e1, pp_dotdot]
481 ppr (FromThen e1 e2) = hcat [ppr e1, comma, space, ppr e2, pp_dotdot]
482 ppr (FromTo e1 e3) = hcat [ppr e1, pp_dotdot, ppr e3]
483 ppr (FromThenTo e1 e2 e3)
484 = hcat [ppr e1, comma, space, ppr e2, pp_dotdot, ppr e3]
486 pp_dotdot = ptext SLIT(" .. ")