ghc/compiler/main/CmdLineOpts.lhs

   1 %
   2 % (c) The University of Glasgow, 1996-2000
   3 %
   4 \section[CmdLineOpts]{Things to do with command-line options}
   5
   6 \begin{code}
   7
   8 module CmdLineOpts (
   9         CoreToDo(..),
  10         SimplifierSwitch(..), isAmongSimpl,
  11         StgToDo(..),
  12         SwitchResult(..),
  13         HscLang(..),
  14         DynFlag(..),    -- needed non-abstractly by DriverFlags
  15         DynFlags(..),
  16
  17         v_Static_hsc_opts,
  18
  19         intSwitchSet,
  20         switchIsOn,
  21         isStaticHscFlag,
  22
  23         opt_PprStyle_NoPrags,
  24         opt_PprUserLength,
  25         opt_PprStyle_Debug,
  26
  27         dopt,
  28
  29         -- other dynamic flags
  30         dopt_CoreToDo,
  31         dopt_StgToDo,
  32         dopt_HscLang,
  33         dopt_OutName,
  34
  35         -- profiling opts
  36         opt_AutoSccsOnAllToplevs,
  37         opt_AutoSccsOnExportedToplevs,
  38         opt_AutoSccsOnIndividualCafs,
  39         opt_AutoSccsOnDicts,
  40         opt_SccProfilingOn,
  41         opt_DoTickyProfiling,
  42
  43         -- language opts
  44         opt_AllStrict,
  45         opt_DictsStrict,
  46         opt_MaxContextReductionDepth,
  47         opt_IrrefutableTuples,
  48         opt_NumbersStrict,
  49         opt_Parallel,
  50         opt_SMP,
  51
  52         -- optimisation opts
  53         opt_DoSemiTagging,
  54         opt_FoldrBuildOn,
  55         opt_LiberateCaseThreshold,
  56         opt_StgDoLetNoEscapes,
  57         opt_UnfoldCasms,
  58         opt_UsageSPOn,
  59         opt_UnboxStrictFields,
  60         opt_SimplNoPreInlining,
  61         opt_SimplDoEtaReduction,
  62         opt_SimplDoLambdaEtaExpansion,
  63         opt_SimplCaseOfCase,
  64         opt_SimplCaseMerge,
  65         opt_SimplPedanticBottoms,
  66         opt_SimplExcessPrecision,
  67
  68         -- Unfolding control
  69         opt_UF_HiFileThreshold,
  70         opt_UF_CreationThreshold,
  71         opt_UF_UseThreshold,
  72         opt_UF_FunAppDiscount,
  73         opt_UF_KeenessFactor,
  74         opt_UF_UpdateInPlace,
  75         opt_UF_CheapOp,
  76         opt_UF_DearOp,
  77
  78         -- misc opts
  79         opt_InPackage,
  80         opt_EmitCExternDecls,
  81         opt_EnsureSplittableC,
  82         opt_GranMacros,
  83         opt_HiVersion,
  84         opt_HistorySize,
  85         opt_IgnoreAsserts,
  86         opt_IgnoreIfacePragmas,
  87         opt_NoHiCheck,
  88         opt_OmitBlackHoling,
  89         opt_OmitInterfacePragmas,
  90         opt_NoPruneTyDecls,
  91         opt_NoPruneDecls,
  92         opt_Static,
  93         opt_Unregisterised,
  94         opt_Verbose
  95     ) where
  96
  97 #include "HsVersions.h"
  98
  99 import Array    ( array, (//) )
 100 import GlaExts
 101 import IOExts   ( IORef, readIORef )
 102 import Constants        -- Default values for some flags
 103 import Util
 104 import FastTypes
 105
 106 import Maybes           ( firstJust )
 107 import Panic            ( panic )
 108
 109 #if __GLASGOW_HASKELL__ < 301
 110 import ArrBase  ( Array(..) )
 111 #else
 112 import PrelArr  ( Array(..) )
 113 #endif
 114 \end{code}
 115
 116 %************************************************************************
 117 %*                                                                      *
 118 \subsection{Command-line options}
 119 %*                                                                      *
 120 %************************************************************************
 121
 122 The hsc command-line options are split into two categories:
 123
 124   - static flags
 125   - dynamic flags
 126
 127 Static flags are represented by top-level values of type Bool or Int,
 128 for example.  They therefore have the same value throughout the
 129 invocation of hsc.
 130
 131 Dynamic flags are represented by an abstract type, DynFlags, which is
 132 passed into hsc by the compilation manager for every compilation.
 133 Dynamic flags are those that change on a per-compilation basis,
 134 perhaps because they may be present in the OPTIONS pragma at the top
 135 of a module.
 136
 137 Other flag-related blurb:
 138
 139 A list of {\em ToDo}s is things to be done in a particular part of
 140 processing.  A (fictitious) example for the Core-to-Core simplifier
 141 might be: run the simplifier, then run the strictness analyser, then
 142 run the simplifier again (three ``todos'').
 143
 144 There are three ``to-do processing centers'' at the moment.  In the
 145 main loop (\tr{main/Main.lhs}), in the Core-to-Core processing loop
 146 (\tr{simplCore/SimplCore.lhs), and in the STG-to-STG processing loop
 147 (\tr{simplStg/SimplStg.lhs}).
 148
 149 %************************************************************************
 150 %*                                                                      *
 151 \subsection{Datatypes associated with command-line options}
 152 %*                                                                      *
 153 %************************************************************************
 154
 155 \begin{code}
 156 data SwitchResult
 157   = SwBool      Bool            -- on/off
 158   | SwString    FAST_STRING     -- nothing or a String
 159   | SwInt       Int             -- nothing or an Int
 160 \end{code}
 161
 162 \begin{code}
 163 data CoreToDo           -- These are diff core-to-core passes,
 164                         -- which may be invoked in any order,
 165                         -- as many times as you like.
 166
 167   = CoreDoSimplify      -- The core-to-core simplifier.
 168         (SimplifierSwitch -> SwitchResult)
 169                         -- Each run of the simplifier can take a different
 170                         -- set of simplifier-specific flags.
 171   | CoreDoFloatInwards
 172   | CoreDoFloatOutwards Bool    -- True <=> float lambdas to top level
 173   | CoreLiberateCase
 174   | CoreDoPrintCore
 175   | CoreDoStaticArgs
 176   | CoreDoStrictness
 177   | CoreDoWorkerWrapper
 178   | CoreDoSpecialising
 179   | CoreDoUSPInf
 180   | CoreDoCPResult
 181   | CoreDoGlomBinds
 182   | CoreCSE
 183
 184   | CoreDoNothing        -- useful when building up lists of these things
 185 \end{code}
 186
 187 \begin{code}
 188 data StgToDo
 189   = StgDoStaticArgs
 190   | StgDoLambdaLift
 191   | StgDoMassageForProfiling  -- should be (next to) last
 192   -- There's also setStgVarInfo, but its absolute "lastness"
 193   -- is so critical that it is hardwired in (no flag).
 194   | D_stg_stats
 195 \end{code}
 196
 197 \begin{code}
 198 data SimplifierSwitch
 199   = MaxSimplifierIterations Int
 200   | SimplInlinePhase Int
 201   | DontApplyRules
 202   | NoCaseOfCase
 203   | SimplLetToCase
 204 \end{code}
 205
 206 %************************************************************************
 207 %*                                                                      *
 208 \subsection{Dynamic command-line options}
 209 %*                                                                      *
 210 %************************************************************************
 211
 212 \begin{code}
 213 data DynFlag
 214
 215    -- debugging flags
 216    = Opt_D_dump_all
 217    | Opt_D_dump_most
 218    | Opt_D_dump_absC
 219    | Opt_D_dump_asm
 220    | Opt_D_dump_cpranal
 221    | Opt_D_dump_deriv
 222    | Opt_D_dump_ds
 223    | Opt_D_dump_flatC
 224    | Opt_D_dump_foreign
 225    | Opt_D_dump_inlinings
 226    | Opt_D_dump_occur_anal
 227    | Opt_D_dump_parsed
 228    | Opt_D_dump_realC
 229    | Opt_D_dump_rn
 230    | Opt_D_dump_simpl
 231    | Opt_D_dump_simpl_iterations
 232    | Opt_D_dump_spec
 233    | Opt_D_dump_stg
 234    | Opt_D_dump_stranal
 235    | Opt_D_dump_tc
 236    | Opt_D_dump_types
 237    | Opt_D_dump_rules
 238    | Opt_D_dump_usagesp
 239    | Opt_D_dump_cse
 240    | Opt_D_dump_worker_wrapper
 241    | Opt_D_show_passes
 242    | Opt_D_dump_rn_trace
 243    | Opt_D_dump_rn_stats
 244    | Opt_D_dump_stix
 245    | Opt_D_dump_simpl_stats
 246    | Opt_D_source_stats
 247    | Opt_D_verbose_core2core
 248    | Opt_D_verbose_stg2stg
 249    | Opt_D_dump_hi_diffs
 250    | Opt_D_dump_minimal_imports
 251    | Opt_DoCoreLinting
 252    | Opt_DoStgLinting
 253    | Opt_DoUSPLinting
 254
 255    | Opt_WarnDuplicateExports
 256    | Opt_WarnHiShadows
 257    | Opt_WarnIncompletePatterns
 258    | Opt_WarnMissingFields
 259    | Opt_WarnMissingMethods
 260    | Opt_WarnMissingSigs
 261    | Opt_WarnNameShadowing
 262    | Opt_WarnOverlappingPatterns
 263    | Opt_WarnSimplePatterns
 264    | Opt_WarnTypeDefaults
 265    | Opt_WarnUnusedBinds
 266    | Opt_WarnUnusedImports
 267    | Opt_WarnUnusedMatches
 268    | Opt_WarnDeprecations
 269
 270    -- language opts
 271    | Opt_AllowOverlappingInstances
 272    | Opt_AllowUndecidableInstances
 273    | Opt_GlasgowExts
 274    | Opt_Generics
 275    | Opt_NoImplicitPrelude
 276
 277    -- misc
 278    | Opt_ReportCompile
 279    deriving (Eq)
 280
 281 data DynFlags = DynFlags {
 282   coreToDo   :: [CoreToDo],
 283   stgToDo    :: [StgToDo],
 284   hscLang    :: HscLang,
 285   hscOutName :: String,  -- name of the file in which to place output
 286   flags      :: [DynFlag]
 287  }
 288
 289 dopt :: DynFlag -> DynFlags -> Bool
 290 dopt f dflags  = f `elem` (flags dflags)
 291
 292 dopt_CoreToDo :: DynFlags -> [CoreToDo]
 293 dopt_CoreToDo = coreToDo
 294
 295 dopt_StgToDo :: DynFlags -> [StgToDo]
 296 dopt_StgToDo = stgToDo
 297
 298 dopt_OutName :: DynFlags -> String
 299 dopt_OutName = hscOutName
 300
 301 data HscLang
 302   = HscC
 303   | HscAsm
 304   | HscJava
 305   | HscInterpreted
 306     deriving Eq
 307
 308 dopt_HscLang :: DynFlags -> HscLang
 309 dopt_HscLang = hscLang
 310 \end{code}
 311
 312 %************************************************************************
 313 %*                                                                      *
 314 \subsection{Classifying command-line options}
 315 %*                                                                      *
 316 %************************************************************************
 317
 318 \begin{code}
 319 -- v_Statis_hsc_opts is here to avoid a circular dependency with
 320 -- main/DriverState.
 321 GLOBAL_VAR(v_Static_hsc_opts, [], [String])
 322
 323 lookUp           :: FAST_STRING -> Bool
 324 lookup_int       :: String -> Maybe Int
 325 lookup_def_int   :: String -> Int -> Int
 326 lookup_def_float :: String -> Float -> Float
 327 lookup_str       :: String -> Maybe String
 328
 329 unpacked_static_opts = unsafePerformIO (readIORef v_Static_hsc_opts)
 330 packed_static_opts   = map _PK_ unpacked_static_opts
 331
 332 lookUp     sw = sw `elem` packed_static_opts
 333
 334 lookup_str sw = firstJust (map (startsWith sw) unpacked_static_opts)
 335
 336 lookup_int sw = case (lookup_str sw) of
 337                   Nothing -> Nothing
 338                   Just xx -> Just (read xx)
 339
 340 lookup_def_int sw def = case (lookup_str sw) of
 341                             Nothing -> def              -- Use default
 342                             Just xx -> read xx
 343
 344 lookup_def_float sw def = case (lookup_str sw) of
 345                             Nothing -> def              -- Use default
 346                             Just xx -> read xx
 347
 348
 349 {-
 350  Putting the compiler options into temporary at-files
 351  may turn out to be necessary later on if we turn hsc into
 352  a pure Win32 application where I think there's a command-line
 353  length limit of 255. unpacked_opts understands the @ option.
 354
 355 unpacked_opts :: [String]
 356 unpacked_opts =
 357   concat $
 358   map (expandAts) $
 359   map _UNPK_ argv  -- NOT ARGV any more: v_Static_hsc_opts
 360   where
 361    expandAts ('@':fname) = words (unsafePerformIO (readFile fname))
 362    expandAts l = [l]
 363 -}
 364 \end{code}
 365
 366 %************************************************************************
 367 %*                                                                      *
 368 \subsection{Static options}
 369 %*                                                                      *
 370 %************************************************************************
 371
 372 \begin{code}
 373 -- debugging opts
 374 opt_PprStyle_NoPrags            = lookUp  SLIT("-dppr-noprags")
 375 opt_PprStyle_Debug              = lookUp  SLIT("-dppr-debug")
 376 opt_PprUserLength               = lookup_def_int "-dppr-user-length" 5 --ToDo: give this a name
 377
 378 -- profiling opts
 379 opt_AutoSccsOnAllToplevs        = lookUp  SLIT("-fauto-sccs-on-all-toplevs")
 380 opt_AutoSccsOnExportedToplevs   = lookUp  SLIT("-fauto-sccs-on-exported-toplevs")
 381 opt_AutoSccsOnIndividualCafs    = lookUp  SLIT("-fauto-sccs-on-individual-cafs")
 382 opt_AutoSccsOnDicts             = lookUp  SLIT("-fauto-sccs-on-dicts")
 383 opt_SccProfilingOn              = lookUp  SLIT("-fscc-profiling")
 384 opt_DoTickyProfiling            = lookUp  SLIT("-fticky-ticky")
 385
 386 -- language opts
 387 opt_AllStrict                   = lookUp  SLIT("-fall-strict")
 388 opt_DictsStrict                 = lookUp  SLIT("-fdicts-strict")
 389 opt_IrrefutableTuples           = lookUp  SLIT("-firrefutable-tuples")
 390 opt_MaxContextReductionDepth    = lookup_def_int "-fcontext-stack" mAX_CONTEXT_REDUCTION_DEPTH
 391 opt_NumbersStrict               = lookUp  SLIT("-fnumbers-strict")
 392 opt_Parallel                    = lookUp  SLIT("-fparallel")
 393 opt_SMP                         = lookUp  SLIT("-fsmp")
 394
 395 -- optimisation opts
 396 opt_DoSemiTagging               = lookUp  SLIT("-fsemi-tagging")
 397 opt_FoldrBuildOn                = lookUp  SLIT("-ffoldr-build-on")
 398 opt_LiberateCaseThreshold       = lookup_def_int "-fliberate-case-threshold" (10::Int)
 399 opt_StgDoLetNoEscapes           = lookUp  SLIT("-flet-no-escape")
 400 opt_UnfoldCasms                 = lookUp SLIT("-funfold-casms-in-hi-file")
 401 opt_UsageSPOn                   = lookUp  SLIT("-fusagesp-on")
 402 opt_UnboxStrictFields           = lookUp  SLIT("-funbox-strict-fields")
 403
 404 {-
 405    The optional '-inpackage=P' flag tells what package
 406    we are compiling this module for.
 407    The Prelude, for example is compiled with '-package prelude'
 408 -}
 409 opt_InPackage                   = case lookup_str "-inpackage=" of
 410                                     Just p  -> _PK_ p
 411                                     Nothing -> SLIT("Main")     -- The package name if none is specified
 412
 413 opt_EmitCExternDecls            = lookUp  SLIT("-femit-extern-decls")
 414 opt_EnsureSplittableC           = lookUp  SLIT("-fglobalise-toplev-names")
 415 opt_GranMacros                  = lookUp  SLIT("-fgransim")
 416 opt_HiVersion                   = lookup_def_int "-fhi-version=" 0 -- what version we're compiling.
 417 opt_HistorySize                 = lookup_def_int "-fhistory-size" 20
 418 opt_IgnoreAsserts               = lookUp  SLIT("-fignore-asserts")
 419 opt_IgnoreIfacePragmas          = lookUp  SLIT("-fignore-interface-pragmas")
 420 opt_NoHiCheck                   = lookUp  SLIT("-fno-hi-version-check")
 421 opt_OmitBlackHoling             = lookUp  SLIT("-dno-black-holing")
 422 opt_OmitInterfacePragmas        = lookUp  SLIT("-fomit-interface-pragmas")
 423
 424 -- Simplifier switches
 425 opt_SimplNoPreInlining          = lookUp SLIT("-fno-pre-inlining")
 426         -- NoPreInlining is there just to see how bad things
 427         -- get if you don't do it!
 428 opt_SimplDoEtaReduction         = lookUp SLIT("-fdo-eta-reduction")
 429 opt_SimplDoLambdaEtaExpansion   = lookUp SLIT("-fdo-lambda-eta-expansion")
 430 opt_SimplCaseOfCase             = lookUp SLIT("-fcase-of-case")
 431 opt_SimplCaseMerge              = lookUp SLIT("-fcase-merge")
 432 opt_SimplPedanticBottoms        = lookUp SLIT("-fpedantic-bottoms")
 433 opt_SimplExcessPrecision        = lookUp SLIT("-fexcess-precision")
 434
 435 -- Unfolding control
 436 opt_UF_HiFileThreshold          = lookup_def_int "-funfolding-interface-threshold" (45::Int)
 437 opt_UF_CreationThreshold        = lookup_def_int "-funfolding-creation-threshold"  (45::Int)
 438 opt_UF_UseThreshold             = lookup_def_int "-funfolding-use-threshold"       (8::Int)     -- Discounts can be big
 439 opt_UF_FunAppDiscount           = lookup_def_int "-funfolding-fun-discount"        (6::Int)     -- It's great to inline a fn
 440 opt_UF_KeenessFactor            = lookup_def_float "-funfolding-keeness-factor"    (1.5::Float)
 441 opt_UF_UpdateInPlace            = lookUp  SLIT("-funfolding-update-in-place")
 442
 443 opt_UF_CheapOp  = ( 1 :: Int)   -- Only one instruction; and the args are charged for
 444 opt_UF_DearOp   = ( 4 :: Int)
 445
 446 opt_NoPruneDecls                = lookUp SLIT("-fno-prune-decls")
 447 opt_NoPruneTyDecls              = lookUp SLIT("-fno-prune-tydecls")
 448 opt_Static                      = lookUp SLIT("-static")
 449 opt_Unregisterised              = lookUp SLIT("-funregisterised")
 450 opt_Verbose                     = lookUp SLIT("-v")
 451 \end{code}
 452
 453 %************************************************************************
 454 %*                                                                      *
 455 \subsection{List of static hsc flags}
 456 %*                                                                      *
 457 %************************************************************************
 458
 459 \begin{code}
 460 isStaticHscFlag f =
 461   f `elem` [
 462         "fauto-sccs-on-all-toplevs",
 463         "fauto-sccs-on-exported-toplevs",
 464         "fauto-sccs-on-individual-cafs",
 465         "fauto-sccs-on-dicts",
 466         "fscc-profiling",
 467         "fticky-ticky",
 468         "fall-strict",
 469         "fdicts-strict",
 470         "firrefutable-tuples",
 471         "fnumbers-strict",
 472         "fparallel",
 473         "fsmp",
 474         "fsemi-tagging",
 475         "ffoldr-build-on",
 476         "flet-no-escape",
 477         "funfold-casms-in-hi-file",
 478         "fusagesp-on",
 479         "funbox-strict-fields",
 480         "femit-extern-decls",
 481         "fglobalise-toplev-names",
 482         "fgransim",
 483         "fignore-asserts",
 484         "fignore-interface-pragmas",
 485         "fno-hi-version-check",
 486         "fno-implicit-prelude",
 487         "dno-black-holing",
 488         "fomit-interface-pragmas",
 489         "fno-pre-inlining",
 490         "fdo-eta-reduction",
 491         "fdo-lambda-eta-expansion",
 492         "fcase-of-case",
 493         "fcase-merge",
 494         "fpedantic-bottoms",
 495         "fexcess-precision",
 496         "funfolding-update-in-place",
 497         "freport-compile",
 498         "fno-prune-decls",
 499         "fno-prune-tydecls",
 500         "static",
 501         "funregisterised",
 502         "v" ]
 503   || any (flip prefixMatch f) [
 504         "fcontext-stack",
 505         "fliberate-case-threshold",
 506         "fhi-version=",
 507         "fhistory-size",
 508         "funfolding-interface-threshold",
 509         "funfolding-creation-threshold",
 510         "funfolding-use-threshold",
 511         "funfolding-fun-discount",
 512         "funfolding-keeness-factor"
 513      ]
 514 \end{code}
 515
 516 %************************************************************************
 517 %*                                                                      *
 518 \subsection{Switch ordering}
 519 %*                                                                      *
 520 %************************************************************************
 521
 522 These things behave just like enumeration types.
 523
 524 \begin{code}
 525 instance Eq SimplifierSwitch where
 526     a == b = tagOf_SimplSwitch a ==# tagOf_SimplSwitch b
 527
 528 instance Ord SimplifierSwitch where
 529     a <  b  = tagOf_SimplSwitch a <# tagOf_SimplSwitch b
 530     a <= b  = tagOf_SimplSwitch a <=# tagOf_SimplSwitch b
 531
 532
 533 tagOf_SimplSwitch (SimplInlinePhase _)          = _ILIT(1)
 534 tagOf_SimplSwitch (MaxSimplifierIterations _)   = _ILIT(2)
 535 tagOf_SimplSwitch DontApplyRules                = _ILIT(3)
 536 tagOf_SimplSwitch SimplLetToCase                = _ILIT(4)
 537 tagOf_SimplSwitch NoCaseOfCase                  = _ILIT(5)
 538
 539 -- If you add anything here, be sure to change lAST_SIMPL_SWITCH_TAG, too!
 540
 541 lAST_SIMPL_SWITCH_TAG = 5
 542 \end{code}
 543
 544 %************************************************************************
 545 %*                                                                      *
 546 \subsection{Switch lookup}
 547 %*                                                                      *
 548 %************************************************************************
 549
 550 \begin{code}
 551 isAmongSimpl :: [SimplifierSwitch] -> SimplifierSwitch -> SwitchResult
 552 isAmongSimpl on_switches                -- Switches mentioned later occur *earlier*
 553                                         -- in the list; defaults right at the end.
 554   = let
 555         tidied_on_switches = foldl rm_dups [] on_switches
 556                 -- The fold*l* ensures that we keep the latest switches;
 557                 -- ie the ones that occur earliest in the list.
 558
 559         sw_tbl :: Array Int SwitchResult
 560         sw_tbl = (array (0, lAST_SIMPL_SWITCH_TAG) -- bounds...
 561                         all_undefined)
 562                  // defined_elems
 563
 564         all_undefined = [ (i, SwBool False) | i <- [0 .. lAST_SIMPL_SWITCH_TAG ] ]
 565
 566         defined_elems = map mk_assoc_elem tidied_on_switches
 567     in
 568     -- (avoid some unboxing, bounds checking, and other horrible things:)
 569 #if __GLASGOW_HASKELL__ < 405
 570     case sw_tbl of { Array bounds_who_needs_'em stuff ->
 571 #else
 572     case sw_tbl of { Array _ _ stuff ->
 573 #endif
 574     \ switch ->
 575         case (indexArray# stuff (tagOf_SimplSwitch switch)) of
 576 #if __GLASGOW_HASKELL__ < 400
 577           Lift v -> v
 578 #elif __GLASGOW_HASKELL__ < 403
 579           (# _, v #) -> v
 580 #else
 581           (# v #) -> v
 582 #endif
 583     }
 584   where
 585     mk_assoc_elem k@(MaxSimplifierIterations lvl)
 586         = (iBox (tagOf_SimplSwitch k), SwInt lvl)
 587     mk_assoc_elem k@(SimplInlinePhase n)
 588         = (iBox (tagOf_SimplSwitch k), SwInt n)
 589     mk_assoc_elem k
 590         = (iBox (tagOf_SimplSwitch k), SwBool True) -- I'm here, Mom!
 591
 592     -- cannot have duplicates if we are going to use the array thing
 593     rm_dups switches_so_far switch
 594       = if switch `is_elem` switches_so_far
 595         then switches_so_far
 596         else switch : switches_so_far
 597       where
 598         sw `is_elem` []     = False
 599         sw `is_elem` (s:ss) = (tagOf_SimplSwitch sw) ==# (tagOf_SimplSwitch s)
 600                             || sw `is_elem` ss
 601 \end{code}
 602
 603
 604 %************************************************************************
 605 %*                                                                      *
 606 \subsection{Misc functions for command-line options}
 607 %*                                                                      *
 608 %************************************************************************
 609
 610
 611 \begin{code}
 612 switchIsOn :: (switch -> SwitchResult) -> switch -> Bool
 613
 614 switchIsOn lookup_fn switch
 615   = case (lookup_fn switch) of
 616       SwBool False -> False
 617       _            -> True
 618
 619 intSwitchSet :: (switch -> SwitchResult)
 620              -> (Int -> switch)
 621              -> Maybe Int
 622
 623 intSwitchSet lookup_fn switch
 624   = case (lookup_fn (switch (panic "intSwitchSet"))) of
 625       SwInt int -> Just int
 626       _         -> Nothing
 627 \end{code}
 628
 629 \begin{code}
 630 startsWith :: String -> String -> Maybe String
 631 -- startsWith pfx (pfx++rest) = Just rest
 632
 633 startsWith []     str = Just str
 634 startsWith (c:cs) (s:ss)
 635   = if c /= s then Nothing else startsWith cs ss
 636 startsWith  _     []  = Nothing
 637
 638 endsWith  :: String -> String -> Maybe String
 639 endsWith cs ss
 640   = case (startsWith (reverse cs) (reverse ss)) of
 641       Nothing -> Nothing
 642       Just rs -> Just (reverse rs)
 643 \end{code}