-> Either String (m (), [String])
processOneArg action rest arg args
= let dash_arg = '-' : arg
+ rest_no_eq = dropEq rest
in case action of
NoArg a -> ASSERT(null rest) Right (a, args)
- HasArg f | notNull rest -> Right (f rest, args)
+ HasArg f | notNull rest_no_eq -> Right (f rest_no_eq, args)
| otherwise -> case args of
[] -> missingArgErr dash_arg
(arg1:args1) -> Right (f arg1, args1)
[] -> unknownFlagErr dash_arg
(arg1:args1) -> Right (f arg1, args1)
- Prefix f | notNull rest -> Right (f rest, args)
+ Prefix f | notNull rest_no_eq -> Right (f rest_no_eq, args)
| otherwise -> unknownFlagErr dash_arg
- PrefixPred p f | notNull rest -> Right (f rest, args)
- | otherwise -> unknownFlagErr dash_arg
+ PrefixPred p f | notNull rest_no_eq -> Right (f rest_no_eq, args)
+ | otherwise -> unknownFlagErr dash_arg
PassFlag f | notNull rest -> unknownFlagErr dash_arg
| otherwise -> Right (f dash_arg, args)
- OptIntSuffix f | null rest -> Right (f Nothing, args)
- | Just n <- parseInt rest -> Right (f (Just n), args)
+ OptIntSuffix f | null rest -> Right (f Nothing, args)
+ | Just n <- parseInt rest_no_eq -> Right (f (Just n), args)
| otherwise -> Left ("malformed integer argument in " ++ dash_arg)
- IntSuffix f | Just n <- parseInt rest -> Right (f n, args)
+ IntSuffix f | Just n <- parseInt rest_no_eq -> Right (f n, args)
| otherwise -> Left ("malformed integer argument in " ++ dash_arg)
- OptPrefix f -> Right (f rest, args)
+ OptPrefix f -> Right (f rest_no_eq, args)
AnySuffix f -> Right (f dash_arg, args)
AnySuffixPred p f -> Right (f dash_arg, args)
arg_ok (HasArg _) rest arg = True
arg_ok (SepArg _) rest arg = null rest
arg_ok (Prefix _) rest arg = notNull rest
-arg_ok (PrefixPred p _) rest arg = notNull rest && p rest
+arg_ok (PrefixPred p _) rest arg = notNull rest && p (dropEq rest)
arg_ok (OptIntSuffix _) rest arg = True
arg_ok (IntSuffix _) rest arg = True
arg_ok (OptPrefix _) rest arg = True
-- Looks for "433" or "=342", with no trailing gubbins
-- n or =n => Just n
-- gibberish => Nothing
-parseInt s = case reads (dropEq s) of
+parseInt s = case reads s of
((n,""):_) -> Just n
other -> Nothing
import Panic ( panic, GhcException(..) )
import UniqFM ( UniqFM )
import Util ( notNull, splitLongestPrefix, normalisePath )
-import Maybes ( fromJust, orElse )
+import Maybes ( orElse, fromJust )
import SrcLoc ( SrcSpan )
import Outputable
import {-# SOURCE #-} ErrUtils ( Severity(..), Message, mkLocMessage )
import Util ( split )
#endif
-import Data.Char ( isUpper )
+import Data.Char ( isUpper, toLower )
import System.IO ( hPutStrLn, stderr )
-- -----------------------------------------------------------------------------
| Opt_BangPatterns
| Opt_TypeFamilies
| Opt_OverloadedStrings
+ | Opt_GADTs
+ | Opt_RelaxedPolyRec -- -X=RelaxedPolyRec
-- optimisation opts
| Opt_Strictness
, ( "fglasgow-exts", NoArg (mapM_ setDynFlag glasgowExtsFlags) )
, ( "fno-glasgow-exts", NoArg (mapM_ unSetDynFlag glasgowExtsFlags) )
-
-- the rest of the -f* and -fno-* flags
- , ( "fno-", PrefixPred (\f -> isFFlag f) (\f -> unSetDynFlag (getFFlag f)) )
- , ( "f", PrefixPred (\f -> isFFlag f) (\f -> setDynFlag (getFFlag f)) )
+ , ( "f", PrefixPred (isFlag fFlags) (\f -> setDynFlag (getFlag fFlags f)) )
+ , ( "f", PrefixPred (isNoFlag fFlags) (\f -> unSetDynFlag (getNoFlag fFlags f)) )
+
+ -- For now, allow -X flags with -f; ToDo: report this as deprecated
+ , ( "f", PrefixPred (isFlag xFlags) (\f -> setDynFlag (getFlag fFlags f)) )
+
+ -- the rest of the -X* and -Xno-* flags
+ , ( "X", PrefixPred (isFlag xFlags) (\f -> setDynFlag (getFlag xFlags f)) )
+ , ( "X", PrefixPred (isNoFlag xFlags) (\f -> unSetDynFlag (getNoFlag xFlags f)) )
]
-- these -f<blah> flags can all be reversed with -fno-<blah>
( "warn-deprecations", Opt_WarnDeprecations ),
( "warn-orphans", Opt_WarnOrphans ),
( "warn-tabs", Opt_WarnTabs ),
- ( "fi", Opt_FFI ), -- support `-ffi'...
- ( "ffi", Opt_FFI ), -- ...and also `-fffi'
- ( "arrows", Opt_Arrows ), -- arrow syntax
- ( "parr", Opt_PArr ),
- ( "th", Opt_TH ),
- ( "implicit-prelude", Opt_ImplicitPrelude ),
- ( "scoped-type-variables", Opt_ScopedTypeVariables ),
- ( "bang-patterns", Opt_BangPatterns ),
- ( "overloaded-strings", Opt_OverloadedStrings ),
- ( "type-families", Opt_TypeFamilies ),
- ( "monomorphism-restriction", Opt_MonomorphismRestriction ),
- ( "mono-pat-binds", Opt_MonoPatBinds ),
- ( "extended-default-rules", Opt_ExtendedDefaultRules ),
- ( "implicit-params", Opt_ImplicitParams ),
- ( "allow-overlapping-instances", Opt_AllowOverlappingInstances ),
- ( "allow-undecidable-instances", Opt_AllowUndecidableInstances ),
- ( "allow-incoherent-instances", Opt_AllowIncoherentInstances ),
- ( "generics", Opt_Generics ),
( "strictness", Opt_Strictness ),
( "full-laziness", Opt_FullLaziness ),
( "liberate-case", Opt_LiberateCase ),
]
-glasgowExtsFlags = [
- Opt_GlasgowExts,
- Opt_FFI,
- Opt_ImplicitParams,
- Opt_ScopedTypeVariables,
- Opt_TypeFamilies ]
+-- These -X<blah> flags can all be reversed with -Xno-<blah>
+xFlags :: [(String, DynFlag)]
+xFlags = [
+ ( "FI", Opt_FFI ), -- support `-ffi'...
+ ( "FFI", Opt_FFI ), -- ...and also `-fffi'
+ ( "ForeignFunctionInterface", Opt_FFI ), -- ...and also `-fffi'
+
+ ( "Arrows", Opt_Arrows ), -- arrow syntax
+ ( "Parr", Opt_PArr ),
+
+ ( "TH", Opt_TH ),
+ ( "TemplateHaskelll", Opt_TH ),
+
+ ( "Generics", Opt_Generics ),
+
+ ( "ImplicitPrelude", Opt_ImplicitPrelude ), -- On by default
+
+ ( "OverloadedStrings", Opt_OverloadedStrings ),
+ ( "GADTs", Opt_GADTs ),
+ ( "TypeFamilies", Opt_TypeFamilies ),
+ ( "BangPatterns", Opt_BangPatterns ),
+ ( "MonomorphismRestriction", Opt_MonomorphismRestriction ), -- On by default
+ ( "MonoPatBinds", Opt_MonoPatBinds ), -- On by default (which is not strictly H98)
+ ( "RelaxedPolyRec", Opt_RelaxedPolyRec),
+ ( "ExtendedDefaultRules", Opt_ExtendedDefaultRules ),
+ ( "ImplicitParams", Opt_ImplicitParams ),
+ ( "ScopedTypeVariables", Opt_ScopedTypeVariables ),
+ ( "AllowOverlappingInstances", Opt_AllowOverlappingInstances ),
+ ( "AllowUndecidableInstances", Opt_AllowUndecidableInstances ),
+ ( "AllowIncoherentInstances", Opt_AllowIncoherentInstances )
+ ]
+
+impliedFlags :: [(DynFlag, [DynFlag])]
+impliedFlags = [
+ ( Opt_GADTs, [Opt_RelaxedPolyRec] ) -- We want type-sig variables to be completely rigid for GADTs
+ ]
+
+glasgowExtsFlags = [ Opt_GlasgowExts
+ , Opt_FFI
+ , Opt_ImplicitParams
+ , Opt_ScopedTypeVariables
+ , Opt_TypeFamilies ]
+
+------------------
+isNoFlag, isFlag :: [(String,a)] -> String -> Bool
+
+isFlag flags f = is_flag flags (normaliseFlag f)
-isFFlag f = f `elem` (map fst fFlags)
-getFFlag f = fromJust (lookup f fFlags)
+isNoFlag flags no_f
+ | Just f <- noFlag_maybe (normaliseFlag no_f) = is_flag flags f
+ | otherwise = False
+
+is_flag flags nf = any (\(ff,_) -> normaliseFlag ff == nf) flags
+ -- nf is normalised alreadly
+
+------------------
+getFlag, getNoFlag :: [(String,a)] -> String -> a
+
+getFlag flags f = get_flag flags (normaliseFlag f)
+
+getNoFlag flags f = getFlag flags (fromJust (noFlag_maybe (normaliseFlag f)))
+ -- The flag should be a no-flag already
+
+get_flag flags nf = head [ opt | (ff, opt) <- flags, normaliseFlag ff == nf]
+
+------------------
+noFlag_maybe :: String -> Maybe String
+-- The input is normalised already
+noFlag_maybe ('n' : 'o' : f) = Just f
+noFlag_maybe other = Nothing
+
+normaliseFlag :: String -> String
+-- Normalise a option flag by
+-- * map to lower case
+-- * removing hyphens
+-- Thus: -X=overloaded-strings or -XOverloadedStrings
+normaliseFlag [] = []
+normaliseFlag ('-':s) = normaliseFlag s
+normaliseFlag (c:s) = toLower c : normaliseFlag s
-- -----------------------------------------------------------------------------
-- Parsing the dynamic flags.
dfs <- getCmdLineState
putCmdLineState $! (f dfs)
+--------------------------
setDynFlag, unSetDynFlag :: DynFlag -> DynP ()
-setDynFlag f = upd (\dfs -> dopt_set dfs f)
+setDynFlag f = upd (\dfs -> foldl dopt_set (dopt_set dfs f) deps)
+ where
+ deps = [ d | (f', ds) <- impliedFlags, f' == f, d <- ds ]
+ -- When you set f, set the ones it implies
+ -- When you un-set f, however, we don't un-set the things it implies
+ -- (except for -fno-glasgow-exts, which is treated specially)
+
unSetDynFlag f = upd (\dfs -> dopt_unset dfs f)
+--------------------------
setDumpFlag :: DynFlag -> OptKind DynP
setDumpFlag dump_flag
= NoArg (setDynFlag Opt_ForceRecomp >> setDynFlag dump_flag)
</thead>
<tbody>
<row>
- <entry><option>-fallow-overlapping-instances</option></entry>
+ <entry><option>-fglasgow-exts</option></entry>
+ <entry>Enable most language extensions</entry>
+ <entry>dynamic</entry>
+ <entry><option>-fno-glasgow-exts</option></entry>
+ </row>
+ <row>
+ <entry><option>-X=AllowOverlappingInstances</option></entry>
<entry>Enable <link linkend="instance-overlap">overlapping instances</link></entry>
<entry>dynamic</entry>
- <entry><option>-fno-allow-overlapping-instances</option></entry>
+ <entry><option>-X=NoAllowOverlappingInstances</option></entry>
</row>
<row>
- <entry><option>-fallow-incoherent-instances</option></entry>
+ <entry><option>-X=AllowIncoherentInstances</option></entry>
<entry>Enable <link linkend="instance-overlap">incoherent instances</link>.
- Implies <option>-fallow-overlapping-instances</option> </entry>
+ Implies <option>-X=AllowOverlappingInstances</option> </entry>
<entry>dynamic</entry>
- <entry><option>-fno-allow-incoherent-instances</option></entry>
+ <entry><option>-X=NoAllowIncoherentInstances</option></entry>
</row>
<row>
- <entry><option>-fallow-undecidable-instances</option></entry>
+ <entry><option>-X=AllowUndecidableInstances</option></entry>
<entry>Enable <link linkend="undecidable-instances">undecidable instances</link></entry>
<entry>dynamic</entry>
- <entry><option>-fno-allow-undecidable-instances</option></entry>
+ <entry><option>-X=NoAllowUndecidableInstances</option></entry>
</row>
<row>
<entry><option>-fcontext-stack=N</option><replaceable>n</replaceable></entry>
<entry><option>20</option></entry>
</row>
<row>
- <entry><option>-farrows</option></entry>
+ <entry><option>-X=Arrows</option></entry>
<entry>Enable <link linkend="arrow-notation">arrow
notation</link> extension</entry>
<entry>dynamic</entry>
- <entry><option>-fno-arrows</option></entry>
+ <entry><option>-X=NoArrows</option></entry>
</row>
<row>
- <entry><option>-ffi</option> or <option>-fffi</option></entry>
+ <entry><option>-X=FFI</option> or <option>-X=ForeignFunctionInterface</option></entry>
<entry>Enable <link linkend="ffi">foreign function interface</link> (implied by
<option>-fglasgow-exts</option>)</entry>
<entry>dynamic</entry>
- <entry><option>-fno-ffi</option></entry>
+ <entry><option>-X=NoFFI</option></entry>
</row>
<row>
- <entry><option>-fgenerics</option></entry>
+ <entry><option>-X=Generics</option></entry>
<entry>Enable <link linkend="generic-classes">generic classes</link></entry>
<entry>dynamic</entry>
- <entry><option>-fno-fgenerics</option></entry>
- </row>
- <row>
- <entry><option>-fglasgow-exts</option></entry>
- <entry>Enable most language extensions</entry>
- <entry>dynamic</entry>
- <entry><option>-fno-glasgow-exts</option></entry>
+ <entry><option>-X=NoGenerics</option></entry>
</row>
<row>
- <entry><option>-fimplicit-params</option></entry>
+ <entry><option>-X=ImplicitParams</option></entry>
<entry>Enable <link linkend="implicit-parameters">Implicit Parameters</link>.
Implied by <option>-fglasgow-exts</option>.</entry>
<entry>dynamic</entry>
- <entry><option>-fno-implicit-params</option></entry>
+ <entry><option>-X=NoImplicitParams</option></entry>
</row>
<row>
<entry><option>-firrefutable-tuples</option></entry>
<entry><option>-fno-irrefutable-tuples</option></entry>
</row>
<row>
- <entry><option>-fno-implicit-prelude</option></entry>
+ <entry><option>-X=NoImplicitPrelude</option></entry>
<entry>Don't implicitly <literal>import Prelude</literal></entry>
<entry>dynamic</entry>
- <entry><option>-fimplicit-prelude</option></entry>
+ <entry><option>-X=ImplicitPrelude</option></entry>
</row>
<row>
- <entry><option>-fno-monomorphism-restriction</option></entry>
+ <entry><option>-X=NoMonomorphismRestriction</option></entry>
<entry>Disable the <link linkend="monomorphism">monomorphism restriction</link></entry>
<entry>dynamic</entry>
- <entry><option>-fmonomorphism-restriction</option></entry>
+ <entry><option>-X=MonomorphismRrestriction</option></entry>
</row>
<row>
- <entry><option>-fno-mono-pat-binds</option></entry>
+ <entry><option>-X=NoMonoPatBinds</option></entry>
<entry>Make <link linkend="monomorphism">pattern bindings polymorphic</link></entry>
<entry>dynamic</entry>
- <entry><option>-fmono-pat-binds</option></entry>
+ <entry><option>-X=MonoPatBinds</option></entry>
</row>
<row>
- <entry><option>-fextended-default-rules</option></entry>
+ <entry><option>-X=ExtendedDefaultRules</option></entry>
<entry>Use GHCi's <link linkend="extended-default-rules">extended default rules</link> in a normal module</entry>
<entry>dynamic</entry>
- <entry><option>-fno-extended-default-rules</option></entry>
+ <entry><option>-X=NoExtendedDefaultRules</option></entry>
</row>
<row>
- <entry><option>-foverloaded-strings</option></entry>
+ <entry><option>-X=OverloadedStrings</option></entry>
<entry>Enable <link linkend="overloaded-strings">overloaded string literals</link>.
</entry>
<entry>dynamic</entry>
- <entry><option>-fno-overloaded-strings</option></entry>
+ <entry><option>-X=OverloadedStrings</option></entry>
</row>
<row>
- <entry><option>-fscoped-type-variables</option></entry>
+ <entry><option>-X=ScopedTypeVariables</option></entry>
<entry>Enable <link linkend="scoped-type-variables">lexically-scoped type variables</link>.
Implied by <option>-fglasgow-exts</option>.</entry>
<entry>dynamic</entry>
- <entry><option>-fno-scoped-type-variables</option></entry>
+ <entry><option>-X=NoScopedTypeVariables</option></entry>
</row>
<row>
- <entry><option>-fth</option></entry>
+ <entry><option>-X=TH</option> or <option>-X=TemplateHaskell</option></entry>
<entry>Enable <link linkend="template-haskell">Template Haskell</link>.
No longer implied by <option>-fglasgow-exts</option>.</entry>
<entry>dynamic</entry>
- <entry><option>-fno-th</option></entry>
+ <entry><option>-X=NoTH</option></entry>
</row>
<row>
- <entry><option>-ftype-families</option></entry>
+ <entry><option>-X=TypeFamilies</option></entry>
<entry>Enable <link linkend="type-families">type families</link>.</entry>
<entry>dynamic</entry>
- <entry><option>-fno-type-families</option></entry>
+ <entry><option>-X=NoTypeFamilies</option></entry>
</row>
<row>
- <entry><option>-fbang-patterns</option></entry>
+ <entry><option>-X=BangPtterns</option></entry>
<entry>Enable <link linkend="bang-patterns">bang patterns</link>.</entry>
<entry>dynamic</entry>
- <entry><option>-fno-bang-patterns</option></entry>
+ <entry><option>-X=NoBangPatterns</option></entry>
</row>
</tbody>
</tgroup>
<indexterm><primary>extensions</primary><secondary>options controlling</secondary>
</indexterm>
- <para>These flags control what variation of the language are
+ <para>The language option flag control what variation of the language are
permitted. Leaving out all of them gives you standard Haskell
98.</para>
- <para>NB. turning on an option that enables special syntax
+ <para>Generally speaking, all the language options are introduced by "<option>-X</option>" or "<option>-X=</option>";
+ e.g. <option>-X=TemplateHaskell</option>. Before anything else is done, the string following
+ "<option>-X</option>" is normalised by removing hyphens and converting
+ to lower case. So <option>-X=TemplateHaskell</option>, <option>-XTemplateHaskell</option>, and
+ <option>-Xtemplate-haskell</option> are all equivalent.
+ </para>
+
+ <para> All the language options can be turned off by using the prefix "<option>No</option>";
+ e.g. "<option>-X=NoTemplateHaskell</option>".</para>
+
+ <para> Language options recognised by Cabal can also be enabled using the <literal>LANGUAGE</literal> pragma,
+ thus <literal>{-# LANGUAGE TemplateHaskell #-}</literal> (see <xref linkend="language-pragma"/>>). </para>
+
+ <para> All the language options can be introduced with "<option>-f</option>" as well as "<option>-X</option>",
+ but this is a deprecated feature for backward compatibility. Use the "<option>-X</option>"
+ or LANGUAGE-pragma form.</para>
+
+ <para>Turning on an option that enables special syntax
<emphasis>might</emphasis> cause working Haskell 98 code to fail
to compile, perhaps because it uses a variable name which has
become a reserved word. So, together with each option below, we
<para>This simultaneously enables all of the extensions to
Haskell 98 described in <xref
linkend="ghc-language-features"/>, except where otherwise
- noted. </para>
+ noted. We are trying to move away from this portmanteau flag,
+ and towards enabling features individaully.</para>
<para>New reserved words: <literal>forall</literal> (only in
types), <literal>mdo</literal>.</para>
<replaceable>float</replaceable><literal>##</literal>,
<literal>(#</literal>, <literal>#)</literal>,
<literal>|)</literal>, <literal>{|</literal>.</para>
+
+ <para>Implies these specific language options:
+ <option>-X=ForeignFunctionInterface</option>,
+ <option>-X=ImplicitParams</option>,
+ <option>-X=ScopedTypeVariables</option>,
+ <option>-X=GADTs</option>,
+ <option>-X=TypeFamilies</option>. </para>
</listitem>
</varlistentry>
<varlistentry>
<term>
- <option>-ffi</option> and <option>-fffi</option>:
- <indexterm><primary><option>-ffi</option></primary></indexterm>
- <indexterm><primary><option>-fffi</option></primary></indexterm>
+ <option>-X=ffi</option> and <option>-X=ForeignFunctionInterface</option>:
+ <indexterm><primary><option>-X=FFI</option></primary></indexterm>
</term>
<listitem>
<para>This option enables the language extension defined in the
<varlistentry>
<term>
- <option>-fno-monomorphism-restriction</option>,<option>-fno-mono-pat-binds</option>:
+ <option>-X=MonomorphismRestriction</option>,<option>-X=MonoPatBinds</option>:
</term>
<listitem>
<para> These two flags control how generalisation is done.
<varlistentry>
<term>
- <option>-fextended-default-rules</option>:
- <indexterm><primary><option>-fextended-default-rules</option></primary></indexterm>
+ <option>-X=ExtendedDefaultRules</option>:
+ <indexterm><primary><option>-X=ExtendedDefaultRules</option></primary></indexterm>
</term>
<listitem>
<para> Use GHCi's extended default rules in a regular module (<xref linkend="extended-default-rules"/>).
<varlistentry>
<term>
- <option>-fallow-overlapping-instances</option>
- <indexterm><primary><option>-fallow-overlapping-instances</option></primary></indexterm>
+ <option>-X=AllowOverlappingInstances</option>
+ <indexterm><primary><option>-X=AllowOverlappingInstances</option></primary></indexterm>
</term>
<term>
- <option>-fallow-undecidable-instances</option>
- <indexterm><primary><option>-fallow-undecidable-instances</option></primary></indexterm>
+ <option>-X=AllowUndecidableInstances</option>
+ <indexterm><primary><option>-X=AllowUndecidableInstances</option></primary></indexterm>
</term>
<term>
- <option>-fallow-incoherent-instances</option>
- <indexterm><primary><option>-fallow-incoherent-instances</option></primary></indexterm>
+ <option>-X=AllowIncoherentInstances</option>
+ <indexterm><primary><option>-X=AllowIncoherentInstances</option></primary></indexterm>
</term>
<term>
<option>-fcontext-stack=N</option>
<varlistentry>
<term>
- <option>-farrows</option>
- <indexterm><primary><option>-farrows</option></primary></indexterm>
+ <option>-X=Arrows</option>
+ <indexterm><primary><option>-X=Arrows</option></primary></indexterm>
</term>
<listitem>
<para>See <xref linkend="arrow-notation"/>. Independent of
<varlistentry>
<term>
- <option>-fgenerics</option>
- <indexterm><primary><option>-fgenerics</option></primary></indexterm>
+ <option>-X=Generics</option>
+ <indexterm><primary><option>-X=Generics</option></primary></indexterm>
</term>
<listitem>
<para>See <xref linkend="generic-classes"/>. Independent of
</varlistentry>
<varlistentry>
- <term><option>-fno-implicit-prelude</option></term>
+ <term><option>-X=NoImplicitIrelude</option></term>
<listitem>
- <para><indexterm><primary>-fno-implicit-prelude
+ <para><indexterm><primary>-XnoImplicitPrelude
option</primary></indexterm> GHC normally imports
<filename>Prelude.hi</filename> files for you. If you'd
rather it didn't, then give it a
- <option>-fno-implicit-prelude</option> option. The idea is
+ <option>-XnoImplicitPrelude</option> option. The idea is
that you can then import a Prelude of your own. (But don't
call it <literal>Prelude</literal>; the Haskell module
namespace is flat, and you must not conflict with any
translation for list comprehensions continues to use
<literal>Prelude.map</literal> etc.</para>
- <para>However, <option>-fno-implicit-prelude</option> does
+ <para>However, <option>-X=NoImplicitPrelude</option> does
change the handling of certain built-in syntax: see <xref
linkend="rebindable-syntax"/>.</para>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>-fimplicit-params</option></term>
+ <term><option>-X=ImplicitParams</option></term>
<listitem>
<para>Enables implicit parameters (see <xref
linkend="implicit-parameters"/>). Currently also implied by
</varlistentry>
<varlistentry>
- <term><option>-foverloaded-strings</option></term>
+ <term><option>-X=OverloadedStrings</option></term>
<listitem>
<para>Enables overloaded string literals (see <xref
linkend="overloaded-strings"/>).</para>
</varlistentry>
<varlistentry>
- <term><option>-fscoped-type-variables</option></term>
+ <term><option>-X=ScopedTypeVariables</option></term>
<listitem>
<para>Enables lexically-scoped type variables (see <xref
linkend="scoped-type-variables"/>). Implied by
</varlistentry>
<varlistentry>
- <term><option>-fth</option></term>
+ <term><option>-X=TH</option>, <option>-X=TemplateHaskell</option></term>
<listitem>
<para>Enables Template Haskell (see <xref
linkend="template-haskell"/>). This flag must
hierarchy. It completely defeats that purpose if the
literal "1" means "<literal>Prelude.fromInteger
1</literal>", which is what the Haskell Report specifies.
- So the <option>-fno-implicit-prelude</option> flag causes
+ So the <option>-X=NoImplicitPrelude</option> flag causes
the following pieces of built-in syntax to refer to
<emphasis>whatever is in scope</emphasis>, not the Prelude
versions:
may use different notation to that implemented in GHC.
</para>
<para>
-The rest of this section outlines the extensions to GHC that support GADTs.
+The rest of this section outlines the extensions to GHC that support GADTs. The extension is enabled with
+<option>-X=GADTs</option>.
<itemizedlist>
<listitem><para>
A GADT can only be declared using GADT-style syntax (<xref linkend="gadt-style"/>);
</para>
<para>
Nevertheless, GHC allows you to experiment with more liberal rules. If you use
-the experimental flag <option>-fallow-undecidable-instances</option>
-<indexterm><primary>-fallow-undecidable-instances
-option</primary></indexterm>, both the Paterson Conditions and the Coverage Condition
+the experimental flag <option>-X=AllowUndecidableInstances</option>
+<indexterm><primary>-X=AllowUndecidableInstances</primary></indexterm>,
+both the Paterson Conditions and the Coverage Condition
(described in <xref linkend="instance-rules"/>) are lifted. Termination is ensured by having a
fixed-depth recursion stack. If you exceed the stack depth you get a
sort of backtrace, and the opportunity to increase the stack depth
In general, <emphasis>GHC requires that that it be unambiguous which instance
declaration
should be used to resolve a type-class constraint</emphasis>. This behaviour
-can be modified by two flags: <option>-fallow-overlapping-instances</option>
-<indexterm><primary>-fallow-overlapping-instances
+can be modified by two flags: <option>-X=AllowOverlappingInstances</option>
+<indexterm><primary>-X=AllowOverlappingInstances
</primary></indexterm>
-and <option>-fallow-incoherent-instances</option>
-<indexterm><primary>-fallow-incoherent-instances
+and <option>-X=AllowIncoherentInstances</option>
+<indexterm><primary>-X=AllowIncoherentInstances
</primary></indexterm>, as this section discusses. Both these
flags are dynamic flags, and can be set on a per-module basis, using
an <literal>OPTIONS_GHC</literal> pragma if desired (<xref linkend="source-file-options"/>).</para>
</para>
<para>
-The <option>-fallow-overlapping-instances</option> flag instructs GHC to allow
+The <option>-X=AllowOverlappingInstances</option> flag instructs GHC to allow
more than one instance to match, provided there is a most specific one. For
example, the constraint <literal>C Int [Int]</literal> matches instances (A),
(C) and (D), but the last is more specific, and hence is chosen. If there is no
GHC does not commit to instance (C), because in a particular
call of <literal>f</literal>, <literal>b</literal> might be instantiate
to <literal>Int</literal>, in which case instance (D) would be more specific still.
-So GHC rejects the program. If you add the flag <option>-fallow-incoherent-instances</option>,
+So GHC rejects the program. If you add the flag <option>-X=AllowIncoherentInstances</option>,
GHC will instead pick (C), without complaining about
the problem of subsequent instantiations.
</para>
<para>
The willingness to be overlapped or incoherent is a property of
the <emphasis>instance declaration</emphasis> itself, controlled by the
-presence or otherwise of the <option>-fallow-overlapping-instances</option>
-and <option>-fallow-incoherent-instances</option> flags when that mdodule is
+presence or otherwise of the <option>-X=AllowOverlappingInstances</option>
+and <option>-X=AllowIncoherentInstances</option> flags when that mdodule is
being defined. Neither flag is required in a module that imports and uses the
instance declaration. Specifically, during the lookup process:
<itemizedlist>
<listitem><para>
An instance declaration is ignored during the lookup process if (a) a more specific
match is found, and (b) the instance declaration was compiled with
-<option>-fallow-overlapping-instances</option>. The flag setting for the
+<option>-X=AllowOverlappingInstances</option>. The flag setting for the
more-specific instance does not matter.
</para></listitem>
<listitem><para>
does unify with it, so that it might match when the constraint is further
instantiated. Usually GHC will regard this as a reason for not committing to
some other constraint. But if the instance declaration was compiled with
-<option>-fallow-incoherent-instances</option>, GHC will skip the "does-it-unify?"
+<option>-X=AllowIncoherentInstances</option>, GHC will skip the "does-it-unify?"
check for that declaration.
</para></listitem>
</itemizedlist>
</para>
<para>
If an instance declaration is compiled without
-<option>-fallow-overlapping-instances</option>,
+<option>-X=AllowOverlappingInstances</option>,
then that instance can never be overlapped. This could perhaps be
inconvenient. Perhaps the rule should instead say that the
<emphasis>overlapping</emphasis> instance declaration should be compiled in
this way, rather than the <emphasis>overlapped</emphasis> one. Perhaps overlap
at a usage site should be permitted regardless of how the instance declarations
-are compiled, if the <option>-fallow-overlapping-instances</option> flag is
+are compiled, if the <option>-X=AllowOverlappingInstances</option> flag is
used at the usage site. (Mind you, the exact usage site can occasionally be
hard to pin down.) We are interested to receive feedback on these points.
</para>
-<para>The <option>-fallow-incoherent-instances</option> flag implies the
-<option>-fallow-overlapping-instances</option> flag, but not vice versa.
+<para>The <option>-X=AllowIncoherentInstances</option> flag implies the
+<option>-X=AllowOverlappingInstances</option> flag, but not vice versa.
</para>
</sect3>
due to Jeff Lewis.)</para>
<para>Implicit parameter support is enabled with the option
-<option>-fimplicit-params</option>.</para>
+<option>-X=ImplicitParams</option>.</para>
<para>
A variable is called <emphasis>dynamically bound</emphasis> when it is bound by the calling
<para>
GHC supports <emphasis>overloaded string literals</emphasis>. Normally a
string literal has type <literal>String</literal>, but with overloaded string
-literals enabled (with <literal>-foverloaded-strings</literal>)
+literals enabled (with <literal>-X=OverloadedStrings</literal>)
a string literal has type <literal>(IsString a) => a</literal>.
</para>
<para>
from module <literal>GHC.Exts</literal>.
</para>
<para>
-Haskell's defaulting mechanism is extended to cover string literals, when <option>-foverloaded-strings</option> is specified.
+Haskell's defaulting mechanism is extended to cover string literals, when <option>-X-OverloadedStrings</option> is specified.
Specifically:
<itemizedlist>
<listitem><para>
guide when it has stabilised.
</para>
<para>
-Type families are enabled by the flag <option>-ftype-families</option>.
+Type families are enabled by the flag <option>-X=TypeFamilies</option>.
</para>
<para> Template Haskell has the following new syntactic
constructions. You need to use the flag
- <option>-fth</option><indexterm><primary><option>-fth</option></primary>
+ <option>-X=TemplateHaskell</option> or <option>-X=TH</option>
+ <indexterm><primary><option>-X=TemplateHaskell</option></primary>
</indexterm>to switch these syntactic extensions on
- (<option>-fth</option> is no longer implied by
+ (<option>-X=TemplateHaskell</option> is no longer implied by
<option>-fglasgow-exts</option>).</para>
<itemizedlist>
<para>Now run the compiler (here we are a Cygwin prompt on Windows):
</para>
<programlisting>
-$ ghc --make -fth main.hs -o main.exe
+$ ghc --make -X=TemplateHaskell main.hs -o main.exe
</programlisting>
<para>Run "main.exe" and here is your output:</para>
</itemizedlist>
and the arrows web page at
<ulink url="http://www.haskell.org/arrows/"><literal>http://www.haskell.org/arrows/</literal></ulink>.
-With the <option>-farrows</option> flag, GHC supports the arrow
+With the <option>-X=Arrows</option> flag, GHC supports the arrow
notation described in the second of these papers.
What follows is a brief introduction to the notation;
it won't make much sense unless you've read Hughes's paper.
than the material below.
</para>
<para>
-Bang patterns are enabled by the flag <option>-fbang-patterns</option>.
+Bang patterns are enabled by the flag <option>-X=BangPatterns</option>.
</para>
<sect2 id="bang-patterns-informal">
<itemizedlist>
<listitem>
<para>Use the flags <option>-fglasgow-exts</option> (to enable the extra syntax),
- <option>-fgenerics</option> (to generate extra per-data-type code),
+ <option>-X=Generics</option> (to generate extra per-data-type code),
and <option>-package lang</option> (to make the <literal>Generics</literal> library
available. </para>
</listitem>
<sect2>
<title>Switching off the dreaded Monomorphism Restriction</title>
- <indexterm><primary><option>-fno-monomorphism-restriction</option></primary></indexterm>
+ <indexterm><primary><option>-X=NoMonomorphismRestriction</option></primary></indexterm>
<para>Haskell's monomorphism restriction (see
<ulink url="http://haskell.org/onlinereport/decls.html#sect4.5.5">Section
4.5.5</ulink>
of the Haskell Report)
can be completely switched off by
-<option>-fno-monomorphism-restriction</option>.
+<option>-X=NoMonomorphismRestriction</option>.
</para>
</sect2>
<sect2>
<title>Monomorphic pattern bindings</title>
- <indexterm><primary><option>-fno-mono-pat-binds</option></primary></indexterm>
- <indexterm><primary><option>-fmono-pat-binds</option></primary></indexterm>
+ <indexterm><primary><option>-X=NoMonoPatBinds</option></primary></indexterm>
+ <indexterm><primary><option>-X=MonoPatBinds</option></primary></indexterm>
<para> As an experimental change, we are exploring the possibility of
making pattern bindings monomorphic; that is, not generalised at all.
[x] = e -- A pattern binding
</programlisting>
Experimentally, GHC now makes pattern bindings monomorphic <emphasis>by
-default</emphasis>. Use <option>-fno-mono-pat-binds</option> to recover the
+default</emphasis>. Use <option>-X=MonoPatBinds</option> to recover the
standard behaviour.
</para>
</sect2>