Ah yes, thanks; TypeOperators is needed for the (':), but DataKinds for everything else. I'll modify. Simon | -----Original Message----- | From: ghc-devs [mailto:ghc-devs-bounces@haskell.org] On Behalf Of | Gabor Greif | Sent: 15 December 2014 17:27 | To: ghc-devs@haskell.org | Subject: Re: [commit: ghc] master: Improve documentation of syntax for | promoted lists (a972bdd) | | Hmm, shouldn't that be -XDataKinds (instead of -XTypeOperators)? | | | also: | umambiguous ---> unambiguous | becuase ---> because | | Cheers, | | Gabor | | On 12/15/14, git@git.haskell.org wrote: | > Repository : ssh://git@git.haskell.org/ghc | > | > On branch : master | > Link : | > | http://ghc.haskell.org/trac/ghc/changeset/a972bddfc8115d80d774383a5520 | > 2a293dc68595/ghc | > | >>--------------------------------------------------------------- | > | > commit a972bddfc8115d80d774383a55202a293dc68595 | > Author: Simon Peyton Jones | > Date: Mon Dec 15 17:08:29 2014 +0000 | > | > Improve documentation of syntax for promoted lists | > | > THe documentation in 7.9.4 of promoted list and tuple types was | > misleading, which led to Trac #9882. This patch makes explicit | > that only type-level with two or more elements can have the | > quote omitted. | > | > | >>--------------------------------------------------------------- | > | > a972bddfc8115d80d774383a55202a293dc68595 | > compiler/parser/Parser.y | 8 ++++++-- | > docs/users_guide/glasgow_exts.xml | 19 ++++++++++++++++--- | > 2 files changed, 22 insertions(+), 5 deletions(-) | > | > diff --git a/compiler/parser/Parser.y b/compiler/parser/Parser.y | index | > bffe6e1..235d34a 100644 | > --- a/compiler/parser/Parser.y | > +++ b/compiler/parser/Parser.y | > @@ -1483,6 +1483,10 @@ atype :: { LHsType RdrName } | > [mo $2,mc | $4] } | > | SIMPLEQUOTE var { sLL $1 $> $ | HsTyVar $ | > unLoc $2 } | > | > + -- Two or more [ty, ty, ty] must be a promoted list type, | just as | > + -- if you had written '[ty, ty, ty] | > + -- (One means a list type, zero means the list type | constructor, | > + -- so you have to quote those.) | > | '[' ctype ',' comma_types1 ']' {% ams (sLL $1 $> $ | > HsExplicitListTy | > | placeHolderKind ($2 : | > $4)) | > [mo $1, mj | AnnComma | > $3,mc $5] } @@ -1503,11 +1507,11 @@ inst_types1 :: { [LHsType | RdrName] | > } | > | inst_type ',' inst_types1 {% addAnnotation (gl $1) | AnnComma | > (gl $2) | > >> return ($1 : $3) } | > | > -comma_types0 :: { [LHsType RdrName] } | > +comma_types0 :: { [LHsType RdrName] } -- Zero or more: ty,ty,ty | > : comma_types1 { $1 } | > | {- empty -} { [] } | > | > -comma_types1 :: { [LHsType RdrName] } | > +comma_types1 :: { [LHsType RdrName] } -- One or more: ty,ty,ty | > : ctype { [$1] } | > | ctype ',' comma_types1 {% addAnnotation (gl $1) | AnnComma | > (gl $2) | > >> return ($1 : $3) } | diff | > --git a/docs/users_guide/glasgow_exts.xml | > b/docs/users_guide/glasgow_exts.xml | > index e12703f..7edca07 100644 | > --- a/docs/users_guide/glasgow_exts.xml | > +++ b/docs/users_guide/glasgow_exts.xml | > @@ -6882,9 +6882,9 @@ is a single quote.</para> </sect2> | > | > <sect2 id="promoted-lists-and-tuples"> -<title>Promoted lists and | > tuples types</title> | > +<title>Promoted list and tuple types</title> | > <para> | > -Haskell's list and tuple types are natively promoted to kinds, and | > enjoy the | > +With <option>-XTypeOperators</option>, Haskell's list and tuple | types | > +are | > natively promoted to kinds, and enjoy the same convenient syntax at | > the type level, albeit prefixed with a quote: | > <programlisting> | > data HList :: [*] -> * where | > @@ -6893,8 +6893,21 @@ data HList :: [*] -> * where | > | > data Tuple :: (*,*) -> * where | > Tuple :: a -> b -> Tuple '(a,b) | > + | > +foo0 :: HList '[] | > +foo0 = HNil | > + | > +foo1 :: HList '[Int] | > +foo1 = HCons (3::Int) HNil | > + | > +foo2 :: HList [Int, Bool] | > +foo2 = ... | > </programlisting> | > -Note that this requires <option>-XTypeOperators</option>. | > +For type-level lists of <emphasis>two or more elements</emphasis>, | > +such as the signature of <literal>foo2</literal> above, the quote | may | > +be | > omitted because the meaning is | > +umambiguous. But for lists of one or zero elements (as in | > <literal>foo0</literal> | > +and <literal>foo1</literal>), the quote is required, becuase the | > +types | > <literal>[]</literal> | > +and <literal>[Int]</literal> have existing meanings in Haskell. | > </para> | > </sect2> | > | > | > _______________________________________________ | > ghc-commits mailing list | > ghc-commits@haskell.org | > http://www.haskell.org/mailman/listinfo/ghc-commits | > | _______________________________________________ | ghc-devs mailing list | ghc-devs@haskell.org | http://www.haskell.org/mailman/listinfo/ghc-devs