diff options
Diffstat (limited to 'docs/users_guide/using.rst')
| -rw-r--r-- | docs/users_guide/using.rst | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/docs/users_guide/using.rst b/docs/users_guide/using.rst index e22622e394..553269cc75 100644 --- a/docs/users_guide/using.rst +++ b/docs/users_guide/using.rst @@ -306,7 +306,7 @@ The available mode flags are: :shortdesc: Stop after generating C (``.hc`` file) :type: mode :category: phases - + Stop after generating C (``.hc`` file) .. ghc-flag:: -S @@ -320,7 +320,7 @@ The available mode flags are: :shortdesc: Stop after generating object (``.o``) file :type: mode :category: phases - + Stop after generating object (``.o``) file This is the traditional batch-compiler mode, in which GHC can @@ -770,7 +770,7 @@ messages and in GHCi: This flag also enables the printing of *inferred* type variables inside braces. See :ref:`inferred-vs-specified`. - + .. ghc-flag:: -fprint-explicit-kinds :shortdesc: Print explicit kind foralls and kind arguments in types. See also :ghc-flag:`-XKindSignatures` @@ -785,15 +785,27 @@ messages and in GHCi: .. code-block:: none ghci> :set -XPolyKinds - ghci> data T a = MkT + ghci> data T a (b :: l) = MkT ghci> :t MkT - MkT :: forall (k :: Type) (a :: k). T a + MkT :: forall k l (a :: k) (b :: l). T a b ghci> :set -fprint-explicit-kinds ghci> :t MkT - MkT :: forall (k :: Type) (a :: k). T k a + MkT :: forall k l (a :: k) (b :: l). T @{k} @l a b ghci> :set -XNoPolyKinds ghci> :t MkT - MkT :: T * a + MkT :: T @{*} @* a b + + In the output above, observe that ``T`` has two kind variables + (``k`` and ``l``) and two type variables (``a`` and ``b``). Note that + ``k`` is an *inferred* variable and ``l`` is a *specified* variable + (see :ref:`inferred-vs-specified`), so as a result, they are displayed + using slightly different syntax in the type ``T @{k} @l a b``. The + application of ``l`` (with ``@l``) is the standard syntax for visible + type application (see :ref:`visible-type-application`). The application + of ``k`` (with ``@{k}``), however, uses a hypothetical syntax for visible + type application of inferred type variables. This syntax is not currently + exposed to the programmer, but it is nevertheless displayed when + :ghc-flag:`-fprint-explicit-kinds` is enabled. .. ghc-flag:: -fprint-explicit-runtime-reps :shortdesc: Print ``RuntimeRep`` variables in types which are |