diff options
Diffstat (limited to 'docs/users_guide/exts/quantified_constraints.rst')
| -rw-r--r-- | docs/users_guide/exts/quantified_constraints.rst | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/docs/users_guide/exts/quantified_constraints.rst b/docs/users_guide/exts/quantified_constraints.rst index 717da9eda6..769570fea2 100644 --- a/docs/users_guide/exts/quantified_constraints.rst +++ b/docs/users_guide/exts/quantified_constraints.rst @@ -95,7 +95,7 @@ Syntax changes class ::= qtycls tyvar | qtycls (tyvar atype1 ... atypen) -We to extend ``class`` (warning: this is a rather confusingly named non-terminal symbol) with two extra forms, namely precisely what can appear in an instance declaration +We extend ``class`` (warning: this is a rather confusingly named non-terminal symbol) with two extra forms, namely precisely what can appear in an instance declaration .. code-block:: none @@ -108,13 +108,13 @@ The ``context =>`` part is optional. That is the only syntactic change to the l Notes: -- Where GHC allows extensions instance declarations we allow exactly the same extensions to this new form of ``class``. Specifically, with :extension:`ExplicitForAll` and :extension:`MultiParamTypeClasses` the syntax becomes +- Where GHC allows extensions in instance declarations we allow exactly the same extensions to this new form of ``class``. Specifically, with :extension:`ExplicitForAll` and :extension:`MultiParamTypeClasses` the syntax becomes .. code-block:: none class ::= ... - | [forall tyavrs .] [context =>] qtycls inst1 ... instn - | [forall tyavrs .] [context =>] tyvar inst1 ... instn + | [forall tyvars .] [context =>] qtycls inst1 ... instn + | [forall tyvars .] [context =>] tyvar inst1 ... instn Note that an explicit ``forall`` is often absolutely essential. Consider the rose-tree example :: @@ -222,7 +222,7 @@ trying to solve a class constraint ``C t`` 1. First see if there is a given un-quantified constraint ``C t``. If so, use it to solve the constraint. -2. If not, look at all the available given quantified constraints; if exactly one one matches ``C t``, choose it; if more than one matches, report an error. +2. If not, look at all the available given quantified constraints; if exactly one matches ``C t``, choose it; if more than one matches, report an error. 3. If no quantified constraints match, look up in the global instances, as described in :ref:`instance-resolution` and :ref:`instance-overlap`. |