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| author | simonpj@microsoft.com <unknown> | 2008-10-28 13:30:09 +0000 |
|---|---|---|
| committer | simonpj@microsoft.com <unknown> | 2008-10-28 13:30:09 +0000 |
| commit | bc35c8edb6c1ee607d17e381c19820b3f026e59f (patch) | |
| tree | c081af6b63d2d95d06b17ccb24e0d1d6a3a6a07b /docs | |
| parent | a5984078ff9369276c92135a80027ce7d98d1c56 (diff) | |
| download | haskell-bc35c8edb6c1ee607d17e381c19820b3f026e59f.tar.gz | |
Clarify documentatoin
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/glasgow_exts.xml | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml index aafe421c67..78983eb06b 100644 --- a/docs/users_guide/glasgow_exts.xml +++ b/docs/users_guide/glasgow_exts.xml @@ -5322,9 +5322,13 @@ f xs = ys ++ ys ys :: [a] ys = reverse xs </programlisting> -The type signature for <literal>f</literal> brings the type variable <literal>a</literal> into scope; it scopes over -the entire definition of <literal>f</literal>. -In particular, it is in scope at the type signature for <varname>ys</varname>. +The type signature for <literal>f</literal> brings the type variable <literal>a</literal> into scope, +because of the explicit <literal>forall</literal> (<xref linkend="decl-type-sigs"/>). +The type variables bound by a <literal>forall</literal> scope over +the entire definition of the accompanying value declaration. +In this example, the type variable <literal>a</literal> scopes over the whole +definition of <literal>f</literal>, including over +the type signature for <varname>ys</varname>. In Haskell 98 it is not possible to declare a type for <varname>ys</varname>; a major benefit of scoped type variables is that it becomes possible to do so. |