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| author | Richard Eisenberg <eir@cis.upenn.edu> | 2016-01-10 19:10:03 -0500 |
|---|---|---|
| committer | Richard Eisenberg <eir@cis.upenn.edu> | 2016-01-15 15:43:44 -0500 |
| commit | 3a7f204f5d713ed4ac034d371fc10d8bedb39efa (patch) | |
| tree | 242547bb1ab0ca347cf9fad840d7b7604d9f99c9 | |
| parent | 6c07f1426e58232092043e28d56717aa489d3670 (diff) | |
| download | haskell-3a7f204f5d713ed4ac034d371fc10d8bedb39efa.tar.gz | |
Clarify topological sorting of spec vars in manual
This is mentioned in #11376.
| -rw-r--r-- | docs/users_guide/glasgow_exts.rst | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/docs/users_guide/glasgow_exts.rst b/docs/users_guide/glasgow_exts.rst index 0ec5bd4f1c..e77a7c0243 100644 --- a/docs/users_guide/glasgow_exts.rst +++ b/docs/users_guide/glasgow_exts.rst @@ -2237,6 +2237,15 @@ Here are the details: will have its type variables ordered as ``m, a, b, c``. +- If any of the variables depend on other variables (that is, if some + of the variables are *kind* variables), the variables are reordered + so that kind variables come before type variables, preserving the + left-to-right order as much as possible. That is, GHC performs a + stable topological sort on the variables. + + For example: if we have ``bar :: Proxy (a :: (j, k)) -> b``, then + the variables are ordered ``j``, ``k``, ``a``, ``b``. + - Class methods' type arguments include the class type variables, followed by any variables an individual method is polymorphic in. So, ``class Monad m where return :: a -> m a`` means |