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| author | Fumiaki Kinoshita <fumiexcel@gmail.com> | 2015-03-25 13:30:25 +0900 |
|---|---|---|
| committer | Herbert Valerio Riedel <hvr@gnu.org> | 2015-03-25 14:47:22 +0100 |
| commit | 9db005a444722e31aca1956b058e069bcf3cacbd (patch) | |
| tree | 47c433696d584c5a3138eff13e638832027d30c1 /libraries/base/GHC/Base.hs | |
| parent | 33cfa5ff9db4e7886b3e7c2eed5ac1c75436bc4c (diff) | |
| download | haskell-9db005a444722e31aca1956b058e069bcf3cacbd.tar.gz | |
Add Monad instance for `((,) a)` (#10190)
This was proposed a couple of times in the past, e.g.
- https://mail.haskell.org/pipermail/libraries/2011-November/017153.html
- https://mail.haskell.org/pipermail/libraries/2013-July/020446.html
but its implementation had been blocked by the fact that `Monoid` wasn't
in scope where the `Monad` class was defined. Since the AMP/FTP restructuring
this is no longer the case.
Diffstat (limited to 'libraries/base/GHC/Base.hs')
| -rw-r--r-- | libraries/base/GHC/Base.hs | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/libraries/base/GHC/Base.hs b/libraries/base/GHC/Base.hs index 7e04ab4f0e..d9192d7a99 100644 --- a/libraries/base/GHC/Base.hs +++ b/libraries/base/GHC/Base.hs @@ -308,6 +308,9 @@ instance Monoid a => Applicative ((,) a) where pure x = (mempty, x) (u, f) <*> (v, x) = (u `mappend` v, f x) +instance Monoid a => Monad ((,) a) where + return x = (mempty, x) + (u, a) >>= k = case k a of (v, b) -> (u `mappend` v, b) {- | The 'Functor' class is used for types that can be mapped over. Instances of 'Functor' should satisfy the following laws: |