diff options
Diffstat (limited to 'compiler/utils/Util.lhs')
| -rw-r--r-- | compiler/utils/Util.lhs | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/compiler/utils/Util.lhs b/compiler/utils/Util.lhs index c5f1c0c2ed..ad678fd45d 100644 --- a/compiler/utils/Util.lhs +++ b/compiler/utils/Util.lhs @@ -32,6 +32,7 @@ module Util ( -- * Tuples fstOf3, sndOf3, thirdOf3, + firstM, first3M, -- * List operations controlled by another list takeList, dropList, splitAtList, split, @@ -104,7 +105,7 @@ import Data.List hiding (group) import FastTypes #endif -import Control.Monad ( unless ) +import Control.Monad ( unless, liftM ) import System.IO.Error as IO ( isDoesNotExistError ) import System.Directory ( doesDirectoryExist, createDirectory, getModificationTime ) @@ -210,6 +211,14 @@ sndOf3 (_,b,_) = b thirdOf3 (_,_,c) = c \end{code} +\begin{code} +firstM :: Monad m => (a -> m c) -> (a, b) -> m (c, b) +firstM f (x, y) = liftM (\x' -> (x', y)) (f x) + +first3M :: Monad m => (a -> m d) -> (a, b, c) -> m (d, b, c) +first3M f (x, y, z) = liftM (\x' -> (x', y, z)) (f x) +\end{code} + %************************************************************************ %* * \subsection[Utils-lists]{General list processing} |