Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: c98abb6a by Hai / @BestYeen at 2025-10-14T21:52:08-04:00 Update occurrences of return to pure and add a sample for redefining :m to mean :main - - - - - 1 changed file: - docs/users_guide/ghci.rst Changes: ===================================== docs/users_guide/ghci.rst ===================================== @@ -403,7 +403,7 @@ it can be *instantiated* to ``IO a``. For example .. code-block:: none - ghci> return True + ghci> pure True True Furthermore, GHCi will print the result of the I/O action if (and only @@ -419,7 +419,7 @@ For example, remembering that ``putStrLn :: String -> IO ()``: ghci> putStrLn "hello" hello - ghci> do { putStrLn "hello"; return "yes" } + ghci> do { putStrLn "hello"; pure "yes" } hello "yes" @@ -443,12 +443,12 @@ prompt must be in the ``IO`` monad. .. code-block:: none - ghci> x <- return 42 + ghci> x <- pure 42 ghci> print x 42 ghci> -The statement ``x <- return 42`` means “execute ``return 42`` in the +The statement ``x <- pure 42`` means “execute ``pure 42`` in the ``IO`` monad, and bind the result to ``x``\ ”. We can then use ``x`` in future statements, for example to print it as we did above. @@ -2389,7 +2389,7 @@ commonly used commands. .. code-block:: none - ghci> let date _ = Data.Time.getZonedTime >>= print >> return "" + ghci> let date _ = Data.Time.getZonedTime >>= print >> pure "" ghci> :def date date ghci> :date 2017-04-10 12:34:56.93213581 UTC @@ -2399,16 +2399,16 @@ commonly used commands. .. code-block:: none - ghci> let mycd d = System.Directory.setCurrentDirectory d >> return "" + ghci> let mycd d = System.Directory.setCurrentDirectory d >> pure "" ghci> :def mycd mycd ghci> :mycd .. - Or I could define a simple way to invoke "``ghc --make Main``" + Or we could define a simple way to invoke "``ghc --make Main``" in the current directory: .. code-block:: none - ghci> :def make (\_ -> return ":! ghc --make Main") + ghci> :def make (\_ -> pure ":! ghc --make Main") We can define a command that reads GHCi input from a file. This might be useful for creating a set of bindings that we want to @@ -2430,6 +2430,15 @@ commonly used commands. a double colon (eg ``::load``). It's not possible to redefine the commands ``:{``, ``:}`` and ``:!``. + For historical reasons, ``:m`` in ghci is shorthand for ``:module``. + If we want to override that to mean ``:main``, in a way that also + works when the implicit Prelude is deactivated, we can do it like + this using ``:def!``: + + .. code-block:: none + + ghci> :def! m \_ -> Prelude.pure ":main" + .. ghci-cmd:: :delete; * | ⟨num⟩ ... Delete one or more breakpoints by number (use :ghci-cmd:`:show breaks` to @@ -2912,7 +2921,7 @@ commonly used commands. .. code-block:: none - *ghci> :def cond \expr -> return (":cmd if (" ++ expr ++ ") then return \"\" else return \":continue\"") + *ghci> :def cond \expr -> pure (":cmd if (" ++ expr ++ ") then pure \"\" else pure \":continue\"") *ghci> :set stop 0 :cond (x < 3) To ignore breakpoints for a specified number of iterations use View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c98abb6ac0f422df318691405ddd4b5d... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c98abb6ac0f422df318691405ddd4b5d... You're receiving this email because of your account on gitlab.haskell.org.