#10843: Allow do blocks without dollar signs as arguments -------------------------------------+------------------------------------- Reporter: agibiansky | Owner: agibiansky Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 (Parser) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #11706 | Differential Rev(s): Phab:D1219 Wiki Page: | -------------------------------------+------------------------------------- @@ -46,0 +46,2 @@ + + Wiki page: [wiki:ArgumentDo] New description: I would like the following to be valid Haskell code: {{{#!hs main = when True do putStrLn "Hello!" }}} Instead of requiring a dollar sign before the "do". This would parse as {{{#!hs main = when True (do putStrLn "Hello!") }}} Similarly, allow lambdas in the same way {{{#!hs main = forM values \value -> print value }}} parses as {{{#!hs main = forM values (\value -> print value) }}} One possible question: does this also do the same thing for LambdaCase? I think that since people expect lambda case to just be a simple desugaring it should also work, so then {{{#!hs main = forM values \case Just x -> print x Nothing -> print y }}} parses as {{{#!hs main = forM values (\case Just x -> print x Nothing -> print y) }}} Wiki page: [wiki:ArgumentDo] -- Comment (by simonpj): Akio has made a wiki page to specify the feature: [wiki:ArgumentDo] -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10843#comment:20 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler