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September 2007

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[Hugs] #77: Binding variables on the prompt
by Hugs 17 Sep '07

17 Sep '07

#77: Binding variables on the prompt -------------------------------------------------+-------------------------- Reporter: apfelmus | Owner: nobody Type: enhancement | Status: new Priority: major | Milestone: Component: hugs | Version: current Keywords: interactive prompt variable binding | -------------------------------------------------+-------------------------- In GHCi, it's possible to bind variables at the interactive prompt, like {{{ > let x = 1 > x + 1 2 > y <- readFile "Foo.bar" "Hello World" > length y 11 }}} The rule is that the bindings are legal in the do-notation for the IO- monad. For details, see [http://www.haskell.org/ghc/docs/latest/html/users_guide/ch03s04.html Interactive evaluation at the prompt] in the GHC user's guide. I'm dearly missing this feature in Hugs! -- Ticket URL: <http://hackage.haskell.org/trac/hugs/ticket/77> Hugs <http://www.haskell.org/hugs/> Hugs 98, an interpreter for Haskell

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curiosity, bug, or just dead code?
by Claus Reinke 10 Sep '07

10 Sep '07

consider this module, which is accepted by ghci-6.6.1: module T where import qualified Prelude as T(length) import Prelude(length) length = 0 there is no way to refer to either length, as both 'length' and 'T.length' are ambiguous (ghci complains on uses of either name). but is it a bug? then again, everything is implicitly exported, and there are two possible 'T.length'.. (hugs [20051031] complains about conflicting exports, on loading T). now for the good part: module Q where import T main = print T.length loads fine, and running main returns 0. Ok, modules loaded: Q, T. *Q> main 0 so this must be a bug, right? or a matter of interpretation? not everything is exported implicitly: imported items, whether unqualified or qualified and renamed to share the current module as qualifier are not exported by default. and changing module T where to module T(module T) where leads to conflicting export errors on load in ghci. currently, i think ghci is right, and hugs is wrong (note that my hugs is rather old, though), but it wasn't what i expected. claus

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