- Yhc - Haskell.org

Re: [Yhc] instance Monad IO bug
by shackell＠cs.york.ac.uk 12 Mar '07

12 Mar '07

Ah oops, tried to remove the Either as an optimization, forgot that IO isn't strict in the value ;-) It should probably be something like newtype IO a = IO (World -> _E a) where _E is just a box to prevent evaluation (it's used in primitive handling already). data _E a = _E a Then the IO monad would be instance Monad IO where (IO x) >>= yf = IO $ \ w -> let xe = x w in case xe of _E xv -> case yf xv of IO y -> y w (IO x) >> (IO y) = IO $ \ w -> case x w of _E _ -> y w return a = IO $ \ w -> _E a > Maybe an artificial "dependingOn", like > seq but that doesn't even evaluate its argument to WHNF, is needed? > (inspired by jhc's primitive dependingOn :: a -> b -> a, which is the > OPPOSITE argument order (like const, rather than seq) and I'm not sure > if it has the semantics I'm suggesting, but, whatever...) Unfortunately the problem isn't (>>), it's return. return a = IO $ \ w -> a -- necessarily evaluates a = wrong Thus 'return undefined' as soon as you apply it to World (i.e. deIO it) it goes bang. The amuzing thing is that none of the conformance tests (and some of them are serious programs) rely on the laziness of IO values. Otherwise I'm sure I would have spotted my braino ;-) Tom

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Re: [Yhc] instance Monad IO bug
by Bernie Pope 11 Mar '07

11 Mar '07

> for a file > main = print "hi" >> return undefined >> print "bye" > ghc, hugs and nhc98 print > "hi" > "bye" > yhc prints > "hi" > Prelude.undefined That is strange. In my version of Yhc it works as expected (same as Hugs and GHC). The instance of IO for Monad in my version is: \begin{code} instance Monad IO where x >>= y = IO (primBind1 x y) where primBind1 (IO xf) y w = case xf w of Right xv -> case y xv of IO yv -> yv w Left err -> Left err -- Changing type x >> y = IO (primBind2 x y) where primBind2 (IO xf) y w = case xf w of Right xv -> case y of IO yv -> yv w Left err -> Left err -- Changing type return a = IO (primReturn a) where primReturn a w = Right a \end{code} To my eyes there is no strictness problem in this definition. Also, in my version IO is defined this way: \begin{code} data World = World newtype IO a = IO (World -> Either IOError a) \end{code} >From memory this is the same as it was in nhc98. I haven't done a darcs pull for a week or so; perhaps my version is older than yours? Cheers, Bernie.

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instance Monad IO bug
by Isaac Dupree 11 Mar '07

11 Mar '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 for a file main = print "hi" >> return undefined >> print "bye" ghc, hugs and nhc98 print "hi" "bye" yhc prints "hi" Prelude.undefined In other words, IO's (>>=) and (>>) (defined in src/packages/yhc-base-1.0/Prelude.hs) are too strict. (at least I assume that behavior is considered wrong...) I can't see a simple way to fix it, given Yhc's representation of IO (no other compiler, not even nhc98, uses newtype IO a = IO (World -> a)), but maybe someone else does. Maybe an artificial "dependingOn", like seq but that doesn't even evaluate its argument to WHNF, is needed? (inspired by jhc's primitive dependingOn :: a -> b -> a, which is the OPPOSITE argument order (like const, rather than seq) and I'm not sure if it has the semantics I'm suggesting, but, whatever...) Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFF8+T6HgcxvIWYTTURAlDyAJ4omDQnum4klKb+tD+p3PMFwRwZawCfZLjV vBZPV5y9j/uVI0Lf58nxKBA= =H9Lt -----END PGP SIGNATURE-----

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buildbot failure in linux_ppc
by andrewjwilkinsonw＠gmail.com 10 Mar '07

10 Mar '07

The Buildbot has detected a new failure of linux_ppc. Full details are available at: http://www.indiegigs.co.uk:8010/linux_ppc/builds/91 Buildbot URL: http://www.indiegigs.co.uk:8010/ Buildslave for this Build: linuxppc Build Reason: Build Source Stamp: HEAD Blamelist: Neil Mitchell BUILD FAILED: failed failed slave lost sincerely, -The Buildbot

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how to get a new front-end - idea
by Isaac Dupree 09 Mar '07

09 Mar '07

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 (Front-end meaning parser and type-checker, from which Yhc would extract an untyped representation) Perhaps we can steal one from another compiler like Jhc? Maybe it's separate enough from the rest of the compiler that the code can be shared without too much modification; I haven't looked very closely. It seems it could be beneficial not to have too many different Haskell front-end implementations, especially for projects like us that don't seem particularly interested in that area(?). (I'm biased in favor of Jhc's because it handles recursive modules transparently in the front-end - and I don't think this is inherently connected to full program transformations; Jhc can precompile libraries after all) (Then there's always license issues: Jhc is GPL'd, what is Yhc currently?, does that matter?) Isaac -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFF7/LvHgcxvIWYTTURAqx4AKCgCifSfSETsxH80XcmTlSIwtPgYACgjs8i vinPbpDsALA5tpazTlJrSl0= =ZVPi -----END PGP SIGNATURE-----

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buildbot failure in gentoo_amd64
by andrewjwilkinsonw＠gmail.com 08 Mar '07

08 Mar '07

The Buildbot has detected a new failure of gentoo_amd64. Full details are available at: http://www.indiegigs.co.uk:8010/gentoo_amd64/builds/105 Buildbot URL: http://www.indiegigs.co.uk:8010/ Buildslave for this Build: gentooamd64 Build Reason: Build Source Stamp: HEAD Blamelist: Neil Mitchell BUILD FAILED: failed yhi sincerely, -The Buildbot

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buildbot failure in slack_x86
by andrewjwilkinsonw＠gmail.com 08 Mar '07

08 Mar '07

The Buildbot has detected a new failure of slack_x86. Full details are available at: http://www.indiegigs.co.uk:8010/slack_x86/builds/140 Buildbot URL: http://www.indiegigs.co.uk:8010/ Buildslave for this Build: slackx86 Build Reason: Build Source Stamp: HEAD Blamelist: Neil Mitchell BUILD FAILED: failed yhi sincerely, -The Buildbot

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buildbot failure in macosx_ppc_3
by andrewjwilkinsonw＠gmail.com 08 Mar '07

08 Mar '07

The Buildbot has detected a new failure of macosx_ppc_3. Full details are available at: http://www.indiegigs.co.uk:8010/macosx_ppc_3/builds/36 Buildbot URL: http://www.indiegigs.co.uk:8010/ Buildslave for this Build: macosxppc3 Build Reason: Build Source Stamp: HEAD Blamelist: Neil Mitchell BUILD FAILED: failed yhi sincerely, -The Buildbot

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buildbot failure in linux_ppc
by andrewjwilkinsonw＠gmail.com 08 Mar '07

08 Mar '07

The Buildbot has detected a new failure of linux_ppc. Full details are available at: http://www.indiegigs.co.uk:8010/linux_ppc/builds/85 Buildbot URL: http://www.indiegigs.co.uk:8010/ Buildslave for this Build: linuxppc Build Reason: Build Source Stamp: HEAD Blamelist: Neil Mitchell BUILD FAILED: failed yhi sincerely, -The Buildbot

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buildbot failure in debian_amd64
by andrewjwilkinsonw＠gmail.com 08 Mar '07

08 Mar '07

The Buildbot has detected a new failure of debian_amd64. Full details are available at: http://www.indiegigs.co.uk:8010/debian_amd64/builds/147 Buildbot URL: http://www.indiegigs.co.uk:8010/ Buildslave for this Build: debianamd64 Build Reason: Build Source Stamp: HEAD Blamelist: Neil Mitchell BUILD FAILED: failed yhi sincerely, -The Buildbot

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