There is a weird type-checking bug in 7.0.1 that causes loopy behavior:

http://hackage.haskell.org/trac/ghc/ticket/4809

Not sure if that is what is happening to you or not. Though in my experience it did not actually print <<loop>>, it just hung.

- jeremy

On Jan 25, 2011, at 10:48 AM, Pavel Perikov wrote:


On 25.01.2011, at 18:37, Bjorn Buckwalter wrote:
(I
suspect the type inferencer is looping), but maybe you've figured out
something workable for you already.

I told you I'm exhausted right now, didn't I? :) This is definitely not type inferencer. The bug causes compiled program looping. And I have at least one case when let-trick fixes the behavior in compiled program.

Pavel.



Thanks,
Bjorn

(Sorry for the re-repost, Pavel, my incompetence is matched only by my
perseverance.)


On Tue, Jan 25, 2011 at 22:02, Pavel Perikov <perikov@gmail.com> wrote:
in ghci:
Prelude> import Numeric.Units.Dimensional.Prelude as D
Prelude Numeric.Units.Dimensional.Prelude> D.sqrt $ let s = 9 *~ (meter D.*
meter) in s
3.0 m
Prelude Numeric.Units.Dimensional.Prelude> D.sqrt $ 9 *~ (meter D.* meter)
ghci hangs.
complied and optimized code detects <<loop>> and let-trick from the above
does not help.
Here's the complete ghci -v session which contains all package versions

ghci -v
GHCi, version 7.0.1: http://www.haskell.org/ghc/  :? for help
Glasgow Haskell Compiler, Version 7.0.1, for Haskell 98, stage 2 booted by
GHC version 6.12.3
Using binary package database:
/Library/Frameworks/GHC.framework/Versions/7.0.1-i386/usr/lib/ghc-7.0.1/package.conf.d/package.cache
Using binary package database:
/Users/pavel/.ghc/i386-darwin-7.0.1/package.conf.d/package.cache
hiding package containers-0.3.0.0 to avoid conflict with later version
containers-0.4.0.0
hiding package QuickCheck-2.3.0.2 to avoid conflict with later version
QuickCheck-2.4.0.1
wired-in package ghc-prim mapped to
ghc-prim-0.2.0.0-0713122c5f9038c6f0355a37e294e054
wired-in package integer-gmp mapped to
integer-gmp-0.2.0.2-bfb191b8468e4d812a2bb92622cb246e
wired-in package base mapped to
base-4.3.0.0-1ea085b64a078bd9d5eaa9d8d525e35e
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to
template-haskell-2.5.0.0-f262af1f92a427f5cf4133bff041044f
wired-in package dph-seq not found.
wired-in package dph-par not found.
Hsc static flags: -static
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.
Prelude> import Numeric.Units.Dimensional.Prelude as D
hiding package containers-0.3.0.0 to avoid conflict with later version
containers-0.4.0.0
hiding package QuickCheck-2.3.0.2 to avoid conflict with later version
QuickCheck-2.4.0.1
wired-in package ghc-prim mapped to
ghc-prim-0.2.0.0-0713122c5f9038c6f0355a37e294e054
wired-in package integer-gmp mapped to
integer-gmp-0.2.0.2-bfb191b8468e4d812a2bb92622cb246e
wired-in package base mapped to
base-4.3.0.0-1ea085b64a078bd9d5eaa9d8d525e35e
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to
template-haskell-2.5.0.0-f262af1f92a427f5cf4133bff041044f
wired-in package dph-seq not found.
wired-in package dph-par not found.
*** Parser:
hiding package containers-0.3.0.0 to avoid conflict with later version
containers-0.4.0.0
hiding package QuickCheck-2.3.0.2 to avoid conflict with later version
QuickCheck-2.4.0.1
wired-in package ghc-prim mapped to
ghc-prim-0.2.0.0-0713122c5f9038c6f0355a37e294e054
wired-in package integer-gmp mapped to
integer-gmp-0.2.0.2-bfb191b8468e4d812a2bb92622cb246e
wired-in package base mapped to
base-4.3.0.0-1ea085b64a078bd9d5eaa9d8d525e35e
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to
template-haskell-2.5.0.0-f262af1f92a427f5cf4133bff041044f
wired-in package dph-seq not found.
wired-in package dph-par not found.
Prelude Numeric.Units.Dimensional.Prelude> D.sqrt $ let s = 9 *~ (meter D.*
meter) in s
hiding package containers-0.3.0.0 to avoid conflict with later version
containers-0.4.0.0
hiding package QuickCheck-2.3.0.2 to avoid conflict with later version
QuickCheck-2.4.0.1
wired-in package ghc-prim mapped to
ghc-prim-0.2.0.0-0713122c5f9038c6f0355a37e294e054
wired-in package integer-gmp mapped to
integer-gmp-0.2.0.2-bfb191b8468e4d812a2bb92622cb246e
wired-in package base mapped to
base-4.3.0.0-1ea085b64a078bd9d5eaa9d8d525e35e
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to
template-haskell-2.5.0.0-f262af1f92a427f5cf4133bff041044f
wired-in package dph-seq not found.
wired-in package dph-par not found.
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
Loading package old-locale-1.0.0.2 ... linking ... done.
Loading package time-1.2.0.3 ... linking ... done.
Loading package numtype-1.0 ... linking ... done.
Loading package dimensional-0.8.0.1 ... linking ... done.
3.0 m
hiding package containers-0.3.0.0 to avoid conflict with later version
containers-0.4.0.0
hiding package QuickCheck-2.3.0.2 to avoid conflict with later version
QuickCheck-2.4.0.1
wired-in package ghc-prim mapped to
ghc-prim-0.2.0.0-0713122c5f9038c6f0355a37e294e054
wired-in package integer-gmp mapped to
integer-gmp-0.2.0.2-bfb191b8468e4d812a2bb92622cb246e
wired-in package base mapped to
base-4.3.0.0-1ea085b64a078bd9d5eaa9d8d525e35e
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to
template-haskell-2.5.0.0-f262af1f92a427f5cf4133bff041044f
wired-in package dph-seq not found.
wired-in package dph-par not found.
Prelude Numeric.Units.Dimensional.Prelude> D.sqrt $ 9 *~ (meter D.* meter)
hiding package containers-0.3.0.0 to avoid conflict with later version
containers-0.4.0.0
hiding package QuickCheck-2.3.0.2 to avoid conflict with later version
QuickCheck-2.4.0.1
wired-in package ghc-prim mapped to
ghc-prim-0.2.0.0-0713122c5f9038c6f0355a37e294e054
wired-in package integer-gmp mapped to
integer-gmp-0.2.0.2-bfb191b8468e4d812a2bb92622cb246e
wired-in package base mapped to
base-4.3.0.0-1ea085b64a078bd9d5eaa9d8d525e35e
wired-in package rts mapped to builtin_rts
wired-in package template-haskell mapped to
template-haskell-2.5.0.0-f262af1f92a427f5cf4133bff041044f
wired-in package dph-seq not found.
wired-in package dph-par not found.
*** Parser:
*** Desugar:
*** Simplify:
*** CorePrep:
*** ByteCodeGen:
HANG!




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