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Today's Topics:
1. Re: "stage restriction" when using Data.Heap (Brent Yorgey)
2. Re: "stage restriction" when using Data.Heap (Daniel Fischer)
3. hsmagic & core dump (Sergey Bushnyak)
----------------------------------------------------------------------
Message: 1
Date: Tue, 8 Jan 2013 12:02:45 -0500
From: Brent Yorgey <[email protected]>
Subject: Re: [Haskell-beginners] "stage restriction" when using
Data.Heap
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
On Tue, Jan 08, 2013 at 07:03:20AM +0100, Martin Drautzburg wrote:
> When I :load this into ghci
>
> import Data.Heap
>
> heap = empty :: MinHeap (Int,String)
> insert (1,"kjh") heap
>
> I get
>
> GHC stage restriction: `heap'
> is used in a top-level splice or annotation,
> and must be imported, not defined locally
> In the second argument of `insert', namely `heap'
> In the expression: insert (1, "kjh") heap
>
> But when I type in
>
> import Data.Heap
>
> let heap = empty :: MinHeap (Int,String)
> insert (1,"kjh") heap
>
> everything works and I get
>
> fromList [(1,"kjh")]
>
> Why is that so and what can I do to prevent the "stage restriction"?
Twan's analysis is correct. But wow, that's a horrible error
message. Do you by any chance have the TemplateHaskell extension
enabled (either with {-# LANGUAGE TemplateHaskell #-} at the top or
your file, or with :set -XTemplateHaskell in a .ghci file, or anything
like that)? If not this should really be filed as a bug, GHC has no
business giving TH-related error messages without TH being turned on.
-Brent
------------------------------
Message: 2
Date: Tue, 08 Jan 2013 18:40:27 +0100
From: Daniel Fischer <[email protected]>
Subject: Re: [Haskell-beginners] "stage restriction" when using
Data.Heap
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"
On Tuesday 08 January 2013, 12:02:45, Brent Yorgey wrote:
> Twan's analysis is correct. But wow, that's a horrible error
> message. Do you by any chance have the TemplateHaskell extension
> enabled (either with {-# LANGUAGE TemplateHaskell #-} at the top or
> your file, or with :set -XTemplateHaskell in a .ghci file, or anything
> like that)?
Must be:
module Naked where
start :: Int
start = 13
start + 5
======
$ ghci Naked
GHCi, version 7.6.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Naked ( Naked.hs, interpreted )
Naked.hs:6:1: Parse error: naked expression at top level
Failed, modules loaded: none.
======
$ ghci -XTemplateHaskell Naked
GHCi, version 7.6.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Naked ( Naked.hs, interpreted )
Naked.hs:6:1:
GHC stage restriction:
`start' is used in a top-level splice or annotation,
and must be imported, not defined locally
In the first argument of `(+)', namely `start'
In the expression: start + 5
Failed, modules loaded: none.
The message without TH is clear and good.
> If not this should really be filed as a bug, GHC has no
> business giving TH-related error messages without TH being turned on.
>
> -Brent
------------------------------
Message: 3
Date: Wed, 09 Jan 2013 11:51:20 +0200
From: Sergey Bushnyak <[email protected]>
Subject: [Haskell-beginners] hsmagic & core dump
To: "[email protected]" <[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Trying to work with images via hsmagic package, use something like this
scaleTest :: FilePath -> IO()
scaleTest dst = do
initializeMagick
image <- readImage dst
let image' = scaleImage 450 450 image
writeImage dst image'
but get core dump, when compiling. Types are ok, and path are valid, can
it be problem of os or I'm doing something wrong?
------------------------------
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End of Beginners Digest, Vol 55, Issue 8
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