Heap profiling dumped NULs
Hi, I can't reproduce it, but on one occasion running profiling with -hd, I got corrupt .hp output, with a large block of NULs in an otherwise normal output (The output is large, but I can make it available if anybody wants it). Rerunning the exact same command line produced a normal .hp. Just in case you'd like to know. (GHC 6.0 from RPM on RH 9) -kzm -- If I haven't seen further, it is by standing in the footprints of giants ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
[ ghc-Bugs-806622 ] fileExist throws exception when file does not exist
Bugs item #806622, was opened at 2003-09-15 16:19 Message generated for change (Settings changed) made by simonmar You can respond by visiting: https://sourceforge.net/tracker/?func=detailatid=108032aid=806622group_id=8032 Category: hslibs/posix Group: 6.0.1 Status: Closed Resolution: Fixed Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Simon Marlow (simonmar) Summary: fileExist throws exception when file does not exist Initial Comment: In ghc 6.0.1 function fileExist incorrectly throws exception when file does not exist. -- Comment By: Simon Marlow (simonmar) Date: 2003-09-23 14:41 Message: Logged In: YES user_id=48280 Fixed, thanks. -- You can respond by visiting: https://sourceforge.net/tracker/?func=detailatid=108032aid=806622group_id=8032 ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
[ ghc-Bugs-806633 ] doesDirectoryExist / == False
Bugs item #806633, was opened at 2003-09-15 16:35 Message generated for change (Comment added) made by simonmar You can respond by visiting: https://sourceforge.net/tracker/?func=detailatid=108032aid=806633group_id=8032 Category: None Group: None Status: Closed Resolution: Fixed Priority: 5 Submitted By: Nobody/Anonymous (nobody) Assigned to: Simon Marlow (simonmar) Summary: doesDirectoryExist / == False Initial Comment: doesDirectoryExist gives False when called with root dir, /. I think that the following patch corrects this (I have not tried yet): $ diff -u Directory.hs,orig Directory.hs --- Directory.hs,orig 2003-04-11 12:11:24.0 +0200 +++ Directory.hs2003-09-15 18:22:56.0 +0200 @@ -597,7 +597,7 @@ fileNameEndClean :: String - String fileNameEndClean name = - if i = 0 (ec == '\' || ec == '/') then + if i 0 (ec == '\' || ec == '/') then fileNameEndClean (take i name) else name [EMAIL PROTECTED] -- Comment By: Simon Marlow (simonmar) Date: 2003-09-23 14:46 Message: Logged In: YES user_id=48280 Fixed, thanks. -- You can respond by visiting: https://sourceforge.net/tracker/?func=detailatid=108032aid=806633group_id=8032 ___ Glasgow-haskell-bugs mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
[ ghc-Bugs-631320 ] {-# OPTIONS -O0 #-} not allowed
Bugs item #631320, was opened at 2002-10-30 23:57
Message generated for change (Comment added) made by simonmar
You can respond by visiting:
https://sourceforge.net/tracker/?func=detailatid=108032aid=631320group_id=8032
Category: Compiler
Group: 5.04.1
Status: Closed
Resolution: Fixed
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: {-# OPTIONS -O0 #-} not allowed
Initial Comment:
When I tried to turn off the pessimizer for certain
files it complained that the -O0 option was not allowed
in the file. Very annoying.
[EMAIL PROTECTED]
--
Comment By: Simon Marlow (simonmar)
Date: 2003-09-23 14:53
Message:
Logged In: YES
user_id=48280
Fixed, eventually.
--
You can respond by visiting:
https://sourceforge.net/tracker/?func=detailatid=108032aid=631320group_id=8032
___
Glasgow-haskell-bugs mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: Haddock interface file for standard libraries
Simon Marlow writes: /usr/share/ghc-6.0.1/html/*/*.haddock. Hmm, why is it that every question I asks resolves in a way that makes me look blind or dumb? :-) Thanks for the quick help! Peter ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
RE: Haddock interface file for standard libraries
I have another short question concerning the build process: Is there any easy way to generate a Haddock interface file for the standard libraries? I'd like my own documentation to contain links to standard data types and functions, but processing the library sources directly turned out to be difficult because of pre-processor use etc. A GHC distribution comes with the appropriate .haddock files - take a look in eg. /usr/share/ghc-6.0.1/html/*/*.haddock. Cheers, Simon ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
WINNING NOTIFICATION !
ELGORDO DE LAPRIMITIVA C/GUZMAN EL BUENO,137 MADRID - ESPAÑA TELE/ FAX:+34 916 470 023 E-mail: [EMAIL PROTECTED] FROM: THE DESK OF THE PROMOTIONS MANAGER, INTERNATIONAL PROMOTIONS/PRIZE AWARD DEPARTMENT, REF: LP/26510460037/03 BATCH: 24/00319/IPD RE: AWARD NOTIFICATION FINAL NOTICE We are pleased to inform you of the release today, 23rd September 2003,of the ELGORDO SWEEPSTAKE LOTTERY/INTER-NATIONAL PROGRAMS held on the 14th September,2003. Your name attached to ticket number 025 11464992-750 with serial number 2113-05 drew the lucky number 3-18-19-30-32-39, which consequently won the lottery in the 3rd category. You are therefore been approve for the lump sum pay out of uros 1,547,000.87 (One Million Five Hundred and Fourty Seven Thousand Eighty Seven Cents .) in cash credit to the file REF: LP/26510460037/03. This is from a total prize of uros 26,299,000.00 share among the seventeen (17) International winners in this category. CONGRATULATION! Your fund is now deposited with a Security Company EURO CREDIT COMMISION. Due to the mixed up of some numbers and names, we ask that you keep this award a top secret from the public notice until your claim as been processed and your prize money remitted to your account as this is a part of our Security protocol to avoid double claiming award or unwarranted taking advantage of this program by participants. All participants were selected through a computer ballot system drawn from 25,000 names from Australia, USA, Europe, Asia ,New Zealand, Middle-East and South-North America .As part of our international promotions program, which we conducted once in a year. We hope with a part of your prize, you will take part in our end of the year high stake uros 300 Million International Lottery. To being your claim, please contact the issuing authority, your prize claim agent, Mr. Barry Hanson, (Foreign Service Manager) for processing and remittance of your prize money to a designated account of your choice. Tel: +34 -639 280 825 .Email:[EMAIL PROTECTED], Remember, all prize money must be claimed not later until than the 23rd September, 2003. After this date, all funds will be returned as unclaimed. Note: In order to avoid unnecessary delays and complications, please remember to quote your reference and batch numbers in every of your correspondence with your agent. Furthermore, should there be any address do inform your claims agent as soon as possible. Please remember to ask for your prize claim certificate. Congratulation again from all member of our staff and thank you for being part of our promotion program. Best regards, MARIA JOSE SANCHEZ. ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
COOPERATION
Dear Ladies and Gentlemen Those yahcts which listed below will offer you %10 commission, In this list below the prices are very low than the worlds market. O L G A P R I C E 440.000 PROPERTIESEQUIPMENTSACOMMODATION Type Ketch Dingy, 21 kWa Generator4Double Cabins Wc+ Shower Loan 26.00 mt 80ft Hydrolic Lift, Music System1Master cabin Wc+shower Beam 6,80 mt 20ft Tv, Vhf, Radar, Gps, Sonar,Full air conditioned,Hot Water Fuel Tank 4,000 lt Fishing Diving EquipmentHolding Tang, Ice Maker Rigging Furling Wind Surf, Canoe, Jet skiDeep Freeze, Max.14 Person Water Tank 7,000 lt Life Rafts for 25 personsDate of building 2001 Engines 440 Man Turbo Original Marin ===Motor Yacht, Sunseeker P R I C E 1.550.000 At the moment Sunseeker Manhattan 74 is moored in Bodrum. (very close to Kos Island). We will be glad to guide you in Bodrum. TVA is paid. it s built in 1999 in POOL , ENGLAND LOA: 22 m (66ft) BEAM: 7 m (21ft), 2 generators 20 V and 12 V, 220 V 2 engines 1100 hp Man navigation time: 351 hours Kitchen includes dish washer, refrigerator, microwave, hotplate, ice maker. 2 deepfreeze electric windows, 4 cabins + 1 cabin for crew. Each cabin has a tv and music system wc and shower. central aircondition. diving equipment. As you understand from navigation time boat is not used regularly. Boat never faced with an accident. Boat was not used for charters ==T U Z L A P I A N OPRICE 135.000 == Type : Motor BoatMain Engine: 150 Hp CumminsEquipment Tv Stereo Musi System Port: Bodrum TURKEYGenerator: 12 kvA 220 VRefrigirator Dingy2.60 Date of Construction: 1992 Water Tanks: 1200 ltZodiak Boat LOA: 13.20m-40 ftFuel Tanks : 1000 lt BEAM:4.30m-13 ftAcommodation: 2 Master Cabin ==S A D K O 282PRICE 125.000 = LOA : 22.50 M / 74 FT ENGINE: 240HP DELPHIN BUILT: 1994 HULL: PINE / MAHOGANYI NTERIOR: MAHOGANY CABINS : 8 DOUBLE CABINS ALL CABINS WITH EN-SUITE WC+SHOWER GUEST CAPACITY: 16 ELECTRICITY : 12V WCs SHOWERS : FLUSH TYPE WCs ENCLOSED SHOWERS CREW : 1CAPTAIN, 1CHEF, 2 DECHANDS WATER CAPACITY: 6.000L FUEL CAPACITY: 2.000L WASTE WATER CAPACITY : 1.500L OTHER EQUIPMENT - TEAK DECK, GALVANIZED RIGGING, ALL CABINS WITH EN-SUITE WC SHOWERS AND HOT WATER, ICE BOXES , 2 STEERING POSITIONS, HYDRAULIC WINDLASS, SUN MATRESSES, DECK CHA Your sincerely Sadko Travel Yachting General Manager HacýAKDEMIR Manager Sadettin AKDEMIR Mobile:+ 90 536 6371646 +90 537 2732137 Tel: +90 252 3135235 Fax: +90 252 3135236 BODRUM OFFICE ISTANBUL OFFICE MOSCOW OFFICE Cumhuriyet caddesi No:53Ordu Caddesi No:292 Minsk Otel Kat: 7 Bodrum-MUGLA/TURKEYLaleli-ISTANBUL/TURKEYMOSCOW/RUSSIA http://www.sadkoyachting.com [EMAIL PROTECTED] [EMAIL PROTECTED] [EMAIL PROTECTED] We wish you a great success in your business. ___ Glasgow-haskell-users mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: pretty newby
Luc Taesch [EMAIL PROTECTED] writes: are there any facility to pretty print an haskell program ? im aware of HPJ combinators library, but i was looking for a command line utility, rather.. am i missing an entry in HPJ ? To some extent, you can use an ordinary Haskell compiler to pretty-print your Haskell code. For instance, among the various debugging options in nhc98, the compiler has the option +CTS -parse -CTS to show the abstract syntax tree of a module immediately after parsing it. (Other options show the syntax tree at other stages of the compilation, such as after desugaring of field-syntax, type-checking, etc.) I'm sure that ghc must have something similar. In nhc98 there are also various options to control the 'look' of the output of the pretty-printer, e.g. -showqualified -noshowqualified -showwidth=80 -showident=4 Regards, Malcolm ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: pretty newby
On Tuesday 23 September 2003 16.05, Luc Taesch wrote:
are there any facility to pretty print an haskell program ?
im aware of HPJ combinators library, but i was looking for a command line
utility, rather.. am i missing an entry in HPJ ?
thanks
Luc
___
Haskell mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/haskell
Hi,
In GHC (and HUGS?) you can use the 'haskell-src' package which contains
functions for parsing and pretty-printing haskell code. Using these, it only
takes a couple of lines to make your own command line, pretty-printer for
haskell code. If you want to, you can use my implementation which I attach to
this mail. The problem with the parser, however, is that it doesn't handle
comments at all.
Regards
Per-- FILE: HsIndent.hs
-- AUTH: Per Larsson
-- DATE: 03/10/2003
-- CODE: Haskell Code
module Main where
import System.Environment
import System.Exit
import System.IO
import Control.Monad
import Language.Haskell.Parser
import Language.Haskell.Pretty
import System.Console.GetOpt
header = hsindent [OPTION ...] FILE
version = hsindent 1.0
usage = usageInfo header options
data Config = Config {showHelp, showVersion :: Bool, pmode :: PPHsMode}
defaultConfig = Config False False defaultStyle
defaultStyle :: PPHsMode
defaultStyle = PPHsMode {
classIndent = 8,
doIndent = 3,
caseIndent = 5,
letIndent = 4,
whereIndent = 6,
onsideIndent = 2,
spacing = True,
layout = PPOffsideRule,
linePragmas = False,
comments = True
}
options :: [OptDescr (Config - Config)]
options =
[ opt 'h' help print this help information and exit
(\c - c {showHelp = True})
, opt 'v' version print version information and exit
(\c - c {showVersion = True})
, opt 'u' nospacing don't insert blank lines
(\c - c {pmode = (pmode c) {spacing = False}})
, opt 'p' pragmas insert source pragmas
(\c - c {pmode = (pmode c) {linePragmas = True}})
, opt 'e' comments keep comments
(\c - c {pmode = (pmode c) {comments = True}})
, arg 's' class N indent class declarations N columns
(\s c - c {pmode = (pmode c) {classIndent = read s}})
, arg 'd' do N indent do expressions N columns
(\s c - c {pmode = (pmode c) {doIndent = read s}})
, arg 'w' where N indent where expressions N columns
(\s c - c {pmode = (pmode c) {whereIndent = read s}})
, arg 'l' let N indent let expressions N columns
(\s c - c {pmode = (pmode c) {letIndent = read s}})
, arg 'c' case N indent case expressions N columns
(\s c - c {pmode = (pmode c) {caseIndent = read s}})
, arg 'o' onside N indent at line continuations N columns
(\s c - c {pmode = (pmode c) {onsideIndent = read s}})
, arg 'y' layout ARG set layout style to ARG, one of\n\
\ 'OffsideRule', 'SemiColon', 'Inline' or 'NoLayout'
(\s c - c {pmode = (pmode c) {layout = toLayout s}})
]
where
opt short long msg update =
Option [short] [long] (NoArg update) msg
arg short long argdescr msg update =
Option [short] [long] (ReqArg update argdescr) msg
toLayout :: String - PPLayout
toLayout OffsideRule = PPOffsideRule
toLayout SemiColon = PPSemiColon
toLayout InLine = PPInLine
toLayout NoLayout= PPNoLayout
toLayout _ = error toLayout
--
main = do
args - getArgs
(conf,files) - case getOpt Permute options args of
(o,n,[]) - return (foldr ($) defaultConfig o, n)
(_,_,errs) - error (concat errs ++ usageInfo header options)
when (showHelp conf) (exitSuccess usage)
when (showVersion conf) (exitSuccess version)
unless (length files == 1) (exitFail usage)
file - return (head files)
h - openFile file ReadMode
s - hGetContents h
result - return (parseModuleWithMode (ParseMode file) s)
case result of
ParseOk hsModule -
exitSuccess (prettyPrintWithMode (pmode conf) hsModule)
ParseFailed pos msg -
exitFail (Parse Error at: ++ show pos ++ \n ++ show msg)
where
exitSuccess msg = (putStrLn msg exitWith ExitSuccess)
exitFail msg = (putStrLn msg exitFailure)
___
Haskell mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/haskell
Re: pretty newby
Alle 16:05, martedì 23 settembre 2003, Luc Taesch ha scritto: are there any facility to pretty print an haskell program ? If what you need is an external program and not a library, have a look at GNU a2ps. Vincenzo ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: lexer puzzle
Thus, the only possible lexical interpretation is the one you first suggested, namely a constructor A followed by a three-dot operator A... should be split into A.. and . I found a compromise: let's make it a lexing error! :-) -- __( Marcin Kowalczyk \__/ [EMAIL PROTECTED] ^^ http://qrnik.knm.org.pl/~qrczak/ ___ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
Re: Thanks: (was Question about categories)
Bill Halchin wrote: Here is the book plus many other llongo papers: http://www.di.ens.fr/users/llongo/download.html s/llongo/longo/ ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: garbage collection and Ptr/ForeignPtr/StablePtr
On Monday 22 September 2003 12:10 pm, Bayley, Alistair wrote: Should I expect that Ptr memory allocated with malloc is garbage collected when no longer used by the Haskell runtime? The FFI spec doesn't say so explicitly (that I could see); C programs use pointers in many ways: pointers to static objects, pointers to stack-allocated objects, etc. as well as pointers to malloc-allocated objects. These are all represented with a 'Ptr' in Haskell but only one of them should be freed. Also, there are many ways to free a malloced object in C programs. You might have to decrement a reference count, you might have to first free any objects it contains pointers to, you might call a library-specific free routine called 'xfree', you might call a type-specific freeing routine or you might just call free. For all these reasons, Haskell's garbage collector cannot just call 'free' for you. AFAICT this is how the pointer types behave: Ptr : freed when no longer used/referenced No. If it needs freed, you have to explicitly deallocate this by calling an appropriate routine. This effectively means that you use Ptr for things accessed inside the IO monad. ForeignPtr : like Ptr, but will also run a finaliser when freed Yes. The finalizer is (a pointer to) any C function you like. ForeignPtr is especially useful for datatypes accessed outside the IO monad. e.g., if you wanted to use a complex number library, you might use ForeignPtr for the freeing function. ForeignPtr is also useful even if you are in the IO monad when you don't have a simple access pattern like 'allocate; use; free;'. Note that the ffi libraries provide functions called 'malloc' and 'free' and a finalizer called 'finalizerFree'. It is tempting to think that these are the C library 'malloc'/'free' and (a pointer to) 'free'. This is not necessarily so and you must take care that: - you only use MarshallAlloc.free and MarshallAlloc.finalizerFree with memory allocated using MarshallAlloc.malloc - you only use libc's 'free' with memory allocated using libc's 'malloc'. StablePtr : not freed or collected Yes. StablePtrs are in a different category because they are pointers from C into Haskell (in contrast, Ptrs and ForeignPtrs are pointers from Haskell into C). Since C doesn't have garbage collection, it is up to your C code to explicitly call 'freeStablePtr'. (I haven't tested this; I've only read the FFI spec.) I had a quick reread of sections 5.4 and 5.5 and I think your confusion is understandable. It doesn't say anything about deallocation so you might plausibly guess that the story is the same as for Int8 (say) which also says nothing about deallocation. ForeignPtrs are contrasted with Ptrs but only in whether or not they have finalizers. I think the ffi spec has now been finalized so it's too late to fix this but perhaps the next revision could include the following wording (inserted after the first sentence of section 5.4). Objects of type 'Ptr a' and 'FunPtr a' are garbage collected in the normal way but the objects they _point to_ are not garbage collected. If the objects pointed to require deallocation, this must be done by explicitly calling an appropriate function such as the C library function 'free'. I have put some of the above in my FFI guide at: http://www.reid-consulting-uk.ltd.uk/docs/ffi.html -- Alastair Reid www.haskell-consulting.com ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Generating setMember functions for record structures
Peter Simons [EMAIL PROTECTED] writes:
setFoo:: State - [Int] - State
setFoo st x= State { foo = x
, bar = bar st
}
There is an easier way to do this, using the record update syntax
rather than record construction syntax. e.g.
setFoo st x= st { foo = x }
All the unmentioned fields retain their previous values from the
'st' structure.
Regards,
Malcolm
___
Haskell-Cafe mailing list
[EMAIL PROTECTED]
http://www.haskell.org/mailman/listinfo/haskell-cafe
Database interface - would like advice on oracle library binding
(2nd attempt; mailman thinks I'm not a list member, but it still keeps
sending me mail.)
Still making slow progress on an Oracle database binding... now I'm trying
to fit the API I have into some sort of abstract interface (like the one(s)
discussed previously:
http://haskell.org/pipermail/haskell-cafe/2003-August/004957.html ).
1. Is the left-fold the best/only interface to expose? I think yes, but that
doesn't allow fine-grained control over cursors i.e. being able to open many
cursors at once and interleave fetches from them. Or does it?
2. I'm finding it hard to write a doQuery function that takes an extraction
function that isn't a pig to write. Some advice would be useful here... (and
a long-ish explanation follows):
The Oracle Call Interface (OCI) requires that I allocate buffers for the
result of a single row fetch, before the first row is fetched. So a query
involves:
- prepare statement etc
- allocate buffers (one for each column - call OCI C function
DefineByPos)
- fetch row
- extract/marshal data from buffer into Haskell types (which are then
processed by fold function)
- fetch, marshal (repeat until no more rows)
- free buffers
i.e. the same buffers are re-used for each row.
The problem for me is how to specify the left-fold function in terms of the
low-level API. If I want to supply extraction functions (to extract Haskell
values from result buffer), how do I manage the buffer allocation in the
doQuery function? The buffer allocate/free code also needs to know the
column positions and types, in the same manner as the extract functions.
I want to be able to write code like this:
results - doQuery dbconn sqltext [] \row results - do
name- stringv row 1
address - stringv row 2
return (name,address):results
.. where the stringv function extracts/marshals a Haskell String from the
result buffer.
The intermediate approach I currently have means I have to pass an IO action
into the doQuery function that, when evaluated, allocates the buffer and
returns two more actions:
- an action that extracts the row as a tuple
- another action that frees the buffer
The doQuery function evaluates the initial action (to allocate the buffer),
uses the extract action to build the result (at present a list), and when
there are no more rows, uses the free action to free the buffer.
This approach is quite awkward (especially w.r.t. writing extract
functions), and it's hard for me to see how to build a better interface.
Hard, because of the memory management requirements.
Here's a chunk of the code. A lot of it is OCI plumbing, but I hope you can
see how awkward it is to create an extract function (see ex3 at the bottom).
Given pointers to the buffer, extract a string of variable length (you have
to terminate it yourself).
fetchStringVal :: OCIColInfo - IO String
fetchStringVal (_, bufptr, nullindptr, retsizeptr) = do
retsize - liftM cShort2Int (peek retsizeptr)
nullind - liftM cShort2Int (peek nullindptr) -- unused
pokeByteOff (castPtr bufptr) retsize nullByte
val - peekCString (castPtr bufptr)
return val
Free a single column's buffer.
freeColBuffer :: OCIColInfo - IO ()
freeColBuffer (_, bufptr, nullindptr, retsizeptr) = do
free bufptr
free retsizeptr
free nullindptr
Create a buffer for a string column, and return the extract and free IO
actions.
getExtractFnString :: Int - ErrorHandle - StmtHandle - IO (IO String,
IO ())
getExtractFnString posn err stmt = do
c - defineCol err stmt posn 2000 oci_SQLT_CHR
return ((fetchStringVal c), (freeColBuffer c))
doQuery uses the extractFns action to create the result buffer,
and the two actions (extract and free) which are passed to doQuery2.
doQuery2 :: ErrorHandle - StmtHandle - IO a - IO () - [a] - IO [a]
doQuery2 err stmt extractData freeMem results = do
rc - fetch err stmt
if rc == oci_NO_DATA
then do
freeMem
return results
else do
v - extractData
doQuery2 err stmt extractData freeMem (v:results)
doQuery :: Session - String - (ErrorHandle - StmtHandle - IO (IO a, IO
())) - IO [a]
doQuery (Sess env err con) qry extractFns = do
stmt - getStmt env err
prepare err stmt qry
execute err con stmt
(extractData, freeMem) - extractFns err stmt
doQuery2 err stmt extractData freeMem []
The interface provided by doQuery means I have to write extract functions
like this.
Here's one for a select that returns three String columns.
It's quite awkward...
ex3 :: ErrorHandle - StmtHandle - IO (IO (String, String, String), IO
())
ex3 err stmt = do
(fetchcol1, freecol1) - getExtractFnString 1 err stmt
(fetchcol2, freecol2) - getExtractFnString 2 err stmt
(fetchcol3, freecol3) - getExtractFnString 3 err stmt
return
( do { s1 - fetchcol1; s2 - fetchcol2; s3 - fetchcol3; return (s1,
s2, s3) }
, do { freecol1; freecol2; freecol3 }
)
Database interface - would like advice on oracle library binding
Bayley, Alistair writes: : | Still making slow progress on an Oracle database binding... now I'm trying | to fit the API I have into some sort of abstract interface (like the one(s) | discussed previously: | http://haskell.org/pipermail/haskell-cafe/2003-August/004957.html ). | | | 1. Is the left-fold the best/only interface to expose? I think yes, | but that doesn't allow fine-grained control over cursors i.e. being | able to open many cursors at once and interleave fetches from | them. Or does it? It looks like the interleaving would be limited to a nested loop structure: a cursor could be processed in full during one extraction for another cursor. Application-side nested loop structures are often a poor substitute for server-side joins. | 2. I'm finding it hard to write a doQuery function that takes an | extraction function that isn't a pig to write. Some advice would be | useful here... (and a long-ish explanation follows): : Here's my attempt to summarise the piggishness you describe: The interface to Oracle requires that you initialise a cursor by allocating a suitably typed buffer for each column prior to fetching the first row, and finalise a cursor by freeing those buffers after fetching the last row. This means that we must iterate over the columns 3 times. We would prefer to express this iteration only once, and have the other 2 happen automatically within the library. (As opposed to what ex3 does, which is to iterate for getExtractFnString, iterate for fetchcolN, and iterate for freecolN.) Here's one approach: find the OCI equivalent of JDBC's ResultSetMetaData, and use it to drive the allocation and freeing of buffers. Here's another: Add a mode attribute to the abstract data type which encompasses ErrorHandle and StmtHandle. (I'll persist in referring to that ADT as Cursor.) Expect extraction functions to be written along these lines: \cursor result - do field1 - getIntcursor field2 - getString cursor field3 - getString cursor return ((field1, field2, field3):result, True) Make getInt (and friends) behave differently depending on the mode of the cursor they're passed: either allocate a buffer and return _|_, decode and return the current column of the current row, or free a buffer and return _|_. doQuery could then apply the extraction function once in Allocate mode after opening the cursor, once per fetched row in Decode mode, and once in Free mode at the end. There's nothing to stop an extraction function from varying the number of get___ functions it applies, or trying to match their results when not in Decode mode. These weakness could be mitigated by: Pointing out that some database connection standards (JDBC, and for all I know also ODBC) don't guarantee that you can still get at a row's 1st column after you've looked at its 2nd column, i.e. there's a precedent for such fragility. Complicating the extraction functions by giving them the type (Cursor - b - IO (IO (b, Bool))) , expecting that all the get___ functions are applied in the outer IO layer, and undertaking that the inner IO layer will only be used in Decode mode. Regards, Tom ___ Haskell-Cafe mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell-cafe
