RE: RULES pragmas
I've started a Wiki page, attached to GHC's collaborative documentation,
as a place to collect advice about RULES.
http://haskell.org/haskellwiki/GHC/Using_Rules
Please feel free to elaborate it.
Simon
| -Original Message-
| From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]
| On Behalf Of Donald Bruce Stewart
| Sent: 12 July 2006 01:41
| To: Malcolm Wallace
| Cc: glasgow-haskell-users@haskell.org
| Subject: Re: RULES pragmas
|
| Malcolm.Wallace:
| I have a question about {-# RULES #-} pragmas. Here is a very
simple
| attempt to use them:
|
| module Simplest where
| {-# RULES
| simplestRule forall x. id (id x) = x
|#-}
| myDefn = id (id 42)
|
| I want to verify whether ghc-6.4.1 does actually fire this rule, but
| have so far been unable to do so. According to the manual (section
| 7.10.5), the flag -ddump-rules should list simplestRule if it has
been
| parsed correctly, and -ddump-simpl-stats should list the number of
times
| it has fired. But it does not appear in either listing.
|
| Reasoning that I have the syntax wrong, I have tried numerous
variations
| on the indentation, added type signatures, etc., all to no avail.
|
| So what am I doing wrong? And is there any way to ask the compiler
to
| give a warning if the RULES pragma contains errors?
|
| In this case, it's because it's missing -fglasgow-exts, I think.
| The following works for me with both 6.4 and 6.5 compilers:
|
| module Simplest where
|
| {-# RULES
| simplestRule forall x. id (id x) = x
| #-}
|
| myDefn = id (id 42)
|
| when compiled with:
| $ ghc-6.4.2 -fglasgow-exts -c -ddump-simpl-stats A.hs
|
| Grand total simplifier statistics
| Total ticks: 11
|
| 2 PreInlineUnconditionally
| 3 PostInlineUnconditionally
| 1 UnfoldingDone
| 1 RuleFired
| 1 simplestRule
| 4 BetaReduction
| 2 SimplifierDone
|
| However, in general, you need to be careful that your identifiers
| weren't inlined in the first phase. To control this we add an INLINE
[1]
| pragma to identifiers we want to match in rules, to ensure they
haven't
| disappeared by the time the rule matching comes around.
|
| Also, you need -O to have rules kick in locally.
|
| So,
| module Simplest where
|
| {-# RULES
| simplestRule forall x. myid (myid x) = x
| #-}
|
| myDefn = myid (myid 42)
|
| myid x = x
| {-# INLINE [1] myid #-}
|
| And:
| $ ghc-6.4.2 -fglasgow-exts -O -c -ddump-simpl-stats A.hs
|
| Grand total simplifier statistics
| Total ticks: 15
|
| 6 PreInlineUnconditionally
| 2 UnfoldingDone
| 1 RuleFired
| 1 simplestRule
| 5 BetaReduction
| 1 KnownBranch
| 8 SimplifierDone
|
| Cheers,
| Don
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| Glasgow-haskell-users@haskell.org
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Re: RULES pragmas
[EMAIL PROTECTED] (Donald Bruce Stewart) wrote: So what am I doing wrong? And is there any way to ask the compiler to give a warning if the RULES pragma contains errors? In this case, it's because it's missing -fglasgow-exts, I think. Ah, thank you. The missing (and undocumented) option. Is there any reason why -fglasgow-exts should be required? Judging by the flag reference material in section 4.17.15, -frules-off is used to turn RULES off explicitly, but there is no corresponding flag to turn them on - hence I assumed they would be enabled by default when -O or -O2 is set. Regards, Malcolm ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: RULES pragmas
Malcolm Wallace [EMAIL PROTECTED] wrote: Ah, thank you. The missing (and undocumented) option. Actually, now I came to submit a patch to the manual, I discover that it /is/ documented, but at the beginning of section 7. (But on the index page on the web, the link to section 7 is two whole screenfuls away from the link to 7.10, so it is no wonder I didn't think to look there first.) Maybe there are other subsections of 7 that could usefully gain a similar pointer to the need for -fglasgow-exts? For instance, are other pragmas (INCLUDE, INLINE, UNPACK) only activated by -fglasgow-exts? Regards, Malcolm ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: RULES pragmas
Malcolm Wallace wrote: Malcolm Wallace [EMAIL PROTECTED] wrote: Ah, thank you. The missing (and undocumented) option. Actually, now I came to submit a patch to the manual, I discover that it /is/ documented, but at the beginning of section 7. (But on the index page on the web, the link to section 7 is two whole screenfuls away from the link to 7.10, so it is no wonder I didn't think to look there first.) Maybe there are other subsections of 7 that could usefully gain a similar pointer to the need for -fglasgow-exts? For instance, are other pragmas (INCLUDE, INLINE, UNPACK) only activated by -fglasgow-exts? I believe RULES is the only pragma that requires -fglasgow-exts, the reason being that the syntax inside RULES uses the 'forall' keyword, which is only enabled by -fglasgow-exts. If you could submit a doc patch, that would be great. Cheers, Simon ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: RULES pragmas
Malcolm.Wallace:
I have a question about {-# RULES #-} pragmas. Here is a very simple
attempt to use them:
module Simplest where
{-# RULES
simplestRule forall x. id (id x) = x
#-}
myDefn = id (id 42)
I want to verify whether ghc-6.4.1 does actually fire this rule, but
have so far been unable to do so. According to the manual (section
7.10.5), the flag -ddump-rules should list simplestRule if it has been
parsed correctly, and -ddump-simpl-stats should list the number of times
it has fired. But it does not appear in either listing.
Reasoning that I have the syntax wrong, I have tried numerous variations
on the indentation, added type signatures, etc., all to no avail.
So what am I doing wrong? And is there any way to ask the compiler to
give a warning if the RULES pragma contains errors?
In this case, it's because it's missing -fglasgow-exts, I think.
The following works for me with both 6.4 and 6.5 compilers:
module Simplest where
{-# RULES
simplestRule forall x. id (id x) = x
#-}
myDefn = id (id 42)
when compiled with:
$ ghc-6.4.2 -fglasgow-exts -c -ddump-simpl-stats A.hs
Grand total simplifier statistics
Total ticks: 11
2 PreInlineUnconditionally
3 PostInlineUnconditionally
1 UnfoldingDone
1 RuleFired
1 simplestRule
4 BetaReduction
2 SimplifierDone
However, in general, you need to be careful that your identifiers
weren't inlined in the first phase. To control this we add an INLINE [1]
pragma to identifiers we want to match in rules, to ensure they haven't
disappeared by the time the rule matching comes around.
Also, you need -O to have rules kick in locally.
So,
module Simplest where
{-# RULES
simplestRule forall x. myid (myid x) = x
#-}
myDefn = myid (myid 42)
myid x = x
{-# INLINE [1] myid #-}
And:
$ ghc-6.4.2 -fglasgow-exts -O -c -ddump-simpl-stats A.hs
Grand total simplifier statistics
Total ticks: 15
6 PreInlineUnconditionally
2 UnfoldingDone
1 RuleFired
1 simplestRule
5 BetaReduction
1 KnownBranch
8 SimplifierDone
Cheers,
Don
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syntax of RULES pragmas?
Hi,
I was trying to play with GHC 5.02's RULES pragmas, but failed due to
syntax problems.
When trying:
{-# RULES map/map forall f g xs. map f (map g xs) = map (f.g) xs #-}
main = print (map id (map id Hello))
I get:
ghc5 test.hs -O
test.hs:1: Variable not in scope: `forall'
test.hs:1: Variable not in scope: `f'
test.hs:1: Variable not in scope: `g'
test.hs:1: Variable not in scope: `xs'
test.hs:1: Variable not in scope: `f'
test.hs:1: Variable not in scope: `g'
test.hs:1: Variable not in scope: `xs'
test.hs:1: Variable not in scope: `f'
test.hs:1: Variable not in scope: `g'
test.hs:1: Variable not in scope: `xs'
Exit 1
With:
{-# RULES map/map forall f g xs.
map f (map g xs) = map (f.g) xs #-}
main = print (map id (map id Hello))
I get:
test.hs:2: parse error (possibly incorrect indentation)
Exit 1
In the user's doc on http://www.haskell.org/ghc/ I also saw the syntax:
{-# RULES map/map forall f,g,xs. map f (map g xs) = map (f.g) xs #-}
main = print (map id (map id Hello))
which fails with:
test.hs:1: parse error on input `,'
Exit 1
So how exactly do I have to specify a rewrite rule? Any hints
appreciated.
Thanks, Janis.
--
Janis Voigtlaender
http://wwwtcs.inf.tu-dresden.de/~voigt/
mailto:[EMAIL PROTECTED]
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RE: syntax of RULES pragmas?
You need -fglasgow-exts. (Should ignore a pragma without
-fglasgow-exts,
and does so now, but 5.03 gave the bad message you found.)
The manual is wrong; spaces between the variables is right.
Simon
| -Original Message-
| From: Janis Voigtlaender [mailto:[EMAIL PROTECTED]]
| Sent: 16 May 2002 14:49
| To: [EMAIL PROTECTED]
| Subject: syntax of RULES pragmas?
|
|
| Hi,
|
| I was trying to play with GHC 5.02's RULES pragmas, but
| failed due to syntax problems.
|
| When trying:
|
| {-# RULES map/map forall f g xs. map f (map g xs) = map
| (f.g) xs #-}
|
| main = print (map id (map id Hello))
|
| I get:
|
| ghc5 test.hs -O
| test.hs:1: Variable not in scope: `forall'
|
| test.hs:1: Variable not in scope: `f'
|
| test.hs:1: Variable not in scope: `g'
|
| test.hs:1: Variable not in scope: `xs'
|
| test.hs:1: Variable not in scope: `f'
|
| test.hs:1: Variable not in scope: `g'
|
| test.hs:1: Variable not in scope: `xs'
|
| test.hs:1: Variable not in scope: `f'
|
| test.hs:1: Variable not in scope: `g'
|
| test.hs:1: Variable not in scope: `xs'
| Exit 1
|
|
| With:
|
| {-# RULES map/map forall f g xs.
| map f (map g xs) = map (f.g) xs #-}
|
| main = print (map id (map id Hello))
|
| I get:
|
| test.hs:2: parse error (possibly incorrect indentation)
| Exit 1
|
|
| In the user's doc on http://www.haskell.org/ghc/ I also saw
| the syntax:
|
| {-# RULES map/map forall f,g,xs. map f (map g xs) = map
| (f.g) xs #-}
|
| main = print (map id (map id Hello))
|
| which fails with:
|
| test.hs:1: parse error on input `,'
| Exit 1
|
|
| So how exactly do I have to specify a rewrite rule? Any hints
| appreciated.
|
| Thanks, Janis.
|
|
| --
| Janis Voigtlaender
| http://wwwtcs.inf.tu-dresden.de/~voigt/
| mailto:[EMAIL PROTECTED]
| ___
| Glasgow-haskell-users mailing list
| [EMAIL PROTECTED]
| http://www.haskell.org/mailman/listinfo/glasgow-| haskell-users
|
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