Frank A. Christoph: FastString in GHC
I have been looking at the GHC 4.04 sources a little lately and in the
module FastString (in ghc/compiler/utils), the instance for Eq is defined as
follows:
instance Eq FastString where
a == b = case cmpFS a b of { LT - False; EQ - true; GT - False }
...
and cmpFS will return EQ if the unique IDs of a and b match, otherwise it
just does a ccall to strcmp.
What I don't understand is why you don't just define (==) so that to
FastStrings are equal if and _only_ if their unique IDs are equal. Isn't the
whole point of FastString that identical strings and only identical strings
will get the same ID? The ID's not the string's hash value, as far as I can
see, and with the present definition you will check each character in the
string when the result of (==) is False.
Am I missing something?
- --FC
Re: Cyclic compilation dependencies...
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X-URL: http://WWW.CS.Yale.EDU/homes/reid-alastair/
Date: Tue, 06 Oct 1998 09:58:33 -0300
From: Alastair Reid [EMAIL PROTECTED]
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Tim Hemel [EMAIL PROTECTED] writes:
I am trying to make a port skeleton for the BSD ports selection for GHC.
[but happy depends on ghc depends on happy ...]
How do I get out of this mutual recursion?
You start off with a binary distribution of one of the packages.
Simon Marlow writes:
You'll need GHC installed in order to compile GHC in any case
Or you can use Hugs to execute happy using something like this:
runhugs -h10m Happy.hs MyGrammar.y and other options
It'll probably take a few minutes to run but you've only got to do it once.
(btw I've never tried this route with GHC's parser - but I've done it when
working on the greencard parser and it worked pretty well.)
Alastair
Re: Extra output lines from trace.
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X-URL: http://WWW.CS.Yale.EDU/homes/reid-alastair/
Date: Thu, 30 Jul 1998 14:29:45 -0300
From: Alastair Reid [EMAIL PROTECTED]
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Lars Lundgren [EMAIL PROTECTED] writes:
Not a bug, but annoying:
Every application of trace generates three extra lines which makes it less
usefull IMO (compared to trace in hugs).
Simon Marlow replies:
Compile and link the following C code with your Haskell program [...]
I personally prefer GHC's way of doing things since it pretty much guarantees
that people will not try to use trace as a sneaky way round Haskell's IO monad.
I also like what HBC (or maybe it's GHC - I forget) does which is to keep track
of nested calls to trace and indent the output accordingly. This is trivial to
implement using GHC's Pre/PostTraceHooks (if it's not already being done).
[GHC folks: IOExts.trace doesn't say much about what trace is meant to do.
I'm happy to say it does what GHC does.]
--
Alastair Reid Yale Haskell Project Hacker
[EMAIL PROTECTED] http://WWW.CS.Yale.EDU/homes/reid-alastair/
Re: problems compiling ghc 3.01 for linux
8Qxd$QC/sdeK{93/{KA]T@gir{b8(rd5/zL85UcsTGty!z9Nx%Z+0e193YVEXFcWdM.]+uyVYA6
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X-URL: http://WWW.CS.Yale.EDU/homes/reid-alastair/
Date: Mon, 11 May 1998 11:03:09 -0300
From: Alastair Reid [EMAIL PROTECTED]
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we still don't have any recent Linux installations here
to test out a proper fix on.
Surely someone at Glasgow CS dept can lend you the Redhat CD ROM
and boot disk?
If not, Computer World (I think that's the name) isn't too far away.
Or you could order direct from Redhat. Or save money by ordering
from Cheap Bytes (but better to pay extra to RH to support further
development).
Or you can upgrade by ftp - I'm sure there's a mirror near you.
Upgrading only takes about 15 minutes of work - and a couple of hours
of ignoring the machine while it copies files.
(Time estimate based on my experience of Redhat 5.0. I'm not sure
how good the other distributions are for upgrading.)
Alastair
Re: Anomaly in IO in GHC (I think)
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Date: Wed, 25 Mar 1998 11:51:40 -0500
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[Reply redirected to bug mailing lists and copied to the library czar]
Sigbjorn writes:
GHC's behaviour [of Prelude.interact] is consistent with the
report, Hugs' isn't.
Hugs deliberately deviates from the report (ie turns
echoing off when running interact) because the report is
clearly broken.
The only reason for including "interact" in the Prelude is so
that you can write:
interact (map toUpper)
and the like. This is only useful if echoing is turned off - so we do.
Alastair
ps The URL Sigbjorn posted should be:
http://www.dcs.gla.ac.uk/mail-www/haskell/msg00270.html
and this doesn't contain a link to all the followups:
http://www.dcs.gla.ac.uk/mail-www/haskell/msg00272.html
http://www.dcs.gla.ac.uk/mail-www/haskell/msg00273.html
http://www.dcs.gla.ac.uk/mail-www/haskell/msg00277.html
(Sigbjorn: any chance of adding a "possible followups"
list as well as the "followups" list?)
