[Haskell-cafe] Proposal: Hackage's packages should be seperated by buildable
I'm sick for checking whether package is obsolete or not. I think packages build failed long time ago should be collected and moved to another page until someone fix them, or hackage pages should have a filter for checking obsolete packages. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] reasons why Template Haskell does not propose something similar to Python exec() or eval()
Tobias Dammers wrote: IIRC you can use haskell-src-exts to parse a string into TH AST structures. There might even be a quasi-quoter for that; I don't have a real computer at hand right more, so you'll need to do some research of your own. Thanks Tobias, it led me to the right path. There is indeed a solution in Language.Haskell.Meta: $ ghci :m Language.Haskell.Meta parseDecs s=s+1 Right [ValD (VarP s) (NormalB (UInfixE (VarE s) (VarE +) (LitE (IntegerL 1 []] parseExp x+1 Right (UInfixE (VarE x) (VarE +) (LitE (IntegerL 1))) :i parseDecs parseDecs :: String - Either String [Language.Haskell.TH.Syntax.Dec] -- Defined in `Language.Haskell.Meta.Parse' :i parseExp parseExp :: String - Either String Language.Haskell.TH.Syntax.Exp -- Defined in `Language.Haskell.Meta.Parse' Thanks, TP ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Proposal: Hackage's packages should be seperated by buildable
On Sun, Aug 25, 2013 at 12:48 AM, He-chien Tsai depot...@gmail.com wrote: I'm sick for checking whether package is obsolete or not. I think packages build failed long time ago should be collected and moved to another page until someone fix them, or hackage pages should have a filter for checking obsolete packages. I don't believe hackage can (currently) do this with a sufficient level of precision. *Many* packages fail to build on hackage because they depend on c-libraries that need to be installed externally from cabal. There are some mitigations for this in the works (although, it's been that way for some time now...). Hackage 2 should have some community-involvement features (such as ratings, tags, etc..) that can enable better rankings of packages, and there is a hackage reverse-dependencies database that can also be used as a rough indicator of stability. That said, I do firmly believe that we should have multiple instances of hackage at various levels of stability (and at corresponding levels of scrutiny). At the moment, we have the Haskell Platform on one end of this continuum of stability, and hackage at the other. It would be useful to have something in the middle. --Rogan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] reasons why Template Haskell does not propose something similar to Python exec() or eval()
There's a
proposalhttp://ghc.haskell.org/trac/ghc/blog/Template%20Haskell%20Proposal#PartD:quasiquotationfor
adding a proper Haskell
QuasiQuoter as part of template-haskell. Until then, as others have noted
your best option is the haskell-src-meta package, but be aware that this
uses a separate parser.
On Sat, Aug 24, 2013 at 11:36 AM, TP paratribulati...@free.fr wrote:
Hi everybody,
I continue to learn and test Template Haskell (one more time thanks to John
Lato for his post at:
http://www.mail-archive.com/haskell-cafe@haskell.org/msg106696.html
that made me understand a lot of things).
I have a question about the way Template Haskell is working. Why Template
Haskell does not propose something similar to Python (or bash) exec() or
eval(), i.e. does not offer the possibility to take a (quoted) string in
input, to make abstract syntax in output (to be executed later in a splice
$()).
For example, in Python, to make an affectation 'a=a' programatically, I
can simply do (at runtime; even if I am here only concerned with what
Template Haskell could do, i.e. at compile time):
def f(s): return '%s = \'%s\'' % (s,s)
exec(f(a))
a
'a'
With Template Haskell, I am compelled to make a function returning the
abstract syntax corresponding to variable declaration:
ValD (VarP $ mkName s) (NormalB $ LitE $ StringL s)
(see complete example in Post Scriptum).
This works fine, but it is less direct. I am sure that the Template Haskell
approach has many advantages, but I am unable to list them. I think it is
important to have the reasons in mind. Could you help me?
Thanks in advance,
TP
PS: the complete Haskell example:
---
module MakeVard where
import Language.Haskell.TH
makeVard :: Monad m = String - m [Dec]
-- Equivalent to %s = \%s\
makeVard s = return [ ValD (VarP $ mkName s) (NormalB $ LitE $ StringL s)
[]
]
---
tested by
---
{-# LANGUAGE TemplateHaskell #-}
import MakeVard
$(makeVard a)
main = do
print a
---
resulting in
$ runghc -ddump-splices test.hs
test_makeVar.hs:1:1: Splicing declarations
makeVard a
==
test_makeVar.hs:4:3-14
a = a
a
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Re: [Haskell-cafe] Renumbered mailing list posts
Austin: Do you have any update on this? On 11/08/13 04:48, Austin Seipp wrote: Henning, Thanks for the report. I'm currently investigating this, and think it should be possible to keep all of the old URLs intact. On Sat, Aug 10, 2013 at 11:01 AM, Niklas Hambüchen m...@nh2.me wrote: On 11/08/13 00:50, Brandon Allbery wrote: Those at least are recoverable, just replace hpaste.org http://hpaste.org with lpaste.net http://lpaste.net (content is still there). But still. Unfortunately I cannot amend emails that I have sent. Could we not just have kept the domain and set a CNAME entry to the new one? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Template Haskell: let statement in a splice put in the main = do part of a program?
On Sat, Aug 24, 2013 at 11:00 AM, TP paratribulati...@free.fr wrote:
that has type Stmt, in an ExpQ that seems to be the only thing that we can
put in a splice. I have found that it can only be done by doE (or DoE) and
compE (or CompE) according to
http://www.haskell.org/ghc/docs/latest/html/libraries/template-haskell-2.8.0.0/Language-Haskell-TH.html#v:doE
But doE is not a solution as we have seen above, and compE is to construct
list comprehensions, which is a different thing.
So, is there any solution to my problem?
Hi TP,
TH quotes limited as you've noticed. One way to generate similar code
is to note that:
do
let x = y
z
is the same as let x = y in do z. You can generate the latter with
something like the following file, but the `a' isn't in scope for the
second argument to makeLetStatement. The uglier $(dyn a) works,
though I suppose it's more verbose than manually in-lining the
variable a.
{-# LANGUAGE TemplateHaskell #-}
import Language.Haskell.TH
main = $(let
makeLetStatement :: String - ExpQ - ExpQ
makeLetStatement s rest = letE [ valD (varP (mkName s))
(normalB $ stringE s) []]
rest
in makeLetStatement a [| print $(dyn a) |] )
--
Adam
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