Re: [Haskell-cafe] Can Haskell outperform C++?
One thing that baffles me is the comparison Haskell V. Java: http://shootout.alioth.debian.org/u32/benchmark.php?test=alllang=ghclang2=java Would've expected always shorter code and better performances on average. 2012/5/8 Silvio Frischknecht silvio.fris...@gmail.com -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Can anyone provide a code in Haskell that performs better in terms of execution speed than a well-written C/C++ program? http://shootout.alioth.debian.org/ compares a lot of programming languages on a lot of problems. Haskell is never as fast as C++, but for some problems it comes close. Also I challenge anyone to improve one of the haskell programs there. It'd be cool if we could make haskell get a higher rank. I recently managed to improve the Fasta algorithm, but not by much. Also I think the benchmarks don't use llvm flag. It says somewhere that they don't measure llvm because they don't have time. But I think they are refering to clang. So maybe someone should tell them to turn on the llvm flag since it makes a lot of haskell programs faster. Silvio -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQIcBAEBAgAGBQJPqKicAAoJEDLsP+zrbatWmSIP+gNSI61KMvY2VRsWRhd7+j5U YAO3CnBTt6lSbMNplFf5AZnbPnY3NVJSG2ZUN12n7ZcaOawmwub3H+N9e0XTXv38 vOEGzFb/t/OTIx4GHXiWz6kZfzyiTVQpEhzoqx/ZX4KZqrUBt5ZuSpmWtPrPXCfF joCZiBZIwxfOkI/l1zsb8vW3Xaqxs9dfRQOJEf7GLB5zGXwUA2ZLWG5HYvAUHu0G 9xB9cBgaX7HKdBwo3af2WZEFznZnZ1LUpc8TuacL54wVmLpLNJU2EaeqH2LsH0R3 VxX9yU1TIQUBubDa1Tui73xJ2L4Ns7AVD7Kx14yK5cu61wpz/KeUOU/wgedp+wNe o54alfqzrfOC+GAJGJFg+3aIkXuij4j1jTXZ+/3ya7nofcBZwtqoZUWCvjYSoEaI xecxuHLCK2pd3zwPk7ZUnG0Mo0vu4ZpVKpCs4u8nPRzVl0101mGkHSVTVXjVP8R/ d3AIPwy74B4nvCk9gohxHwtsvsmzxoRZr7E5XkGDTQdbj0Ly5bJfBW3c1X/jvq9c FHvxCspERGf6S+aX9L6lg9v3/aje/av2q0zUL7jizA4no3q7D/ZvWkmIWF5ySyRh +QrC39I6GHDMvxXn0HIp9m2226sNGL4vpvBTgucJWJcHUX+FdytFIe7VQ0ZvdXvx IjxCrgMAPVy5/TH44PP+ =TaFj -END PGP SIGNATURE- ___ 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] Can Haskell outperform C++?
On 06/05/2012 07:40, Janek S. wrote: a couple of times I've encountered a statement that Haskell programs can have performance comparable to programs in C/C++. I've even read that thanks to functional nature of Haskell, compiler can reason and make guarantess about the code and use that knowledge to automatically parallelize the program without any explicit parallelizing commands in the code. I haven't seen any sort of evidence that would support such claims. Can anyone provide a code in Haskell that performs better in terms of execution speed than a well-written C/C++ program? Both Haskell and C programs should implement the same algorithm (merge sort in Haskell outperforming bubble sort in C doesn't count), though I guess that using Haskell-specific idioms and optimizations is of course allowed. On the subject of parallelism in particular, there is no fully implicit parallelism in Haskell at the moment. When people ask about this I typically point to this paper: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.145.8183 which shows that it is possible to get some gains doing this, but it is hard and the gains were not great. However, what Haskell does give you is a guarantee that you can safely call any function in parallel (with itself or with something else), as long as the function does not have an IO type. This is about as close to automatic parallelisation as you can practically get. Take any pure function from a library that someone else wrote, and you can use it with parMap or call it from multiple threads, and reasonably expect to get a speedup. Furthermore with parMap you're guaranteed that the result will be deterministic, and there are no race conditions or deadlocks to worry about. Cheers, Simon ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can Haskell outperform C++?
On May 8, 2012, at 12:18 PM, Yves Parès wrote: Would've expected always shorter code It's not so surprising if you consider that some of the programs are practically imperative programs in Haskell. To give an example: http://shootout.alioth.debian.org/u32/program.php?test=fannkuchreduxlang=ghcid=3 -- Daniël ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Annotaing abstract syntax trees
Hello.
I am reading Martijn's MSc Thesis Generic Selections of
Subexpressions, where one can found some discussions about annotating
abstract syntax trees (AST).
In order to follow the discussion I wrote the attached Haskell program,
which is an interpreter for an simple typed expression language. The
Annotations package is used.
The expression pattern is represented by a single recursive data
type. Annotations are used for positions in the input source, and also
for the type of expressions and subexpressions.
I would like somebody to review the code and comment on it, as I am not
sure I am using the concepts right.
Also I would like the type checker to produce an expression annotated
with both positions and calculated types. Currently it discards the
position annotations. Any sugestions on how to modify it is welcome.
Next step is adding a new form of expression to introduce local variable
bindings.
After that I want to start working with ASTs represented by mutually
recursive data types. Then I will need multirec...
Romildo
{-# LANGUAGE FlexibleContexts #-}
module Main where
import Control.Applicative (Applicative(pure,(*)),($),($),(*))
import Data.Traversable (Traversable(traverse))
import Data.Foldable (Foldable(foldr))
import Text.Parsec hiding (chainl1)
import Data.Char (isDigit,isAlpha,isAlphaNum)
import Data.Tree (Tree(Node),drawTree)
import Annotations.F.Fixpoints
import Annotations.F.Annotated
import Annotations.Except
-- the goal is to implement an interpreter for a simple language of
-- typed expressions using annotations on recursive data types
-- type of expressions
data ExprType
= NUMERIC
| LOGIC
deriving (Show)
-- value of an expression
data ExprValue
= Numeric Double
| Logic Bool
deriving (Show)
-- identifiers are strings
type Id = String
-- binary operators used in expressions
data Op
= Add | Sub | Mul | Div -- arithmetic
| Eq | Ne | Gt | Ge | Lt | Le -- relational
| And | Or -- logical
deriving (Show)
-- pattern of an expression
data ExprF r
= Num Double -- numeric literal
| Log Bool -- logical literal
| Var Id -- variable
| Bin Op r r -- binary operation
deriving (Show)
-- mapping a function over an expression pattern
instance Functor ExprF where
fmap _ (Num n) = Num n
fmap _ (Log b) = Log b
fmap _ (Var v) = Var v
fmap f (Bin op x y) = Bin op (f x) (f y)
-- traversing an expression pattern
instance Traversable ExprF where
traverse _ (Num n) = pure (Num n)
traverse _ (Log b) = pure (Log b)
traverse _ (Var v) = pure (Var v)
traverse f (Bin op x y) = Bin op $ f x * f y
-- folding an expression pattern
instance Foldable ExprF where
foldr _ z (Num _) = z
foldr _ z (Log _) = z
foldr _ z (Var _) = z
foldr f z (Bin op l r) = f l (f r z)
-- bare expressions
newtype Expr
= Expr { runExpr :: Fix ExprF }
deriving (Show)
-- range of source positions: used to delimit where something appeared
-- in a source input
data Range
= Range SourcePos SourcePos
instance Show Range where
show (Range p1 p2)
| n1 == n2 = if null n1
then showLC lc1 ++ - ++ showLC lc2
else showN n1 ++ ++ showLC lc1 ++ - ++ showLC lc2
| otherwise = showN n1 ++ ++ showLC lc1 ++ - ++ showN n2 ++ ++ showLC lc2
where
n1 = sourceName p1
lc1 = (sourceLine p1,sourceColumn p1)
n2 = sourceName p2
lc2 = (sourceLine p2,sourceColumn p2)
showN n = \ ++ n ++ \
showLC (l,c) = show l ++ : ++ show c
-- expressions annoted with positions
newtype PosExpr
= PosExpr { runPosExpr :: Fix (Ann Range ExprF) }
deriving (Show)
-- convert an expression to a rose tree of strings
-- this helps to visualize the expression structure
exprTree :: Algebra ExprF (Tree String)
exprTree (Num n) = Node (Num: ++ show n) []
exprTree (Log b) = Node (Log: ++ show b) []
exprTree (Var v) = Node (Var: ++ v) []
exprTree (Bin op l r) = Node (Bin: ++ show op) [l,r]
-- convert an annotated expression to a tree of strings
-- this helps to visualize the annotated expression structure
annExprTree :: Show a = Algebra (Ann a ExprF) (Tree String)
annExprTree (Ann z expr) =
case expr of
Num n - Node (annot (Num: ++ show n)) []
Log b - Node (annot (Log: ++ show b)) []
Var v - Node (annot (Var: ++ v)) []
Bin op l r - Node (annot (Bin: ++ show op)) [l,r]
where
annot x = x ++ ++ show z
-- a memory is just an association list between
-- variable names and values
type Memory = [(Id,ExprValue)]
-- an algebra to find the value of an expression annotated with
-- positions, given a memory
exprEval :: Memory - ErrorAlgebra ExprF String ExprValue
exprEval _ (Num n) = Right (Numeric n)
exprEval _ (Log b) = Right (Logic b)
exprEval m (Var v) = case lookup v m of
Just x - Right x;
Nothing - Left (undefined
[Haskell-cafe] anyone else driven mad by trying to setup a gmp free version of haskell platform?
i would really like to be able to ship haskell based linux binaries, but the gmp dependency makes it virtually impossible. so what version of host os, host ghc, and haskell-platform sources are known to build a working compiler? any reason why the dependency on gmp is static? are the interfaces between versions actually different? or can we build a version fo the compiler that loads the library via dlopen on demand? Thanks, Anatoly ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Unit and pair
Hi café, a quick question. Is there a somewhat standard class like this: class Something c where unit :: c () () pair :: c x y - c u v - c (x, u) (y, v) ? I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything. I know about arrows; this, however, is something more general, and it's instances aren't always arrows. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unit and pair
On Tue, May 8, 2012 at 2:36 PM, MigMit miguelim...@yandex.ru wrote: Hi café, a quick question. Is there a somewhat standard class like this: class Something c where unit :: c () () pair :: c x y - c u v - c (x, u) (y, v) ? I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything. I know about arrows; this, however, is something more general, and it's instances aren't always arrows. Are you aware of generalized arrows [1]? It's still a lot more than your Something, though. [1] http://www.cs.berkeley.edu/~megacz/garrows/ -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unit and pair
On 8 May 2012, at 21:42, Felipe Almeida Lessa wrote: On Tue, May 8, 2012 at 2:36 PM, MigMit miguelim...@yandex.ru wrote: Hi café, a quick question. Is there a somewhat standard class like this: class Something c where unit :: c () () pair :: c x y - c u v - c (x, u) (y, v) ? I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything. I know about arrows; this, however, is something more general, and it's instances aren't always arrows. Are you aware of generalized arrows [1]? It's still a lot more than your Something, though. I've heard of them, but some instances of my Something class aren't categories either, which rules out GArrows too. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Can Haskell outperform C++?
2012/5/8 Silvio Frischknecht Also I challenge anyone to improve one of the haskell programs there. It'd be cool if we could make haskell get a higher rank. I recently managed to improve the Fasta algorithm, but not by much. Also I think the benchmarks don't use llvm flag. It says somewhere that they don't measure llvm because they don't have time. But I think they are refering to clang. So maybe someone should tell them to turn on the llvm flag since it makes a lot of haskell programs faster. Several GHC versions have come and gone since the Haskell benchmarks game programs were written, so perhaps it is time that a dozen new programs were written to replace those old programs - new programs that take advantage of GHC 7.4.1 and -llvm. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Handcranked install of ghc / cabal-install and warning from ghc-pkg check
Have installed 7.4.1 ghc and 0.14.0 cabal-install and then did alex, happy haddock. When I do a ghc-pkg check I get $ ghc-pkg check Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/random-1.0.1.1/html/random.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/random-1.0.1.1/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/zlib-0.5.3.3/html/zlib.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/zlib-0.5.3.3/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/HTTP-4000.2.3/html/HTTP.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/HTTP-4000.2.3/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/network-2.3.0.11/html/network.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/network-2.3.0.11/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/parsec-3.1.2/html/parsec.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/parsec-3.1.2/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/text-0.11.2.0/html/text.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/text-0.11.2.0/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/mtl-2.1/html/mtl.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/mtl-2.1/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/Cellar/cabal-install/0.14.0/share/doc/transformers-0.3.0.0/html/transformers.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/Cellar/cabal-install/0.14.0/share/doc/transformers-0.3.0.0/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/share/doc/haddock-2.10.0/html/haddock.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/share/doc/haddock-2.10.0/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/share/doc/xhtml-3000.2.0.5/html/xhtml.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/share/doc/xhtml-3000.2.0.5/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/share/doc/ghc-paths-0.1.0.8/html/ghc-paths.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/share/doc/ghc-paths-0.1.0.8/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/share/doc/mtl-2.1.1/html/mtl.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/share/doc/mtl-2.1.1/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/share/doc/transformers-0.3.0.0/html/transformers.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/share/doc/transformers-0.3.0.0/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/share/doc/QuickCheck-2.4.2/html/QuickCheck.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/share/doc/QuickCheck-2.4.2/html doesn't exist or isn't a directory Warning: haddock-interfaces: /usr/local/share/doc/random-1.0.1.1/html/random.haddock doesn't exist or isn't a file Warning: haddock-html: /usr/local/share/doc/random-1.0.1.1/html doesn't exist or isn't a directory Any suggestions to fix this ? Thanks ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unit and pair
FullBinaryTreeRelation? :P On Tue, May 8, 2012 at 1:36 PM, MigMit miguelim...@yandex.ru wrote: Hi café, a quick question. Is there a somewhat standard class like this: class Something c where unit :: c () () pair :: c x y - c u v - c (x, u) (y, v) ? I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything. I know about arrows; this, however, is something more general, and it's instances aren't always arrows. ___ 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] Unit and pair
To expand on that, this class basically allows you to prove your relation cholds pointwise across arbitrary binary trees, represented by nested tuples and terminated by ()s. If individual instances of the class had additional ways of constructing values (i.e., proving the relation for the two type parameters), then your trees could contain other types. For example, if you had another type data Iso a b = Iso (a - b) (b - a) -- the functions must be inverses you could write an instance of Something for Iso and build a proof that ((), (a, ((), b)) is isomorphic to ((), (c, ((), d)) given Iso a c and Iso b dusing your class. I'm not sure I'd bundle the two parts together, but I'd call your pairmethod (or the class it lives in) something like congruent or ProductsRespectThisRelation :) Dan On Tue, May 8, 2012 at 3:15 PM, Daniel Peebles pumpkin...@gmail.com wrote: FullBinaryTreeRelation? :P On Tue, May 8, 2012 at 1:36 PM, MigMit miguelim...@yandex.ru wrote: Hi café, a quick question. Is there a somewhat standard class like this: class Something c where unit :: c () () pair :: c x y - c u v - c (x, u) (y, v) ? I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything. I know about arrows; this, however, is something more general, and it's instances aren't always arrows. ___ 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
[Haskell-cafe] bytestring, array and Safe Haskell
Why are http://hackage.haskell.org/packages/archive/bytestring/0.9.2.1/doc/html/Data-ByteString-Unsafe.html and http://hackage.haskell.org/packages/archive/array/0.4.0.0/doc/html/Data-Array-Unsafe.html Safe-inferred? The first one uses inlinePerformIO, so it clearly shouldn't be marked as Safe. Maybe Safe Haskell doesn't check that function? The second is a bit messier since it uses unboxed types and primitive operations... But they clearly should be marked as Unsafe, and it surprises me that Safe Haskell is that relaxed when checking for safe functions. Francesco. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unit and pair
That's an interesting idea, thanks. Отправлено с iPad 08.05.2012, в 23:31, Daniel Peebles pumpkin...@gmail.com написал(а): To expand on that, this class basically allows you to prove your relation c holds pointwise across arbitrary binary trees, represented by nested tuples and terminated by ()s. If individual instances of the class had additional ways of constructing values (i.e., proving the relation for the two type parameters), then your trees could contain other types. For example, if you had another type data Iso a b = Iso (a - b) (b - a) -- the functions must be inverses you could write an instance of Something for Iso and build a proof that ((), (a, ((), b)) is isomorphic to ((), (c, ((), d)) given Iso a c and Iso b d using your class. I'm not sure I'd bundle the two parts together, but I'd call your pair method (or the class it lives in) something like congruent or ProductsRespectThisRelation :) Dan On Tue, May 8, 2012 at 3:15 PM, Daniel Peebles pumpkin...@gmail.com wrote: FullBinaryTreeRelation? :P On Tue, May 8, 2012 at 1:36 PM, MigMit miguelim...@yandex.ru wrote: Hi café, a quick question. Is there a somewhat standard class like this: class Something c where unit :: c () () pair :: c x y - c u v - c (x, u) (y, v) ? I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything. I know about arrows; this, however, is something more general, and it's instances aren't always arrows. ___ 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] bytestring, array and Safe Haskell
The reasoning is outlined in the user manual here: http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/safe-haskell.html#safe-inference Basically, these modules will compile without error if they were to be compiled with -XSafe enabled. Thus, they are safe-inferred. The check does not scrutinize individual functions in any way; all of SH works on the level of module boundaries, as well as packages (whether or not to enforce package trust when compiling clients.) As to why they are safe-inferred, considering they are importing primitive libraries/modules, and the module inlinePerformIO lives in should be marked unsafe, well, I don't know. This is just a simple check, and anything more powerful would likely be considerably more complex and difficult to get right. They should be marked as -XUnsafe since their use in a safe program could cause crashes. It's likely not a conscious choice that this is the case, as much as it is probably an oversight. Many of the core libraries have needed refactoring/changes at the module level due to Safe Haskell (and hence there is now a proliferation of *.Unsafe and *.Safe modules, a la ForeignPtr.) I do not know if the next major version of the ByteString library (0.10) or array has marked these as unsafe or not. They should be if not. Perhaps someone else who's more aware of the new Safe Haskell design can comment further. On Tue, May 8, 2012 at 3:03 PM, Francesco Mazzoli f...@mazzo.li wrote: Why are http://hackage.haskell.org/packages/archive/bytestring/0.9.2.1/doc/html/Data-ByteString-Unsafe.html and http://hackage.haskell.org/packages/archive/array/0.4.0.0/doc/html/Data-Array-Unsafe.html Safe-inferred? The first one uses inlinePerformIO, so it clearly shouldn't be marked as Safe. Maybe Safe Haskell doesn't check that function? The second is a bit messier since it uses unboxed types and primitive operations... But they clearly should be marked as Unsafe, and it surprises me that Safe Haskell is that relaxed when checking for safe functions. Francesco. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Regards, Austin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] bytestring, array and Safe Haskell
On 08/05/12 21:45, Austin Seipp wrote: The reasoning is outlined in the user manual here: http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/safe-haskell.html#safe-inference Yes, I was looking at that while writing that message. Mine wasn't that much a complaint regarding the wrong inference (even if it looks like it should be possible to fix the inference those instance - especially the bytestring one), but rather regarding the fact that those modules should be marked unsafe manually. Francesco. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Unit and pair
On 09/05/12 03:49, MigMit wrote: On 8 May 2012, at 21:42, Felipe Almeida Lessa wrote: On Tue, May 8, 2012 at 2:36 PM, MigMit miguelim...@yandex.ru wrote: Hi café, a quick question. Is there a somewhat standard class like this: class Something c where unit :: c () () pair :: c x y - c u v - c (x, u) (y, v) ? I'm using it heavily in my current project, but I don't want to repeat somebody else's work, and it seems general enough to be defined somewhere; but my quick search on Hackage didn't reveal anything. I know about arrows; this, however, is something more general, and it's instances aren't always arrows. Are you aware of generalized arrows [1]? It's still a lot more than your Something, though. I've heard of them, but some instances of my Something class aren't categories either, which rules out GArrows too. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe data-lens has something similar (Tensor): http://hackage.haskell.org/packages/archive/data-lens/2.10.0/doc/html/Control-Category-Product.html -- Tony Morris http://tmorris.net/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Fixed point newtype confusion
Hmm, I don't understand how that would work. I wish I could define something like this: class (Functor f) = Fixpoint f x | x - f where fix :: x - Fix f instance (Functor f) = Fixpoint f (forall a. f a) where fix = id instance (Functor f, Fixpoint f x) = Fixpoint f (f x) where fix = Fix . fmap fix but instances with polymorphic types aren't allowed. (Why is that?) Alternatively if I could write a function that could turn e :: forall a. F (F (F ... (F a) ... )) into specialize e :: F (F (F ... (F X) ... )) that would work too, but I don't see how that's possible. On Mon, May 7, 2012 at 6:59 PM, wren ng thornton w...@freegeek.org wrote: On 5/7/12 8:55 PM, Sebastien Zany wrote: To slightly alter the question, is there a way to define a class class (Functor f) = Fixpoint f x where ... You can just do that (with MPTCs enabled). Though the usability will be much better if you use fundeps or associated types in order to constrain the relation between fs and xs. E.g.: -- All the following require the laws: -- fix . unfix == id -- unfix . fix == id -- With MPTCs and fundeps: class (Functor f) = Fixpoint f x | f - x where fix :: f x - x unfix :: x - f x class (Functor f) = Fixpoint f x | x - f where fix :: f x - x unfix :: x - f x class (Functor f) = Fixpoint f x | f - x, x - f where fix :: f x - x unfix :: x - f x -- With associated types: -- (Add a type/data family if you want both Fix and Pre.) class (Functor f) = Fixpoint f where type Fix f :: * fix :: f (Fix f) - Fix f unfix :: Fix f - f (Fix f) class (Functor f) = Fixpoint f where data Fix f :: * fix :: f (Fix f) - Fix f unfix :: Fix f - f (Fix f) class (Functor (Pre x)) = Fixpoint x where type Pre x :: * - * fix :: Pre x x - x unfix :: x - Pre x x class (Functor (Pre x)) = Fixpoint x where data Pre x :: * - * fix :: Pre x x - x unfix :: x - Pre x x Indeed, that last one is already provided in the fixpoint[1] package, though the names are slightly different. The differences between using x - f, f - x, or both, and between using data or type, are how it affects inference. That is, implicitly there are two relations on types: Fix \subseteq * \cross * Pre \subseteq * \cross * And we need to know: (1) are these relations functional or not? And, (2) are they injective or not? The answers to those questions will affect how you can infer one of the types (f or x) given the other (x or f). [1] http://hackage.haskell.org/**package/fixpointhttp://hackage.haskell.org/package/fixpoint -- Live well, ~wren __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://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] Fixed point newtype confusion
Er, sorry – fix = id should be fix = Fix. On Tue, May 8, 2012 at 5:24 PM, Sebastien Zany sebast...@chaoticresearch.com wrote: Hmm, I don't understand how that would work. I wish I could define something like this: class (Functor f) = Fixpoint f x | x - f where fix :: x - Fix f instance (Functor f) = Fixpoint f (forall a. f a) where fix = id instance (Functor f, Fixpoint f x) = Fixpoint f (f x) where fix = Fix . fmap fix but instances with polymorphic types aren't allowed. (Why is that?) Alternatively if I could write a function that could turn e :: forall a. F (F (F ... (F a) ... )) into specialize e :: F (F (F ... (F X) ... )) that would work too, but I don't see how that's possible. On Mon, May 7, 2012 at 6:59 PM, wren ng thornton w...@freegeek.orgwrote: On 5/7/12 8:55 PM, Sebastien Zany wrote: To slightly alter the question, is there a way to define a class class (Functor f) = Fixpoint f x where ... You can just do that (with MPTCs enabled). Though the usability will be much better if you use fundeps or associated types in order to constrain the relation between fs and xs. E.g.: -- All the following require the laws: -- fix . unfix == id -- unfix . fix == id -- With MPTCs and fundeps: class (Functor f) = Fixpoint f x | f - x where fix :: f x - x unfix :: x - f x class (Functor f) = Fixpoint f x | x - f where fix :: f x - x unfix :: x - f x class (Functor f) = Fixpoint f x | f - x, x - f where fix :: f x - x unfix :: x - f x -- With associated types: -- (Add a type/data family if you want both Fix and Pre.) class (Functor f) = Fixpoint f where type Fix f :: * fix :: f (Fix f) - Fix f unfix :: Fix f - f (Fix f) class (Functor f) = Fixpoint f where data Fix f :: * fix :: f (Fix f) - Fix f unfix :: Fix f - f (Fix f) class (Functor (Pre x)) = Fixpoint x where type Pre x :: * - * fix :: Pre x x - x unfix :: x - Pre x x class (Functor (Pre x)) = Fixpoint x where data Pre x :: * - * fix :: Pre x x - x unfix :: x - Pre x x Indeed, that last one is already provided in the fixpoint[1] package, though the names are slightly different. The differences between using x - f, f - x, or both, and between using data or type, are how it affects inference. That is, implicitly there are two relations on types: Fix \subseteq * \cross * Pre \subseteq * \cross * And we need to know: (1) are these relations functional or not? And, (2) are they injective or not? The answers to those questions will affect how you can infer one of the types (f or x) given the other (x or f). [1] http://hackage.haskell.org/**package/fixpointhttp://hackage.haskell.org/package/fixpoint -- Live well, ~wren __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://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] anyone else driven mad by trying to setup a gmp free version of haskell platform?
can we build a version of the compiler that loads [GMP] via dlopen on demand? An explanation from well-typed: http://www.well-typed.com/blog/32 But that was ~3 years ago. Anybody still looking at possible solutions? Maintaining the INTEGER_SIMPLE branch of GHC, minor as it is, is still a pain. If you follow the GHC recommendation of getting GHC from the Haskell Platform distribution, it means finding the matching GHC version, hoping you got all the build dependencies right, and then either overlaying the result in the HP installation or pointing HP to the new build. Not a ton of work, but not something I want to do each HP release. What are other commercial users of GHC doing? Thanks, Greg On Tue, May 8, 2012 at 8:07 AM, Anatoly Yakovenko aeyakove...@gmail.com wrote: i would really like to be able to ship haskell based linux binaries, but the gmp dependency makes it virtually impossible. so what version of host os, host ghc, and haskell-platform sources are known to build a working compiler? any reason why the dependency on gmp is static? are the interfaces between versions actually different? or can we build a version fo the compiler that loads the library via dlopen on demand? Thanks, Anatoly ___ 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
[Haskell-cafe] LLVM M.D. source code?
A paper, LLVM M.D.: A Denotational Translation Validator, mentions the source code for LLVM M.D is available here: http://llvm-md.seas.harvard.edu/ I can't seem to spot it there or on Hackage. Anyone seen it? Thanks, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] [Q] multiparam class undecidable types - how to get this example to typecheck?
Hi everybody,
I am torturing the ghc type inference extensions, and I think i
managed to break something, either in ghc or (more likely) in my
brain:
| {-# language FlexibleInstances, MultiParamTypeClasses, UndecidableInstances
#-}
|
| module Main
| where
|
| class Table table cell where
| toLists :: table - [[cell]]
| fromLists :: [[cell]] - table
|
| instance Table [[cell]] cell where
| toLists = id
| fromLists = id
|
| -- why i am using a class (not relevant for my question) -
| -- data FastTable a = FastTable ...
| -- instance Table (FastTable a) a where ...
|
| instance (Table a c, Show c) = Show a where
| showsPrec p t = showParen (p 10) $ showString fromLists . shows
(toLists t)
ghc 7.0.3 sais:
| Overlapping instances for Show [[cell0]]
| arising from a use of `shows'
| Matching instances:
| instance Show a = Show [a] -- Defined in GHC.Show
| instance (Table a c, Show c) = Show a
| -- Defined at /home/mf/tmp/z.hs:18:10-38
| In the second argument of `(.)', namely `shows (toLists t)'
I would have thought that there is on overlap: the instance in my code
above defines how to show a table if the cell is showable; the
(allegedly) overlapping instance defines how to show lists of alpha if
alpha is showable.
So I was expecting the reduction to go something like:
. table ~ [[cell]] (via whichever instance of class Table applies)
. [[cell]] ~ [cell] (via instance Show a = Show [a])
. [cell] ~ cell (via instance Show a = Show [a])
But it gets worse. I decided to ignore the problem for now and be
happy with at least showing the first cell in the upper left corner of
the table:
| instance (Table a c, Show c) = Show a where
| showsPrec p t = showParen (p 10) $ showString fromLists . shows (head
. head $ toLists t)
to that, ghc 7.0.3 sais:
| /home/mf/tmp/z.hs:19:66:
| Context reduction stack overflow; size = 21
| Use -fcontext-stack=N to increase stack size to N
| $dShow :: Show c19
| $dShow :: Show c18
| [...]
shouldn't type inference be able to determine that
| ((head . head $ toLists t) :: c
and use the instance guaranteed by the instance declaration's class
constraint (Show c)?
I suspect that there should be a type annotation that would make this
approach possible, but even then I am curious what this behavior
means.
Should I upgrade to a more grown-up release of ghc?
Any hints or pointers appreciated. (:
Thanks,
Cheers,
Matthias
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