Re: [Haskell-cafe] parsing exercise
I don't think you can do this simply as you think you would always have to build a parse tree. If the input is valid Haskell you could follow Chung-chieh Shan's suggestion, otherwise you could parse to a skeleton syntax tree - look for work by Jonathan Bacharach on Dylan macros and Java Syntax Extension. In practice, if you follow the skeleton syntax tree style you might find not caring about the details of syntax is almost as much work as caring about them. I've tried a couple of times to make a skeleton parser that does paren nesting and little else, but always given up and just used a proper parser as the skeleton parser never seemed robust. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Delivery to haskell-platf...@projects.haskell.org
On 23/01/11 00:00, Erik de Castro Lopo wrote: Magnus Therning wrote: I'm receiving emails saying that email can't be delivered: Delivery to the following recipient has been delayed: haskell-platf...@projects.haskell.org Message will be retried for 1 more day(s) Technical details of temporary failure: The recipient server did not accept our requests to connect. Learn more at http://mail.google.com/support/bin/answer.py?answer=7720 [projects.haskell.org (1): Connection timed out] Who should I turn to to get this sorted out? I reported this problem to this and the haskell list on Jan 14th. On the 18th, Yitzchak Gale said he'd look into it. Unfortunately it is still unresolved. Ouch! Yes, I saw your email about a week ago, but I assumed that had already been resolved and that I was seeing another failure, but apparently not :-( Hopefully it'll be resolved soon. /M -- Magnus Therning OpenPGP: 0xAB4DFBA4 email: mag...@therning.org jabber: mag...@therning.org twitter: magthe http://therning.org/magnus signature.asc Description: OpenPGP digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] parsing exercise
On Sun, Jan 23, 2011 at 4:31 PM, Chung-chieh Shan
ccs...@post.harvard.eduwrote:
Maybe Text.Show.Pretty.parseValue in the pretty-show package can help?
That's what I was looking for, thanks!
On Sun, Jan 23, 2011 at 5:23 PM, Stephen Tetley stephen.tet...@gmail.com
wrote:
I don't think you can do this simply as you think you would always
have to build a parse tree.
Isn't it enough to maintain a stack of open parens, brackets, char- and
string-terminators and escape chars? Below is my attempt at solving the
problem without an expression parser.
In practice, if you follow the skeleton syntax tree style you might
find not caring about the details of syntax is almost as much work
as caring about them. I've tried a couple of times to make a skeleton
parser that does paren nesting and little else, but always given up
and just used a proper parser as the skeleton parser never seemed
robust.
Indeed I doubt that the implementation below is robust and it's too tricky
to be easily maintainable. I include it for reference. Let me know if you
spot an obvious mistake..
Sebastian
splitTLC :: String - [String]
splitTLC = parse
type Stack = String
parse :: Stack - String - [String]
parse _ = []
parse st (c:cs) = next c st $ parse (updStack c st) cs
next :: Char - Stack - [String] - [String]
next c []xs = if c==',' then [] : xs else c : xs
next c (_:_) xs = c : xs
infixr 0 :
(:) :: Char - [String] - [String]
c : [] = [[c]]
c : (x:xs) = (c:x):xs
updStack :: Char - Stack - Stack
updStack char stack =
case (char,stack) of
-- char is an escaped character
(_ ,'\\':xs) - xs -- the next character is not
-- char is the escape character
('\\', xs) - '\\':xs -- push it on the stack
-- char is the string terminator
('' , '':xs) - xs -- closes current string literal
('' , ''':xs) - ''':xs -- ignored inside character
('' , xs) - '':xs -- opens a new string
-- char is the character terminator
(''' , ''':xs) - xs -- closes current character literal
(''' , '':xs) - '':xs -- ignored inside string
(''' , xs) - ''':xs -- opens a new character
-- parens and brackets
(_ , '':xs) - '':xs -- are ignored inside strings
(_ , ''':xs) - ''':xs -- and characters
('(' , xs) - '(':xs -- new opening paren
(')' , '(':xs) - xs -- closing paren
('[' , xs) - '[':xs -- opening bracket
(']' , '[':xs) - xs -- closing bracket
-- other character don't modify the stack (ignoring record syntax)
(_ , xs) - xs
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[Haskell-cafe] Tool for evaluating GHCi lines in a source file
Hi, some time ago I read of a small tool that extracts lines like GHCi some_expression from a source file and appends GHCi's output to them. Now I can't find it again. Does anyone remember its name? Thanks. Steffen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Delivery to haskell-platf...@projects.haskell.org
but I assumed that had already been resolved and that I was seeing another failure, but apparently not :-( Hopefully it'll be resolved soon. If anyone with sysadmin experience on Debian can suggest why telnet localhost 25 hangs on community.haskell.org, even though both exim and clamd are running, we would be grateful for some insight. We just don't know what is wrong, so fixing it is not likely to be easy. Ideas to haskell-infrastruct...@community.galois.com please. Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Is SHE (the Strathclyde Haskell Enhancement) portable?
It may be strange question but: - Is SHE portable (assuming that the compiler have the extensions)? - If yes why there is only information how to use it with GHC? Regards signature.asc Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Delivery to haskell-platf...@projects.haskell.org
After a reboot, community.haskell.org is now responding again on port 25. Please check to see if the mailing lists are working again. Thanks, Yitz ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HMatrix Vector/Matrix interpolation ala Matlab interp/interp2 ??
Hi Phil, On 22/01/11 23:13, gutti wrote: - are t a b c d points or curve parameters ? a b c d are points, t is the interpolation coefficient (between 0 and 1) - how does lifting to matrix create a 1d spline to a 2d spline ? -- I don't see how it works essentially, it creates a matrix of 1d splines, but now I see that this isn't what you wanted... for interpolated 2d matrix lookup, something like this, perhaps: -- using the cubic interpolator from earlier in the thread m @@+ (x, y) = let (i, j) = (floor x, floor y) (s, t) = (x - fromIntegral i, y - fromIntegral j) cx j' = cubic s (m@@(i-1,j')) (m@@(i,j')) (m@@(i+1,j')) (m@@(i+2,j')) in cubic t (cx (j-1)) (cx j) (cx (j+1)) (cx (j+2)) test = let m = (1616) [0 ..] n = 36 r = 5 (x0, y0) = (8, 8) in [ m @@+ (x, y) | a - [0 .. n - 1] , let a' = 2 * pi * fromIntegral a / fromIntegral n , let x = x0 + r * cos a' , let y = y0 + r * sin a' ] Claude -- http://claudiusmaximus.goto10.org ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is SHE (the Strathclyde Haskell Enhancement) portable?
It probably is portable, but I'd think only GHC has all the necessary extensions. On Sun, Jan 23, 2011 at 12:27 PM, Maciej Piechotka uzytkown...@gmail.comwrote: It may be strange question but: - Is SHE portable (assuming that the compiler have the extensions)? - If yes why there is only information how to use it with GHC? Regards ___ 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] Is SHE (the Strathclyde Haskell Enhancement) portable?
On 23 Jan 2011, at 11:27, Maciej Piechotka wrote: It may be strange question but: - Is SHE portable (assuming that the compiler have the extensions)? I have no idea. - If yes why there is only information how to use it with GHC? I'm lucky I even know how to get it to work with GHC. It'd be a bonus if it turned out to be portable. If anyone figures out how to bolt it on the front of other compilers, I'd be happy to relay (with attribution) the relevant instructions on the SHE website. All the best Conor ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tool for evaluating GHCi lines in a source file
On Sun, Jan 23, 2011 at 12:35, Steffen Schuldenzucker sschuldenzuc...@uni-bonn.de wrote: Hi, some time ago I read of a small tool that extracts lines like GHCi some_expression from a source file and appends GHCi's output to them. Now I can't find it again. Does anyone remember its name? No, but I can guess (it's the same as the Python original, modulo capitalisation): http://hackage.haskell.org/package/DocTest ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is SHE (the Strathclyde Haskell Enhancement) portable?
On Sun, 2011-01-23 at 18:42 +0100, Lennart Augustsson wrote: It probably is portable, but I'd think only GHC has all the necessary extensions. I imagine some parts (idiom brackets) works with minimal amount of extentions - maybe it would be benefitial to have instructions to run SHE with other compilers? Regards signature.asc Description: This is a digitally signed message part ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Tool for evaluating GHCi lines in a source file
On 01/23/2011 06:48 PM, Max Rabkin wrote: On Sun, Jan 23, 2011 at 12:35, Steffen Schuldenzucker sschuldenzuc...@uni-bonn.de wrote: Hi, some time ago I read of a small tool that extracts lines like GHCi some_expression from a source file and appends GHCi's output to them. Now I can't find it again. Does anyone remember its name? No, but I can guess (it's the same as the Python original, modulo capitalisation): http://hackage.haskell.org/package/DocTest Exactly what I was looking for, thanks. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] HMatrix Vector/Matrix interpolation ala Matlab interp/interp2 ??
On Sun, 23 Jan 2011, Claude Heiland-Allen wrote: essentially, it creates a matrix of 1d splines, but now I see that this isn't what you wanted... for interpolated 2d matrix lookup, something like this, perhaps: Interpolated matrix or vector lookup can of course be written as interpolation of sub-matrices or sub-vectors. For lazy matrices and vectors this would be almost as efficient. interp i v = vectorIndex (floor i) $ interpolateVectorSpace (fraction i) (Vector.take (n-3) $ Vector.drop 0 v) (Vector.take (n-3) $ Vector.drop 1 v) (Vector.take (n-3) $ Vector.drop 2 v) (Vector.take (n-3) $ Vector.drop 3 v) (Sorry for the many fictional functions.) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Adding a builder to the bytestring package?
Patch done and sent to the bytestring maintainers. For the interested, here's the benchmark chart for binary, cereal, and blaze-builder/bytestring: http://i.imgur.com/xw3TL.png On Wed, Jan 19, 2011 at 15:30, Johan Tibell johan.tib...@gmail.com wrote: On Thu, Jan 20, 2011 at 12:16 AM, John Millikin jmilli...@gmail.com wrote: blaze-builder already implements the binary builder interface, minus the putWord* functions. I think those would be trivial to reimplement on top of Write. Since it sounds like everyone agrees with / has already thought of moving Builder into bytestring, I'll start poking at a patch. Who is the current patch-reviewer for binary and bytestring? I'd suggest addressing the patch to Don Stewart, Duncan Coutts, and Lennart Kolmodin. Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: follower 0.0.1
Hello Cafe, I'm happy to announce the first version of the anonymous Twitter following tool: follower Basically the tool allows you to follow people's tweets without having a Twitter account. It keeps a list of the people you follow and keeps track of the tweets you already saw. Thanks to the authors of those nice libraries on hackage, it's just a little more than a hundred lines (probably would be much less using the right *morphisms) hacked up in an hour or so. Any comments, bug reports, rants, requests and patches are welcome. Get it from hackage: http://hackage.haskell.org/package/follower -- R. Emre Başar İstanbul Bilgi University Department of Computer Science signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Is SHE (the Strathclyde Haskell Enhancement) portable?
On 23 Jan 2011, at 18:19, Maciej Piechotka wrote: On Sun, 2011-01-23 at 18:42 +0100, Lennart Augustsson wrote: It probably is portable, but I'd think only GHC has all the necessary extensions. I imagine some parts (idiom brackets) works with minimal amount of extentions - maybe it would be benefitial to have instructions to run SHE with other compilers? Yes, idiom brackets, default superclass instances, that sort of stuff is all good clean H98 fun. I'm open to code and/or doc patches, but I'm unlikely to have time to take the initiative. All the best Conor ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Adding a builder to the bytestring package?
On 24 January 2011 07:29, John Millikin jmilli...@gmail.com wrote: Patch done and sent to the bytestring maintainers. For the interested, here's the benchmark chart for binary, cereal, and blaze-builder/bytestring: http://i.imgur.com/xw3TL.png Can has units? Conrad. On Wed, Jan 19, 2011 at 15:30, Johan Tibell johan.tib...@gmail.com wrote: On Thu, Jan 20, 2011 at 12:16 AM, John Millikin jmilli...@gmail.com wrote: blaze-builder already implements the binary builder interface, minus the putWord* functions. I think those would be trivial to reimplement on top of Write. Since it sounds like everyone agrees with / has already thought of moving Builder into bytestring, I'll start poking at a patch. Who is the current patch-reviewer for binary and bytestring? I'd suggest addressing the patch to Don Stewart, Duncan Coutts, and Lennart Kolmodin. Johan ___ 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] building hslogger error windows
Hi cafe, I just get a build error on install config-file (which depends on hslogger), C:\Documents and Settings\lenovocabal install hslogger Resolving dependencies... Downloading hslogger-1.1.1... Configuring hslogger-1.1.1... Preprocessing library hslogger-1.1.1... Preprocessing executables for hslogger-1.1.1... Building hslogger-1.1.1... src\System\Log\Handler\Rotating.hs:48:7: Could not find module `System.FilePath.Windows': It is a member of the hidden package `filepath-1.1.0.4'. Perhaps you need to add `filepath' to the build-depends in your .cabal fil e. Use -v to see a list of the files searched for. cabal: Error: some packages failed to install: hslogger-1.1.1 failed during the building phase. The exception was: ExitFailure 1 I am using platform-2.0, How can I solve it? Thanks in advance Gang ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Adding a builder to the bytestring package?
No units -- I generated the chart with Progression, which by default
normalises the data so the first library (here, binary) in each
benchmark is 1.0. It can also generate absolute-time charts:
Runtime in seconds, grouped by benchmark: http://i.imgur.com/f0EOa.png
Runtime in seconds, grouped by library: http://i.imgur.com/PXW97.png
Benchmark source files attached, if you'd like to poke at them.
On Sun, Jan 23, 2011 at 17:21, Conrad Parker con...@metadecks.org wrote:
On 24 January 2011 07:29, John Millikin jmilli...@gmail.com wrote:
Patch done and sent to the bytestring maintainers. For the interested,
here's the benchmark chart for binary, cereal, and
blaze-builder/bytestring:
http://i.imgur.com/xw3TL.png
Can has units?
Conrad.
module Main where
import Control.DeepSeq
import Data.Monoid
import Criterion.Types
import Progression.Config
import Progression.Main
import qualified Data.ByteString as B
import qualified Data.ByteString.Lazy as BL
import qualified Data.Binary.Builder as Binary
instance NFData B.ByteString
instance NFData BL.ByteString where
rnf a = rnf (BL.toChunks a)
bytes_100 :: B.ByteString
bytes_100 = B.replicate 100 0x61
build_strict :: Int - B.ByteString
build_strict n = BL.toStrict (Binary.toLazyByteString builder) where
chunks = replicate n (Binary.fromByteString bytes_100)
builder = foldr Binary.append Binary.empty chunks
build_lazy :: Int - BL.ByteString
build_lazy n = Binary.toLazyByteString builder where
chunks = replicate n (Binary.fromByteString bytes_100)
builder = foldr Binary.append Binary.empty chunks
build_strict_mconcat :: Int - B.ByteString
build_strict_mconcat n = BL.toStrict (Binary.toLazyByteString builder) where
chunks = replicate n (Binary.fromByteString bytes_100)
builder = mconcat chunks
build_lazy_mconcat :: Int - BL.ByteString
build_lazy_mconcat n = Binary.toLazyByteString builder where
chunks = replicate n (Binary.fromByteString bytes_100)
builder = mconcat chunks
benchmarks :: [Benchmark]
benchmarks =
[ bench strict (nf build_strict 1000)
, bench strict +mconcat (nf build_strict_mconcat 1000)
, bench lazy (nf build_lazy 1000)
, bench lazy +mconcat (nf build_lazy_mconcat 1000)
]
main :: IO ()
main = defaultMainWith config (bgroup all benchmarks)
config = Config
{ cfgMode = Nothing
, cfgRun = RunSettings [] (Just 01_binary)
, cfgGraph = mempty
}
module Main where
import Control.DeepSeq
import Data.Monoid
import Criterion.Types
import Progression.Config
import Progression.Main
import qualified Data.ByteString as B
import qualified Data.ByteString.Lazy as BL
import qualified Blaze.ByteString.Builder as Blaze
import qualified Blaze.ByteString.Builder.Internal.Types as Blaze
instance NFData B.ByteString
instance NFData BL.ByteString where
rnf a = rnf (BL.toChunks a)
bytes_100 :: B.ByteString
bytes_100 = B.replicate 100 0x61
builderEmpty :: Blaze.Builder
builderEmpty = Blaze.Builder id
{-# INLINE builderEmpty #-}
builderAppend :: Blaze.Builder - Blaze.Builder - Blaze.Builder
builderAppend (Blaze.Builder b1) (Blaze.Builder b2) = Blaze.Builder (b1 . b2)
{-# INLINE builderAppend #-}
builderConcat :: [Blaze.Builder] - Blaze.Builder
builderConcat = foldr builderAppend builderEmpty
{-# INLINE builderConcat #-}
build_strict :: Int - B.ByteString
build_strict n = Blaze.toByteString builder where
chunks = replicate n (Blaze.fromByteString bytes_100)
builder = builderConcat chunks
build_lazy :: Int - BL.ByteString
build_lazy n = Blaze.toLazyByteString builder where
chunks = replicate n (Blaze.fromByteString bytes_100)
builder = builderConcat chunks
build_strict_mconcat :: Int - B.ByteString
build_strict_mconcat n = Blaze.toByteString builder where
chunks = replicate n (Blaze.fromByteString bytes_100)
builder = mconcat chunks
build_lazy_mconcat :: Int - BL.ByteString
build_lazy_mconcat n = Blaze.toLazyByteString builder where
chunks = replicate n (Blaze.fromByteString bytes_100)
builder = mconcat chunks
benchmarks :: [Benchmark]
benchmarks =
[ bench strict (nf build_strict 1000)
, bench strict +mconcat (nf build_strict_mconcat 1000)
, bench lazy (nf build_lazy 1000)
, bench lazy +mconcat (nf build_lazy_mconcat 1000)
]
main :: IO ()
main = defaultMainWith config (bgroup all benchmarks)
config = Config
{ cfgMode = Nothing
, cfgRun = RunSettings [] (Just 03_blaze)
, cfgGraph = mempty
}
module Main where
import Control.DeepSeq
import Data.Monoid
import Criterion.Types
import Progression.Config
import Progression.Main
import qualified Data.ByteString as B
import qualified Data.ByteString.Lazy as BL
import qualified Data.Serialize.Builder as Cereal
instance NFData B.ByteString
instance NFData BL.ByteString where
rnf a = rnf (BL.toChunks a)
bytes_100 :: B.ByteString
bytes_100 = B.replicate 100 0x61
build_strict :: Int - B.ByteString
build_strict n = Cereal.toByteString builder where
chunks = replicate n (Cereal.fromByteString bytes_100)
builder = foldr Cereal.append Cereal.empty chunks
build_lazy ::
Re: [Haskell-cafe] building hslogger error windows
On Monday 24 January 2011 02:33:17, Gang Yu wrote: Hi cafe, I just get a build error on install config-file (which depends on hslogger), C:\Documents and Settings\lenovocabal install hslogger Resolving dependencies... Downloading hslogger-1.1.1... You can try with hslogger-1.1.0, which built on 6.12 and 7.0 on hackage, or maybe with hslogger-1.1.2 (which hasn't yet been built on hackage since it was uploaded only yesterday). hslogger-1.1.1 had the same build failure on hackage. I am using platform-2.0, How can I solve it? Thanks in advance Gang ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Proposal: Applicative = Monad: Call for consensus
On January 21, 2011 14:01:36 Ryan Ingram wrote:
Interesting little paper, Tyson.
Hi Ryan,
Thanks for comments and kind words.
I think what a programmer actually wants from ambiguity resolution is
something *predictable*; C++'s system is definitely stretching the
boundaries of predictability, but any case where I have to break out a
calculator to decide whether the compiler is going to choose
specification A or specification B for my program seems like a
failure. I'd much rather the solution wasn't always 'the most
probable' but at least was easy for me to figure out without thinking
too hard.
I think you really hit the nail on the head there. To be useful at all, it is
absolutely critical that you don't have to reach for your calculator.
Fortunately I believe this is the case. The basic result of the paper was
that assuming
- self-similarity (functional programming) and
- finite-length (typed programs)
you get
p(n) = 1 / 2^{2n-1)
as the probability of a specific shape composed of n elementary components.
Note that the measure is defined on the shape: the way elementary types are
composed, not what they are. Double and Char are indistinguishable from a
shapes perspective, Int - Double - Char and (Int - Double) - Char are not.
An example of the probabilities give same types (shapes) would then be
Double: p(1) = 1/2 (elementary components: Double)
Char: p(1) = 1/2 (elementary components: Char)
[Int]: p(2) = 1/8 (elementary components: [], Int)
[Char] - IO (): p(5) = 1/512 (elementary components: [], Char, -, IO, ())
As p(n) is monotonically decreasing function in n, the more elementary types
the shape is composed of, the less probable it is.
I really don't think there could be a much more pleasing result in terms of a
predictable measure. It is very simple, and I believe it corresponds well to
our intuition. The more stuff in a type, the more complex it is.
It may seem strange to have went to such ends for such a simple result, but
that is just because these simple examples don't show the depth. Specifically
- we gained the ability to encode the intuition into a piece of software, and
- we can now go beyond where our intuition starts to break down.
To see this last point, consider the shapes represented by Double vs Double -
Int. The formulation says the former shape will arise more frequently in
programs, and I imagine we agree. But are we more likely to see the shape
(a - b - a) - a - [b] - a
where a and b are place holders for any internal shape, or
Int - Char - Int
Suddenly it is not so easy for us. The former is a more complex composition,
but it is also a less rigid composition. The formulation has no such problem.
The goal is to easily know when I have to manually specify ambiguity
resolution and when I can trust the compiler to do it for me. I
didn't completely follow the math in your paper, so maybe it turns out
simply if it was implemented, but it wasn't clear to me. At the
least, I think you should add examples of the types of ambiguity
resolution you'd like the compiler to figure out and what your
probability measure chooses as the correct answer in each case.
The specific ambiguous situation I was looking at resolving when I came up with
the framework was figuring out what application operator to use.
Consider various applications incorporating a computation context c (e.g., [])
\f - f :: (a - b) - a - b
\f - fmap f :: (a - b) - c a - c b
\f - f . pure :: (c a - b) - a - b
\f - apply f :: c (a - b) - c a - c b
\f - apply f . pure :: c (a - b) - (a - c b)
\f - apply f . pure . pure :: c (c a - b)) - a - c b
\f - join . func f :: (a - c b) - c a - c b
\f - join . apply f :: c (a - c b) - c a - c b
\f - join . apply f . pure :: c (a - c b) - a - c b
\f - join . apply f . pure . pure :: c (ca - cb) - a - c b
where I've listed them in order of increasing structure requirements on c (the
bottom four requiring a monad, the prior three require applicative, etc.)
In any one situation, more than one application may be possible (such as the
under, over, state, wear example mentioned by Conor). I want a
rigorous argument for ordering these to follow the least surprise principal.
I probably should be more specific about this in the paper, but I really liked
the framework, and didn't want to pigeon hole it to this specific application.
Cheers! -Tyson
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