Re: [Haskell-cafe] Functional Parsers in GHCI
Amiruddin Nagri amir.na...@gmail.com writes: Hi All, I am a newbie to Haskell, and have been using Programming in Haskell along with Eric Meijer videos covering the book syllabus. I am currently on Chapter 8 Functional Parsers, and trying to implement few of the examples given in the book. Following is the example : item = \inp - case inp of [] - [] (x:xs) - [(x,xs)] p = do x - item y - item z - item return (x,y,z) = When I compile it using GHCI, I get the following error : [1 of 1] Compiling Main ( parser.hs, interpreted ) parser.hs:5:8: No instance for (Monad ((-) [t])) arising from a do statement at parser.hs:5:8-16 Try importing Control.Monad.Instances and see if that gets it to work. Possible fix: add an instance declaration for (Monad ((-) [t])) In a stmt of a 'do' expression: x - item In the expression: do x - item y - item z - item return (x, y, z) In the definition of `p': p = do x - item y - item z - item Failed, modules loaded: none. = I tried googling for samples, above error message etc. But not getting to solution. Can anyone guide me as to what am I doing wrong and how can I fix this. Regards, Amiruddin Nagri, India GTalk : amir.na...@gmail.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Functional Parsers in GHCI
Hi The code in this chapter isn't actually Haskell - some details are elided to make the presentation clearer. To run the code you want to get the file mentioned in the closing remarks of the chapter (page 85, section 8.9). http://www.cs.nott.ac.uk/~gmh/book.html http://www.cs.nott.ac.uk/~gmh/parser.lhs Best wishes Stephen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Functional Parsers in GHCI
On 23 May 2010 08:41, Stephen Tetley stephen.tet...@gmail.com wrote: The code in this chapter isn't actually Haskell - some details are elided to make the presentation clearer. There is also the paper - Monadic Parsing in Haskell - which presents the parsers as legal Haskell98: http://www.cs.nott.ac.uk/~gmh/pearl.pdf ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Proof question -- (==) over Bool
Alexander Solla a...@2piix.com writes: On May 22, 2010, at 1:32 AM, Jon Fairbairn wrote: Since Bool is a type, and all Haskell types include ⊥, you need to add conditions in your proofs to exclude it. Not really. Bottom isn't a value, so much as an expression for computations that don't refer to real values. It's close enough to be treated as a value in many contexts, but this isn't one of them. It seems to me relevant here, because one of the uses to which one might put the symmetry rule is to replace an expression “e1 == e2” with “e2 == e1”, which can turn a programme that terminates into a programme that does not. -- Jón Fairbairn jon.fairba...@cl.cam.ac.uk http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2009-01-31) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Proof question -- (==) over Bool
On May 23, 2010, at 1:35 AM, Jon Fairbairn wrote: It seems to me relevant here, because one of the uses to which one might put the symmetry rule is to replace an expression “e1 == e2” with “e2 == e1”, which can turn a programme that terminates into a programme that does not. I don't see how that can be (but if you have a counter example, please show us). Even if we extend == to apply to equivalence classes of bottom values, we would have to evaluate both e1 and e2 to determine the value of e1 == e2 or e2 == e1. Prelude undefined == True *** Exception: Prelude.undefined Prelude True == undefined *** Exception: Prelude.undefined Prelude undefined == undefined *** Exception: Prelude.undefined That is, if one case is exceptional, so is the other. You can't really even quantify over bottoms in Haskell, as a language. The language runtime is able to do some evaluation and sometimes figure out that a bottom is undefined. Sometimes. But the runtime isn't a part of the language. The runtime is an implementation of the language's interpetation function. Bottoms are equivalent by conceptual fiat (in other words, vacuously) since not even the id :: a - a function applies to them.___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Proof question -- (==) over Bool
For Bool, I'm not sure, but for, e.g., () it's certainly true. Take this definition of == () == _ = True Using case analysis of just the constructors, ignoring the value bottom, you can easily prove symmetry. But '() == undefined' terminates, whereas 'undefined == ()' does not. Ignore bottom at your own peril. BTW, the id function works fine on bottom, both from a semantic and implementation point of view. -- Lennart On Sun, May 23, 2010 at 11:23 AM, Alexander Solla a...@2piix.com wrote: On May 23, 2010, at 1:35 AM, Jon Fairbairn wrote: It seems to me relevant here, because one of the uses to which one might put the symmetry rule is to replace an expression “e1 == e2” with “e2 == e1”, which can turn a programme that terminates into a programme that does not. I don't see how that can be (but if you have a counter example, please show us). Even if we extend == to apply to equivalence classes of bottom values, we would have to evaluate both e1 and e2 to determine the value of e1 == e2 or e2 == e1. Prelude undefined == True *** Exception: Prelude.undefined Prelude True == undefined *** Exception: Prelude.undefined Prelude undefined == undefined *** Exception: Prelude.undefined That is, if one case is exceptional, so is the other. You can't really even quantify over bottoms in Haskell, as a language. The language runtime is able to do some evaluation and sometimes figure out that a bottom is undefined. Sometimes. But the runtime isn't a part of the language. The runtime is an implementation of the language's interpetation function. Bottoms are equivalent by conceptual fiat (in other words, vacuously) since not even the id :: a - a function applies to them.___ 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] double2Float is faster than (fromRational . toRational)
Daniel Fischer wrote: There are more rules elsewhere. If you compile with optimisations, GHC turns your realToFrac into double2Float# nicely, so it's okay to use realToFrac. However, without optimisations, no rules fire, so you'll get (fromRational . toRational). That must be new, because it didn't used to be the case. Also, rewrite rules can be fragile. Not to mention that the (fromRational . toRational) definition is incorrect for converting between Float and Double because Rational cannot properly encode the transfinite values in Float/Double. The robust solution is to use the RealToFrac class from the logfloat package: http://hackage.haskell.org/packages/archive/logfloat/0.12.1/doc/html/Data-Number-RealToFrac.html -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Declaring a tuple of instances of Enums as an instance of the Enum class
Say I've got a type Month declared as an instance of the Enum class, and a type MonthPair declared as a pair of months: data Month = January | February | March | April | May | June | July | August | September | October | November | December deriving (Eq, Enum, Ord, Show) type MonthPair = (Month, Month) deriving (Enum) The deriving on MonthPair gives me the error parse error on input 'deriving'. Why is this error generated? Is there a syntax error, or is there a conceptual problem with enumerating a Cartesian product, such as Month x Month? The cardinality of the Cartesian product is finite (including the bottom values, cardinality = 1 + (12 + 1)*(12 + 1) = 170), and so the product is amenable at least to some arbitrary enumeration (such as Cantor's diagonal method). Thanks. _ The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail. http://www.windowslive.com/campaign/thenewbusy?tile=multicalendarocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_5___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] double2Float is faster than (fromRational . toRational)
On Sunday 23 May 2010 13:12:16, wren ng thornton wrote: Daniel Fischer wrote: There are more rules elsewhere. If you compile with optimisations, GHC turns your realToFrac into double2Float# nicely, so it's okay to use realToFrac. However, without optimisations, no rules fire, so you'll get (fromRational . toRational). That must be new, because it didn't used to be the case. GHC.Float.lhs contains the rules for (realToFrac :: (Float|Double) - (Float|Double)) since 6.8.1 at least, I didn't look at previous releases. Also, rewrite rules can be fragile. True. I don't see how you would construct such a situation for these rules, but if several rules match a piece of code, you can't know which one fires first, perhaps making the others not match anymore. And inlining may prevent rules from matching, too. If you need rewrite rules, it is advisable to check whether they actually fired. Not to mention that the (fromRational . toRational) definition is incorrect for converting between Float and Double because Rational cannot properly encode the transfinite values in Float/Double. The robust solution is to use the RealToFrac class from the logfloat package: http://hackage.haskell.org/packages/archive/logfloat/0.12.1/doc/html/Dat a-Number-RealToFrac.html Yes. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Declaring a tuple of instances of Enums as an instance of the Enum class
R J rj248...@hotmail.com writes: Say I've got a type Month declared as an instance of the Enum class, and a type MonthPair declared as a pair of months: data Month = January | February | March | April | May | June | July | August | September | October | November | December deriving (Eq, Enum, Ord, Show) type MonthPair = (Month, Month) deriving (Enum) The deriving on MonthPair gives me the error parse error on input deriving'. You can't derive instances for type aliases (as its mainly there for documentation reasons, etc.). However, pairs don't have Enum instances by default so you still can't use its instance. If you define data MonthPair = MonthPair Month Month then you should be able to derive Enum. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell and scripting
As some people were advising me to peek in Lua, I did so. Well, I find it far too laxist and bug prone : weak-typing, variables which are global by default, non-existing variables which contain nil when we access them instead of failing... I mean, I like Haskell especially because it is rigorous and because the type-system continually saves the day: Lua is the total opposite. I don't hope to enjoy Haskell's tightness with a scripting language, but being interpreted and dynamically typed doesn't prevent to be somewhat painstaking (Python is, for instance)**. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Declaring a tuple of instances of Enums as an instance of the Enum class
On Sunday 23 May 2010 15:33:58, Ivan Lazar Miljenovic wrote: R J rj248...@hotmail.com writes: Say I've got a type Month declared as an instance of the Enum class, and a type MonthPair declared as a pair of months: data Month = January | February | March | April | May | June | July | August | September | October | November | December deriving (Eq, Enum, Ord, Show) type MonthPair = (Month, Month) deriving (Enum) The deriving on MonthPair gives me the error parse error on input deriving'. You can't derive instances for type aliases (as its mainly there for documentation reasons, etc.). However, pairs don't have Enum instances by default so you still can't use its instance. If you define data MonthPair = MonthPair Month Month then you should be able to derive Enum. No, per the report (http://haskell.org/onlinereport/derived.html) Derived instance declarations for the class Enum are only possible for enumerations (data types with only nullary constructors). You can derive Enum instances for newtype wrappers around Enums with GHC (possibly others), but for types such as MonthPair you have to give the instances yourself (maybe you can let them be generated by tools like Derive). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Declaring a tuple of instances of Enums as an instance of the Enum class
Daniel Fischer daniel.is.fisc...@web.de writes: On Sunday 23 May 2010 15:33:58, Ivan Lazar Miljenovic wrote: R J rj248...@hotmail.com writes: Say I've got a type Month declared as an instance of the Enum class, and a type MonthPair declared as a pair of months: data Month = January | February | March | April | May | June | July | August | September | October | November | December deriving (Eq, Enum, Ord, Show) type MonthPair = (Month, Month) deriving (Enum) The deriving on MonthPair gives me the error parse error on input deriving'. You can't derive instances for type aliases (as its mainly there for documentation reasons, etc.). However, pairs don't have Enum instances by default so you still can't use its instance. If you define data MonthPair = MonthPair Month Month then you should be able to derive Enum. No, per the report (http://haskell.org/onlinereport/derived.html) Derived instance declarations for the class Enum are only possible for enumerations (data types with only nullary constructors). Whoops, you're right. -- Ivan Lazar Miljenovic ivan.miljeno...@gmail.com IvanMiljenovic.wordpress.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Clean proof?
Given the following definition of either, from the prelude:
either :: (a - c, b - c) - Either a b - c
either (f, g) (Left x) = f xeither (f, g) (Right x) = g x
what's a clean proof that:
h . either (f, g) = either (h . f, g . h)?
The only proof I can think of requires the introduction of an anonymous
function of z, with case analysis on z (Case 1: z = Left x, Case 2: z = Right
y), but the use of anonymous functions and case analysis is ugly, and I'm not
sure how to tie up the two cases neatly at the end. For example here's the
Left case:
h . either (f, g) ={definition of \} \z - (h . either (f,
g)) z ={definition of .} \z - (h (either (f, g) z)
={definition of either in case z = Left x} \z - (h (f x)) =
{definition of .} \z - (h . f) x ={definition of .} h . f
Thanks.
_
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Re: [Haskell-cafe] Clean proof?
There is no clean proof of that statement because it is false.
(Consider the argument 'undefined'.)
2010/5/23 R J rj248...@hotmail.com:
Given the following definition of either, from the prelude:
either :: (a - c, b - c) - Either a b - c
either (f, g) (Left x) = f x
either (f, g) (Right x) = g x
what's a clean proof that:
h . either (f, g) = either (h . f, g . h)?
The only proof I can think of requires the introduction of an anonymous
function of z, with case analysis on z (Case 1: z = Left x, Case 2: z =
Right y), but the use of anonymous functions and case analysis is ugly, and
I'm not sure how to tie up the two cases neatly at the end. For example
here's the Left case:
h . either (f, g)
= {definition of \}
\z - (h . either (f, g)) z
= {definition of .}
\z - (h (either (f, g) z)
= {definition of either in case z = Left x}
\z - (h (f x))
= {definition of .}
\z - (h . f) x
= {definition of .}
h . f
Thanks.
The New Busy is not the too busy. Combine all your e-mail accounts with
Hotmail. Get busy.
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[Haskell-cafe] Clean proof -- correction
Correction: the theorem is
h . either (f, g) = either (h . f, h . g)
(Thanks to Lennart for pointing out the typo.)
From: rj248...@hotmail.com
To: haskell-cafe@haskell.org
Subject: Clean proof?
Date: Sun, 23 May 2010 15:41:20 +
Given the following definition of either, from the prelude:
either :: (a - c, b - c) - Either a b - c
either (f, g) (Left x) = f xeither (f, g) (Right x) = g x
what's a clean proof that:
h . either (f, g) = either (h . f, g . h)?
The only proof I can think of requires the introduction of an anonymous
function of z, with case analysis on z (Case 1: z = Left x, Case 2: z = Right
y), but the use of anonymous functions and case analysis is ugly, and I'm not
sure how to tie up the two cases neatly at the end. For example here's the
Left case:
h . either (f, g) ={definition of \} \z - (h . either (f,
g)) z ={definition of .} \z - (h (either (f, g) z)
={definition of either in case z = Left x} \z - (h (f x)) =
{definition of .} \z - (h . f) x ={definition of .} h . f
Thanks.
The New Busy is not the too busy. Combine all your e-mail accounts with
Hotmail. Get busy.
_
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Re: [Haskell-cafe] Clean proof -- correction
Lennart wasn't pointing out a typo. He was pointing out a fundamental
issue with such identities in a partial call-by-name language. If
h = const 42
then
(h . either (f, g)) undefined
evaluates to 42. But the evaluation of
(either (h . f, h . g)) undefined
is non-terminating.
This is a canonical example of an equation that holds in a partial
call-by-value language but not in a partial call-by-name language:
CBV has more sum equations; CBN has more product equations.
-Per
2010/5/23 R J rj248...@hotmail.com:
Correction: the theorem is
h . either (f, g) = either (h . f, h . g)
(Thanks to Lennart for pointing out the typo.)
From: rj248...@hotmail.com
To: haskell-cafe@haskell.org
Subject: Clean proof?
Date: Sun, 23 May 2010 15:41:20 +
Given the following definition of either, from the prelude:
either :: (a - c, b - c) - Either a b - c
either (f, g) (Left x) = f x
either (f, g) (Right x) = g x
what's a clean proof that:
h . either (f, g) = either (h . f, g . h)?
The only proof I can think of requires the introduction of an anonymous
function of z, with case analysis on z (Case 1: z = Left x, Case 2: z =
Right y), but the use of anonymous functions and case analysis is ugly, and
I'm not sure how to tie up the two cases neatly at the end. For example
here's the Left case:
h . either (f, g)
= {definition of \}
\z - (h . either (f, g)) z
= {definition of .}
\z - (h (either (f, g) z)
= {definition of either in case z = Left x}
\z - (h (f x))
= {definition of .}
\z - (h . f) x
= {definition of .}
h . f
Thanks.
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Re: [Haskell-cafe] Clean proof -- correction
On Sunday 23 May 2010 18:24:50, R J wrote: Correction: the theorem is h . either (f, g) = either (h . f, h . g) Still not entirely true, const True . either (undefined, undefined) $ undefined = True while either (const True . undefined, const True . undefined) undefined = undefined But if we ignore bottom, h . either (f, g) $ Left x = h (either (f,g) (Left x)) = h (f x) either (h . f, h . g) $ Left x = (h . f) x = h (f x) h . either (f,g) $ Right y = h (either (f,g) (Right y)) = h (g y) either (h .f, h . g) $ Right y = (h . g) y = h (g y) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Clean proof -- correction
Actually, I didn't notice the typo. It's still not a true statement.
(h . either (f, g)) undefined /= (either (h . f, h . g)) undefined
Also, it's not exactly the function either from the Prelude.
-- Lennart
2010/5/23 R J rj248...@hotmail.com:
Correction: the theorem is
h . either (f, g) = either (h . f, h . g)
(Thanks to Lennart for pointing out the typo.)
From: rj248...@hotmail.com
To: haskell-cafe@haskell.org
Subject: Clean proof?
Date: Sun, 23 May 2010 15:41:20 +
Given the following definition of either, from the prelude:
either :: (a - c, b - c) - Either a b - c
either (f, g) (Left x) = f x
either (f, g) (Right x) = g x
what's a clean proof that:
h . either (f, g) = either (h . f, g . h)?
The only proof I can think of requires the introduction of an anonymous
function of z, with case analysis on z (Case 1: z = Left x, Case 2: z =
Right y), but the use of anonymous functions and case analysis is ugly, and
I'm not sure how to tie up the two cases neatly at the end. For example
here's the Left case:
h . either (f, g)
= {definition of \}
\z - (h . either (f, g)) z
= {definition of .}
\z - (h (either (f, g) z)
= {definition of either in case z = Left x}
\z - (h (f x))
= {definition of .}
\z - (h . f) x
= {definition of .}
h . f
Thanks.
The New Busy is not the too busy. Combine all your e-mail accounts with
Hotmail. Get busy.
The New Busy is not the old busy. Search, chat and e-mail from your inbox.
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Re: [Haskell-cafe] Clean proof -- correction
On Sun, May 23, 2010 at 11:38 AM, Daniel Fischer daniel.is.fisc...@web.de wrote: On Sunday 23 May 2010 18:24:50, R J wrote: Correction: the theorem is h . either (f, g) = either (h . f, h . g) Still not entirely true, const True . either (undefined, undefined) $ undefined = True while either (const True . undefined, const True . undefined) undefined = undefined But if we ignore bottom, If we ignore bottom we say By parametricity. The theorem is a free theorem. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] An online forum for Haskell questions
Hey all, I thought I might just draw attention to a relatively new forum for Haskell information on the interwebs, that hasn't been mentioned here before. The Stack Overflow Haskell questions forum: http://stackoverflow.com/questions/tagged/haskell We've had more than 1000 questions asked and answered about Haskell there now, and for many readers of haskell-cafe@ it might be a more efficient way to get quick questions answered. Norman Ramsey is waiting patiently to help you! :-) For in-depth, or open questions, haskell-cafe exploration is more appropriate, in my opinion -- and we continue to have special communities for particular projects (e.g. libraries@ , glasgow-haskell-users@, happstack@ xmonad@) . But if you have a problem you know others might have solved already, consider the haskell tag on SO. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
I keep asking myself the question is Haskell and/or FRP even suitable for game programming. And if so are there any design patterns. 2010/5/19 Patai Gergely patai_gerg...@fastmail.fm I that the saw sleep time at each loop is fixed (0.02). So game speed will depend on processor speed, since with a more powerful CPU frames will be computed quicklier? Yes, that's how it works. So we don't have (with the Simple branch) some way to say I want my sprite to move 100 pixels *per second* on the left, except if we provide ourselves a time signal? That's exactly the case, although I'd probably provide a delta time signal. The Simple version is a discrete stream library, and it doesn't pretend to have continuous-time abstractions. Gergely -- http://www.fastmail.fm - Access your email from home and the web ___ 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] [reactive] A pong and integrate
IMO: For AAA game programming? Definitely not. For exploring new ways of doing game programming and having a lot of fun and frustration? Sure! For making casual games? I don't know. On Sun, May 23, 2010 at 9:09 PM, Ben Christy ben.chri...@gmail.com wrote: I keep asking myself the question is Haskell and/or FRP even suitable for game programming. And if so are there any design patterns. 2010/5/19 Patai Gergely patai_gerg...@fastmail.fm I that the saw sleep time at each loop is fixed (0.02). So game speed will depend on processor speed, since with a more powerful CPU frames will be computed quicklier? Yes, that's how it works. So we don't have (with the Simple branch) some way to say I want my sprite to move 100 pixels *per second* on the left, except if we provide ourselves a time signal? That's exactly the case, although I'd probably provide a delta time signal. The Simple version is a discrete stream library, and it doesn't pretend to have continuous-time abstractions. Gergely -- http://www.fastmail.fm - Access your email from home and the web ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
On May 23, 2010, at 15:09 , Ben Christy wrote: I keep asking myself the question is Haskell and/or FRP even suitable for game programming. Well, that's the question. FRP is a research project, not a production framework/paradigm; anyone working on it currently is there to help answer that question. If you're looking for a mature framework, this is not (yet) the place for you. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon universityKF8NH PGP.sig 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] [reactive] A pong and integrate
On 05/23/2010 02:17 PM, Peter Verswyvelen wrote: IMO: For AAA game programming? Definitely not. Why not? I suppose it may depend on your definition of AAA, since there doesn't seem to be any consensus on it. I have seen it mean various combinations of the following, but rarely, if ever, all of them: * Big development budget * Big marketing budget * High quality * Large number of sales and/or high revenue * High hardware requirements * Released by one of a small group of accepted AAA publishers While I think it's very unlikely that the last one will happen any time soon, I don't see any reason that Haskell and/or FRP (or as I now prefer to call my research in the area, Denotative Continuous-Time Programming, or DCTP) inherently can't be a major part of the development of a game that fits any of the definitions in the list. I suppose DCTP is not itself *ready* for somebody to risk a business investment on it, although it may be in the future, but Haskell as a whole would not be all that risky, in my opinion. - Jake ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
Assuming Haskell is ready has any work gone into creating design patterns or the like. One of the biggest problems is ALL of the literature regarding game programming is written in an imperative style. My goal for learning Haskell is to make a hobby game written in a Functional language but I am at a loss how to go about it. I an imperative language I would set up a central entity management system and then have subsystems register with it and either transform the entities such as AI or user interface or do something with them IE graphics. This paradigm just will not work as far as I can imagine in Haskell. On Sun, May 23, 2010 at 6:30 PM, Jake McArthur jake.mcart...@gmail.comwrote: On 05/23/2010 02:17 PM, Peter Verswyvelen wrote: IMO: For AAA game programming? Definitely not. Why not? I suppose it may depend on your definition of AAA, since there doesn't seem to be any consensus on it. I have seen it mean various combinations of the following, but rarely, if ever, all of them: * Big development budget * Big marketing budget * High quality * Large number of sales and/or high revenue * High hardware requirements * Released by one of a small group of accepted AAA publishers While I think it's very unlikely that the last one will happen any time soon, I don't see any reason that Haskell and/or FRP (or as I now prefer to call my research in the area, Denotative Continuous-Time Programming, or DCTP) inherently can't be a major part of the development of a game that fits any of the definitions in the list. I suppose DCTP is not itself *ready* for somebody to risk a business investment on it, although it may be in the future, but Haskell as a whole would not be all that risky, in my opinion. - Jake ___ 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] [reactive] A pong and integrate
On Mon, May 24, 2010 at 12:30 AM, Jake McArthur jake.mcart...@gmail.com wrote: On 05/23/2010 02:17 PM, Peter Verswyvelen wrote: IMO: For AAA game programming? Definitely not. Why not? I suppose it may depend on your definition of AAA, since there doesn't seem to be any consensus on it. I have seen it mean various combinations of the following, but rarely, if ever, all of them: * Big development budget * Big marketing budget * High quality * Large number of sales and/or high revenue * High hardware requirements * Released by one of a small group of accepted AAA publishers While I think it's very unlikely that the last one will happen any time soon, I don't see any reason that Haskell and/or FRP (or as I now prefer to call my research in the area, Denotative Continuous-Time Programming, or DCTP) inherently can't be a major part of the development of a game that fits any of the definitions in the list. I'm not saying it will never happen, I'm just saying that IMO Haskell is not ready for doing AAA development (and with that I meant your first 5 bullets) right now. I suppose DCTP is not itself *ready* for somebody to risk a business investment on it, although it may be in the future, but Haskell as a whole would not be all that risky, in my opinion. Well, in my opinion - based on hands on experience - Haskell was very risky for serious game development a couple of years ago. Not sure if this is still the case today... ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
I guess Im thinking of a overarching pattern for creating games in a functional language similar to http://www.acims.arizona.edu/PUBLICATIONS/PDF/JeffPlummerMSthesis_wo_Appendix.pdf . On Sun, May 23, 2010 at 6:51 PM, Ben Christy ben.chri...@gmail.com wrote: Assuming Haskell is ready has any work gone into creating design patterns or the like. One of the biggest problems is ALL of the literature regarding game programming is written in an imperative style. My goal for learning Haskell is to make a hobby game written in a Functional language but I am at a loss how to go about it. I an imperative language I would set up a central entity management system and then have subsystems register with it and either transform the entities such as AI or user interface or do something with them IE graphics. This paradigm just will not work as far as I can imagine in Haskell. On Sun, May 23, 2010 at 6:30 PM, Jake McArthur jake.mcart...@gmail.comwrote: On 05/23/2010 02:17 PM, Peter Verswyvelen wrote: IMO: For AAA game programming? Definitely not. Why not? I suppose it may depend on your definition of AAA, since there doesn't seem to be any consensus on it. I have seen it mean various combinations of the following, but rarely, if ever, all of them: * Big development budget * Big marketing budget * High quality * Large number of sales and/or high revenue * High hardware requirements * Released by one of a small group of accepted AAA publishers While I think it's very unlikely that the last one will happen any time soon, I don't see any reason that Haskell and/or FRP (or as I now prefer to call my research in the area, Denotative Continuous-Time Programming, or DCTP) inherently can't be a major part of the development of a game that fits any of the definitions in the list. I suppose DCTP is not itself *ready* for somebody to risk a business investment on it, although it may be in the future, but Haskell as a whole would not be all that risky, in my opinion. - Jake ___ 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] [reactive] A pong and integrate
What papers did you read? When I read most of the Yampa papers, most of the design patterns became obvious for AFRP (arrow-based FRP) style of programming. That doesn't mean I could apply the design patterns immediately; I understood them but writing a game in it was difficult since I also was too used to the imperative approach. Note that in AFRP the design patterns are actually functions and combinators itself (dpSwitch and the like), and no fuzzy descriptions like in imperative programming. Regarding user interfaces, FRUIT (also AFRP based) is also nice IMO. But above systems suffer from scalability and performance (and the annoying fact that a random number generator is not embedded in the framework) , although for simple games, I don't think this would be an issue. Newer work like Reactive is much more faithful to functional programming (no arrow syntax needed), but since no pong game was never made with it yet, I would classify this as ongoing research. Elerea finds middle ground between the two, and unlike Yampa, it's examples would still work I guess. On Mon, May 24, 2010 at 12:51 AM, Ben Christy ben.chri...@gmail.com wrote: Assuming Haskell is ready has any work gone into creating design patterns or the like. One of the biggest problems is ALL of the literature regarding game programming is written in an imperative style. My goal for learning Haskell is to make a hobby game written in a Functional language but I am at a loss how to go about it. I an imperative language I would set up a central entity management system and then have subsystems register with it and either transform the entities such as AI or user interface or do something with them IE graphics. This paradigm just will not work as far as I can imagine in Haskell. On Sun, May 23, 2010 at 6:30 PM, Jake McArthur jake.mcart...@gmail.com wrote: On 05/23/2010 02:17 PM, Peter Verswyvelen wrote: IMO: For AAA game programming? Definitely not. Why not? I suppose it may depend on your definition of AAA, since there doesn't seem to be any consensus on it. I have seen it mean various combinations of the following, but rarely, if ever, all of them: * Big development budget * Big marketing budget * High quality * Large number of sales and/or high revenue * High hardware requirements * Released by one of a small group of accepted AAA publishers While I think it's very unlikely that the last one will happen any time soon, I don't see any reason that Haskell and/or FRP (or as I now prefer to call my research in the area, Denotative Continuous-Time Programming, or DCTP) inherently can't be a major part of the development of a game that fits any of the definitions in the list. I suppose DCTP is not itself *ready* for somebody to risk a business investment on it, although it may be in the future, but Haskell as a whole would not be all that risky, in my opinion. - Jake ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] ANN: atom-1.0.4
Atom [1] is an Haskell DSL for hard realtime embedded programming. This release adds 'exactPhase' to precisely control the phasing of Atom rule executions. This patch was contributed by Lee Pike. BTW, I created a google group [2] for discussions related to the use for functional programming in embedded systems. -Tom [1] http://hackage.haskell.org/package/atom [2] http://groups.google.com/group/fp-embedded ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Proposal to solve Haskell's MPTC dilemma
Sorry to correct myself: On Sat, May 22, 2010 at 10:24 PM, Carlos Camarao carlos.cama...@gmail.comwrote: ... = PS: I think that a definition of orphan/non-orphan instance definition for MPTCs should be different. Letting: ... instance-def(I,C,M,tv) = I is an instance definition of class C, occurring in module M, that instantiates class variable tv Should be: instance-def(I,C,M,tv,T) = I is an instance def of class C, occurring in module M, that instanticates class variable tv to datatype T and replace occurrences of instance-def(I,C,M,tv) to instance-def(I,C,M,tv,T). And I think a correct definition of orphan/non-orphan for MPTCs should be along the line: ... That is, an instance should be considered non-orphan if there exists at least one datatype to which a class type variable in such instance is instantiated, because other instances which instantiate such class type variable to such datatype would be non-orphan. (delete non-.) ... type variable to such datatype would be orphan. Cheers, Carlos ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] [reactive] A pong and integrate
Elerea finds middle ground between the two, and unlike Yampa, it's examples would still work I guess. Yes that's the big problem of Yampa: all of the examples are very old, and some even don't work anymore. It's the same for the papers/tutorials (they're all 6 years old or more), and it would be less of a problem if the functions were documented! (Check hackage, you'll see...) I find Elerea fine so far, but it is still experimental and more limited than Yampa. 2010/5/24 Peter Verswyvelen bugf...@gmail.com What papers did you read? When I read most of the Yampa papers, most of the design patterns became obvious for AFRP (arrow-based FRP) style of programming. That doesn't mean I could apply the design patterns immediately; I understood them but writing a game in it was difficult since I also was too used to the imperative approach. Note that in AFRP the design patterns are actually functions and combinators itself (dpSwitch and the like), and no fuzzy descriptions like in imperative programming. Regarding user interfaces, FRUIT (also AFRP based) is also nice IMO. But above systems suffer from scalability and performance (and the annoying fact that a random number generator is not embedded in the framework) , although for simple games, I don't think this would be an issue. Newer work like Reactive is much more faithful to functional programming (no arrow syntax needed), but since no pong game was never made with it yet, I would classify this as ongoing research. Elerea finds middle ground between the two, and unlike Yampa, it's examples would still work I guess. On Mon, May 24, 2010 at 12:51 AM, Ben Christy ben.chri...@gmail.com wrote: Assuming Haskell is ready has any work gone into creating design patterns or the like. One of the biggest problems is ALL of the literature regarding game programming is written in an imperative style. My goal for learning Haskell is to make a hobby game written in a Functional language but I am at a loss how to go about it. I an imperative language I would set up a central entity management system and then have subsystems register with it and either transform the entities such as AI or user interface or do something with them IE graphics. This paradigm just will not work as far as I can imagine in Haskell. On Sun, May 23, 2010 at 6:30 PM, Jake McArthur jake.mcart...@gmail.com wrote: On 05/23/2010 02:17 PM, Peter Verswyvelen wrote: IMO: For AAA game programming? Definitely not. Why not? I suppose it may depend on your definition of AAA, since there doesn't seem to be any consensus on it. I have seen it mean various combinations of the following, but rarely, if ever, all of them: * Big development budget * Big marketing budget * High quality * Large number of sales and/or high revenue * High hardware requirements * Released by one of a small group of accepted AAA publishers While I think it's very unlikely that the last one will happen any time soon, I don't see any reason that Haskell and/or FRP (or as I now prefer to call my research in the area, Denotative Continuous-Time Programming, or DCTP) inherently can't be a major part of the development of a game that fits any of the definitions in the list. I suppose DCTP is not itself *ready* for somebody to risk a business investment on it, although it may be in the future, but Haskell as a whole would not be all that risky, in my opinion. - Jake ___ 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 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] ANN: hledger 0.10 released
hledger 0.10 is released, with installation and bug fixes and api improvements. Best, -Simon home: http://hledger.org Release notes: 2010/05/23 hledger 0.10 * fix too-loose testpack dependency, missing safe dependency * fix ghc 6.12 compatibility with -fweb * fix handling of non-ascii arguments with ghc 6.12 * fix 0.8 in --version output * fix an occasional stack overflow error due to infinite recursion in Posting/Transaction equality tests * the -fwebhappstack build flag is gone for now, to avoid a cabal problem * parsing: if there is no description, don't require a space after the transaction date * parsing: balance balanced-virtual postings separately, allow them to have an implicit amount * parsing: timelog entries now generate balanced transactions, using virtual postings * parsing: simpler high-level parse error message * parsing: clearer bad date errors * add: fix wrongful program exit on bad dates * print: negative account patterns now exclude transactions containing any posting to a matched account * vty: rename the ui command to vty for consistency * vty: fix restricted account scope when backing up to top level * web: fix non-ascii handling with ghc 6.12 * web: fix a bug possibly affecting reload-on-change * consolidate module namespace under Hledger, api cleanups Stats: 44 days, 81 commits since last release. Now at 4904 lines of code including tests, 144 tests, 53% coverage. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Best way to instance Fix?
Hi!
I'm trying to work out the best way to generate (ideally derive) instances for
the Fix type. Here's a cut down example:
data Greet x = AlloAllo x x | AuRevoir deriving Show
newtype Fix f = In { out :: f (Fix f) } -- deriving Show -- DOESN'T COMPILE
-- workaround
instance Show (Fix Greet) where show (In i) = In ++ show i
In other words, given a number of parametised types that I can derive, say,
Ord, Eq and Show for, how should I go about getting the instances for the Fix-d
version of them as well? I've tried a few things, but no luck so far.
Any clues?
Cheers,
Sam
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[Haskell-cafe] Haskell, Queries and Monad Comprehension
Hi all, is there anybody currently using Haskell to construct or implement a query language? I have read a couple of papers on Monad Comprehension Calculus and similar but none using Haskell nor any other existing programming language to build an actual implementation. Most papers give some sort of Pseudo code, but I couldn't find any meat. Günther ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Best way to instance Fix?
On 24 May 2010 11:13, Sam Martin sam.mar...@geomerics.com wrote:
Hi!
I'm trying to work out the best way to generate (ideally derive) instances
for the Fix type. Here's a cut down example:
data Greet x = AlloAllo x x | AuRevoir deriving Show
newtype Fix f = In { out :: f (Fix f) } -- deriving Show -- DOESN'T COMPILE
I think this is because for Fix to have a Show instance, it needs f to
have a Show instance, which only works if the parameter passed to it
has a Show instance, which means Fix needs to have a Show instance,
etc. My guess is that the deriving tool doesn't like infinite
loops...
-- workaround
instance Show (Fix Greet) where show (In i) = In ++ show i
Are you using OverlappingInstances or something to get this to work?
In other words, given a number of parametised types that I can derive, say,
Ord, Eq and Show for, how should I go about getting the instances for the
Fix-d version of them as well? I've tried a few things, but no luck so far.
Does (==) = (==) `on` out works for the Eq instance?
--
Ivan Lazar Miljenovic
ivan.miljeno...@gmail.com
IvanMiljenovic.wordpress.com
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Re: [Haskell-cafe] Best way to instance Fix?
On Mon, May 24, 2010 at 02:13:32AM +0100, Sam Martin wrote:
Hi!
I'm trying to work out the best way to generate (ideally derive) instances
for the Fix type. Here's a cut down example:
data Greet x = AlloAllo x x | AuRevoir deriving Show
newtype Fix f = In { out :: f (Fix f) } -- deriving Show -- DOESN'T COMPILE
-- workaround
instance Show (Fix Greet) where show (In i) = In ++ show i
In other words, given a number of parametised types that I can derive, say,
Ord, Eq and Show for, how should I go about getting the instances for the
Fix-d version of them as well? I've tried a few things, but no luck so far.
Any clues?
You can use GHC's standalone deriving mechanism for this, described at
http://www.haskell.org/ghc/docs/6.12.2/html/users_guide/deriving.html
{-# LANGUAGE StandaloneDeriving, FlexibleContexts, UndecidableInstances #-}
data Greet x = AlloAllo x x | AuRevoir deriving Show
newtype Fix f = In { out :: f (Fix f) }
deriving instance Show (f (Fix f)) = Show (Fix f)
Regards,
Reid Barton
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RE: [Haskell-cafe] TagSoup 0.9
Thanks Neil, Using Network.HTTP worked. However something else I have just run into concerns some web pages that start with: ?xml version=1.0 encoding=iso-8859-1? !DOCTYPE html PUBLIC -//W3C//DTD XHTML 1.0 Transitional//EN http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd; I get the following bad result: TagText HTTP/1.1 200 OK\r\nContent-Type: text/html\r\nLast-Modified: Tue, 27 Oct 2009 19:30:40 GMT\r\nETag: \6f248cf73b57ca1:25e2\\r\nDate: Sun, 23 May 2010 22:46:41 GMT\r\nTransfer-Encoding: chunked\r\nConnection: close\r\nConnection: Transfer-Encoding\r\n\r\n4000\r\n\255\254\NUL?\NULx\NULm\NULl\NUL \NULv\NULe\NULr\NULs\NULi\NULo\NULn\NUL=\NUL\\NUL1\NUL.\NUL0\NUL\\NUL \NULe\NULn\NULc\NULo\NULd\NULi\NULn\NULg\NUL=\NUL\\NULi\NULs\NULo\NUL-\NUL8 \NUL8\NUL5\NUL9\NUL-\NUL1\NUL\\NUL etc etc Is this an easy thing to fix? I've started to look over the code. -Original Message- From: Neil Mitchell [mailto:ndmitch...@gmail.com] Sent: Wednesday, May 19, 2010 12:19 PM To: Ralph Hodgson Cc: Daniel Fischer; haskell-cafe@haskell.org; Don Stewart Subject: Re: [Haskell-cafe] TagSoup 0.9 Hi Ralph, I was using TagSoup 0.8 with great success. On upgrading to 0.9 I have this error: TQ\TagSoup\TagSoupExtensions.lhs:29:17: `Tag' is not applied to enough type arguments Expected kind `*', but `Tag' has kind `* - *' In the type synonym declaration for `Bundle' Failed, modules loaded: TQ.Common.TextAndListHandling. My change notes have this being a change between 0.6 and 0.8. As Malcolm says, any old uses of Tag should become Tag String. The reason is that Tag is now parameterised, and you can use Tag ByteString etc. However, I should point out that Tag ByteString won't be any faster than Tag String in this version (it's in the future work pile). Forgot to add: I now need to understand the following warnings on this line import Text.HTML.Download: Everyone's comments have been right. I previously included Text.HTML.Download so that it was easy to test tagsoup against the web. Since I first wrote that snippet the HTTP downloading libraries have improved substantially, so people should use those in favour of the version in tagsoup - you'll be able to connect to more websites in more reliable ways, go through proxies etc. I don't intend to remove the Download module any time soon, but I will do eventually. Thanks, Neil ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
