[Haskell-cafe] Why isn't ArrowChoice a parent of of ArrowApply?
In Control.Arrow we have: |leftApp ::ArrowApply a = a b c - a (Either b d) (Either c d)| Any instance of |ArrowApply| can be made into an instance of |ArrowChoice| by defining |left = leftApp|. So why isn't |ArrowChoice| a parent of |ArrowApply|? Best regards, Petr ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why isn't ArrowChoice a parent of of ArrowApply?
On Thu, Jun 20, 2013 at 09:02:48AM +0200, Petr Pudlák wrote: In Control.Arrow we have: leftApp :: ArrowApply a = a b c - a (Either b d) (Either c d) Any instance of ArrowApply can be made into an instance of ArrowChoice by defining left = leftApp. So why isn't ArrowChoice a parent of ArrowApply? Probably because it wasn't in John Hughes's original paper. I agree that it would make sense. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] The promising world of Monadic formlets
Here is the example with better rendering and additional information as well as some identifies issues to be solved. http://haskell-web.blogspot.com.es/2013/06/the-promising-land-of-monadic-formlets.html And I made strong statements there. What do you think? If you have questions or want to be involved in the development of this and other related concepts, please send me a message. 2013/6/20 Alberto G. Corona agocor...@gmail.com I don´t know how, but the google mail has changed the applicative functor operator after (,) Left and Rigth by -. 2013/6/19 Alberto G. Corona agocor...@gmail.com Hi, This is just to let you know the promising results of some experimentation: Formlets are about applicative instances, but what about monadic instances? What a Monad instance of formlets means? I recently experimented with this and the results are very interesting and powerful- It mixes the best of web forms, with the flexibility of console applications. ???!! Althoug this example is for the formlets of the MFlow https://github.com/agocorona/MFlowframework , it can be ported to other formlet implementations. Although the MFLow formlets include web formatting that is not supported in other formlets implementations. Static HTML templating don´t work well with monadic formlets, so it is important to include the formatting as a part of the computation: import MFlow.Wai.Blaze.Html.All dynamicForm= wform $ do (n,s) - (,) - p Who are you? ++ getString Nothing ! hint name ++ br * getString Nothing ! hint surname ++ br ** submitButton ok ++ br flag - b do you ++ getRadio[radiob work?,radiob study?] ++ br r-case flag of work - pageFlow l $ Left - b do you enjoy your work? ++ getBool True yes no ** submitButton ok ++ br study- pageFlow r $ Right - b do you study in ++ getRadio[radiob University ,radiob High School] p (You are ++n++ ++s) ++ case r of Left fl - p (You work and it is ++ show fl ++ that you enjoy your work) ++ noWidget Right stu - p (You study at the ++ stu) ++ noWidget hint s= [(placeholder,s)] onClickSubmit= [(onclick,this.form.submit())] radiob s n= text s ++ setRadio s n ! onClickSubmit Here wform, getBool, getString , getRadio etc are formlet elements The first sentence is an applicative composition that generate a 2 tuple, to show that applicative and monadic can be mixed. the operations ++ add html to the formlet. the operatior ! add attributes to the formlet element.. noWidget is a dumb formlet that does not validate. The second monadic statement is an election between two options. The beauty of the monadic instance is that the rest of the form can vary depending on the previous answers. Since the formlets validate the input, unless the election is made, the radio will not validate, so the monadic execution will be aborted beyond any unanswered question, so nothing will appear after the question. The rest of the form will appear when the user choose one of the two options. once one or the other option is chosen, then another binary question is presented. (either he likes his work or where he study). When the questions are finised, the results are presented. I hope that you get the idea. The benefit is not only the familiar coding and presentation of a sequential console application: Since the form encloses all the fields, At any time the user can change previous inputs and the form will reflect these changes. For example if the user change from work to study (second statements) the where do you study will appear and the work related questions and answers will disappear. That is wonderfully useful for heavily interactive applications. There is a problem however and it is the issue of the formlet identifiers. Unlike in an applicative presentation, now the number and type of the formlets will vary, so the response to a previous form create a new kind of form, and the post response can be misinterpreted. To avoid that , the pageFlow call creates fixed field labels for each branch of execution. I will release a version of MFlow that support this kind of monadic composition of fomlets, but In essence it is nothing but to add Monad instance to formlets. A single server procedure, that executes the formlet code can support all the interaction so any framework can do it. The usability of that is huge:It is possible to interact in a web page in a console style with questions and answers with the versatitly of a dynamic foms: Any modification in the form change the subsequent flow of interaction. Another application of this monadic
Re: [Haskell-cafe] TH clause Pat selection
Have you tried dataToPatQ and dataToExpQ? http://hackage.haskell.org/packages/archive/template-haskell/latest/doc/html/Language-Haskell-TH-Quote.html Geoff On 06/19/2013 11:23 PM, Brian Lewis wrote: I want to use TH to generate functions like foo :: c - h foo ... = ... foo ... = ... ... from lists of pairs :: [(c, h)] For example, $(genFoo ''Int ''Bool [(0,False), (1,True)]) would generate foo 0 = False foo 1 = True The problem is, I don't know how to generate the function's clauses. foo 0 = ... seems to be a LitP pattern. But foo True = ... seems to be a ConP pattern. The appropriate pattern depends on type c. Here's code with more explanation and examples: http://hpaste.org/90163 ___ 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] ANNOUNCE: haskell-names-0.1
I am pleased to announce the first public release of haskell-names, a name resolution library for haskell-src-exts AST. Namely, it can do the following: * for a module, compute its interface, i.e. the set of entities exported by the module, together with their original names. * for each name in the module, figure out what it refers to — whether it's bound locally (say, by a where clause) or globally (and then give its origin). Thanks to haskell-packages, this library is fully integrated with Cabal, so that you can easily generate name interfaces for any Cabalized package. See more details in the README: http://documentup.com/haskell-suite/haskell-names This library is based on the code written by Lennart Augustsson in 2010. Little of that code survived, but nevertheless it's been a great help. Roman ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Ann: Cascading 0.1.0, DSL for Cascading Style Sheets
Hi there,
I've just released the first version of [cascading], library for
writing/generating Cascading Style Sheets (CSS) in Haskell. The API
design is inspired by many other projects, including blaze-html, HSP and
Yesod's Lucius.
[cascading]: http://hackage.haskell.org/package/cascading
Features:
* Style sheets are monoids and can be MonadWritered.
* All non-appendix properties of CSS level 2.1 are implemented and
exposed through a type-safe API. It's easy enough to set properties
for which no type-safe API exists. See the example below.
* Easy to integrate into all monadic web frameworks, easy to
interleave stylesheets with framework operations.
* Builtin support for web-routes.
* Color space awareness through the colour library.
* Fully encoding-aware with one caveat: If you bypass PropValue and
use ByteStrings as property values directly, then UTF-8 is assumed.
Example:
stylesheet :: (MonadWriter CSS m) = m ()
stylesheet =
onAll $ do
select [p] $ do
margin . Edges $ [zeroLen]
padding . Edges $ [_Em # 1, _Ex # 2]
select [em] $ do
fontWeight BolderWeight
select [ul, ol] . below [li] $ do
borderColor (LeftEdge green)
borderWidth (LeftEdge ThickWidth)
vendors $ borderRadius $= (3mm :: PropValue)
This results in the following stylesheet:
p { margin: 0;
padding: 1em 2ex }
em { font-weight: bolder }
ul li, ol li {
border-left-color: #008000;
border-left-width: thick;
border-radius: 3mm;
-moz-border-radius: 3mm;
-ms-border-radius: 3mm;
-o-border-radius: 3mm;
-webkit-border-radius: 3mm
}
Please visit the [homepage]. Feedback is always welcome. If you find
bugs, please don't hesitate to [report] them.
[homepage]: http://hub.darcs.net/ertes/cascading
[report]: http://hub.darcs.net/ertes/cascading/issues
Greets,
Ertugrul
--
Not to be or to be and (not to be or to be and (not to be or to be and
(not to be or to be and ... that is the list monad.
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Re: [Haskell-cafe] Ann: Cascading 0.1.0, DSL for Cascading Style Sheets
Ertugrul Söylemez e...@ertes.de wrote: vendors $ borderRadius $= (3mm :: PropValue) Typo: vendors $ border-radius $= (3mm :: PropValue) Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad. signature.asc Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] TH clause Pat selection
Hi. On 19 June 2013 23:23, Brian Lewis br...@lorf.org wrote: The problem is, I don't know how to generate the function's clauses. foo 0 = ... seems to be a LitP pattern. But foo True = ... seems to be a ConP pattern. The appropriate pattern depends on type c. I've used haskell-src-meta for this purpose before. See: http://hackage.haskell.org/packages/archive/haskell-src-meta/0.6.0.2/doc/html/Language-Haskell-Meta-Parse.html#v:parsePat Hope this helps, Ozgur ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
