February 2011 - web-devel

Application context?
by Petter Egesund 17 Feb '11

17 Feb '11

Hi and thanks for writing such cool software! I am wondering about how to deal with a problem which is releated to what is called application-context in some other web-frameworks. The problem is like this: 1) I would like to do some calculations and put the results in a judy-table (or a regular hash-table) 2) I would like to serve results from this calculations in yesod. So how do I pass my hash as a parameter to functions which is serving content? I was thinking about changing the yesod-code and copy some of the handling from sessions and/or databasehandlers, but it did not seem right - I do not want to maintain my own branch. Is there a better way to do this? Cheers, Petter

2 2

[Hamlet] CSS size wrapper
by Dmitry Kurochkin 17 Feb '11

17 Feb '11

Hi Yesod developers. Attached are two modules to implement CSS size wrappers for Hamlet. It implements several types for different CSS units: * em - EmSize * ex - ExSize * px - PixelSize * % - PercentageSize * cm, in, mm, pc, pt - AbsoluteSize You can create them using an mkSize Template Haskell function, e.g. let size = $(mkSize "100%") All types are instances of Show, Eq, Ord, Num, Fractional and ToCss. This allows you to do math and interpolate it to Hamlet. Ideally, I wanted to have only one type and make an implicit conversion from string literals. But I do not know how to forbid mixing of incompatible units in math (e.g. 10px + 10cm) with a single type. And I do not know how to make implicit conversion from string literals with multiple types. I would appreciate any comments. Including on naming style, type design, API and overall usefulness. Keep in mind that this is the first time I use Template Haskell, so the code may be not optimal and plain ugly (e.g. can we use quasi quotes instead of directly messing with TH?) BTW Michael, one more thing I miss in Hamlet is defining variables in templates. I would prefer to put simple CSS-related constants directly in Cassius instead of a dedicated module. Is it possible to implement? Regards, Dmitry

2 8

Examples and/or tutorials for WAI
by Thomas Sutton 15 Feb '11

15 Feb '11

Hi All, I spent a few hours last night trying to hook a HaXR XML-RPC server up with WAI instead of using the built-in CGI support. Alas, I failed dismally. Is there any more thorough tutorial-style documentation for WAI? Or a good example project that does something more sophisticated than "Hello, Web!"? What tripped me up was trying to figure out the enumerator part of the API so that I can read the request body (and turn it into a String) and run the XML-RPC request handler. Any help would be appreciated! Cheers, Thomas Sutton

3 3

Yesod/WAI and multipart/form-data encoded post requests
by Max Cantor 14 Feb '11

14 Feb '11

Are there any issues with handling multi-part/form-data encoded POST request? Here are my request headers: headers: [("Host","192.168.0.187:6000"),("User-Agent","Consumer-iOS-Phonegap/1.0 CFNetwork/485.12.7 Darwin/10.4.0"),("Content-Length","618"),("Content-Type","multipart/form-data; boundary=BEGINBOUNDARYooooeflkscdlksjlkwrglk238sd723987sdiii"),("Accept","*/*"),("Accept-Language","en-us"),("Accept-Encoding","gzip, deflate"),("Cookie","_SESSION=TZsUfNyzruNnYeETdR/BB2Y/7ns5KRUVMgRkEkghOAo2lXbZ709DsPhclsOndiFmyEttOw5FHCfzW+MVM/eIfJQEruHeE3oFeSrrfdlmSEiZq3H7x+fPOyejZPq0Sd5x"),("Connection","keep-alive")] And what WAI gives back as the params: ("geoLong","103.83032\r\nBEGINBOUNDARYooooeflkscdlksjlkwrglk238sd723987sdiii\r\nContent-Disposition: form-data; name=\"geoLat\"\r\nContent-Type: text/plain\r\n\r\n1.296149\r\nBEGINBOUNDARYooooeflkscdlksjlkwrglk238sd723987sdiii\r\nContent-Disposition: form-data; name=\"geoAccuracy\"\r\nContent-Type: text/plain\r\n\r\n65\r\nBEGINBOUNDARYooooeflkscdlksjlkwrglk238sd723987sdiii\r\nContent-Disposition: form-data; name=\"scannedTime\"\r\nContent-Type: text/plain\r\n\r\n1297677177.991\r\r\nBEGINBOUNDARYooooeflkscdlksjlkwrglk238sd723987sdiii--") Note that the entire request body is treated as one value to the first param instead of being broken up into multiple params. As an HTTP newbie, Its probable that I'm constructing the HTTP request wrong but I dont see what i'm doing wrong. Any help would be greatly appreciated. Max

4 4

Re: [web-devel] [Yesod] Creating a static link
by Michael Snoyman 13 Feb '11

13 Feb '11

On Sun, Feb 13, 2011 at 5:26 PM, Rafael Cunha de Almeida <rafael-lists(a)kontesti.me> wrote: > Michael Snoyman <michael(a)snoyman.com> disse: >> You could go either way on that one. The content of an interpolation >> is specifically *not* a fully-powered Haskell expression. > > Why is that? I have a little experience with RoR, there I could do > something like this: > > - @people.each do |person| > = person.name > > I think you don't want to have a fully-powered Haskell expression to > avoid people adding too much code to the view (thinking in MVC pattern). > However, it's not like people can't do it just because it's a little > harder. Meanwhile, there are a lot of useful things that could be done > if all (or most) haskell syntax was allowed to be interpolated. > > Instead of having special syntax like $forall, wouldn't it be better to > just provide monad tranformers to allow for those sort of loops? > Something like Control.Monad.LoopWhile module provides. That way hamlet > would need only to provide a ${} syntax that allow for adding haskell > code which will be evaluated but won't print anything to the site. That > way things could work a lot like in ruby, which I think makes things a > lot simpler. > > Allowing for a new sort of interpolation and any sort of haskell > expression to be interpolated, hamlet wouldn't need to create its own > flow control statements. The user could write their views freely using > only haskell syntax when code logic is required. There's a few reasons for this: 1) I do *not* think it is a good thing for a template language to expose the full power of the programming language. As it is, I think Hamlet already stretches the bounds of what a designer would feel comfortable with. 2) This needs to get coded at some point, and frankly I don't feel like completely reinventing a full-blown Haskell parser. I'm aware of packages like haskell-src-exts-qq, but they are very heavy-weight and introduce a huge body of possible bugs/unanticipated behavior to Hamlet. 3) I'm not quite certain how you would intend to completely replace all of the control structures with some variable splicing, I think that would require further elucidation. However, I *highly* doubt it will come out as concise as a forall statement currently is. My goal for Hamlet isn't to provide absolute power in templates: it's to provide a user-friendly, terse syntax to achieve 95% of what people want to do easily. And for that extra 5%, it's very easy to call out to a helper Haskell function. The list syntax itself does not really bother me, though it does just beg the question of where we draw the line. For instance, I have *no* intention of implementing do-notation inside an interpolation. To bring up Dmitry's suggestion: operators introduce all kinds of precedence issues, since we won't have access to the precedence levels Haskell is aware of. I think barking up *that* tree is a recipe for very unintuitive behavior. Michael

2 3

Re: [web-devel] [Yesod] Creating a static link
by Dmitry Kurochkin 13 Feb '11

13 Feb '11

On Sun, 13 Feb 2011 13:26:24 -0200, Rafael Cunha de Almeida <rafael-lists(a)kontesti.me> wrote: > Michael Snoyman <michael(a)snoyman.com> disse: > > You could go either way on that one. The content of an interpolation > > is specifically *not* a fully-powered Haskell expression. > > Why is that? I have a little experience with RoR, there I could do > something like this: > > - @people.each do |person| > = person.name > > I think you don't want to have a fully-powered Haskell expression to > avoid people adding too much code to the view (thinking in MVC pattern). > However, it's not like people can't do it just because it's a little > harder. Meanwhile, there are a lot of useful things that could be done > if all (or most) haskell syntax was allowed to be interpolated. > > Instead of having special syntax like $forall, wouldn't it be better to > just provide monad tranformers to allow for those sort of loops? > Something like Control.Monad.LoopWhile module provides. That way hamlet > would need only to provide a ${} syntax that allow for adding haskell > code which will be evaluated but won't print anything to the site. That > way things could work a lot like in ruby, which I think makes things a > lot simpler. > > Allowing for a new sort of interpolation and any sort of haskell > expression to be interpolated, hamlet wouldn't need to create its own > flow control statements. The user could write their views freely using > only haskell syntax when code logic is required. > I join the question! I have some style-related constants in Style module, e.g. sizes and colors. Then I want to do computations using these constants in Cassius, something similar to SCSS. E.g. width: #{Style.width1 + Style.width2} (not talking about appending "px" suffix for now). Currently, because of artificial limitations on Hamlet interpolations, I have to define (plus = (+)) (minus = (-)) and so on. Would be nice if it allowed full-featured Haskell. Regards, Dmitry > []'s > Rafael > > _______________________________________________ > web-devel mailing list > web-devel(a)haskell.org > http://www.haskell.org/mailman/listinfo/web-devel

2 1

[Yesod] Creating a static link
by Rafael Cunha de Almeida 13 Feb '11

13 Feb '11

Hello, >From what I could gather, the way to create a link to a static page, like a picture is: StaticR $ StaticRoute ["figure.png"] [] I wanted to add a static picture in my site's template so I added <img alt="" src=@{StaticR $ StaticRoute ["figure.png"] []}> to my template. Unfortunately, that didn't work. It seems like creating lists inside @{} or even #{} is impossible. For instance #{head ["test"]} doesn't work either. Is that a bug? Or is it how it's supposed to work?

3 5

Yesod. Routes. Resources. Authorization. ACL
by Антон Чешков 12 Feb '11

12 Feb '11

Hi Michael. I want to make authorization in Yesod application build on ACL principle. We have in Yesod "*Routes*". *"Route"* is resource. I have the list : *Resource | Access* ---------------------------------- RouteA | Allow RouteB | Deny I would like to : 1. save, read this list outward yesod 2. check, that the concrete route satisfy or not satisfy the list 3. have more flexible way to define *resource pattern* in list. For example i have *RouteX String Int. *I wish to define pattern * "RouteX * 666"* * * If i had this, i would to implement *Yesod.isAuthorized* method similar *isAuthorized _ = do* * acl <- getACL* * route <- getCurrentRoute* * case check acl route of* * True -> return Authorized* * **False -> return Unauthorized* * * * * I do not know, may be there is the way to make this now. How i can put it into practice ? Thanks. -- Best regards, Cheshkov Anton Phone: +7 909 005 18 82 Skype: cheshkov_anton

2 1

[Yesod][Auth][OpenId]
by いとうかつとし 12 Feb '11

12 Feb '11

Hi, I have a question. OpenId plugin in yesod-auth 0.2.0.3 don't support OP identifier? for example, i try japanese SNS mixi.jp, Claimed identifier: https://id.mixi.jp/<myid> => success and login my developed site. OP identifier: https://mixi.jp => fail!! I success to login to mixi, but mixi say the error message: `Given OpenID is not yours, your OpenID is http://id.mixi.jp/<myid>. confirm and try again.' the mixi's developer center say mixi 's OP identifier is https://mixi.jp. anyone success to login by using OP identifier? regards.

3 4

Re: [web-devel] Rich Internet Applications using Haskell
by Greg Weber 10 Feb '11

10 Feb '11

I am just going to chime in with links to a few tools that might be useful that you probably already know about :) Algebraic Data Types in JavaScript http://w3future.com/weblog/stories/2008/06/16/adtinjs.xml Javascript Pattern Matching http://www.bramstein.com/projects/junify/ Javascript Arrows http://blog.tupil.com/look-ma-no-callbacks/ haskell client-server state transferring http://blog.on-a-horse.org/

2 1