[racket-users] Capturing sets of options in a splicing syntax class?
When using syntax/parse, is there a good way to do something like this? (define-splicing-syntax-class options (pattern (~seq (~or (~optional (~seq (~and #:a a?))) (~optional (~seq (~and #:b b?))) (~optional (~seq (~and #:c c?))) (~optional (~seq (~and #:d d? ...) #:attr a/b #'(a? b?) #:attr c/d #'(c? d?))) When using the above syntax class to parse #'(#:a #:d #:b), then the a/b attribute should be #'(#:a #:b) and the c/d attribute should be #'(#:d). However, this doesn't work, of course, because if one of the options isn't defined, the attribute will be #f, and the attribute binding will fail. I can get around that by doing something like this: (define-splicing-syntax-class options (pattern (~seq (~or (~optional (~seq (~and #:a a?))) (~optional (~seq (~and #:b b?))) (~optional (~seq (~and #:c c?))) (~optional (~seq (~and #:d d? ...) #:attr a/b #`(#,@(if (attribute a?) #'(a?) #'()) #,@(if (attribute b?) #'(b?) #'())) #:attr c/d #`(#,@(if (attribute c?) #'(c?) #'()) #,@(if (attribute d?) #'(d?) #'() But that's rather long-winded and verbose. Even better would be a way to group the clauses within the pattern, something like this: (define-splicing-syntax-class options (pattern (~seq (~or (~and (~seq (~optional (~seq (~and #:a a?))) (~optional (~seq (~and #:b b? a/b) (~and (~seq (~optional (~seq (~and #:c c?))) (~optional (~seq (~and #:d d? c/d)) ...))) But that obviously doesn't work, and I'm not sure what it would do even if it compiled. Anyway, is there a more concise way to do this? I know it's relatively easy using `template` from syntax/parse/experimental/template, but this is going into the Typed Racket code, so we're intentionally avoiding a dependency on that. Alexis -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Simple Interdependent Units?
On May 26, 2015, at 1:10 AM, Michael Tiedtke wrote: Sorry, ut I call it a workaround. Please read up on programming language design. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] exn-string
I think user-friendly 500 page should be designed separately just as web devs do for 404 page. In practice, a user happens to meet an uncaught runtime exception, and he's browsing a buggy website, perhaps he do not have the will to report the problem, nor the way to report it. Finally, devs will fix it certainly by checking a place, say, logging system, where saved this exception rather than asking user for the screen snapshot. So I think it's devs' fault if they forget to hide their exceptions. This situation should never happen in a high-value project. On Mon, May 25, 2015 at 11:16 PM, Greg Hendershott greghendersh...@gmail.com wrote: Maybe I'm over-thinking this and/or misunderstanding the use case, but: Should there maybe be a parameter to control whether exn-string returns anything interesting? And, should it be #f by default? Roughly, for example: ;; When current-exn-string-enabled? is #f -- the default -- ;; exn-string simply returns error. ;; ;; (The idea here is that net apps shouldn't provide this information ;; by default, exn-string is probably being used to provide debug ;; info, and this should be enabled intentionally not by default.) (define current-exn-string-enabled? (make-parameter #f)) ;; exn-string : (or/c exn any) - string (define (exn-string exn) (cond [(not (current-exn-string-enabled?)) error] [(exn? exn) (parameterize ([current-error-port (open-output-string)]) ((error-display-handler) (exn-message exn) exn) (get-output-string (current-error-port)))] [else (format ~s\n exn Admittedly, just because there's a switch to turn it on and off, doesn't mean people will use it. (Source: Use the web for a week and encounter .NET apps deployed to show debug stack traces on error.) But there should be a switch, so that people can forget to use it. :) Admittedly, most Racket web apps are probably not high-value targets, today. But they ought to be someday, so why not plan for that? Again, I'm sorry if I'm over-thinking this. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] exn-string
For the purposes of the Web server, I don't think that's the right thing to do. The right thing to do if you don't like the error display is to change the arguments to #:servlet-loading-responder and #:servlet-responder to print less, or just put with-handlers in your servlet and do something else. Jay On Tue, May 26, 2015 at 1:39 PM, Tony Garnock-Jones to...@ccs.neu.edu wrote: On 05/25/2015 11:16 AM, Greg Hendershott wrote: Should there maybe be a parameter to control whether exn-string returns anything interesting? And, should it be #f by default? That's an interesting idea. I know of examples where Racket error reports have disclosed sensitive information. Such mistakes can be extremely subtle and difficult to anticipate, and even skilled, experienced engineers make them. Perhaps, if a parameter is a good idea (I'm not sure it is), when it is #f, exn-string could yield an instructive message such as #error redacted to avoid accidental information leak; see documentation for current-exn-string-enabled? plus suitable RED FONT DANGER TEXT in the documentation making it clear to users that they should think about the contexts in which the resulting strings will be published. Tony -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- Jay McCarthy http://jeapostrophe.github.io Wherefore, be not weary in well-doing, for ye are laying the foundation of a great work. And out of small things proceedeth that which is great. - DC 64:33 -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] exn-string
Amen On Tuesday, May 26, 2015, WarGrey Gyoudmon Ju juzhenli...@gmail.com wrote: I think user-friendly 500 page should be designed separately just as web devs do for 404 page. In practice, a user happens to meet an uncaught runtime exception, and he's browsing a buggy website, perhaps he do not have the will to report the problem, nor the way to report it. Finally, devs will fix it certainly by checking a place, say, logging system, where saved this exception rather than asking user for the screen snapshot. So I think it's devs' fault if they forget to hide their exceptions. This situation should never happen in a high-value project. On Mon, May 25, 2015 at 11:16 PM, Greg Hendershott greghendersh...@gmail.com javascript:_e(%7B%7D,'cvml','greghendersh...@gmail.com'); wrote: Maybe I'm over-thinking this and/or misunderstanding the use case, but: Should there maybe be a parameter to control whether exn-string returns anything interesting? And, should it be #f by default? Roughly, for example: ;; When current-exn-string-enabled? is #f -- the default -- ;; exn-string simply returns error. ;; ;; (The idea here is that net apps shouldn't provide this information ;; by default, exn-string is probably being used to provide debug ;; info, and this should be enabled intentionally not by default.) (define current-exn-string-enabled? (make-parameter #f)) ;; exn-string : (or/c exn any) - string (define (exn-string exn) (cond [(not (current-exn-string-enabled?)) error] [(exn? exn) (parameterize ([current-error-port (open-output-string)]) ((error-display-handler) (exn-message exn) exn) (get-output-string (current-error-port)))] [else (format ~s\n exn Admittedly, just because there's a switch to turn it on and off, doesn't mean people will use it. (Source: Use the web for a week and encounter .NET apps deployed to show debug stack traces on error.) But there should be a switch, so that people can forget to use it. :) Admittedly, most Racket web apps are probably not high-value targets, today. But they ought to be someday, so why not plan for that? Again, I'm sorry if I'm over-thinking this. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com javascript:_e(%7B%7D,'cvml','racket-users%2bunsubscr...@googlegroups.com'); . For more options, visit https://groups.google.com/d/optout. -- Jay McCarthy http://jeapostrophe.github.io Wherefore, be not weary in well-doing, for ye are laying the foundation of a great work. And out of small things proceedeth that which is great. - DC 64:33 -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Simple Interdependent Units?
Il giorno 26/mag/2015, alle ore 17.11, Matthias Felleisen ha scritto: On May 26, 2015, at 11:00 AM, Michael Tiedtke michael.tied...@o2online.de wrote: Il giorno 26/mag/2015, alle ore 14.17, Matthias Felleisen ha scritto: On May 26, 2015, at 1:10 AM, Michael Tiedtke wrote: Sorry, ut I call it a workaround. Please read up on programming language design. I consider the term programming language to be some kind of marketing label. Codings systems and their abstraction sometimes even capture concepts ... othertimes it's syntactic sugar. Please read up on programming language design. I am sorry for repeating myself. Yes, they all start out with maths but I would base it on music with repeat instead of loop just to eventually see a lot of playing cards on my virtual music rack. ;-) Well strings might be useful, too. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Flower Garden: Open Flowers '[1 1]
This is a maintenance release. It's on PLaneT, too. But I can't load it ... http://planet.racket-lang.org/display.ss?package=Open%20Flowers.pltowner=mti -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. Open Flowers.plt Description: Binary data -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. Title: README README Table of Contents 1 Open Flowers (Revision '[1 1]) 2 Description Rules 3 NaL (Not a License) 4 Technical Note: 5 Source Tree Layout 6 Sketch: Object Relations / Data Structure 7 Sketch: Class Hierarchy 8 Message Passing (see Open Flowers.rkt) 8.1 Protocol: Game Rules 8.2 Protocol: Other Program Actions (see also Parallel Objects) 8.3 Protocol: Layout 8.4 Protocol: Stateful Objects 9 Description of the User Interaction 10 Parallel Objects 11 Event Handling 12 Animations 13 Bugs and Maintenance 1 Open Flowers (Revision '[1 1]) This is the message passing approach to the patience solitaire game Flower Garden. This is the variant Flower Venus Garden with Laughing Flowers based on a relaxed ruleset. You can move only one card at time but from anywhere to anywhere. Sequences in the flower beds have to be build by suit. The foundations are built from ace to king but cards can be moved back into the game. You can double click a card and if possible it will find its place in the foundations. You can place up to sixteen cards in the bouquet. There is a good chance of winning the game. (The layout of the bouquet, i.e. the reserve of cards at the bottom of the table is done automatically but only after a card has been moved successfully. Rethinking and correcting this is left as exercise for the interested player.) 2 Description Rules One deck of 52 cards. from wikipedia Thirty-six cards are dealt in to six columns, each containing six cards. The columns are called the "flower beds" and the entire tableau is sometimes called "the garden." The sixteen leftover cards become the reserve, or "the bouquet." The top cards of each flower-bed and all of the cards in the bouquet are available for play. Cards can only be moved one at a time and can be built either on the foundations or on the other flower beds. The foundations are built up by suit, from Ace to King (a general idea of the game is to release the aces first). The cards in the garden, on the other hand, can be built down regardless of suit and any empty flower bed can be filled with any card. The cards in the bouquet can be used to aid in building, be put into the foundations, or fill an empty flower bed. The game is won when all cards end up in the foundations. end from wikipedia 3 NaL (Not a License) This is free source code - free as in "free like a bird". This is open source and marketing (which is a little bit like gardening): if someone gives you a pen at no cost and you have to refill it to write down you're favourite poem with it and someone else sings it and the producer of that song makes a whole lot of money with it then never forget: they could have used any pen to do the job. Don't break my pencils! 4 Technical Note: While it is written in a rather traditional way without mixins, traits or an emphasis on surrogates it might contain ideas, concepts and terms that go beyond today's message passing "customs". A new message passing primitive "broadcast" and the term hub for certain classes are consequences of thinking about the future of message passing, parallel objects and one new program code abstraction system "to rule them all" especially when it comes to open source and the user's ability to adapt and program the shiny some thousand money units worth machine in front of him. From LISP machines to BSD to Mach message passing microkernel to NextStep to but that is far away: for me it was from QBASIC to RISC assembler to NetBeans to Dr. Racket to whatever comes in handy. 5 Source Tree Layout This implementation of Flower Garden started as one file and the one file approach ended at about 1300 lines of text. Then some parts have been cut out and are now called sections and the whole was renamed "Open Flowers". Afterwards with features like the hint system and additional animations the complexity has risen as have the prerequisites on the side of the programmer to substantially change the program. /Open Flowers/README.txt This little text. /Open FLowers/info.rkt PLT software package information. /Open Flowers/Open Flowers.rkt: Classes: stack and subclasses, garden (program action
Re: [racket-users] exn-string
I was thinking the parameter could be a handy runtime switch, defaulting to safe. However realistically there's probably a lot of other ground to cover when it comes to debug vs. production deployments. Maybe this needs a more comprehensive approach than nibbling away one switch at a time. Maybe a doc warning is sufficient: It is probably unwise to put this information in a network response (like a web page) in production. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] Generic collections in Racket
Alexis, think of a lazy sequence as something that the rest of the program will explore. In addition to a GUI-based exploration, I would love to see a programmatic one. Imagine (explore-lazy lazy-sequence:exp strictness-pattern:exp) where (the value of) strictness-pattern is a function that pokes around lazy-sequence and displays. You could provide default strictness-pattern values and you could even provide strictness-patterns that dump values into a scrollable snip. But others could program their own strictness-patterns. The key would be to keep it simple. I've thought about this some more since you sent me this message, and I've come up with a few potentially interesting ideas for inspecting sequence types. I may try and implement some of them to play with that idea. To put it simply, I think it would be helpful to allow sequences to expose some information about themselves through optional method implementations that would be displayed and organized via inspection methods. I've already tried something like that in the form of `known-finite?` from gen:countable, and it would certainly be possible to include some additional methods for extracting sequence metadata. It might even be possible to use some of that metadata to produce a sequence-custom-write structure type property for default printing of sequence, similar to the property already exposed for contracts. Note that contracts for lazy sequences could also check via strictness-patterns and memoize the exploration path. If the rest of the program re-explores it's cached in the proxy and if it goes beyond that exploration, consider it a contract violation. I will note here that Racket streams automatically perform memoization, so once a stream has been evaluated, its elements are automatically cached. This itself has its tradeoffs (forcing the same sequence twice for the side-effects won't work), but it's probably what would be desired in the large majority of cases. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] exn-string
On 05/25/2015 11:16 AM, Greg Hendershott wrote: Should there maybe be a parameter to control whether exn-string returns anything interesting? And, should it be #f by default? That's an interesting idea. I know of examples where Racket error reports have disclosed sensitive information. Such mistakes can be extremely subtle and difficult to anticipate, and even skilled, experienced engineers make them. Perhaps, if a parameter is a good idea (I'm not sure it is), when it is #f, exn-string could yield an instructive message such as #error redacted to avoid accidental information leak; see documentation for current-exn-string-enabled? plus suitable RED FONT DANGER TEXT in the documentation making it clear to users that they should think about the contexts in which the resulting strings will be published. Tony -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
