So what I want to do is click on a button in Winforms ( C# ), and it would run a task in a library written in F#. I am using .Net 5.0. I need it to run on a separate thread so it doesn't make the form freeze. It seems like there are a few directions I could go in - but I am leaning more towards a functional programming approach - trying to move away from OOP where possible.
I am thinking:
send the background worker object into the library function ( doesn't seem like a good approach )
Implement observer pattern. Something like http://www.fssnip.net/7j/title/Observer-pattern
Use Reactive Extensions? https://github.com/dotnet/reactive
Something else?
I'm not sure what direction people would take here. I have read somewhere that if you use events there is an issue with memory leaking.
Related
i am making business card studio(Editor) for web to print solution. and some peoples told me that using mxml is harmful for performance of software so that just use action-script instead of using flex mxml. So I am pretty confused that what to do ?
ActionScript is quicker than MXML, but for what you're going to do, you're trading speed for convenience - MXML comes with all the different UI classes (List, Scrollbars etc) already there; in pure AS3, you'd have to roll your own, or use something like MinimalComps: http://www.minimalcomps.com/
In any case, for what you're doing, performance doesn't matter (as long as it's not terrible :D) - a business card editor doesn't need to run at 60fps, so just use what you're familiar with/is the most convenient.
I'm trying to find a straightforward way to consume arbitrary iOS libraries from MonoTouch. At the moment, I need this calendar functionality, but the question applies to any such component.
I've read the Xamarin article on creating iOS bindings, but the process of building these bindings looks so complex (and tedious and likely error prone) that I think it would actually be easier for me to re-implement the given functionality in C# from scratch than it would to go through this process. Creating these bindings would require a deep dive into ObjectiveC, and I'm using Xamarin precisely so I don't have to do that.
As it stands, I am torn because I really want the ability to access some iOS libs, but don't have the time to master this process enough to create these bindings. Is there any other way to access these libraries?
(I wonder if there is or could be any sort of automated binding generator? It seems to me that 95% of the work is boilerplate translation of ObjectiveC headers to C# idioms, and an automated tool could do this, and then the final tweaking could be done by hand.)
You can:
Consume the ones that are already bound: you can find many on github, in particular in monotouch-bindings, and in the (just announced) Xamarin's Components Store;
Bind them yourself. That does require some Objective-C knowledge. Some tools/scripts exists but, in the end, the manual by hand editing is where the Objective-C knowledge is needed. There are general unit test (e.g. for Touch.Unit) that you can re-use that will dramatically reduce the number of bugs in them (blog post will be coming up soon to describe them in details).
Convert (or write from scratch) some into C# components;
I am currently working on an F# project that contains many parallel calculations. As being bound to the trimmed .Net 4 Silverlight Framework (because of the required Silverlight compatibility) I cannot use the available .Net implmenetations and may only use the Monitor object and simple locking by using the lock Keyword.
Do you have any idea how a Shared-Exclusive lock implementation for F# might be desigend best?
I did some functional programming before but haven't concentrated on doing that parallel stuff (yet).
I'm not quite sure what exactly you need - if you need standard mutual exclusion, then the lock function is available in the Silverlight version of F# runtime.
If you need something more complex (such as multiple readers, single writer), then you can rewrite your code to use F# agents and solve the problem more elegantly. If you can add more details about the higher-level structure of your code, then someone can post an example how to solve your particular problem.
Anyway, the following SO answer shows how to write a reusable agent for multiple readers/single writer:
Implement CCR Interleave Arbiter in F#
As mentioned in the comment, you should probably try to avoid writing locks and low-level synchronization primitives explicitly, as this is a source of infinite number of bugs. F# agents give you a higher-level abstraction that is easier to use.
Theres an excellent chapter on this in Expert F# 2.0, Chapter 13 Reactive, Asynchronous, and Parallel Programming.
See example 13.13 shows a nice Request gate, something similar may be of use.
I'm working on Windows XP/Delphi 7. I need to add some procedures (or functions) inside a program that is running, and I do not want to re-compile it once again after I finished it.
I just have a host application with 5 functions to send different types of alarms, but there are other new alarm types, so I have to do new functions to send those alarms, but I should not re-build the host application. I have a class named TAlarmManager that it's invoked calling those functions.
Maybe a plugin?? OK, but how can I "insert" new functions??? Tutorial, manual, book, etc.. for learning about this, or any advice on how to do this???
I have studied plugins (I'm totally new on this theme), but no one "talks" about adding functions to a host application. It seems to me that plugins add functionality from itself, I mean, they have been developed with self code to do something, not to "add" code to the host application... How can I do this??
For the technical side: How does the Delphi IDE do it? That would be the first place for me to look.
To understand plugins, you must understand that you can't add new functions. You could but since the old code doesn't know how to call it, they wouldn't be called.
So what you do is you add a "register" or "start" function to your plugin. That start function gets a data structure as parameter which it can examine or extend. In your case, that would be the list of alarms. Alarms always work the same (my guess), so it can add additional alarms.
The main code will then, after registering all plugins, just walk over the list of alarms and invoke the standard alarm function on each of them. It no longer cares where each alarm comes from and what it really does.
The key here: You need to define an interface which both sides subscribe to. The main code calls the interface functions and your plugin code implements them.
Another option available is to use a scripting component to your project. One which works quite well is PascalScript. This would allow you to load external scripts after the fact and then run them as needed to interact with your application. As Aaron suggested you will also need to still provide an interface of some sort for your script to interact with your application.
See also Plugins system for Delphi application - bpl vs dll? here on Stackoverflow.
I'm not quite sure what you mean by "alarms", so I'm making a couple of assumptions.
1) If you don't need additional code for the alarms, I would try to make them data driven. Keep the different kinds of alarms in a database or configuration file, which makes it easy to update applications in the field without recompiling or reinstalling.
2) If you need special code for each alarm, you could use run time packages as plug-ins for your application. Search for Delphi runtime packages to get some ideas and tutorials. Here are a couple of links I found:
http://delphi.wikia.com/wiki/Creating_Packages
http://delphi.about.com/od/objectpascalide/a/bpl_vs_dll.htm
3) Scripting, as skamradt already mentioned. If it makes sense for your application, this could also let your customers write their own add-on functionality without requiring a recompile on your part.
You almost definitely want to use Pascalscript, as skamradt suggests. You should start here, and seriously consider this option. There are many possibilities that come out of being able to serialize live code as text. The only downside is possibly speed of execution, but that may not matter for your application domain. I would have upvoted skamradt, but I don't have enough reputation to upvote :)
Some time ago I was looking at a situation sort of like what you're describing.
My answer was .DLLs. I put the variable code in a .DLL that was dynamically loaded, the name specified in a configuration file. I passed in a record containing everything I knew about the situation.
In my case there was only a success/fail return and no screen output, this worked quite well. (It was commanding a piece of machinery.)
This sounds like a place where a scripting language or "Domain Specific Language" may make sense. There are several approaches to this:
Implement alarm functions in VBscript (.vbs files written in notepad) that accesses your Delphi code via COM API. Using the COM API gives you access to a large range of programming tools for writing functions, including Delphi. This is the most clumsy solution, but easiest to do. It may also be a benefit to your sales process, and it is always good to think about how to sell things.
Implement your own function language in Delphi. This way you can make it so easy, that your endusers can write their own alarm functions. If you do it as an expression evaluator, you can write an alarm as 2*T1>T2. There are several expression evaluators out there, and you can also write your own if they don't match your needs.
Use a predefined programming language inside your Delphi application, for instance, "Pascal Script", see http://www.remobjects.com/ps.aspx
You should take a look at PaxCompiler, like PascalScript it allows to load scripts, but you can even precompile them before for more performance. Look at the demos section for the solution of your problem.
As a side note, the web page really looks bad, but the package is really powerful and stable.
I think that the scripting solution it's good for this situation.
There are many scripting packages that you can evaluate:
Context Scripting Suite
Fast Script
RemObjects Pascal Script
TMS Scripter Studio
paxScript
Other packages that you can find on Torry, DSP, VClComponents,...
Regards.
I am building a site that has a lot in common with a person-on-person chess site. I was thinking of using Rails for the front-end(User Registration, Navigation, etc) and something like Scala or Erlang for the engine(Game state and maybe AI). I was wondering -
Is this a good situation to use that type of design?
How exactly would be best to divide up the functionality between the components?
How would they best communicate with each other?
I'm open to any technologies or ideas.
If you're using Rails for the front-end, why not use Ruby?
If you like the idea of using Scala, why not use Lift for the front-end?
Chess is turn-based, and has a very simple board that can be handled with HTML and/or Javascript enhancements - so the basic model flows quite nicely with existing web frameworks.
With this in mind, Rails is a great choice for creating a web-based application. Rails is not just limited to crud applications, and in fact I think can write your entire app in Rails/Ruby - you don't really need to have an external engine.
Within the browser space, polling for turn updates can be done using XMLHttpRequest and a database can maintain the current game and turn state.
Looks like a simple Lift application to me. I'm not experienced with Lift, mind you, but it doesn't seem particularly more complex than the chat application that is so often demoed.
I would start by reading http://www.htdp.org/ How to Design Programs. The questions you have asked are very broad and difficult to answer without prefixing statements with "I believe that..."
I would code it in clojure (but that's just me).
I'm currently developing a suite of online games, using Scala. It's been absolutely fantastic - my game logic is much easier to get right with the static typing etc, and dealing with server/client protocol (a flash client, in this case) is made simpler via the use of Google Protocol Buffers.
If you're a huge fan of RoR, by all means use that. I think most statically typed languages are terrible to program websites in (Java, I'm looking at you here), but Scala gets rid of 90% of the pain, and gives even more safety.
Of course, it might not be your cup of tea. But I'd try just doing the entire thing in Scala, and adding another layer if that doesn't quite do it for you.
For question 1 Yes
And for 2 and 3 you need to give more information in order to get an answer that could help you.
Now I'm doing something like you but for the front end I'm going to use Grails. The reason are very simple: I like Grails, Scala and I want to mix them :)