I just have started to learn CLIPS. I have a question that I didn't find any accurate answer for it on the web or in the CLIPS' ReferenceManual.
How (which command use) to remove specific activation from agenda? I use CLIPSIDE, and if you go to the top tab and choose "Browse" => "Agenda Manager", you can remove specific activation from agenda. But i didn't find any command, which could do the same thing?
There is no corresponding command for removing a specific activation from the agenda. That particular piece of functionality was included with the IDEs when first created over thirty years ago because of the belief that it might be useful when debugging. Since it hasn't turned out to be particularly useful, it was removed from the rewritten macOS IDE in CLIPS 6.3 and the rewritten Windows IDE in CLIPS 6.4.
I am wondering why DataRecevied (or ReadChar()) haven't been implemented in Mono. I couldn't find anything on the notes for the 3.x beta and both are old known issues (The first is even mentioned on the Mono documentation) and seemingly easy to fix.
There are even "workarounds" such as this that feel not-so-hard to integrate.
Is there any solid reason for it being standing so long? Does nobody actually care? Is Mono not really under active development? The 3.x beta would point otherwise...
Mono is under active development. Xamarin is the main company behind it (as in, number of contributions compared to other companies).
This means, of course, that bugs/features that the Mobile offerings use get prioritized faster than other things. Do you have a company that heavily uses the System.IO.Ports namespace? Then consider contributing to it, it hasn't received much love lately.
PS: You do not even need to code to start contributing. For example, first thing you could do is review contributions from others, like this one.
I am playing around with SystemConfiguration on Mac OS X and in Technical Q&A QA1165 the sample code uses a macro MoreSCError that is supposedly define in the sample program MoreSCF - I can't find this sample code in the Xcode documentation or on the Apple Developer Site.
Does anyone know where I might find the code?
I'm looking at MoreSCF.c on my machine here and it's really old. The version I have is "revision 1.5" and dates from 2002.
The fact you can't easily find it on Apple's Developer Site (or Google for that matter), probably indicates that Apple would rather developers not use this code. System Configuration framework is still very much supported on the Macintosh, but I can't think of what has replaced MoreSCF (in terms of sample code) off the top of my head. It would likely be worth your file to find the MoreSCF replacement and work with that.
But... to help you out, I'm making the MoreSCF.h and MoreSCF.c sample code that I have available via PasteBin. I'll set it to expire in a month so if you don't retrieve it before the end of the 30 days, you'll be S.O.L. And even though this is public, redistributable source code, if somebody asks me to remove the links (and especially if they speak up with what the newer source or sample project is), I'll remove it prior to 30 days. These two files come out of the MoreSCF project, which has ~10 or so various C files for making System Configuration stuff easier.
Here are the links:
MoreSCF.h
MoreSCF.c
you can find your required source code here
https://developer.apple.com/legacy/library/samplecode/MoreSCF/Introduction/Intro.html
Bugs can be difficult enough to resolve when they're your (or a coworker's) fault. However, we all know that the technology we use to implement our programs is written by infallible people such as ourselves. So it stands to reason that some people have been affected by bugs in the implementation of the tools they used.
So, have you found a bug in your program that was caused by a widespread underlying technology, such as a programming language or framework? If so, did it fail with some indication, or did it silently overwrite some data? How difficult was it to debug? Did it cause a potential security vulnerability? Were you able to contact the provider and confirm that it was fixed (or fix it yourself)?
Here are some of the worst (in my opinion) technologies to have a bug in (especially one that fails silently):
Programming language
Concurrency framework
Remote API
Database
I deal with one on a daily basis called Internet Explorer.
To be fair though, there are lots of bugs in all of the browsers. I have filed several bugs for Firefox as well, and just the other day I found a strange case where the border doesn't take padding into consideration.
This is a good argument for writing lots of unit tests. If you upgrade your platform to a newer version that has some new bug, hopefully you have a test that reveals the bug
in one case I had, the vendor was working on a brand new API. They were not ready to release the new API, but they were not very keen to fix the bug in the old one either as they considered it dead from a $$ perspective.
A colleague once stumbled across a bug in the Jikes Java compiler. He had something like this:
if (condition)
{
}
else
{
System.out.println("Code that does stuff.");
}
He hadn't intended to leave the top block empty permanently, but just had it that way during development. He discovered that the condition was ignored unless he put a comment in that block so that it was no longer empty.
During my time developing (mostly) with Java I've run into bugs in the following components:
Java compiler
This actually happened several times. Usually we found that ecj (the Eclipse compiler) and javac (the Sun compiler) disagree about the validity of some Java code. Usually I enter bug reports for both systems, one of them gets accepted and the other one is closed as invalid.
Database engine
Those are very rare and very, very nasty, because no one expects the DB itself to have a bug. In our case it was an old product (the bug was already fixed in a newer release) that accepted values in a field that were not within the defined range (similar to having a NOT NULL field containing NULL)
JDBC driver
There were several bug fixes to a JDBC driver due to a project I've been working on. The bug fixes ranged from trivial ("why is there debug output in the production release?") to might-not-even-be-a-real-bug ("you can easily safe one roundtrip per statement by doing that-and-that").
JVM implementations
those are hard to diagnose and often present themselves as effectively random crashes on one JVM and stable operation on another one. We temporarily switched JVM vendor several times due to things like this.
Each time it took quite some time (and usually the involvement of the vendor of the component) before I actually believed it was a bug in that component.
And yes: the cases of false positives (i.e. the bug was actually in my/our code) were orders of magnitude more common.
The only place where bugs in the third-party component are kind-of expected seem to be web browsers. Almost no one questions you when you say "that's a bug in <insert buggy browser of the week>, we need to work around it like this ...".
I guess almost anyone who has programmed JavaScript with Internet Explorer has found a bug in their program which was caused by a widespread underlying technology.
The indication of failure is the blue "e" on your Windows desktop.
The first that comes to mind was with version 1 of the .NET Framework; for some reason, Random.NextDouble() method never produced a value greater than 0.5. I was completely baffled, and having run a test apps that called the method thousands and thousands of times, I had to presume it was a bug and work round it.
Never did find out what the cause was...
I've run into something with the gcc 4.4.0 but as the product I'm currently working on is still pre-alpha, it was fairly easy to repair locally. Hopefully they'll fix it soon.
i found a very strange bug in gcc on Mipsel (openwrt). We was testing a small app (about 3K sloc) that give me sigsev even if the code was corrected in theory.
I don't know the detail of the bug (and I don't have that code anymore) but change the gcc version from 4.1 to 3.6 solve the problem.
I'd like to start experimenting with Cocoa and programming for Mac OSX. I'm not terribly concerned with Objective C syntax/constructs/bheaviors at this point, but more curious as to an efficient setup on in terms of an editor and/or IDE that will get me going quickly. Is there any IDE even remotely similar to Visual Studio (since that's where I've spent most of my time over the last 7 years) in terms of it's solution/project concept? Any other tools, tips, suggestions and/or resources to get up and experimenting quickly?
I'd like to avoid a lot of the intro stuff and get into things like "If you want to create an Mac desktop application, you can use Acme IDE and set up your project like this."
I was afraid Xcode was going to be the answer! :P I tried playing around with that -- literally just getting it off the DVD and just diving in with no idea what to expect (before I even knew that you used Objective C as the language). I figured, the wise guy that I am, that I could just sort of fumble around and get a simple app working ... wrong.
#Andrew - Thanks for the insight on those config settings. Based on my Xcode first impression, I think those may help.
I'd suggest you pick a fun little product and dive in. If you're looking for a book I'd suggest Cocoa Programming for Max OSX which is a very good introduction both to Objective-C and Cocoa.
XCode is pretty much the de facto IDE and free with OSX. It should be on your original install DVD. It's good but not as good as Visual Studio (sorry, it's really not).
As a long-time VS user I found the default XCode config a little odd and hard to adjust to, particularly the way a new floating window would open for every sourcefile. Some tweaks I found particularly helpful;
Settings/General -> All-In-One (unifies editor/debugger window)
Settings/General -> Open counterparts in same editor (single-window edit)
Settings/Debugging - "In Editor Debugger Controls"
Settings/Debugging - "Auto Clear Debug Console"
Settings/Key-binding - lots of binding to match VS (Ctrl+F5/Shift+F5,Shift+Home, Shift+End etc)
I find the debugger has some annoying issues such as breakpoints not correctly mapping to lines and exceptions aren't immediately trapped by the debugger. Nothing deal-breaking but a bit cumbersome.
I would recommend that you make use of the new property syntax that was introduced for Objective-C 2.0. They make for a heck of a lot less typing in many many places. They're limited to OSX 10.5 only though (yeah, language features are tied to OS versions which is a bit odd).
Also don't be fooled into downplaying the differences between C/C++ and Objective-C. They're very much related but ARE different languages. Try and start Objective-C without thinking about how you'd do X,Y,Z in C/C++. It'll make it a lot easier.
The first document to read and digest is the Mem management guide, understand this before moving on. This is a great guide to objective-c too. Infact the developer site at Apple is very good - but you would probably want to read the Hillegas book first.
In regards to Xcode vs Visual Studio - they are different. I wouldn't say one is better than the other - Windows developers come over from VS and expect it to be the same. This is just an arrogant attitude and please don't fall into this crowd. Having used VS since the AppStudio days and Xcode for a year or so now, both have strengths and weaknesses. Xcode is something that out of the box (and especially when coming from VS) doesn't seem that good, but once you start using and understanding it - it becomes very powerful.
Also, there are a lot more tools included with Xcode et al, such as Instruments and Shark that you simply can't get with VS, unless you open your wallet, and even then IMHO aren't as good.
Anyway, good luck. I still enjoy C#, but Objective-C/Cocoa somehow makes programming fun again once you get into it...
Don't bother digging up your OSX DVD as they've released a new version (3.1) of XCode since then.
First, you'll want to join Apple Developer Connection (it's free, and you need it to access their version of MSDN) - it uses your Apple ID so if you've ever had one for the itunes store etc, it's that same username/password
Once you've done that, click on downloads, then click on developer tools, to view this page, and go for the XCode 3.1 Developer DVD
One other suggestion: If you have feature or enhancement requests, or bugs that you've run into, be sure to file them at Apple's Bug Reporter. It's the best way for developers to communicate their needs to Apple, because every issue is tracked through the system.
You might try the demo of textmate and see how you like it for working with objective-c or any other type of text really. It will import xcode project settings so you can still compile and run from textmate rather than having to go back to xcode.
Xcode is the standard for editing source files, though you can use another editor in conjunction with the command line xcodebuild tool if you really want. I used Vim for all my Cocoa editing before finally giving in to Xcode. It's not the greatest IDE in the world, but it gets the job done, and the recent 3.x releases have had some nice improvements.
The real power tool of Cocoa development is Interface Builder. IB does not generate source code like many UI tools. Instead it manipulates real Cocoa views, controls, and objects which it then bundles into an archive (nib) that is loaded by your program at runtime. Most Cocoa programs use at least one nib file, and often many more.
No matter what IDE/editor combination you choose for hacking on source files, I recommend using IB where you can. Even if you're not a fan of other UI layout/generation tools, I suggest keeping an open mind, giving "the Cocoa way" a chance and at least learning what Interface Builder can do for your development process.
AFAIK, pretty much every OS X developer uses Xcode.
That, and Interface Builder for creating the GUIs.
FWIW, try to get hold of a copy of Hillegas's book, as it's a great introductory tutorial, and the reference Docs Apple provides really aren't. (They are generally very good reference docs, however).
Cocoa is huge. The hardest part of learning how to write apps on Mac is learning Cocoa. By the way. You do not need to know ObjC (though it helps tons). You can write Cocoa apps with Python or Ruby (right in the IDE).
I agree VS is a better IDE then Xcode. But if you throw in Interface Builder and all the other tools, I'm not so sure. Mac development is not about 1 giant IDE for everything. But VS is "kinder" on the developer then Xcode is.
Also if you want to do cross platform apps look at RealBasic. A fine tool (Basic though. But it runs on Linux too.) You'd be surprised how many Mac apps are written with RB.
I've heard the books currently out there are pretty out of date. The whole ecosystem seems to evolve very fast with dramatic changes made in every OS release.
He wrote a tutorial which pulls together some Apple documentation and other tutorials which should get you started. I think it covers the basics of using the IDE, writing simple apps, and then goes on to more advanced stuff.
I've been dabbling in Cocoa for the past couple years, and recently picked up Fritz Anderson's "Xcode 3 Unleashed." Highly recommended for getting into Xcode — especially with some of the big changes 3.0/Leopard brought.
Don't forget Hillegass' defacto Cocoa bible, "Cocoa Programming for Mac OS X - Third Edition."
#peter I don't know why you had trouble with getting a simple app working, right off the bat without doing anything your app gets a lot of benefits from the Cocoa framework. If you mean you were trying to do stuff like connect a button to an action and have it print a alert on screen or something like that then yes I could see where your going with it being difficult.
The problem for me starting with Cocoa many years back is that it was so different from anything else that it had a little bit of a learning curve. Whereas many other systems are compile time oriented Cocoa is very dynamic and runtime oriented. Once you get past learning how actions hook up to classes it just becomes a matter of learning how the Cocoa frameworks work.