AnyLogic, Condition to check if an attractor is occupied - if-statement

I am new to AnyLogic and am looking to find a way of checking if an attractor is occupied.
I have a Jib Crane that is supposed to sort items to four different attractors based on whether or not they are occupied.
So far I am using a SelectOutput5 block with randomTrue(0.25) followed by four restricted areas, but I hope to be able to select the output based on whether or not the attractor is empty, (or if the restricted area is empty), whichever is easier.
Any help would be much appreciated.

You cannot check this, attractors are purely visual constructs for positions.
If you want this, you need to add this yourself. One way is to create an agent type with a parameter myAttractor linking to the actual attractor and the agent managing the state "taken" / "free".
But it is entirely manual

Related

Automate sequential integer IDs without using Identity Specification?

Are there any tried/true methods of managing your own sequential integer field w/o using SQL Server's built in Identity Specification? I'm thinking this has to have been done many times over and my google skills are just failing me tonight.
My first thought is to use a separate table to manage the IDs and use a trigger on the target table to manage setting the ID. Concurrency issues are obviously important, but insert performance is not critical in this case.
And here are some gotchas I know I need to look out for:
Need to make sure the same ID isn't doled out more than once when
multiple processes run simultaneously.
Need to make sure any solution to 1) doesn't cause deadlocks
Need to make sure the trigger works properly when multiple records are
inserted in a single statement; not only for one record at a time.
Need to make sure the trigger only sets the ID when it is not already
specified.
The reason for the last bullet point (and the whole reason I want to do this without an Identity Specification field in the first place) is because I want to seed multiple environments at different starting points and I want to be able to copy data between each of them so that the ID for a given record remains the same between environments (and I have to use integers; I cannot use GUIDs).
(Also yes, I could set identity insert on/off to copy data and still use a regular Identity Specification field but then it reseeds it after every insert. I could then use DBCC CHECKIDENT to reseed it back to where it was, but I feel the risk with this solution is too great. It only takes one time for someone to make a mistake and then when we realize it, it would be a real pain to repair the data... probably enough pain that it would have made more sense just to do what I'm doing now in the first place).
SQL Server 2012 introduced the concept of a SEQUENCE database object - something like an "identity" column, but separate from a table.
You can create and use sequence from your code, you can use the values in various place, and more.
See these links for more information:
Sequence numbers (MS Docs)
CREATE SEQUENCE statement (MS Docs)
SQL Server SEQUENCE basics (Red Gate - Joe Celko)

SAS Enterprise Guide - process dependence and parallel execution

I am working on a project in SAS EG (7.1) which involves process dependence and parallel execution, as depicted below:
I have the following questions:
Is there a way to retrieve or set relations (i.e. process_C --> program_D) between the processes programmatically? The maintenance is becoming problematic with complex projects. Ideally, I would like to be able to re-create the links between processes from external table.
I start the whole process with the option “Run branch from <>” process. Let’s assume that we have only 2 processors available. Is there a way to set the order of execution between process_A, B, C? The critical path of the whole flow is “begin -> process_C -> process_D -> end” hence we would like it to start with process_C in order to ensure minimum execution time.
Thank you in advance.
For 1, I think the answer is "no", if you mean a well defined SAS programmatic method. At least for the relatively limited information and example you provide above, anyway. More might be possible with metadata server - not my area of expertise.
You can do some of this at least using scripting via Powershell or VBScript. EG's API is fairly wide open and not all that hard to use. I won't suggest how as my understanding of this is limited also, but it seems like it should be possible to do what you suggest, though probably not easy.
For your second point:
First off, EG typically runs "top to bottom" if it has no other information on how to process a particular choice. So put c->d above a/b to get it processed first.
Second, you could use conditional processing perhaps. There should be a macro variable that tells you how many cpus you have (&SYSNCPU on my machine, hopefully same on other versions). You could use that value to conditionally link to A then B as opposed to A+B simultaneously. I'm not sure how easy this would be to do in a flexible fashion, though.

Programming paradigm; wondering if rewriting/refactoring is necessary

for quite some time I've been working on an application. As programming is just a hobby this project is already taking way too long, but that's besides the point. I'm now at a point where every "problem" becomes terribly difficult to solve. And I'm thinking of refactoring the code, however that would result in a "complete" rewrite.
Let me explain the problem, and how I solved it currently. Basically I have data, and I let things to happen over this data (well I described about every program didn't I?). What happens is:
Data -> asks viewer to display -> viewer displays data based on actual data
viewer returns user input -> data -> asks "executor" to execute it -> new data
Now this used to work very well, and I was thinking originally "hey I might for example change command prompt by qt, or windows - or even take that external (C#) and simply call this program".
However as the program grew it became more and more tiresome. As the most important thing is that the data is displayed in different manners depending on what the data is and -more importantly- where it is located. So I went back to the tree & added someway to "track" what the parent-line is". Then the general viewer would search for the most specific actual widget.
It uses has a list with [location; widget] values, and finds the best matching location.
The problems starts when updating for new "data" - I have to go through all the assets - viewer, saver etc etc. Updating the check-mechanism gave me a lot of errors.. Things like "hey why is it displaying the wrong widget now again?".
Now I can completely swap this around. And instead of the tree datastructure calling to a generic viewer. I would use OO "internal" tree capabilities. The nodes would be childs (& when a new viewer or save-mechanism is needed a new child is formed).
This would remove the difficult checking mechanism, where I check the location in the tree. However it might open up a whole other can of worms.
And I'd like some comments on this? Should I keep the viewer completely separate - having difficulty checking for data? Or is the new approach better, yet it combines data & execution into a single node. (So if I wish to change from qt to say cli/C# it becomes almost impossible)
What method should I pursue in the end? Also is there something else I can do? To keep the viewer separate, yet prevent having to do checks to see what widget should be displayed?
EDIT, just to show some "code" and how my program works. Not sure if this is any good as I said already it has become quite a clusterfuck of methodologies.
It is meant to merge several "gamemaker projects" together (as GM:studio strangely lacks that feature). Gamemaker project files are simply sets of xml-files. (Main xml file with only links to other xml files, and an xml file for each resource -object, sprite, sound, room etc-). However there are some 'quirks' which make it not really possible to read with something like boost property trees or qt: 1) order of attributes/child nodes is very important at certain parts of the files. and 2) white space is often ignored however at other points it is very important to preserve it.
That being said there are also a lot of points where the node is exactly the same.. Like how a background can have <width>200</width> and a room too can have that. Yet for the user it is quite important which width he is talking about.
Anyways, so the "general viewer" (AskGUIFn) has the following typedefs to handle this:
typedef int (AskGUIFn::*MemberFn)(const GMProject::pTree& tOut, const GMProject::pTree& tIn, int) const;
typedef std::vector<std::pair<boost::regex, MemberFn> > DisplaySubMap_Ty;
typedef std::map<RESOURCE_TYPES, std::pair<DisplaySubMap_Ty, MemberFn> > DisplayMap_Ty;
Where "GMProject::pTree" is a tree node, RESOURCE_TYPES is an constant to keep track in what kind of resource I am at the moment (sprite, object etc). The "memberFn" will here simply be something that loads a widget. (Though AskGUIFn is not the only general viewer of course, this one is only opened if other "automatic" -overwrite, skip, rename- handlers have failed).
Now to show how these maps are initialized (everything in namespace "MW" is a qt widget):
AskGUIFn::DisplayMap_Ty AskGUIFn::DisplayFunctionMap_INIT() {
DisplayMap_Ty t;
DisplaySubMap_Ty tmp;
tmp.push_back(std::pair<boost::regex, AskGUIFn::MemberFn> (boost::regex("^instances "), &AskGUIFn::ExecuteFn<MW::RoomInstanceDialog>));
tmp.push_back(std::pair<boost::regex, AskGUIFn::MemberFn> (boost::regex("^code $"), &AskGUIFn::ExecuteFn<MW::RoomStringDialog>));
tmp.push_back(std::pair<boost::regex, AskGUIFn::MemberFn> (boost::regex("^(isometric|persistent|showcolour|enableViews|clearViewBackground) $"), &AskGUIFn::ExecuteFn<MW::ResourceBoolDialog>));
//etc etc etc
t[RT_ROOM] = std::pair<DisplaySubMap_Ty, MemberFn> (tmp, &AskGUIFn::ExecuteFn<MW::RoomStdDialog>);
tmp.clear();
//repeat above
t[RT_SPRITE] = std::pair<DisplaySubMap_Ty, MemberFn>(tmp, &AskGUIFn::ExecuteFn<MW::RoomStdDialog>);
//for each resource type.
Then when the tree datastructure tells the general viewer it wishes to be displayed the viewer executes the following function:
AskGUIFn::MemberFn AskGUIFn::FindFirstMatch() const {
auto map_loc(DisplayFunctionMap.find(res_type));
if (map_loc != DisplayFunctionMap.end()) {
std::string stack(CallStackSerialize());
for (auto iter(map_loc->second.first.begin()); iter != map_loc->second.first.end(); ++iter) {
if (boost::regex_search(stack, iter->first)) {
return iter->second;
}
}
return map_loc->second.second;
}
return BackupScreen;
}
And this is where the problems began to be frank. The CallStackSerialize() function depends on a call-stack.. However that call_stack is stored inside a "handler". I stored it there because everything starts FROM a handler. I'm not really sure where I ought to store this "call_stack". Introduce another object that keeps track of what's going on?
I tried going the route where I store the parent with the node itself. (Preventing the need for a call-stack). However that didn't go as well as I wished: each node simply has a vector containing its child nodes. So using pointers is out of the question to point to the parent note...
(PS: maybe I should reform this in another question..)
Refactoring/rewriting this complicated location checking mechanism out of the viewer into a dedicated class makes sense, so you can improve your solution without affecting the rest of your program. Lets call this NodeToWidgetMap.
Architecture
Seems your heading towards a Model-View-Controller architecture which is a good thing IMO. Your tree structure and its nodes are the models, where as the viewer and the "widgets" are views, and the logic selecting widgets depending on the node would be part of a controller.
The main question remains when and how you choose the widget wN for a given node N and how to store this choice.
NodeToWidgetMap: When to choose
If you can assume that wN does not change during its lifetime even though nodes are moved, you could choose it right when creating the node . Otherwise you'll need to know the location (or path through the XML) and, in consequence, find the parent of a node when requesting it.
Finding Parent Nodes
My solution would be to store pointers to instead of the node instances themselves, perhaps using boost::shared_ptr. This has drawbacks, for example copying nodes forces you to implement your own copy-constructors that uses recursion to create a deep-copy of your sub-tree. (Moving however will not affect the child nodes.)
Alternatives exist, such as keeping child nodes uptodate whenever touching the parent node respective the grandfathers vector. Or you can define a Node::findParentOf(node) function knowing that certain nodes can only (or frequently) be found as child of certain nodes. This is brute but will work reasonably well for small trees, just does not scale very well.
NodeToWidgetMap: How to choose
Try writing down the rules how to choose wN on piece of paper, perhaps just partially. Then try to translate these rules into C++. This might slightly longer in terms of code but will be easier to understand and maintain.
Your current approach is to use regular expressions for matching the XML path (stack).
My idea would be to create a lookup graph whose edges are labelled by the XML element names and whose nodes indicate which widget shall be used. This way your XML path (stack) describes a route through the graph. Then the question becomes whether to explicitly model a graph or whether a group of function calls could be used to mirror this graph.
NodeToWidgetMap: Where to store choice
Associating a unique, numeric id to each node, record the widget choice using a map from node id to widget inside the NodeToWidgetMap.
Rewriting vs Refactoring
If you rewrite you might get good leverage tieing to an existing framework such as Qt in order to focus on your program instead of rewriting the wheels. It can be easier to port a well-written program from on framework to another than to abstract around the pecularities of each platform. Qt is a nice framework for gaining experience and good understanding of the MVC-architectures.
A complete rewrite gives you a chance to rethink everything but implies the risk that you start from scratch and will be without a new version for a good amount of time. And who knows whether you will have enough time to finish? If you choose to refactor the existing structures you will improve it step by step, having a useable version after each step. But there is small risk to remain trapped in old ways of thinking, where as rewriting nearly forces you to rethink everything. So both approaches have their merits, if you enjoy programming I would rewrite. More programming, more joy.
Welcome to the world of programming!
What you describe is the typical life cycle of an application, starts as a small simple app, then it gets more and more features until it is no longer maintainable. You can't imagine how many projects I've seen in this last collapsing phase!
Do you need to refactor? Of course you do! All the time! Do you need to rewrite everything? Not so sure.
In fact the good solution is to work by cycles: you design what you need to code, you code it, you need more functionality, you design this new functionality, you refactor the code so you can integrate the new code, etc. If you don't do it like this then you will arrive to the point where its less expensive to rewrite then to refactor. Get this book: Refactoring - Martin Fowler. If you like it then get this one: Refactoring to Patterns.
As Pedro NF said, Martin Fowler "Refactoring" is the nice place to get familiar with it.
I recommend buying a copy of Robert Martins "Agile Principles, Patterns and Practices in C#" He goes over some very practical case studies that show how to overcome maintenance problems like this.

Qt C++ QTouchEvent & TouchPoint Confusion

Just trying to wrap my head around QTouchEvent. Any help/advice is appreciated.
Specifically I'm a bit confused when a touch event is fired (for e.g. TouchBegin); does this represent only one unique touch point? If so why is there a list of touch points inside QTouchEvent?
If not, is it the case that Qt will group together several TouchBegin instances that happen in a given time fraction and deliver it as one event, with the list of points encapsulated in the event? Likewise a QTouchUpdate event will contain information about several touch points that are being updated at that time?
Also I assume that;
QTouchEvent::TouchPoint::id
will remain consistent throughout TouchBegin, TouchUpdate and TouchEnd. Meaning that in different touch events if I see a point with the same id, it is the same touch point that both events are referring to. Is this assumption correct?
FYI: I've been working with TUIO for sometime, so if someone is familiar with both Qt and TUIO a comparative explanation would be much easier for me to understand. I've read through Qt documentation as well, but wasn't able to find an answer to my question.
Still I'd really appreciate any help at all.
Thank you.
How exactly the events are reported seem to differ in different platforms. If you press it with two fingers, it can start with a single touch point (TouchBegin), and immediately follow that with a new QTouchEvent with two TouchUpdate points. But it can also group two touch points into the TouchBegin QTouchEvent. But I have also witnessed two TouchBegin events, event though this is kind of forbidden (see "Touch Point Grouping" in the QTouchEvent doc).
After the begin, there are again differences in the TouchUpdates. Sometimes you always get two points (or the amount you have fingers down) even if you lift one finger. In this case the pressure is 0 for the lifted finger "id". Alternatively you'll get the amount of touchpoint ids that are actually down.
The best way to understand how these are generated is to install an eventfilter and observe the events while you press them.

How do I create "undo" in C++?

I need to create a function that undoes the previous task/addition/change. How do I do this in Borland C++?
(The program stores strings of text in a text file using "list". It is stored and then erased unless I use the save-function I've created.)
I meant creating an undo function in a simple console application by the way.
I'll give yet another answer, but I think that the coverage has been insufficient so far.
The subject is far from trivial, and googling it returns a good number of results. Many applications implement a "undo" operation, and there are many variants.
There are 2 design patterns which can help us out here:
Command: it's a reification of an action
Memento: which consists in storing state (usually implies some form of serialization)
The Command pattern is heavily used in graphic environments because there is usually various ways to accomplish an action. Think of save in Microsoft Word for example:
you can click on the save icon
you can go into File menu and click on Save
you use the shortcut, typically CTRL+S
And of course save is probably implemented in term of save as.
The advantage of the Command pattern here is twofold:
you can create a stack of objects
you can ask every object to implement an undo operation
Now, there are various issues proper to undo:
some operations cannot be undone (for example, consider rm on Linux or the empty trash bin action on Windows)
some operations are difficult to undo, or it may not be natural (you need to store some state, the object is normally destroyed but here you would need to actually store it within the command for the undo action)
generally we think of undo/redo as a stack, some software (graphics mainly) propose to undo items without actually undoing what has been done afterward, this is much more difficult to achieve, especially when the newer actions have been built on top of the to-undo one...
Because there are various problems, there are various strategies:
For a simple Command, you might consider implementing an undo (for example, adding a character can be undone by removing it)
For a more complex Command, you might consider implementing the undo as restoring the previous state (that's where Memento kick in)
If you have lots of complex Command, that could mean lots of Mementos which consumes space, you can then use an approach which consists in only memorizing one Snapshot every 10 or 20 commands, and then redoing the commands from the latest snapshot up to the undone command
In fact, you can probably mix Command and Memento at leisure, depending on the specifics of your system and thus the complexity of either.
I would only considering undoing the last action executed to begin with (using a stack of action then). The functionality of undoing whatever action the user wishes is much more complicated.
To implement Undo, you need to create an "action stack" in your application. There are two basic approaches, though:
Knowing your baseline (the last time the file was saved, or since the file was created), remember every single change that was made so that when something needs to be undone you just throw away the "top-most" item and regenerate the current view from the baseline plus all of the changes. Clicking "Redo" then just puts that item back on the stack. This has a side benefit of being able to trivially remove items anywhere in the stack without messing up other undo/redo options, although there will be special care needed to make sure that the application of "higher" states is as the user intended.
For each action, store off the change that was made to the previous state as well as the change that would be necessary to restore that previous state if you were to undo. Now when the user clicks "Undo," just do the "undo" steps. When clicking "Redo," reapply the changes that were made. In some cases the "Undo" steps will be "here's what the thing looked like before," but that can cause havoc if you want to allow users to remove items that are not on the top of the stack and then need to remove something above it.
The proper choice depends on a lot of factors, including how much data you can/will carry around. Option #1 is in some sense easier but it could become very slow to undo anything if the action stack is large.
You should check out Command Pattern.
Another reference: Using the Command pattern for undo functionality
Also see the memento pattern. Sometimes the intelligence that must go into a command to undo an operation is pretty involved. Drawing objects in a paint program for example. It can be easier just to store a memento and then restore from that memento to implement undo.
You can store snapshots of state. State is the set of data that an action can modify. When you click undo, the current state is replaced by previous. Actually it is not a trivial task, especially if the state is complex.
I've been experimenting lately on that subject. In case you don't need binary compatibility, check out https://github.com/d-led/undoredo-cpp