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I am new in doing an activity and currently, I am trying to draw one based on given description.
I enter into doubt on a particular section as I am unsure if it should be 'split'.
Under the "Employee", the given description is as follows:
Employee enter in details about physical damage and cleanliness on the
machine. For the cleanliness, there must be a statement to indicate
that the problem is no longer an issue.
As such, I use a foreach as a means to describe that there should be 2 checks - physical and cleanliness (see diagram in the link), before it moves on to the next activity under the System - for the system to record the checks.
Thus, am I on the right track? Thank you in advance for any replies.
Your example is no valid UML. In order to make it proper you need to enclose the fork/join in a expansion region like so:
A fork/join does not accept any sematic labels. They just split the control flow into several parallel ones which join at the end.
However, this still seems odd since you would probably have some control for the different inspections being entered. So I'd guess there's a decision which loops through multiple inspection entries. Personally I use regions only for handling interrupts. ADs are nice to a certain level. But sometimes a tabular text (like suggested by Cockburn) is just easier to write and read. Graphical programming is not the ultimate answer (unlike 42).
First, the 'NO' branch of the decision node must lead somewhere (at the end?).
After, It differs if you want to show the process for ONE or MULTIPLE inspections. But the most logical way is to represent the diagram for an inspection, because you wrote inspection without S ! If you want represent more than one inspection, you can use decision and merge node to represent loop that stop when there is no more inspection.
I am trying to get multiple time-frame data of different trading instrument ( _Symbol ) from MetaTrader4 Terminal to a node.
How can I do it?
Can we do it from the same EA inside a MetaTrader4 Terminal?
A.1: Yes, we can.
A.2: No, that initial idea is not a good one.
While the intention is clear, the idea to use a single EA to send live-data for multiple trading instruments is not working for the said interest well.
MQL4 code-execution environment has some fixed, hard-wired internal logic and due to these + plus due to the reality, how Capital Markets and Broker-type Market access mediators work, the solo-EA will never fit these requirements.
A simple call to
iOpen( aTradingInstrumentSymbolNAME, // iHigh, iLow, iClose, iVolume, iTime
aSelectedTimeFrameDefinedCODE,
aRelativeBarPTR
)
is by far not enough.
Professional solution will require a lot of care for a real-time handling capabilities, for unmasking the actual flow of mutually hiding events, for achieving minimalistic processing latencies, so a quite high engineering expertise will be needed.
Start with learning the basics about Scripts, benchmark all your critical code-sections with recording their actual durations in [us] and assure, your code will remain non-blocking under all circumstances. This will decide, whether more than one code-execution thread(s) will be necessary in prime-time / for peak-hour.
Having managed that, your way just started to lead in a direction towards your expected result.
Next one has to decide about a feasible inter-process / distributed-computing data-flow and signalling, needed for inter-platform integration.
Last, but not least, important point is the legal-side of such undertaking. It depends both on your local juri§$§$§diction and Broker's Terms & Conditions as no one would enjoy to celebrate a technically well mastered Project from inside of jail.
All that, quite an interesting Project.
iOpen(Symbol(),PERIOD_M1,1) - is the way to get data from M1 ( last bar ), if you need another timeframe - replace PERIOD_M1 with another ENUM_TIMEFRAMES. So what is the problem? Usually StackOverflow requires to see your MCVE-based example to help you.
I have a requirement to add fields onto a form based on data from another set of entities. Is this possible using an event script or does it require a plugin?
Given that I understand your assignment correctly, it can be done using JavaScript as well as a plugin. There is a significant difference that you need to take into consideration.
Is the change to the other entities to be made only when an actual user loads a form? If so, JS is the right way.
Or perhaps you need to ensure that those values are written even if a console client or system process retrieves the value of the primary entity? In that case, C# is your only option.
EDIT:
Simply accessing the values from any entity in the onload event can be done using a call to oData. I believe someone else asked a similar question recently. The basic format will look like this.
http://Server:Port/Organization
/XrmServices/2011/OrganizationData.svc
/TheEntityLogicalNameOfYoursSet()?$filter=FieldName eq 'ValueOfIt'
Some extra remarks.
If you're targeting on-line installation, the syntax will differ, of course, because the Schema-Server-Port-Organization are provided in a different pattern (https, orgName.crm4.something.something.com etc.). You can look it up on Settings.
Perhaps it should go without saying and I'm sure you realize it but for completeness' sake, TheEntityLogicalNameOfYours needs to be substituted for the actual name (unless that is your actual name, in which case I'll be worried, haha).
If you're new to this whole oData thingy, keep asking. I got the impression that the info I'm giving you is appreciated but not really producing "aha!" experience for you. You might want to ask separate questions, though. Some examples right off the top of my head.
a. "How do I perform oData call in JavaScript?"
b. "How do I access the fetched data?"
c. "How do I add/remove/hide a field programmatically on a form?"
d. "How do I combine data from...?"
I'm looking for a generic charting solution, ideally not a hosted one that provides the following features:
Charting a tuple of values where the values are:
1) A service identifier (e.g. CPU usage)
2) A client identifier within that service (e.g. server IP)
3) A value
4) A timestamp with millisecond/second resolution.
Optional:
I'd like to also extend the concept of a client identifier further, taking the above example further, I'd like to store statistics for each core separately, so, another identifier would be Core 1/Core 2..
Now, to make sure I'm clearly stating my problem, I don't want a utility that collects these statistics. I'd like something that stores them, but, this is also not mandatory, I can always store them in MySQL, or such.
What I'm looking for is something that takes values such as these, and charts them nicely, in a multitude of ways (timelines, motion, and the usual ones [pie, bar..]). Essentially, a nice visualization package that allows me to make use of all this data. I'd be collecting data from multiple services, multiple applications, and the datapoints will be of varying resolution. Some of the data will include multiple layers of nesting, some none. (For example, CPU would go down to Server IP, CPU#, whereas memory would only be Server IP, but would include a different identifier, i.e free/used/cached as the "secondary' identifier. Something like average request latency might not have a secondary identifier at all, in the case of ping). What I'm trying to get across is that having multiple layers of identifiers would be great. To add one final example of where multiple identifiers would be great: adding an extra identifier on top of ip/cpu#, namely, process name. I think the advantages of that are obvious.
For some applications, we might collect data at a very narrow scope, focusing on every aspect, in other cases, it might be a more general statistic. When stuff goes wrong, both come in useful, the first to quickly say "something just went wrong", and the second to say "why?".
Further, it would be a nice thing if the charting application threw out "bad" values, that is, if for some reason our monitoring program started to throw values of 300% CPU used on a single core for 10 seconds, it'd be nice if the charts themselves didn't reflect it in the long run. Some sort of smoothing, maybe? This could obviously be done at the data-layer though, so its not a requirement at all.
Finally, comparing two points in time, or comparing two different client identifiers of the same service etc without too much effort would be great.
I'm not partial to any specific language, although I'd prefer something in (one of the following) PHP, Python, C/C++, C#, as these are languages I'm familiar with. It doesn't have to be open source, it doesn't have to be a library, I'm open to using whatever fits my purpose the best.
More of a P.S than a requirement: I'd like to have pretty charts that are easy for non-technical people to understand, and act upon too (and like looking at!).
I'm open to clarifying, and, in advance, thanks for your time!
I am pretty sure that protovis meets all your requirements. But it has a bit of a learning curve. You are meant to learn by examples, and there are plenty to work from. It makes some pretty nice graphs by default. Every value can be a function, so you can do things like get rid of your "Bad" values.
I recently heard the term "hook" while talking to some people about a program I was writing. I'm unsure exactly what this term implies although I inferred from the conversation that a hook is a type of function. I searched for a definition but was unable to find a good answer. Would someone be able to give me an idea of what this term generally means and perhaps a small example to illustrate the definition?
Essentially it's a place in code that allows you to tap in to a module to either provide different behavior or to react when something happens.
A hook is functionality provided by software for users of that software to have their own code called under certain circumstances. That code can augment or replace the current code.
In the olden days when computers were truly personal and viruses were less prevalent (I'm talking the '80's), it was as simple as patching the operating system software itself to call your code. I remember writing an extension to the Applesoft BASIC language on the Apple II which simply hooked my code into the BASIC interpreter by injecting a call to my code before any of the line was processed.
Some computers had pre-designed hooks, one example being the I/O stream on the Apple II. It used such a hook to inject the whole disk sub-system (Apple II ROMs were originally built in the days where cassettes were the primary storage medium for PCs). You controlled the disks by printing the ASCII code 4 (CTRL-D) followed by the command you wanted to execute then a CR, and it was intercepted by the disk sub-system, which had hooked itself into the Apple ROM print routines.
So for example, the lines:
PRINT CHR(4);"CATALOG"
PRINT CHR(4);"IN#6"
would list the disk contents then re-initialize the machine. This allowed such tricks as protecting your BASIC programs by setting the first line as:
123 REM XIN#6
then using POKE to insert the CTRL-D character in where the X was. Then, anyone trying to list your source would send the re-initialize sequence through the output routines where the disk sub-system would detect it.
That's often the sort of trickery we had to resort to, to get the behavior we wanted.
Nowadays, with the operating system more secure, it provides facilities for hooks itself, since you're no longer supposed to modify the operating system "in-flight" or on the disk.
They've been around for a long time. Mainframes had them (called exits) and a great deal of mainframe software uses those facilities even now. For example, the free source code control system that comes with z/OS (called SCLM) allows you to entirely replace the security subsystem by simply placing your own code in the exit.
In a generic sense, a "hook" is something that will let you, a programmer, view and/or interact with and/or change something that's already going on in a system/program.
For example, the Drupal CMS provides developers with hooks that let them take additional action after a "content node" is created. If a developer doesn't implement a hook, the node is created per normal. If a developer implements a hook, they can have some additional code run whenever a node is created. This code could do anything, including rolling back and/or altering the original action. It could also do something unrelated to the node creation entirely.
A callback could be thought of as a specific kind of hook. By implementing callback functionality into a system, that system is letting you call some additional code after an action has completed. However, hooking (as a generic term) is not limited to callbacks.
Another example. Sometimes Web Developers will refer to class names and/or IDs on elements as hooks. That's because by placing the ID/class name on an element, they can then use Javascript to modify that element, or "hook in" to the page document. (this is stretching the meaning, but it is commonly used and worth mentioning)
Simple said:
A hook is a means of executing custom code (function) either before, after, or instead of existing code. For example, a function may be written to "hook" into the login process in order to execute a Captcha function before continuing on to the normal login process.
Hooks are a category of function that allows base code to call extension code. This can be useful in situations in which a core developer wants to offer extensibility without exposing their code.
One usage of hooks is in video game mod development. A game may not allow mod developers to extend base functionality, but hooks can be added by core mod library developers. With these hooks, independent developers can have their custom code called upon any desired event, such as game loading, inventory updates, entity interactions, etc.
A common method of implementation is to give a function an empty list of callbacks, then expose the ability to extend the list of callbacks. The base code will always call the function at the same and proper time but, with an empty callback list, the function does nothing. This is by design.
A third party, then, has the opportunity to write additional code and add their new callback to the hook's callback list. With nothing more than a reference of available hooks, they have extended functionality at minimal risk to the base system.
Hooks don't allow developers to do anything that can't be done with other structures and interfaces. They are a choice to be made with consideration to the task and users (third-party developers).
For clarification: a hook allows the extension and may be implemented using callbacks. Callbacks are generally nothing more than a function pointer; the computed address of a function. There appears to be confusion in other answers/comments.
Hooking in programming is a technique employing so-called hooks to make a chain of procedures as an event handler.
Hook denotes a place in the code where you dispatch an event of certain type, and if this event was registered before with a proper function to call back, then it would be handled by this registered function, otherwise nothing happens.
hooks can be executed when some condition is encountered. e.g. some variable changes or some action is called or some event happens. hooks can enter in the process and change things or react upon changes.
Oftentimes hooking refers to Win32 message hooking or the Linux/OSX equivalents, but more generically hooking is simply notifying another object/window/program/etc that you want to be notified when a specified action happens. For instance: Having all windows on the system notify you as they are about to close.
As a general rule, hooking is somewhat hazardous since doing it without understanding how it affects the system can lead to instability or at the very leas unexpected behaviour. It can also be VERY useful in certain circumstances, thought. For instance: FRAPS uses it to determine which windows it should show it's FPS counter on.
A chain of hooks is a set of functions in which each function calls the next. What is significant about a chain of hooks is that a programmer can add another function to the chain at run time. One way to do this is to look for a known location where the address of the first function in a chain is kept. You then save the value of that function pointer and overwrite the value at the initial address with the address of the function you wish to insert into the hook chain. The function then gets called, does its business and calls the next function in the chain (unless you decide otherwise). Naturally, there are a number of other ways to create a chain of hooks, from writing directly to memory to using the metaprogramming facilities of languages like Ruby or Python.
An example of a chain of hooks is the way that an MS Windows application processes messages. Each function in the processing chain either processes a message or sends it to the next function in the chain.
In the Drupal content management system, 'hook' has a relatively specific meaning. When an internal event occurs (like content creation or user login, for example), modules can respond to the event by implementing a special "hook" function. This is done via naming convention -- [your-plugin-name]_user_login() for the User Login event, for example.
Because of this convention, the underlying events are referred to as "hooks" and appear with names like "hook_user_login" and "hook_user_authenticate()" in Drupal's API documentation.
Many answers, but no examples, so adding a dummy one: the following complicated_func offers two hooks to modify its behavior
from typing import List, Callable
def complicated_func(
lst: List[int], hook_modify_element: Callable[[int], int], hook_if_negative=None
) -> int:
res = sum(hook_modify_element(x) for x in lst)
if res < 0 and hook_if_negative is not None:
print("Returning negative hook")
return hook_if_negative
return res
def my_hook_func(x: int) -> int:
return x * 2
if __name__ == "__main__":
res = complicated_func(
lst=[1, 2, -10, 4],
hook_modify_element=my_hook_func,
hook_if_negative=0,
)
print(res)
A function that allows you to supply another function rather than merely a value as an argument, in essence extending it.
In VERY short, you can change the code of an API call such as MessageBox to where it does a different function edited by you (globally will work system wide, locally will work process wide).