I just have this question around the Stax XMLStreamWriter. Best explained by example:
Say I need to produce a document somehow like this:
<buddies>
<buddies name="tim"/>
<buddies name="toady"/>
</buddies>
, where the tim and toady guys are created by some callback that receives the XMLStreamWriter as an argument.
writer.writeElement("buddies");
callback1.writeBuddies(writer);
callback2.writeBuddies(writer);
write.writeEndElement();
Now the thing is, the whole document must conform to a schema that states: If there's a <buddies> element, there must be at least one <buddy> inside, so if none of my callbacks write anything on the stream I'd have an empty element which is invalid. Question is: Can I delay the writeElement("buddies") somehow like this:
// Pseudocode
Mark mark = writer.getPos()
boolean written = callback1.writeBuddies(writer)
written |= callback2.writeBuddies(writer)
if (written){
writer.writeStartElement(mark, "buddies") // write at mark
writer.writeStopElement() // write at the end of stream
}
Or am I completely off the track?
StAX is a forward only streaming API. To achieve what you are asking is a potential requirement for DOM parser where you construct the node "buddies" separately and attach it to the main document if it is not empty.
Related
I want to create an experiment in PsychoPy Builder that conditionally shows a second routine to participants based on their keyboard response.
In the task, I have a loop that first goes through a routine where participants have three options to respond ('left','right','down') and only if they select 'left', regardless of the correct answer, should they see a second routine that asks a follow-up question to respond to. The loop should then restart with routine 1 each time.
I've tried using bits of code in the "begin experiment" section as such:
if response.key=='left':
continueRoutine=True
elif response.key!='left':
continueRoutine=False
But here I get an error saying response.key is not defined.
Assuming your keyboard component is actually called response, the attribute you are looking for is called response.keys. It is pluralised as it returns a list rather than a single value. This is because it is capable of storing multiple keypresses. Even if you only specify a single response, it will still be returned as a list containing just that single response (e.g. ['left'] rather than 'left'). So you either need to extract just one element from that list (e.g. response.keys[0]) and test against that, or use a construction like if 'left' in response.keys to check inside the list.
Secondly, you don't need to have a check that assigns True to continueRoutine, as it defaults to being True at the beginning of a routine. So it is only setting it to False that results in any action. So you could simply do something like this:
if not 'left' in response.keys:
continueRoutine = False
Lastly, for PsychoPy-specific questions, you might get better support via the dedicated forum at https://discourse.psychopy.org as it allows for more to-and-fro discussion than the single question/answer structure here at SO.
I´m trying to draw an UML activity diagram for a fnction that is (highly simplified) represented by the following code snippet. My intention is to have a subactivity for the lines that check the mode parameter (if-else).
ErrorType DoSomething(int mode) {
if(mode==MODE1) {
...
}
else {
return MODE_NOT_AVAILABLE;
}
SomethingElse...
return NO_ERROR;
}
You can see, the return-Statement in the else-Block leads to termination of function DoSomething. So if it´s executed, there is no way for SomethingElse... to be executed.
As I mentioned, this else-block should be in a subactivity.
How do I visualize that an action in a subactivity (return MODE_NOT_AVAILABLE) has the consequence that it´s parental activity diagram has to be in a final state?
In the following picture you can see my try to solve it. Is this a correct solution?
Since you are dealing with some kind of exception, I'd model it with an exception handler like you see here http://www.sparxsystems.com.au/images/screenshots/uml2_tutorial/ad11.GIF. Even though your concrete implementation uses if/else, that should be a way which makes it easy to understand what you want to achieve (prevent the subroutine from being executed in wrong mode).
You can see more details about the notation here: http://edn.embarcadero.com/article/30169
It depends on how much you want to dictate the actual implementation. UML itself is langage-unaware, and so are most stakeholders.
I am trying to implement a pulse generator in SIMULINK that needs to know the previous 2 input values i.e. I need to know the previous 2 state values for the input signal. Also, I need to know the previous output value.
My pseudo code is:
IF !input AND input_prevValue AND !input_prevValue2
output = !output_pv
ELSE
output = output_pv;
I know that I can use legacy function importer and use C code to do this job in SIMULINK. However, the problem arises when you apply a configuration reference set to your model. The key problem is the flexibility. When you use this model somewhere else (say share it with a colleague or whoever), unless you have used a configuration reference set, you can rebuild the code (i.e. from S-Function Block) and run your model. But you cannot rebuild the code if the configuration reference set is applied.
My solution would be to implement the logic in a way that I can do the same without C functions. I tried to use the memory block in SIMULINK but apparently it doesn't do it. Does anyone know how to hold previous values for input and output in SIMULINK (for as long as the model is open)?
Have you tried with a MATLAB Function block? Alternatively, if you have a Stateflow license, this would lend itself nicely to a state chart.
EDIT
Based on your pseudo-code, I would expect the code in the MATLAB Function block to look like this
function op = logic_fcn(ip,ip_prev,ip_prev2,op_prev)
% #codegen
if ~ip && ip_prev && ~ip_prev2
op = ~op_prev;
else
op = op_prev;
end
where ip, ip_prev, ip_prev2 and op_prev are defined as boolean inputs and op as a boolean output. If you are using a fixed-step discrete solver, the memory block should work so that you would for example feed the output of the MATLAB Function block to a memory block (with the correct sample time), and the output of the memory block to the op_prev input of the MATLAB Function block.
You could (and should) test your function in MATLAB first (and/or a test Simulink model) to make sure it works and produces the output you expect for a given input.
This is reasonably straight forward to do with fundamental blocks,
Note that for the Switch block the "Criteria for passing first input:" has been changed to "u2~=0".
I have a bit of a question regarding why my code seems to hang when I run it. The code is for a project I have in a class, but we spent one class period going over Prolog so much of what I've learned is stuff I've searched around for and have taught myself. I do apologize if my code contains horrendous stylistic errors, but again, as we never formally learned how we 'should' use Prolog, this is based mostly on my own experimentation.
The goal of the segment of code I am writing is, more or less, to form a chain that connects one actor to another through a series of movies that they have been in.
I have a function I am calling that is meant to construct connections between a starting actor, all possible linked actors ending actor, and the list of movies that connects them. This is probably a horribly inefficient method of doing this, however implementing it this way solves two parts of the assignment with one segment of code.
The code that calls the function works, and for the sake of making this simpler to read, I will omit it unless asked to share it. In short, it asserts a globalStartingActor, and passes on two empty lists (ActorList = [] and MovieList = []) to a function doActorAssertions.
In turn, we have doActorAssertions. This is the revised version of it, which should be simplified and easier to read, but lacks the massive commenting that it had previously.
doActorAssertions(ActorsName,ActorList,MovieList) :-
isNotInList(ActorsName,ActorList) ->
(
findMoviesIn(ActorsName,MoviesIn),%finds all movies ActorsName is in
howLong(MoviesIn,LenMoviesIn),%Sees how many movies there are.
(
LenMoviesIn ==0;
(
append(ActorsName,ActorList,UpdatedActorList),%this causes errors!
globalStartingActor(GSAName),%asserted starting actor
assert(connectedActors(GSAName,ActorsName,MovieList)), %says that the GSAName is connected to ActorsName by a list of movies MovieList.
write(actorAsserted),
addAndTraverse(MoviesIn,UpdatedActorList,MovieList) %Goes to propegate all movies the actor is in, then actors in those movies, then recursively calls this function again.
)
)
),
true.
As I said previously, the append tag seemed to be the source of the error! This indeed appears to be the case when I simplify the code to what it is above. I simply comment that append out, and the code body works.
Why, then, is append preventing the code from working properly? I need to have append (or similar function) in that part of the code!
Is ActorsName a list? The variable' name suggests it is, as well as the usage in append/3, but then what isNotInList(ActorsName,ActorList) means? Partial or full disjunction? This could be the cause of the endless loop, maybe you should use the difference of those sets to increment the ActorList.
You should try to avoid assert/1, and instead pass around the state in variables. See this other answer for a schema doing something very similar to what you are attempting here.
This is useless, could be a typo, but then I don't understand the ->
...
),
true.
I think should read
...
); % note the semicolon!
true.
I did a separate levelData class to be able to flexibly add levels. I was happy with it until my supervisor ordered me to convert my levelData into XML. I did an XML version of the levelData's data (question, answers, correct answer...). I used the old class and converted it so that it fetches the XML.
All seems well, I did traces of my answers array and it printed nicely...
But the headache started when I tried this.
// This code appears in a different class with
// currentLvl:LevelData initialized in the constructor.
quizHolder.ansA.ansHud.text = currentLvl.choices[1];
quizHolder.ansB.ansHud.text = currentLvl.choices[2];
quizHolder.ansC.ansHud.text = currentLvl.choices[3];
quizHolder.ansD.ansHud.text = currentLvl.choices[4];
// BTW, I can't make a for loop to do the same function as above. So wierd.
I tried to run it. it returned:
TypeError: Error #2007: Parameter text must be non-null.
at flash.text::TextField/set text()
at QuestionPane/setQuiz()
at QuestionPane/setQuestion()
at QuestionPane()
at LearningModule()
Where did I go wrong? I tried making a custom get function for it, only to get the same error. Thanks in advance. If I need to post more of the code, I will gladly do so =)
LevelData Class in PasteBin: http://pastebin.com/aTKC1sBC
Without seeing more of the code it's hard to diagnose, but did you correctly initialize the choices Array before using it? Failing that I think you'll need to post more code.
Another possible issue is the delay in loading the XML data. Make sure your data is set before QuestionPane tries to access it.
When did you call
quizHolder.ansA.ansHud.text = currentLvl.choices[1];
quizHolder.ansB.ansHud.text = currentLvl.choices[2];
quizHolder.ansC.ansHud.text = currentLvl.choices[3];
quizHolder.ansD.ansHud.text = currentLvl.choices[4];
these? You load the XML and on complete you fill the array, what is correct. but is the XML loaded and parsed to the time when you access (fill the TextFields) the choices array already?