I'm trying to put a simple console spinner into my scala application, but I'm not sure how to set the cursor position?
If it's not possible, is there another way of achieving this?
val chars = List("/", "-", "\\", "|")
(0 to 30).foreach { _ => chars.foreach { cc =>
print(s"\u0008$cc")
Thread.sleep(150)
}
}
Idea taken from that answer:
Write to same location in a console window with java
Related
I am trying to learn reactive programming, so forgive me if I ask a silly question. I'm also open to advice on changing my design.
I am working in scala-swing to display the results of a simulator. With one setting, a chart is displayed as a histogram; with the other setting the chart is displayed as the cumulative sum. (I'm probably using the wrong word; in the first setting you might have bin1=2, bin2=5, bin3=3; in the second setting the first height is 2, the second is 2 + 5, the third is 2 + 5 + 3, etc.). The simulator can be slow, so I originally used a Future to compute it, and the set the data into the chart. I decided to try a reactive approach, so my requirements are: 1. I don't want to recreate the data when I change the display mode, and 2. I want to set the Observable once for the chart and have the chart listen to the same Observable permanently.
I got this to work when I started the chain with a PublishSubject and the Future set the data into the start of the chain. When the display mode changed, I created a new PublishSubject().map(newRenderingLogic).subscribe(theChartsObservable). I am now trying to do what looks like the "right way," but it's not working correctly. I've tried to simplify what I have done:
val textObservable: Subject[String] = PublishSubject()
textObservable.subscribe(text => {
println(s"Text: ${text}")
})
var textSubscription: Option[Subscription] = None
val start = Observable.from(Future {
"Base text"
}).cache
var i = 0
val button = new Button() {
text = "Click"
reactions += {
case event => {
i += 1
if (textSubscription.isDefined) {
textSubscription.get.unsubscribe()
}
textSubscription = Some(start.map(((j: Int) => { (base: String) => s"${base} ${j}" })(i)).subscribe(textObservable))
}
}
}
On start, an Observable is created and logic to print some text is added to it. Then, an Observable with the generated data is created and a cache is added so that the result is replayed if the next subscription comes in after its results are generated. Then, a button is created. Then on button clicks a middle observable is chained with unique logic (it's a function that creates a function to append the value of i into the string, run with the current value of i; I tried to make something that couldn't just be reused) that is supposed to change with each click. Then the first Observable is subscribed to it so that the results of the whole chain end up being printed.
In theory, the cache operation takes care of not regenerating the data, and this works once, but onComplete is called on textObservable and then it can't be used again. It works if I subscribe it like this:
textSubscription = Some(start.map(((j: Int) => { (base: String) => s"${base} ${j}" })(i)).subscribe(text => textObservable.onNext(text)))
because the call to onComplete is intercepted, but this looks wrong and I wanted to know if there was a more typical way to do this, or architect it. It makes me think that I don't understand how this is supposed to be done if there isn't an out-of-the-box operation to do this.
Thank you.
I'm not 100% sure if I got the essence of your question right, but: if you have an Observable that may complete and you want to turn it into an Observable that never completes, you can just concatenate it with Observable.never.
For example:
// will complete after emitting those three elements:
val completes = Observable.from(List(1, 2, 3))
// will emit those three elements, but will never complete:
val wontComplete = completes ++ Observable.never
For scala experts this might be a silly question but me as a beginner facing hard time to identify the solution. Any pointers would help.
I've set of 3 files in HDFS location by the names:
fileFirst.dat
fileSecond.dat
fileThird.dat
Not necessarily they'll be stored in any order. fileFirst.dat could be created at very last so a ls every time would show different ordering of the files.
My task is to combine all files in a single file in the order:
fileFirst contents, then fileSecond contents & finally fileThird contents; with newline as the separator, no spaces.
I tried some ideas but couldn't come up with something working. Every time the order of combination messes up.
Below is my function to merge whatever is coming in:
def writeFile(): Unit = {
val in: InputStream = fs.open(files(i).getPath)
try {
IOUtils.copyBytes(in, out, conf, false)
if (addString != null) out.write(addString.getBytes("UTF-8"))
} finally in.close()
}
Files is defined like this:
val files: Array[FileStatus] = fs.listStatus(srcPath)
This is part of a bigger function where I'm passing all the arguments used in this method. After everything is done, I'll do the out.close() to close the output stream.
Any ideas welcome, even if it goes against the file write logic I'm trying to do; just understand that I'm not that good in scala; for now :)
If you can enumerate your Paths directly, you don't really need to use listStatus. You could try something like this (untested):
val relativePaths = Array("fileFirst.dat", "fileSecond.dat", "fileThird.dat")
val paths = relativePaths.map(new Path(srcDirectory, _))
try {
val output = fs.create(destinationFile)
for (path <- paths) {
try {
val input = fs.open(path)
IOUtils.copyBytes(input, output, conf, false)
} catch {
case ex => throw ex // Feel free to do some error handling here
} finally {
input.close()
}
}
} catch {
case ex => throw ex // Feel free to do some error handling here
} finally {
output.close()
}
Let's say I have this ListBuffer that I am filling in a scala foreach like the following:
Tokens.foreach(t => tokens+=new Token(t._1.toString()))
i am wondering whether it is possible to perform another operation at the same time for-example adding to a string something like:
Tokens.foreach(t => tokens+=new Token(t._1.toString()), posTagString+=t._2.toString())
the 2nd example results in a "too many arguments (2) for method foreach" error. Is there a way to do this or shall I just stick too the form of:
for(x<-Tokens){
}
try this? :
Tokens.foreach{t =>
tokens+=new Token(t._1.toString())
posTagString+=t._2.toString()
}
You can achieve your requirement by using map too
Tokens.map(t => {
tokens += new Token(t._1.toString())
posTagString += t._2.toString()
})
I have a long string similar to this:
"tag1, tag2, tag3, tag4"
Now in my play template I would like to create a foreach loop like this:
#posts.foreach { post =>
#for(tag <- #post.tags.split(",")) {
<span>#tag</span>
}
}
With this, I'm getting this error: ')' expected but '}' found.
I switched ) for a } & it just throws back more errors.
How would I do this in Play! using Scala?
Thx in advance
With the help of #Xyzk, here's the answer: stackoverflow.com/questions/13860227/split-string-assignment
Posting this because the answer marked correct isn't necessarily true, as pointed out in my comment. There are only two things wrong with the original code. One, the foreach returns Unit, so it has no output. The code should actually run, but nothing would get printed to the page. Two, you don't need the magic # symbol within #for(...).
This will work:
#for(post <- posts)
#for(tag <- post.tags.split(",")) {
<span>#tag</span>
}
}
There is in fact nothing wrong with using other functions in play templates.
This should be the problem
#for(tag <- post.tags.split(",")) {
<span>#tag</span>
}
I am working on a project using PlayFramework 2.0. After reading a bit of scala I would like to embed some dynamic code in the View template. So, I did the following:
#{
def getMystring(sequence:Int) = {
if(patternForm != null &&
patternForm.get().windowTreatments != null &&
patternForm.get().windowTreatments.size() >= sequence + 1)
sequence+""
else
""
}
}
<input type = "text" value = #getMystring(1)></input>
...
I was quite sure it was going to work but instead I got a "not found: value getMyString Error occurred" . Did I do something obviously wrong?
try starting it like a template, like this
#getMystring(sequence:Int) = {
[...]
have a look at https://github.com/playframework/Play20/blob/master/samples/scala/computer-database/app/views/list.scala.html
The problem being that play defines a very narrow scope and can't recognize defs outside its current curly brackets.
You can change the position of the last curly bracket for your def to include the input tag and then it should work.
Or you can do what opensas suggested.
#getMystring(sequence:Int) = {
[...]