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It's being mentioned that the Io language is homoiconic:
To me homoiconic means "Expressing the language in the data-structure of the same langage" . For exp, LISP, is all LISP list.
I'm trying to understand; is Io actually homoiconic?
Though I can see that the Io programs are objects and message, a given statement is not a data-structure of the language per se.
For example, can someone explain how this statement is homoiconic:
Number / := method (i,
if (i != 0, self origDiv(i), 0)
)
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Consider the following list(1,1,2,2,3,4,4,5,5) I want to print only 3. Since it is the unique one. Can someone help me with the Scala code.
It's not a Spark question, but this function would do it for Scala
def uniqueElems[T](lst: Seq[T]) = {
lst.groupBy(identity).collect { case v if v._2.length == 1 => v._2.head }
}
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im trying to convert a scala list of eithers, as such:
List(Left(3),Left(4),Left(1),Left(5))
Into a either of a list Either[List[Int],Int] like this?
Left(3,4,1,5)
Only using flatmap, map or fold?
ive been hammering at it for a while now and can simply not make it work
Assumed:
val a = List(Left(1), Left(2), Left(3)) // for example
Then following will return a Left[List[Int]]:
Left(a.map(_.value))
// Left(List(1, 2, 3))
Then you can extract the values out of the list, which I don't thin is generally a good idea.
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Given that match will never be None,
Which style is better or can I improve the first?
val tmp = (cols.find(_(0) == id).get)
SomeClass(tmp(0), tmp(1))
cols.find(_(0) == id) match {
case Some(value)=> SomeClass(value(0), value(1))
case None=> NotFound("Given id not found")
}
Since this a question about style, my answer is that neither of these is the best style. Instead, just keep the value in the Option
val opt: Option[SomeClass] = cols.find(_(0) == id).map(v => SomeClass(v(0), v(1)))
Keep processing/testing inside the Option using foreach/exists etc. until you really need the bare value. There is a very rich set of methods on Option that covers most of the things that are needed.
If the rest of the code is structured well, you will likely find that the value never needs to be extracted in a separate operation.
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I have java code shown below, how to convert it to scala?
feature.getFeatures()
.stream()
.filter(a -> a.getFeatureName().equals(feature))
.findFirst()
.map(f -> f.Accounts().contains(accountId))
.orElse(true);
Whenever you see filter or find chained with map, think collect or collectFirst
So something like this should work:
feature.getFeatures()
.collectFirst {
case f if f.getFeatureName().equals(feature) =>
f.Accounts().contains(accountId)
}.getOrElse(true)
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The Swift Programming Guide (Swift 5.1 Edition) says that subscripts can be used to access members of “a collection, list, or sequence.” Collection and Sequence are defined protocols in Swift and are well documented. Do lists exist in Swift as a separate entity? If so, what is the syntax for a list subscript?
It would be better if The Swift Programming Language (the book) didn't say “ a collection, list, or sequence”. As you point out, Swift has standard Collection and Sequence types. It does not have any standard type named List.
The closest thing would be Array:
let words: Array<String> = ["Mark", "Cowan"]
// or words: [String]
let firstWord = words[0]