collections

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All of the collections come in 2 variants: immutable and mutable.

            Iterables

        /        |        \

    Seq     |    Set    |     Map

/        \

IndexedSeq | LinearSeq

There are mutable sets, and immutable sets. With immuable's methods returning new collection

Common Functions on Seq

  • .size

  • ++ to concenate

  • .filter(x => x> 1)

    • remove any elem that X => bool returns false for

    • val sigTrackTopics = allTopics.filter(topic => topic.sigTrackAvailable())

  • Foreach

    • val stuff = Seq(thing1, thing2, thing3, thing4)stuff.foreach { thing => S3.delete(thing)}

    • better than while cuz list's require indexing(linear) less lines and ez parallelism

    • sideeffects only

  • .mkString

    • fancy to string with prefix, separator, suffix

  • conversions i.e .toSet

  • .map(p => p * 3)

    • applies transformation to every elem in collection

Types

Sequences

Array, Lists, Vector, String

Arrays mutable, lists immutable otherwise same

Vector is a shallow tree with 32 children per node, logbase32 x bigO, usually better than list unless you are using head/tail

val fruit: List[String] = List("apples", "oranges", "pears")

fruit.head
fruit.tail
fruit.isEmpty
fruit.size # also length
4::intList //append to list
intList1:::intList2 //concentate list

I Know its a linked list, but I want to index

l(2)
l.lift(2) //return None if out of bounds

Range

Can be represented as single obj with lower bound, upper bound, and step size

1 until 5 //1, 2,3 ,4
val s: Range = 1 to 10 by 3 //1,4,7,10

Functions

  • forall, exists, filter, map, zip, unzip, flatMap, sum, product, max, min

Sets

Tuple

val glazedDonutTuple = Tuple2("Glazed Donut", "Very Tasty")
val hostPort = ("localhost", 80)
val x = 1 -> 2 //(1, 2)
gTuple._1 //1 index => "localhost"
gTuple._2 

hostPort match {
  case ("localhost", port) => ...
  case (host, port) => ...
}

Maps

Functionally list of pairs

Map("foo" -> "bar")
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