Are scala maps ordered?

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Berenice Kshlerin asked a question: Are scala maps ordered?
Asked By: Berenice Kshlerin
Date created: Thu, Mar 18, 2021 12:47 PM
Date updated: Sat, Jul 23, 2022 5:44 AM

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Top best answers to the question «Are scala maps ordered»

Scala offers several ways to deal with Maps and their order. There is the regular Map that doesn't preserve order of items at all, LinkedHashMap that preserves the order, but is not immutable. It is an implemenation of immutable maps using a list-based data structure that preserves insertion order…

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Map order in Scala. Scala offers several ways to deal with Maps and their order. There is the regular Map that doesn’t preserve order of items at all, LinkedHashMap that preserves the order, but is not immutable. Luckily ListMap tries to save the situation.

@LuisMiguelMejíaSuárez They aren't necessarily ordered, but SortedMaps are still Maps. – Alexey Romanov Jul 13 '19 at 6:42 @AlexyRomanov Yeah, that is why I said you can order them by key.

A Map is an Iterable consisting of pairs of keys and values (also named mappings or associations ). Scala’s Predef object offers an implicit conversion that lets you write key -> value as an alternate syntax for the pair (key, value). For instance Map ("x" -> 24, "y" -> 25, "z" -> 26) means exactly the same as Map ( ("x", 24), ("y", 25), ("z", ...

Scala map is a collection of key/value pairs. Any value can be retrieved based on its key. Keys are unique in the Map, but values need not be unique. Maps are also called Hash tables. There are two kinds of Maps, the immutable and the mutable.

scala> import scala.collection.immutable._ scala> val ord: Ordering [ String] = _ compareToIgnoreCase _ scala> TreeMap ( "A" -> 1 ) (ord) == HashMap ( "a" -> 1 ) val res0: Boolean = false scala> HashMap ( "a" -> 1) == TreeMap ( "A" -> 1 ) (ord) val res1: Boolean = true. o. The map to which this map is compared.

You can sort the map by value using sortBy: scala> ListMap (grades.toSeq.sortBy (_._2):_*) res0: scala.collection.immutable.ListMap [String,Int] = Map (Al -> 85, Kim -> 90, Emily -> 91, Hannah -> 92, Melissa -> 95) You can also sort by value in ascending or descending order using sortWith:

Solution. Scala has a wealth of map types to choose from, and you can even use Java map classes. If you’re looking for a basic map class, where sorting or insertion order doesn’t matter, you can either choose the default, immutable Map, or import the mutable Map, as shown in the previous recipe.

scala.collection.mutable - Mutable, sequential data-structures such as ArrayBuffer, StringBuilder, HashMap or HashSet; scala.collection.concurrent - Mutable, concurrent data-structures such as TrieMap; scala.concurrent - Primitives for concurrent programming such as Futures and Promises; scala.io - Input and output operations

Digital maps can vary in accuracy, depending on what scale you are looking at. Paper maps have a consistent level of detail across the whole map series at that scale. Digital maps, again, vary based on what scale you are viewing at. In an interactive digital map, the user can switch on or off different layers. Digital maps are searchable. Paper maps might have an index, eg street directories, which then give a map grid reference.

Maps. A Map is an Iterable consisting of pairs of keys and values (also named mappings or associations ). Scala’s Predef object offers an implicit conversion that lets you write key -> value as an alternate syntax for the pair (key, value). For instance Map ("x" -> 24, "y" -> 25, "z" -> 26) means exactly the same as Map ( ("x", 24), ("y", 25 ...

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