Scala Standard Library2.12.21 < Back
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# Packages

-  package root

  This is the documentation for the Scala standard library.

  This is the documentation for the Scala standard library.

  #### Package structure

  The scala package contains core types like `Int`, `Float`, `Array` or `Option` which are accessible in all Scala compilation units without explicit qualification or imports.

  Notable packages include:

  - `scala.collection` and its sub-packages contain Scala's collections framework
    - `scala.collection.immutable` - Immutable, sequential data-structures such as `Vector`, `List`, `Range`, `HashMap` or `HashSet`
    - `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.collection.parallel.immutable` - Immutable, parallel data-structures such as `ParVector`, `ParRange`, `ParHashMap` or `ParHashSet`
    - `scala.collection.parallel.mutable` - Mutable, parallel data-structures such as `ParArray`, `ParHashMap`, `ParTrieMap` or `ParHashSet`
  - `scala.concurrent` - Primitives for concurrent programming such as `Futures` and `Promises`
  - `scala.io` - Input and output operations
  - `scala.math` - Basic math functions and additional numeric types like `BigInt` and `BigDecimal`
  - `scala.sys` - Interaction with other processes and the operating system
  - `scala.util.matching` - Regular expressions

  Other packages exist. See the complete list on the right.

  Additional parts of the standard library are shipped as separate libraries. These include:

  - `scala.reflect` - Scala's reflection API (scala-reflect.jar)
  - `scala.xml` - XML parsing, manipulation, and serialization (scala-xml.jar)
  - `scala.swing` - A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)
  - `scala.util.parsing` - Parser combinators (scala-parser-combinators.jar)

  #### Automatic imports

  Identifiers in the scala package and the `scala.Predef` object are always in scope by default.

  Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example, `List` is an alias for `scala.collection.immutable.List`.

  Other aliases refer to classes provided by the underlying platform. For example, on the JVM, `String` is an alias for `java.lang.String`.

  Definition Classes
    root
-  package scala

  Core Scala types.

  Core Scala types. They are always available without an explicit import.

  Definition Classes
    root
-  package util
  Definition Classes
    scala
-  package control
  Definition Classes
    util
-  package hashing
  Definition Classes
    util
- ByteswapHashing
- Hashing
- MurmurHash3
-  package matching
  Definition Classes
    util

p

scala.util

# hashing 

#### package hashing

Source
  package.scala

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### Type Members

1.  final class ByteswapHashing[T] extends Hashing[T]

   A fast multiplicative hash by Phil Bagwell.

2.  trait Hashing[T] extends Serializable

   `Hashing` is a trait whose instances each represent a strategy for hashing instances of a type.

   `Hashing` is a trait whose instances each represent a strategy for hashing instances of a type.

   `Hashing`'s companion object defines a default hashing strategy for all objects - it calls their `##` method.

   Note: when using a custom `Hashing`, make sure to use it with the `Equiv` such that if any two objects are equal, then their hash codes must be equal.

   Annotations
     @implicitNotFound( msg = ... )
   Since

     2.10

### Value Members

1.  def byteswap32(v: Int): Int

   Fast multiplicative hash with a nice distribution.

2.  def byteswap64(v: Long): Long

   Fast multiplicative hash with a nice distribution for 64-bit values.

3.  object ByteswapHashing extends Serializable
4.  object Hashing extends Serializable
5.  object MurmurHash3 extends MurmurHash3

   An implementation of Austin Appleby's MurmurHash 3 algorithm (MurmurHash3_x86_32).

   An implementation of Austin Appleby's MurmurHash 3 algorithm (MurmurHash3_x86_32). This object contains methods that hash values of various types as well as means to construct `Hashing` objects.

   This algorithm is designed to generate well-distributed non-cryptographic hashes. It is designed to hash data in 32 bit chunks (ints).

   The mix method needs to be called at each step to update the intermediate hash value. For the last chunk to incorporate into the hash mixLast may be used instead, which is slightly faster. Finally finalizeHash needs to be called to compute the final hash value.

   This is based on the earlier MurmurHash3 code by Rex Kerr, but the MurmurHash3 algorithm was since changed by its creator Austin Appleby to remedy some weaknesses and improve performance. This represents the latest and supposedly final version of the algorithm (revision 136).

   See also

     https://github.com/aappleby/smhasher

### Inherited from AnyRef

### Inherited from Any

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