Scala Compiler2.13.5 < Back
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# Packages

-  package root

  The Scala compiler and reflection APIs.

  The Scala compiler and reflection APIs.

  Definition Classes
    root
-  package scala
  Definition Classes
    root
-  package tools
  Definition Classes
    scala
-  package nsc
  Definition Classes
    tools
-  package transform
  Definition Classes
    nsc
-  package patmat
  Definition Classes
    transform
-  trait PatternExpansion extends AnyRef

  An 'extractor' can be a case class or an unapply or unapplySeq method.

  An 'extractor' can be a case class or an unapply or unapplySeq method.

  In a case class, the class is the unextracted type and the fixed and repeated types are derived from its constructor parameters.

  In an unapply, this is reversed: the parameter to the unapply is the unextracted type, and the other types are derived based on the return type of the unapply method.

  An extractor returns: F1, F2, ..., Fi, opt[Seq[E] or E*] A case matches: P1, P2, ..., Pj, opt[Seq[E]] Put together: P1/F1, P2/F2, ... Pi/Fi, Pi+1/E, Pi+2/E, ... Pj/E, opt[Seq[E]]

  Here Pm/Fi is the last pattern to match the fixed arity section.

  productArity: the value of i, i.e. the number of non-sequence types in the extractor nonStarArity: the value of j, i.e. the number of non-star patterns in the case definition elementArity: j - i, i.e. the number of non-star patterns which must match sequence elements starArity: 1 or 0 based on whether there is a star (sequence-absorbing) pattern totalArity: nonStarArity + starArity, i.e. the number of patterns in the case definition

  Note that productArity is a function only of the extractor, and nonStar/star/totalArity are all functions of the patterns. The key value for aligning and typing the patterns is elementArity, as it is derived from both sets of information.

  If elementArity is...

  - zero: A perfect match between extractor and the fixed patterns. If there is a star pattern it will match any sequence.
  - positive: There are more patterns than products. There will have to be a sequence which can populate at least `elementArity` patterns.
  - negative: There are more products than patterns: compile time error.
  Definition Classes
    patmat
- ExtractorAlignment
- ExtractorSubPatternAlignment

c

scala.tools.nsc.transform.patmat.PatternExpansion

# ExtractorAlignment

###

#### class ExtractorAlignment extends ExtractorSubPatternAlignment

Source
  PatternExpansion.scala

Linear Supertypes
ExtractorSubPatternAlignment, AnyRef, Any
Known Subclasses
ExtractorCall, ExtractorCallProd, ExtractorCallRegular
Type Hierarchy

Ordering

1. Alphabetic
2. By Inheritance

Inherited

1. ExtractorAlignment
2. ExtractorSubPatternAlignment
3. AnyRef
4. Any

Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

1. Hide All
2. Show All

Visibility

1. Public
2. Protected

### Instance Constructors

1.  new ExtractorAlignment(fun: Global.Tree, args: List[Global.Tree])(context: Context)

### Value Members

1.  final def !=(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
2.  final def ##: Int
   Definition Classes
     AnyRef → Any
3.  def +(other: String): String
   Implicit
     This member is added by an implicit conversion from ExtractorAlignment toany2stringadd[ExtractorAlignment] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (ExtractorAlignment, B)
   Implicit
     This member is added by an implicit conversion from ExtractorAlignment toArrowAssoc[ExtractorAlignment] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
5.  final def ==(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
6.  val args: List[Global.Tree]

   Args will be broken down into the concatenation of: `productArity` product patterns (fixed length, corresponding to fields in case class or tuple components in classic unapply, or product selectors in product-based unapply) `elementArity` element patterns (explicit patterns that pick off the prefix of the final sequence-valued component of the unapply, or a repeated case constructor arg) `starArity` star patterns (0 or 1, absorbs the remaining variable-length components)

   Args will be broken down into the concatenation of: `productArity` product patterns (fixed length, corresponding to fields in case class or tuple components in classic unapply, or product selectors in product-based unapply) `elementArity` element patterns (explicit patterns that pick off the prefix of the final sequence-valued component of the unapply, or a repeated case constructor arg) `starArity` star patterns (0 or 1, absorbs the remaining variable-length components)

   Definition Classes
     ExtractorAlignment → ExtractorSubPatternAlignment
7.  final def asInstanceOf[T0]: T0
   Definition Classes
     Any
8.  def clone(): AnyRef
   Attributes
     protected[lang]
   Definition Classes
     AnyRef
   Annotations
     @throws(classOf[java.lang.CloneNotSupportedException]) @native()
9.  def elementArity: Int
10.  def ensuring(cond: (ExtractorAlignment) => Boolean, msg: => Any): ExtractorAlignment
    Implicit
      This member is added by an implicit conversion from ExtractorAlignment toEnsuring[ExtractorAlignment] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: (ExtractorAlignment) => Boolean): ExtractorAlignment
    Implicit
      This member is added by an implicit conversion from ExtractorAlignment toEnsuring[ExtractorAlignment] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  def ensuring(cond: Boolean, msg: => Any): ExtractorAlignment
    Implicit
      This member is added by an implicit conversion from ExtractorAlignment toEnsuring[ExtractorAlignment] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
13.  def ensuring(cond: Boolean): ExtractorAlignment
    Implicit
      This member is added by an implicit conversion from ExtractorAlignment toEnsuring[ExtractorAlignment] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
14.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
15.  def equals(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef → Any
16.  def expectedExtractedType: Global.Type
17.  def finalize(): Unit
    Attributes
      protected[lang]
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.Throwable])
18.  def formatted(fmtstr: String): String
    Implicit
      This member is added by an implicit conversion from ExtractorAlignment toStringFormat[ExtractorAlignment] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()
19.  val fun: Global.Tree
20.  final def getClass(): Class[_ <: AnyRef]
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
21.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
    Annotations
      @native()
22.  def isBool: Boolean
23.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
24.  def isSeq: Boolean
25.  def isSingle: Boolean
26.  val isStar: Boolean
    Definition Classes
      ExtractorSubPatternAlignment
27.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
28.  val nonStarArity: Int
    Definition Classes
      ExtractorSubPatternAlignment
29.  final def notify(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
30.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
    Annotations
      @native()
31.  def productArity: Int
32.  def resultInMonad(extractedBinder: Global.Symbol): Global.Type
33.  def starArity: Int
    Definition Classes
      ExtractorSubPatternAlignment
34.  def subPatTypes(extractedBinder: Global.Symbol): List[Global.Type]
35.  final def synchronized[T0](arg0: => T0): T0
    Definition Classes
      AnyRef
36.  def toString(): String
    Definition Classes
      AnyRef → Any
37.  def totalArity: Int
    Definition Classes
      ExtractorSubPatternAlignment
38.  def unapplyFormals: List[Global.Type]
39.  def unapplySelector: Global.Symbol
40.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
41.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException])
42.  final def wait(arg0: Long): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws(classOf[java.lang.InterruptedException]) @native()

### Deprecated Value Members

1.  def →[B](y: B): (ExtractorAlignment, B)
   Implicit
     This member is added by an implicit conversion from ExtractorAlignment toArrowAssoc[ExtractorAlignment] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @deprecated
   Deprecated

     (Since version 2.13.0) Use `->` instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

### Inherited from ExtractorSubPatternAlignment

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd fromExtractorAlignment to any2stringadd[ExtractorAlignment]

### Inherited by implicit conversion StringFormat fromExtractorAlignment to StringFormat[ExtractorAlignment]

### Inherited by implicit conversion Ensuring fromExtractorAlignment to Ensuring[ExtractorAlignment]

### Inherited by implicit conversion ArrowAssoc fromExtractorAlignment to ArrowAssoc[ExtractorAlignment]

### Ungrouped