Scala Compiler2.12.2-20170504-135222-21d12e9 < 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
- Debugging
- Interface
- Lit
- Logic
- MatchAnalysis
- MatchApproximation
- MatchCodeGen
- MatchCps
- MatchOptimization
- MatchTranslation
- MatchTreeMaking
- MatchWarnings
- PatternExpander
- PatternMatching
- PatternMatchingStats
- ScalaLogic
- ScalacPatternExpanders
- Solving
- TreeAndTypeAnalysis

t

scala.tools.nsc.transform.patmat

# PatternExpander 

###

#### trait PatternExpander[Pattern, Type] extends AnyRef

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.

Source
  PatternExpander.scala

Linear Supertypes
AnyRef, Any
Known Subclasses
ScalacPatternExpander, alignPatterns
Type Hierarchy
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Inherited

1. PatternExpander
2. AnyRef
3. Any

Implicitly

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

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Visibility

1. Public
2. All

### Type Members

1.  final case class Aligned (patterns: Patterns, extractor: Extractor) extends Product with Serializable

   If elementArity is...

   If elementArity is... 0: A perfect match between extractor and the fixed patterns. If there is a star pattern it will match any sequence. > 0: There are more patterns than products. There will have to be a sequence which can populate at least <elementArity> patterns. < 0: There are more products than patterns: compile time error.

2.  final case class Extractor (whole: Type, fixed: List[Type], repeated: Repeated, typeOfSinglePattern: Type) extends Product with Serializable

   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. Decoding what it is that they extract takes place before we arrive here, so that this class can concentrate only on the relationship between patterns and types.

   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.

   In other words, this case class and unapply are encoded the same:

   case class Foo(x: Int, y: Int, zs: Char*) def unapplySeq(x: Foo): Option[(Int, Int, Seq[Char])]

   Both are Extractor(Foo, Int :: Int :: Nil, Repeated(Seq[Char], Char, Char*))

   whole

     The type in its unextracted form

   fixed

     The non-sequence types which are extracted

   repeated

     The sequence type which is extracted

3.  final case class Patterns (fixed: List[Pattern], star: Pattern) extends Product with Serializable
4.  sealed case class Repeated (sequenceType: Type, elementType: Type, repeatedType: Type) extends Product with Serializable

   It's not optimal that we're carrying both sequence and repeated type here, but the implementation requires more unraveling before it can be avoided.

   It's not optimal that we're carrying both sequence and repeated type here, but the implementation requires more unraveling before it can be avoided.

   sequenceType is Seq[T], elementType is T, repeatedType is T*.

5.  final case class TypedPat (pat: Pattern, tpe: Type) extends Product with Serializable

### Abstract Value Members

1.  abstract def NoPattern: Pattern

   You'll note we're not inside the cake.

   You'll note we're not inside the cake. "Pattern" and "Type" are arbitrary types here, and NoPattern and NoType arbitrary values.

2.  abstract def NoType: Type

### Concrete 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 PatternExpander[Pattern, Type] to any2stringadd[PatternExpander[Pattern, Type]] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd
4.  def ->[B](y: B): (PatternExpander[Pattern, Type], B)
   Implicit
     This member is added by an implicit conversion from PatternExpander[Pattern, Type] to ArrowAssoc[PatternExpander[Pattern, Type]] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()
5.  final def ==(arg0: Any): Boolean
   Definition Classes
     AnyRef → Any
6.  final def asInstanceOf[T0]: T0
   Definition Classes
     Any
7.  def clone(): AnyRef
   Attributes
     protected[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )
8.  def ensuring(cond: (PatternExpander[Pattern, Type]) ⇒ Boolean, msg: ⇒ Any): PatternExpander[Pattern, Type]
   Implicit
     This member is added by an implicit conversion from PatternExpander[Pattern, Type] to Ensuring[PatternExpander[Pattern, Type]] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
9.  def ensuring(cond: (PatternExpander[Pattern, Type]) ⇒ Boolean): PatternExpander[Pattern, Type]
   Implicit
     This member is added by an implicit conversion from PatternExpander[Pattern, Type] to Ensuring[PatternExpander[Pattern, Type]] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring
10.  def ensuring(cond: Boolean, msg: ⇒ Any): PatternExpander[Pattern, Type]
    Implicit
      This member is added by an implicit conversion from PatternExpander[Pattern, Type] to Ensuring[PatternExpander[Pattern, Type]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
11.  def ensuring(cond: Boolean): PatternExpander[Pattern, Type]
    Implicit
      This member is added by an implicit conversion from PatternExpander[Pattern, Type] to Ensuring[PatternExpander[Pattern, Type]] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring
12.  final def eq(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
13.  def equals(arg0: Any): Boolean
    Definition Classes
      AnyRef → Any
14.  def finalize(): Unit
    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )
15.  def formatted(fmtstr: String): String
    Implicit
      This member is added by an implicit conversion from PatternExpander[Pattern, Type] to StringFormat[PatternExpander[Pattern, Type]] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()
16.  final def getClass(): Class[_]
    Definition Classes
      AnyRef → Any
17.  def hashCode(): Int
    Definition Classes
      AnyRef → Any
18.  final def isInstanceOf[T0]: Boolean
    Definition Classes
      Any
19.  final def ne(arg0: AnyRef): Boolean
    Definition Classes
      AnyRef
20.  final def notify(): Unit
    Definition Classes
      AnyRef
21.  final def notifyAll(): Unit
    Definition Classes
      AnyRef
22.  final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
      AnyRef
23.  def toString(): String
    Definition Classes
      AnyRef → Any
24.  final def wait(): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
25.  final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
26.  final def wait(arg0: Long): Unit
    Definition Classes
      AnyRef
    Annotations
      @throws( ... )
27.  def →[B](y: B): (PatternExpander[Pattern, Type], B)
    Implicit
      This member is added by an implicit conversion from PatternExpander[Pattern, Type] to ArrowAssoc[PatternExpander[Pattern, Type]] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc
28.  object NoRepeated extends Repeated

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from PatternExpander[Pattern, Type] to any2stringadd[PatternExpander[Pattern, Type]]

### Inherited by implicit conversion StringFormat from PatternExpander[Pattern, Type] to StringFormat[PatternExpander[Pattern, Type]]

### Inherited by implicit conversion Ensuring from PatternExpander[Pattern, Type] to Ensuring[PatternExpander[Pattern, Type]]

### Inherited by implicit conversion ArrowAssoc from PatternExpander[Pattern, Type] to ArrowAssoc[PatternExpander[Pattern, Type]]

### Ungrouped