Packages

t

scala.tools.nsc.transform.patmat

PatternExpansion

trait PatternExpansion extends AnyRef

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.
Source
PatternExpansion.scala
Linear Supertypes
AnyRef, Any
Known Subclasses
patmat, PatternMatching
Type Hierarchy
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. PatternExpansion
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. All

Type Members

  1. class ExtractorAlignment extends ExtractorSubPatternAlignment
  2. trait ExtractorSubPatternAlignment extends AnyRef

    The arities we can derive looking only at the subpatterns (the args of the unapply node)

Abstract Value Members

  1. abstract val global: Global

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 PatternExpansion to any2stringadd[PatternExpansion] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (PatternExpansion, B)
    Implicit
    This member is added by an implicit conversion from PatternExpansion to ArrowAssoc[PatternExpansion] 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
    @native() @throws( ... )
  8. def ensuring(cond: (PatternExpansion) ⇒ Boolean, msg: ⇒ Any): PatternExpansion
    Implicit
    This member is added by an implicit conversion from PatternExpansion to Ensuring[PatternExpansion] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  9. def ensuring(cond: (PatternExpansion) ⇒ Boolean): PatternExpansion
    Implicit
    This member is added by an implicit conversion from PatternExpansion to Ensuring[PatternExpansion] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: Boolean, msg: ⇒ Any): PatternExpansion
    Implicit
    This member is added by an implicit conversion from PatternExpansion to Ensuring[PatternExpansion] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean): PatternExpansion
    Implicit
    This member is added by an implicit conversion from PatternExpansion to Ensuring[PatternExpansion] 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 PatternExpansion to StringFormat[PatternExpansion] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  16. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  17. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  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
    Annotations
    @native()
  21. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  22. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  23. def toString(): String
    Definition Classes
    AnyRef → Any
  24. def unapplyFormals(fun: Global.Tree, args: List[Global.Tree])(context: Context): List[Global.Type]
  25. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  26. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  27. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @throws( ... )
  28. def →[B](y: B): (PatternExpansion, B)
    Implicit
    This member is added by an implicit conversion from PatternExpansion to ArrowAssoc[PatternExpansion] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from PatternExpansion to any2stringadd[PatternExpansion]

Inherited by implicit conversion StringFormat from PatternExpansion to StringFormat[PatternExpansion]

Inherited by implicit conversion Ensuring from PatternExpansion to Ensuring[PatternExpansion]

Inherited by implicit conversion ArrowAssoc from PatternExpansion to ArrowAssoc[PatternExpansion]

Ungrouped