Packages

  • package root
    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
t

scala.tools.nsc.transform.patmat.PatternExpansion

ExtractorSubPatternAlignment

trait ExtractorSubPatternAlignment extends AnyRef

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

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  1. ExtractorSubPatternAlignment
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Abstract Value Members

  1. abstract def 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)

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
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  2. final def ##(): Int
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  3. final def ==(arg0: Any): Boolean
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  7. def equals(arg0: Any): Boolean
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  8. def finalize(): Unit
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  11. final def isInstanceOf[T0]: Boolean
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  12. val isStar: Boolean
  13. final def ne(arg0: AnyRef): Boolean
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  14. val nonStarArity: Int
  15. final def notify(): Unit
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    @native()
  16. final def notifyAll(): Unit
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  17. def starArity: Int
  18. final def synchronized[T0](arg0: ⇒ T0): T0
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  19. def toString(): String
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  20. def totalArity: Int
  21. final def wait(): Unit
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    @throws( ... )
  22. final def wait(arg0: Long, arg1: Int): Unit
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  23. final def wait(arg0: Long): Unit
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