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
elementAritypatterns. - negative: There are more products than patterns: compile time error.
- Source
- PatternExpansion.scala
- Alphabetic
- By Inheritance
- PatternExpansion
- AnyRef
- Any
- by any2stringadd
- by StringFormat
- by Ensuring
- by ArrowAssoc
- Hide All
- Show All
- Public
- All
Type Members
- class ExtractorAlignment extends ExtractorSubPatternAlignment
-
trait
ExtractorSubPatternAlignment extends AnyRef
The arities we can derive looking only at the subpatterns (the args of the unapply node)
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
- Definition Classes
- AnyRef → Any
-
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
-
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()
-
final
def
==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
asInstanceOf[T0]: T0
- Definition Classes
- Any
-
def
clone(): AnyRef
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native()
-
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
-
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
-
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
-
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
-
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
equals(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
def
finalize(): Unit
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
def
hashCode(): Int
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
final
def
isInstanceOf[T0]: Boolean
- Definition Classes
- Any
-
final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
final
def
notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
toString(): String
- Definition Classes
- AnyRef → Any
- def unapplyFormals(fun: Global.Tree, args: List[Global.Tree])(context: Context): List[Global.Type]
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native()
-
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
Deprecated Value Members
-
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
- @deprecated @inline()
- Deprecated
(Since version 2.12.16) Use
formatString.format(value)instead ofvalue.formatted(formatString), or use thef""string interpolator. In Java 15 and later,formattedresolves to the new method in String which has reversed parameters.
The Scala compiler and reflection APIs.