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.
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- PatternExpander.scala
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Type Members
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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.
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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
- final case class Patterns (fixed: List[Pattern], star: Pattern) extends Product with Serializable
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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*.
- final case class TypedPat (pat: Pattern, tpe: Type) extends Product with Serializable
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final
def
!=(arg0: Any): Boolean
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def
##(): Int
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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.
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- any2stringadd
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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.
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def
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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.
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- Ensuring
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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.
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- Ensuring
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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.
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- Ensuring
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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.
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- Ensuring
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final
def
eq(arg0: AnyRef): Boolean
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def
equals(arg0: Any): Boolean
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def
finalize(): Unit
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def
formatted(fmtstr: String): String
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- This member is added by an implicit conversion from PatternExpander[Pattern, Type] to StringFormat[PatternExpander[Pattern, Type]] performed by method StringFormat in scala.Predef.
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- StringFormat
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getClass(): Class[_]
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notify(): Unit
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notifyAll(): Unit
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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
- object NoRepeated extends Repeated
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