The type calculus

Pcore types are parsed from their canonical string form with pcore.Parse(string) (pcore.Type, error). Every Type.String() is canonical and round-trips: pcore.Parse(t.String()) reproduces t.

Scalar

Type	Meaning
Any	every value, including undef
Scalar	Numeric, String, Boolean, Regexp, Timestamp, Timespan
ScalarData	Integer, Float, String, Boolean
Data	ScalarData, Undef, Array[Data], Hash[String, Data]
Numeric	Integer or Float
Integer[min, max]	an integer in the (inclusive) range; bounds may be default
Float[min, max]	a float in the range
String[min, max]	a string whose length is in the range
Boolean	true or false
Undef	the undef value
Default	the literal default

Integer[3] is min = 3, unbounded max; Integer[default, 10] is unbounded min, max = 10.

Collection

Type	Meaning
Array[T, min, max]	an array of T with a size in the range
Hash[K, V, min, max]	a hash with keys K, values V, sized in the range
Tuple[T1, T2, …, min, max]	a positional array; trailing integers give the size
Struct[{ 'k' => V, Optional['o'] => W }]	a hash with named, typed members
Collection[min, max]	any array or hash sized in the range

Array alone is Array[Any, 0, default]; Hash alone is Hash[Any, Any, 0, default]. A Struct is closed — a matching hash has exactly the declared keys. A member is optional to provide when its key is wrapped in Optional[…] or its value type accepts Undef.

Abstract

Type	Meaning
Variant[A, B, …]	any of the member types (a union)
Optional[T]	T or Undef
NotUndef[T]	T excluding Undef
Enum['a', 'b', …]	one of the given strings; a trailing true makes it case-insensitive
Pattern[/re/, …]	a string matching any of the regexps
Regexp[/re/]	a regexp value (or, unparameterized, any regexp)
Type[T]	a type value assignable to T
Sensitive[T]	a value of T wrapped so it is redacted

Rich data

Type	Meaning
Timestamp	an instant in time
Timespan	a duration
Binary	a byte string

Staged for v0.2

Named type aliases and TypeSet are not yet parsed. Timestamp / Timespan range parameters and the Pcore-exact Timespan string form are also staged; the value model and serialization round-trip within this library today.