Scala Library: scala.AnyVal
scala.AnyVal
AnyVal
is the root class of all value types , which describe values not
implemented as objects in the underlying host system. Value classes are
specified in Scala Language Specification, section 12.2.
The standard implementation includes nine AnyVal
subtypes:
scala.Double, scala.Float, scala.Long, scala.Int, scala.Char, scala.Short, and scala.Byte are the numeric value types .
scala.Unit and scala.Boolean are the non-numeric value types .
Other groupings:
- The subrange types are scala.Byte, scala.Short, and scala.Char.
- The integer types include the subrange types as well as scala.Int and scala.Long.
- The floating point types are scala.Float and scala.Double.
Prior to Scala 2.10, AnyVal
was a sealed trait. Beginning with Scala 2.10,
however, it is possible to define a subclass of AnyVal
called a user-defined
value class which is treated specially by the compiler. Properly-defined user
value classes provide a way to improve performance on user-defined types by
avoiding object allocation at runtime, and by replacing virtual method
invocations with static method invocations.
User-defined value classes which avoid object allocation…
- must have a single
val
parameter that is the underlying runtime representation. - can define
def
s, but noval
s,var
s, or nestedtraits
s,class
es orobject
s. - typically extend no other trait apart from
AnyVal
. - cannot be used in type tests or pattern matching.
- may not override
equals
orhashCode
methods.
A minimal example:
It’s important to note that user-defined value classes are limited, and in some circumstances, still must allocate a value class instance at runtime. These limitations and circumstances are explained in greater detail in the Value Classes and Universal Traits.
Value Members From scala.Any
final def ##(): Int
Equivalent to x.hashCode
except for boxed numeric types and null
. For
numerics, it returns a hash value which is consistent with value equality: if
two value type instances compare as true, then ## will produce the same hash
value for each of them. For null
returns a hashcode where null.hashCode
throws a NullPointerException
.
- returns
- a hash value consistent with ==
- Definition Classes
- Any
(defined at scala.Any###)
Instance Constructors From scala.AnyVal
new AnyVal()
(defined at scala.AnyVal)
Full Source:
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