Test two objects for inequality.
Test two objects for inequality.
true if !(this == that), false otherwise.
Equivalent to x.hashCode except for boxed numeric types and null.
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.
a hash value consistent with ==
Test two objects for equality.
Test two objects for equality.
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
true if the receiver object is equivalent to the argument; false otherwise.
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics.
Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at
runtime, while the expression List(1).asInstanceOf[List[String]] will not.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the requested type.
the receiver object.
if the receiver object is not an instance of the erasure of type T0.
Create a copy of the receiver object.
Where enabled, direct or indirect subclasses of trait scala.
Where enabled, direct or indirect subclasses of trait scala.Dynamic can be defined. Unless dynamics is enabled, a definition of a class, trait, or object that has Dynamic as a base trait is rejected. Dynamic member selection of existing subclasses of trait Dynamic are unaffected; they can be used anywhere.
Why introduce the feature? To enable flexible DSLs and convenient interfacing with dynamic languages.
Why control it? Dynamic member selection can undermine static checkability of programs. Furthermore, dynamic member selection often relies on reflection, which is not available on all platforms.
Tests whether the argument (arg0) is a reference to the receiver object (this).
Tests whether the argument (arg0) is a reference to the receiver object (this).
The eq method implements an equivalence relation on
non-null instances of AnyRef, and has three additional properties:
x and y of type AnyRef, multiple invocations of
x.eq(y) consistently returns true or consistently returns false.x of type AnyRef, x.eq(null) and null.eq(x) returns false.null.eq(null) returns true. When overriding the equals or hashCode methods, it is important to ensure that their behavior is
consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they
should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
true if the argument is a reference to the receiver object; false otherwise.
The equality method for reference types.
Only where enabled, existential types that cannot be expressed as wildcard types can be written and are allowed in inferred types of values or return types of methods.
Only where enabled, existential types that cannot be expressed as wildcard
types can be written and are allowed in inferred types of values or return
types of methods. Existential types with wildcard type syntax such as List[_],
or Map[String, _] are not affected.
Why keep the feature? Existential types are needed to make sense of Java’s wildcard types and raw types and the erased types of run-time values.
Why control it? Having complex existential types in a code base usually makes application code very brittle, with a tendency to produce type errors with obscure error messages. Therefore, going overboard with existential types is generally perceived not to be a good idea. Also, complicated existential types might be no longer supported in a future simplification of the language.
The experimental object contains features that have been recently added but have not been thoroughly tested in production yet.
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as
well as the interaction between finalize and non-local returns
and exceptions, are all platform dependent.
A representation that corresponds to the dynamic class of the receiver object.
A representation that corresponds to the dynamic class of the receiver object.
The nature of the representation is platform dependent.
a representation that corresponds to the dynamic class of the receiver object.
not specified by SLS as a member of AnyRef
The hashCode method for reference types.
Only where this flag is enabled, higher-kinded types can be written.
Only where this flag is enabled, higher-kinded types can be written.
Why keep the feature? Higher-kinded types enable the definition of very general abstractions such as functor, monad, or arrow. A significant set of advanced libraries relies on them. Higher-kinded types are also at the core of the scala-virtualized effort to produce high-performance parallel DSLs through staging.
Why control it? Higher kinded types in Scala lead to a Turing-complete type system, where compiler termination is no longer guaranteed. They tend to be useful mostly for type-level computation and for highly generic design patterns. The level of abstraction implied by these design patterns is often a barrier to understanding for newcomers to a Scala codebase. Some syntactic aspects of higher-kinded types are hard to understand for the uninitiated and type inference is less effective for them than for normal types. Because we are not completely happy with them yet, it is possible that some aspects of higher-kinded types will change in future versions of Scala. So an explicit enabling also serves as a warning that code involving higher-kinded types might have to be slightly revised in the future.
Only where enabled, definitions of implicit conversions are allowed.
Only where enabled, definitions of implicit conversions are allowed. An
implicit conversion is an implicit value of unary function type A => B,
or an implicit method that has in its first parameter section a single,
non-implicit parameter. Examples:
implicit def stringToInt(s: String): Int = s.length implicit val conv = (s: String) => s.length implicit def listToX(xs: List[T])(implicit f: T => X): X = ...
implicit values of other types are not affected, and neither are implicit classes.
Why keep the feature? Implicit conversions are central to many aspects of Scala’s core libraries.
Why control it? Implicit conversions are known to cause many pitfalls if over-used. And there is a tendency to over-use them because they look very powerful and their effects seem to be easy to understand. Also, in most situations using implicit parameters leads to a better design than implicit conversions.
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics.
Therefore the expression 1.isInstanceOf[String] will return false, while the
expression List(1).isInstanceOf[List[String]] will return true.
In the latter example, because the type argument is erased as part of compilation it is
not possible to check whether the contents of the list are of the specified type.
true if the receiver object is an instance of erasure of type T0; false otherwise.
Equivalent to !(this eq that).
Equivalent to !(this eq that).
true if the argument is not a reference to the receiver object; false otherwise.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Only where enabled, postfix operator notation (expr op) will be allowed.
Only where enabled, postfix operator notation (expr op) will be allowed.
Why keep the feature? Several DSLs written in Scala need the notation.
Why control it? Postfix operators interact poorly with semicolon inference. Most programmers avoid them for this reason.
Only where enabled, accesses to members of structural types that need reflection are supported.
Only where enabled, accesses to members of structural types that need
reflection are supported. Reminder: A structural type is a type of the form
Parents { Decls } where Decls contains declarations of new members that do
not override any member in Parents. To access one of these members, a
reflective call is needed.
Why keep the feature? Structural types provide great flexibility because they avoid the need to define inheritance hierarchies a priori. Besides, their definition falls out quite naturally from Scala’s concept of type refinement.
Why control it? Reflection is not available on all platforms. Popular tools such as ProGuard have problems dealing with it. Even where reflection is available, reflective dispatch can lead to surprising performance degradations.
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
a String representation of the object.
The
scala.languageobject controls the language features available to the programmer, as proposed in the SIP-18 document.Each of these features has to be explicitly imported into the current scope to become available:
The language features are:
dynamicsenables defining calls rewriting using theDynamictraitpostfixOpsenables postfix operatorsreflectiveCallsenables using structural typesimplicitConversionsenables defining implicit methods and membershigherKindsenables writing higher-kinded typesexistentialsenables writing existential typesexperimentalcontains newer features that have not yet been tested in production