A conversion from the representation type Repr to a GenTraversableLike[A,Repr].
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 ==
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
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.
ClassCastException if the receiver object is not an instance of the erasure of type T0.
Create a copy of the receiver object.
Tests whether the argument (that) is a reference to the receiver object (this).
Tests whether the argument (that) 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.
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.
Returns string formatted according to given format string.
Returns string formatted according to given format string.
Format strings are as for String.format
(@see java.lang.String.format).
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.
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
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.
A trait which can be used to avoid code duplication when defining extension methods that should be applicable both to existing Scala collections (i.e., types extending
GenTraversableLike) as well as other (potentially user-defined) types that could be converted to a Scala collection type. This trait makes it possible to treat Scala collections and types that can be implicitly converted to a collection type uniformly. For example, one can provide extension methods that work both on collection types and onStrings (Strings do not extendGenTraversableLike, but can be converted toGenTraversableLike)IsTraversableprovides two members:A, which represents the element type of the targetGenTraversableLike[A, Repr]conversion, which provides a way to convert between the type we wish to add extension methods to,Repr, andGenTraversableLike[A, Repr].Usage
One must provide
IsTraversableLikeas an implicit parameter type of an implicit conversion. Its usage is shown below. Our objective in the following example is to provide a generic extension methodmapReduceto any type that extends or can be converted toGenTraversableLike. In our example, this includesString.Here, we begin by creating a class
ExtensionMethodswhich contains ourmapReduceextension method. Note thatExtensionMethodstakes a constructor argumentcollof typeGenTraversableLike[A, Repr], whereArepresents the element type andReprrepresents (typically) the collection type. The implementation ofmapReduceitself is straightforward.The interesting bit is the implicit conversion
withExtensions, which returns an instance ofExtensionMethods. This implicit conversion can only be applied if there is an implicit valuetraversableof typeIsTraversableLike[Repr]in scope. SinceIsTraversableLikeprovides value memberconversion, which gives us a way to convert between whatever type we wish to add an extension method to (in this case,Repr) andGenTraversableLike[A, Repr], we can now convertcollfrom typeReprtoGenTraversableLike[A, Repr]. This allows us to create an instance of theExtensionMethodsclass, which we pass our newGenTraversableLike[A, Repr]to.When the
mapReducemethod is called on some type of which it is not a member, implicit search is triggered. Because implicit conversionwithExtensionsis generic, it will be applied as long as an implicit value of typeIsTraversableLike[Repr]can be found. Given thatIsTraversableLikecontains implicit members that return values of typeIsTraversableLike, this requirement is typically satisfied, and the chain of interactions described in the previous paragraph is set into action. (See theIsTraversableLikecompanion object, which contains a precise specification of the available implicits.)Note: Currently, it's not possible to combine the implicit conversion and the class with the extension methods into an implicit class due to limitations of type inference.
Implementing
IsTraversableLikefor New TypesOne must simply provide an implicit value of type
IsTraversableLikespecific to the new type, or an implicit conversion which returns an instance ofIsTraversableLikespecific to the new type.Below is an example of an implementation of the
IsTraversableLiketrait where theReprtype isString.2.10