Substitute To for From and From for To in the type F[To, From], given that F is contravariant in the first argument and covariant in the second. Essentially swaps To and From in ftf's type.
Equivalent in power to each of substituteCo and substituteContra.
This method is impossible to implement without throwing or otherwise "cheating" unless From <: To, so it ensures that this really represents a subtyping relationship.
ftf, but with a (potentially) different type
Test two objects for inequality.
true if !(this == that), false otherwise.
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).
true if the receiver object is equivalent to the argument; false otherwise.
Composes two instances of Function1 in a new Function1, with this function applied first.
a new function f such that f(x) == g(apply(x))
Coerce a From into a To. This is guaranteed to be the identity function.
This method is often called implicitly as an implicit A <:< B doubles as an implicit view A => B.
some value of type From
f, but with a (potentially) different type
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.
The default implementation of the clone method is platform dependent.
a copy of the receiver object.
Composes two instances of Function1 in a new Function1, with this function applied last.
a new function f such that f(x) == apply(g(x))
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.For any non-null instance 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. Default implementation delegates to eq.
See also equals in scala.Any.
true if the receiver object is equivalent to the argument; false otherwise.
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. Format strings are as for String.format (@see java.lang.String.format).
Returns the runtime class representation of the object.
a class object corresponding to the runtime type of the receiver.
The hashCode method for reference types. See hashCode in scala.Any.
the hash code value for this object.
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).
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.
not specified by SLS as a member of AnyRef
Wakes up all threads that are waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Substitute the From in the type F[From], where F is a covariant type constructor, for To.
Equivalent in power to each of substituteBoth and substituteContra.
This method is impossible to implement without throwing or otherwise "cheating" unless From <: To, so it ensures that this really represents a subtyping relationship.
ff, but with a (potentially) different type
Substitute the To in the type F[To], where F is a contravariant type constructor, for From.
Equivalent in power to each of substituteBoth and substituteCo.
This method is impossible to implement without throwing or otherwise "cheating" unless From <: To, so it ensures that this really represents a subtyping relationship.
ft, but with a (potentially) different type
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.
Converts an optional function to a partial function.
Unlike Function.unlift, this UnliftOps.unlift method can be used in extractors.
val of: Int => Option[String] = { i =>
if (i == 2) {
Some("matched by an optional function")
} else {
None
}
}
util.Random.nextInt(4) match {
case of.unlift(m) => // Convert an optional function to a pattern
println(m)
case _ =>
println("Not matched")
}
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Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.13.0/scala/$less$colon$less.html
An instance of
A <:< Bwitnesses thatAis a subtype ofB. Requiring an implicit argument of the typeA <:< Bencodes the generalized constraintA <: B.To constrain any abstract type
Tthat's in scope in a method's argument list (not just the method's own type parameters) simply add an implicit argument of typeT <:< U, whereUis the required upper bound; or for lower-bounds, use:L <:< T, whereLis the required lower bound.In case of any confusion over which method goes in what direction, all the "Co" methods (including apply) go from left to right in the type ("with" the type), and all the "Contra" methods go from right to left ("against" the type). E.g., apply turns a
Frominto aTo, and substituteContra replaces theTos in a type withFroms.In part contributed by Jason Zaugg.
a type which is proved a subtype of
Toa type which is proved a supertype of
Fromscala.Option#flatten
sealed trait Option[+A] { // def flatten[B, A <: Option[B]]: Option[B] = ... // won't work, since the A in flatten shadows the class-scoped A. def flatten[B](implicit ev: A <:< Option[B]): Option[B] = if(isEmpty) None else ev(get) // Because (A <:< Option[B]) <: (A => Option[B]), ev can be called to turn the // A from get into an Option[B], and because ev is implicit, that call can be // left out and inserted automatically. }=:= for expressing equality constraints