Class Upcast<A extends B, B>

java.lang.Object
com.jnape.palatable.lambda.functions.builtin.fn1.Upcast<A,B>
Type Parameters:
A - the covariant type
B - the contravariant type
All Implemented Interfaces:
Fn1<A,B>, Applicative<B,Fn1<A,?>>, Cartesian<A,B,Fn1<?,?>>, Cocartesian<A,B,Fn1<?,?>>, Contravariant<A, Profunctor<?,B,Fn1<?,?>>>, Functor<B,Fn1<A,?>>, Profunctor<A,B,Fn1<?,?>>, Monad<B,Fn1<A,?>>, MonadReader<A,B,Fn1<A,?>>, MonadRec<B,Fn1<A,?>>, MonadWriter<A,B,Fn1<A,?>>
public final class Upcast<A extends B, B> extends Object implements Fn1<A,B>
Upcast a value of type B to a value of type A that B extends. This is principally useful when dealing with parametric types that are invariant in their parameters and a cast is necessary for compatibility purposes.

Example: 


Iterable<String> have = new ArrayList<>();
Iterable<CharSequence> want = map(upcast(), have); // necessary due to invariance in parameter

Note that this is universally safe.

  • Field Details

    • INSTANCE

      private static final Upcast<?,?> INSTANCE

  • Constructor Details

    • Upcast

      private Upcast()

  • Method Details

    • checkedApply

      public B checkedApply(A a)
      Description copied from interface: Fn1
      Invoke this function with the given argument, potentially throwing any Throwable.
      Specified by:
      checkedApply in interface Fn1<A extends B, B>
      Parameters:
      a - the argument
      Returns:
      the result of the function application

    • upcast

      public static <A extends B, B> Upcast<A,B> upcast()

    • upcast

      public static <A extends B, B> B upcast(A a)