Top "Existential-type" questions

Existential types are types that provide a collection of operations that act on an unspecified, or abstract, type.

What is an existential type?

I read through the Wikipedia article Existential types. I gathered that they're called existential types because of the existential operator (∃). …

language-agnostic types type-systems existential-type
scala - Any vs underscore in generics

What is the different between the following Generics definitions in Scala: class Foo[T <: List[_]] and class Bar[T &…

scala generics covariance any existential-type
Unbound Wildcard Type

I was playing around in the Scala REPL when I got error: unbound wildcard type. I tried to declare this (…

scala types existential-type unbounded-wildcard
Existential vs. Universally quantified types in Haskell

What exactly is the difference between these? I think I understand how existential types work, they are like having a …

haskell polymorphism existential-type
Difference between Scala's existential types and Java's wildcard by example?

A bit more specific than Stack Overflow question What is an existential type?, what is the difference between Scala's existential …

java scala type-systems bounded-wildcard existential-type