The Howdy Glossary

Polymorphic recursion is the practice of using parametric polymorphism — where functions can be written without specifying the types they operate on — in recursive function definitions. In other words, it allows a function to be defined in terms of itself or another function with a more general type signature. This technique lets you write more generic code that can handle different types without explicitly defining separate recursive functions for each type. Polymorphic recursion is commonly associated with languages that support higher-kinded types and generics, such as Haskell or Scala. However, it's important to note that not all programming languages support polymorphic recursion out-of-the-box, and its use needs careful consideration due to potential performance implications on runtime behavior.