Programming Clojure, 3rd Edition

Chapter 5Specifications

Statically typed languages like Java create unique, named data structures (classes) for every unit of data in a program. Clojure is dynamically typed and instead relies on reusing a few generic collection types (vectors, maps, sets, lists, and sequences) to represent a program’s data. This approach yields tremendous opportunities for code reuse, simplicity, generality, and extension.

However, one consequence of this approach is that functions in a Clojure program lack the explicit types that programmers in a statically typed language rely on as signposts to understand a piece of code.

For example, a Java program might have a function that takes a recipe ingredient and scales the quantity for a larger recipe. In Java, ...