class

(class x)

Answers the value's kind as a keyword: :map, :vector, :set, :list, :string, :number, :keyword, :symbol, :char, :boolean, :nil, :function or :atom (a sorted map is :map, a sorted set :set). The oracle answers host classes, which no wasm backend has -- the keyword names the kind instead, on every backend alike. A record or deftype answers its tag keyword. An exception or a runtime error answers its class name as a keyword (:java.lang.IllegalArgumentException, :clojure.lang.ExceptionInfo; a runtime error or a refusal the class the oracle throws for it, an error naming no class :java.lang.RuntimeException). A stream (*out*, *in*, *err*, a StringWriter, a reader) answers the host class its printer names as a keyword (:java.io.OutputStreamWriter, :java.io.StringWriter, :java.io.BufferedReader, ...). A host object answers its host class on the interpreter and the JVM, so a class dispatch over one reaches an Object or :default method. .getClass of an exception or a stream answers the same keyword, and a defmethod or a hierarchy operation (isa?, derive, ancestors, ...) naming the class reads it as that keyword. As a value a one-argument lambda.