1. Annotating code

There are two ways to add type-annotations to your code: declare forms, and et-annotate.

Declare annotations

Type annotations can be defined using standard elisp declare forms, without the need for any additional dependencies.

(defun add-numbers (n m)
  (declare (et (n Number) (m Number) (@return Number)))
  (+ n m))

• The only requirement for a function annotation is the @return type.
• Any parameter types which are omitted will default to the Any type.
• Adding (@skip) will tell the type-checker not to type-check the body of this function.

A top-level declare form can be used to define types for global variables.

(declare
 (et (@variable my-number Number)
     (@variable my-local-number Number)))

(defvar my-number 4)
(defvar-local my-local-number 4)

et-annotate

et-annotate.el is a tiny package which defines several useful code-annotation macros.

(et-defun add-numbers (n: Number m: Number) Number
  (+ n m))

;; vvv  expands to  vvv

(cl-defun add-numbers (n m)
  (declare (et (n Number) (m Number) (@return Number)))
  (+ n m))

For global variables:

(et-defvar my-number Number 4)
(et-defvar-local my-local-number Number 4)

;; vvv  expands to  vvv

(defvar my-number 4)
(defvar-local my-local-number 4)

I will use the et-annotate syntax throughout this documentation; however, it is completely optional, and all of et's features are available without the extra dependency.