Getting Started¶

This guide assumes you have already installed Epsilon.

Running Epsilon¶

Start an interactive session:

./epsilon

This launches a REPL with Epsilon's core libraries loaded from the self-contained binary.

Evaluate expressions directly:

./epsilon --eval "(format t \"Hello, World\")"

Load specific modules:

./epsilon --module epsilon.json --eval "(json:encode '(:foo \"bar\"))"

Basic Usage¶

Working with Maps¶

Epsilon provides immutable maps:

;; Create a map
(defparameter *config* 
  (epsilon.map:make-map :host "localhost" 
                            :port 8080))

;; Access values
(epsilon.map:get *config* :host)
;=> "localhost"

;; Update (returns new map, original unchanged)
(epsilon.map:assoc *config* :port 3000)
;=> #<MAP :host "localhost" :port 3000>

Working with Sequences¶

Lazy sequences support functional operations:

;; Transform data
(epsilon.sequence:realize 
  (epsilon.sequence:map #'1+ 
    (epsilon.sequence:seq '(1 2 3 4 5))))
;=> (2 3 4 5 6)

;; Filter values  
(epsilon.sequence:realize 
  (epsilon.sequence:filter #'evenp 
    (epsilon.sequence:seq '(1 2 3 4 5 6))))
;=> (2 4 6)

;; Reduce to single value
(epsilon.sequence:reduce #'+ 
  (epsilon.sequence:seq '(1 2 3 4 5)))
;=> 15

JSON Handling¶

;; Parse JSON
(epsilon.json:decode "{\"status\": \"ok\", \"count\": 42}")
;=> #<MAP "status" "ok" "count" 42>

;; Generate JSON
(epsilon.json:encode 
  (epsilon.map:make-map :status "ok" :count 42))
;=> "{\"status\":\"ok\",\"count\":42}"

Writing Programs¶

You can create standalone Lisp programs that use Epsilon:

(defpackage :hello
  (:use :cl)
  (:local-nicknames
   (:map :epsilon.map)
   (:json :epsilon.json)
   (:seq :epsilon.sequence)))

(in-package :hello)

(defun main ()
  (let ((data (map:make-map 
                :message "Hello from Epsilon"
                :timestamp (get-universal-time))))
    (format t "~A~%" (json:encode data))))

(main)

Run it using the epsilon binary:

./epsilon --eval "(load \"hello.lisp\")"

Building Applications¶

For larger projects, use Epsilon's module system:

Create a module directory with module.lisp
Define your packages and dependencies
Use epsilon binary to load and test modules

See the Application Development Guide for details.