Incremental Development with Lisp: Building a Game and a Website
•Download as KEY, PDF•
1 like•1,417 views
I show how powerful incremental development with Lisp/Scheme is by showing a website and game I created by running the application and developing them real-time.
Report
Share
Incremental Development with Lisp: Building a Game and a Website
- 1. INCREMENTAL DEVELOPMENT WITH LISP Building a Game and a Website @jlongster James Long
- 2. INCREMENTAL DEVELOPMENT • “acyclic software development process developed in response to the weaknesses of the waterfall model” - Wikipedia • Rapidly evolving software by means of frequent small changes
- 3. CODING • Let’s focus on PROGRAMMING, apply the same model to just the programmer • Write small pieces of code, run them, and repeat • Tweak and extend the program while it is running • Advantages: instant results, higher morale, less rabbit trails
- 4. WHY LISP? • Lisp is famous for embracing incremental development • Very expressive and dynamic • Functional simplicity allows for “piece-by-piece” evaluation, or running small chunks of code quickly • Thephilosophy of Lisp is built around incremental development
- 5. IN PRACTICE • How do you actually write code incrementally? • REPL • IDE • Emacs • SLIME • comint-mode
- 6. EXAMPLE #1 VECTORS • Goal: Write a 3d vector library with support for addition (define-type v3 x y z) EVAL (define (v3-add v1 v2) (make-v3 (+ (v3-x v1) (v3-x v2)) (+ (v3-y v1) (v3-y v2)) (+ (v3-z v1) (v3-z v2)))) EVAL • Intimate with what’s going on with the code
- 7. EXAMPLE #1 VECTORS • Goal: Write a 3d vector library with support for addition (define-type v3 (define-type v3 constructor: really-make-vec3d x y z) x y z) EVAL EVAL (define (v3-add v1 v2) (define (make-v3 x y z #!key (scale 1.)) (make-v3 (really-make-vec3d (* x scale) (+ (v3-x v1) (v3-x v2)) (* y scale) (+ (v3-y v1) (v3-y v2)) (* z scale))) (+ (v3-z v1) (v3-z v2)))) EVAL EVAL v3-add is still available • Intimate with what’s going on with the code
- 8. EXAMPLE #2 RENDER QUEUE • Goal: Write a library which queues objects to render (define queue '()) (define (queue-add obj) (set! queue (cons obj queue))) (define (queue-render-all) (for-each (lambda (obj) (write obj)) queue)) EVAL-REGION • Modify a program while its running and never throw away state
- 9. EXAMPLE #2 RENDER QUEUE • Goal: Write a library which queues objects to render (define queue '()) (define (queue-render-all) (define (queue-add obj) (display "--- RENDERED OBJECTS ---n") (set! queue (cons obj queue))) (for-each (lambda (obj) (display obj) (define (queue-render-all) (newline)) (for-each (lambda (obj) queue)) (write obj)) queue)) queue and queue-add are the same as before EVAL-REGION • Modify a program while its running and never throw away state
- 10. INITIAL THOUGHTS? • Emacs greatly enhances the ability for “live coding”, could be done in other editors though • “Scratch buffers” are commonly used to test the system • Your “scratch code” evolves into unit tests
- 11. REAL WORLD EXAMPLE #1 WEBSITE • Clojure is a Lisp dialect which runs on the JVM • Compojure is a web framework developed in Clojure • jlongster.com • Clojure supports SLIME, an incredible development environment fully embracing incremental development
- 12. REAL WORLD EXAMPLE #2 GAME •Iused Gambit Scheme to make an iPhone game, Farmageddon • Wrote a tool that embeds “remote REPLs” in applications so that you can develop it SLIME-style • Extended Emacs keybindings
- 13. REAL WORLD EXAMPLE #2 GAME •Iused Gambit Scheme to make an iPhone game, Farmageddon • Wrote a tool that embeds “remote REPLs” in applications so that you can develop it SLIME-style • Extended Emacs keybindings
- 14. PROBLEMS • Youmust write your code in a way that allows incremental development • Your IDE must support it • Sometimes there’s a lot of overhead for little gain
- 15. WHAT ABOUT YOU? • Most of you don’t use Lisp, probably • Python and many other languages could support this too • It’s a different mindset that I challenge you to try
- 16. • Buymy game, available next week on the App Store for only $1.99 • @farmageddongame • http://farmageddongame.com