Introduction to Scheme I:

The Scheme Homepage The R⁴RS Scheme Manual

Overview

Jscheme is a dialect of the Scheme programming language which has been implemented in Java The principle benefits of Jscheme, as compared to other computer languages are:

Jscheme is a dialect of Scheme.
Jscheme is a powerful language but is simple enough that one can easily learn the core language in a few days.
Jscheme is an interpreted language implemented in Java.
This allows one to write, debug, and run Scheme programs directly from an off-the-shelf web browser. There is no need to download and install any special software. If however you have Java 1.2 installed, you can use Jscheme to implement standalone applications and servlets, as well as applets.
Jscheme has a simple and complete interface to the extensive Java libraries
This allows interactive interaction with the libraries as we will see in the first example below.

You can test out these claims by cutting and pasting the examples below into the green interpreter applet window and pressing the eval button.

The Scheme Interpreter Applet

Assuming you have a browser that is Java 1.1 enabled, the Jscheme interpreter applet will appear below. It may take several minutes to load up if you are loading this page over a slow modem. This applet allows one to enter and run Jscheme programs like the following Hello World demo, which you should cut and paste into the interpreter window.


    ;; cut and paste into interpreter window and press "eval"
    (define win 
       (window "Hello.silk"
          (label "HELLO WORLD!" red (CourierBold 60))))
    (.pack win)
    (.show win)

When this program is evaluated (by pushing the eval button), the Scheme interpreter creates a window with the phrase "Hellow.silk" in the title bar, and it puts a big red box with the words "HELLO WORLD!" into the demo window itself using a 60 point boldface Courier font.

You can then modify the program, say by changing the title to "Second Example" and the label to "Konichi-wa". When you press the eval button a new window will pop up with the specified changes.

Below are a few more examples you can try.

(.setBackground thisContainer (color 120 170 120))

;; fibonacci: cut and paste into interpreter window ;; and press the "eval" button. (define (fib n) (if (< n 3) 1 (+ (fib (- n 1)) (fib (- n 2)))))) (fib 15) (time (fib 15) 1) ;; this calls (fib 15) once and returns the runtime