.gitignore

.packages
*.pyc

README.md

Call/CC: async with synchronous semantics

app.js

var Express = require('express'),
    PG = require('pg'),
    app = Express.createServer();

app.get('/favicon.ico', function(req, res) {
  res.send(404);
});

app.get('/:message?', function(req, res) {
  var message = req.param('message'),
      client;

  PG.connect('tcp://root:@localhost/callcc', function(err, _client) {
    if (err)
      fail(err);
    else {
      client = _client.on('error', fail);
      if (!message)
        showLog();
      else
        client
          .query('INSERT INTO log (message) VALUES ($1)', [message])
          .on('end', showLog);
    }
  });

  function fail(err) {
    res.send((err.stack || err).toString(), 500);
  }

  function showLog() {
    var results = [];

    client
      .query('SELECT stamp, message FROM log ORDER BY stamp DESC LIMIT 100')
      .on('row', function(row) {
        results.push('[' + row.stamp + '] ' + row.message);
      })
      .on('end', function() {
        res.end("<pre>" + results.join("\n") + "</pre>");
      });
  }
});

app.listen(3000);
console.log('Listening on port 3000.');

app.py

import web, psycopg2


## Routes ##

urls = (
    '/favicon.ico', 'favicon',
    '/(.*)', 'log'
)

class log:
    def GET(self, message):
        conn = psycopg2.connect("dbname=callcc user=root")
        cur = conn.cursor()

        if message:
            cur.execute("INSERT INTO log (message) VALUES (%s)", [message])
            conn.commit()

        cur.execute("SELECT stamp, message FROM log ORDER BY stamp DESC LIMIT 100")
        result = "<pre>%s</pre>" % "\n".join('[%s] %s' % r for r in cur)

        cur.close()
        conn.close()

        return result

class favicon:
    def GET(self):
        raise web.NotFound()


## Server

app = web.application(urls, globals())
if __name__ == '__main__':
    app.run()

async.scm

#!/usr/bin/csi -script


;; ## Main Program ##

(define (main message)
  (let ((client #f))
    (define (fail err)
      (error err))

    (define (connected conn)
      (set! client conn)
      (insert conn message showLog))

    (define (showLog err)
      (if err
          (fail err)
          (select-all
           client
           (lambda (err all)
             (if err
                 (fail err)
                 (for-each (lambda (entry)
                             (display entry)
                             (newline))
                           all))))))

    (open-database
     (lambda (err conn)
       (if err
           (fail err)
           (connected conn))))
    ))


;; Fake Database

(define (open-database next)
  (next #f (cons 'database (list "alpha" "beta"))))

(define (insert db entry next)
  (set-cdr! db (append (cdr db) (list entry)))
  (next #f))

(define (select-all db next)
  (next #f (cdr db)))


;; Run it

(apply main (cdddr (argv)))

callcc.scm

#!/usr/bin/csi -script


;; ## Main Program ##

(define (main message)
  (let ((client (open-database)))
    (insert client message)
    (for-each
     (lambda (entry)
       (display entry)
       (newline))
     (select-all client))))


;; Async Interface

(define (open-database)
  (capture
   (lambda (next)
     (%open-database next))))

(define (insert db entry)
  (capture
   (lambda (next)
     (%insert db entry next))))

(define (select-all db)
  (capture
   (lambda (next)
     (%select-all db next))))

(define (capture with-next)
  (call/cc
   (lambda (next)
     (with-next (maybe next)))))

(define (maybe k)
  (lambda (err . success)
    (if err
        (error err)
        (apply k success))))


;; Fake Database

(define (%open-database next)
  (next #f (cons 'database (list "alpha" "beta"))))

(define (%insert db entry next)
  (set-cdr! db (append (cdr db) (list entry)))
  (next #f #:void))

(define (%select-all db next)
  (next #f (cdr db)))


;; Run it

(apply main (cdddr (argv)))

package.json

{
  "name": "demo",
  "version": "0.1.0",

  "dependencies": {
    "express": "1.0.7",
    "connect": "0.5.7"
  },

  "mappings": {
    "pg": "https://github.com/brianc/node-postgres/zipball/v0.2.5"
  }
}