First Stream

Streams are containers. They contain items. You can make a stream with some items using Stream.make(). Just pass it as arguments the items you want to be part of your stream:

var s = Stream.make(10, 20, 30); // s is now a stream containing 10, 20, and 30

Easy enough, s is now a stream containing three items: 10, 20, and 30; in this order. We can look at the length of the stream using s.length() and retrieve particular items by index using s.item(i). The first item of the stream can also be obtained by calling s.head(). Let's see it in action:

var s = Stream.make(10, 20, 30);
console.log( s.length() ); // => 3
console.log( s.head() );   // => 10
console.log( s.item(0) );  // exactly equivalent to the line above
console.log( s.item(1) );  // => 20
console.log( s.item(2) );  // => 30

Continuing, the empty stream can be constructed either using new Stream() or just Stream.make(). The stream containing all the items of the original stream except the head can be obtained using s.tail(). Calling s.head() or s.tail() on an empty stream yields an error. You can check if a stream is empty using s.empty() which returns either true or false.

var s = Stream.make(10, 20, 30);
var t = s.tail();        // returns the stream that contains two items: 20 and 30
console.log( t.head() ); // => 20
var u = t.tail();        // returns the stream that contains one item: 30
console.log( u.head() ); // => 30
var v = u.tail();        // returns the empty stream
console.log( v.empty() ); // => true

Here's a way to print all the elements in a stream:

var s = Stream.make(10, 20, 30);
while (!s.empty()) {
  console.log( s.head() );
  s = s.tail();
}

There's a convenient shortcut for that: s.print() shows all the items in your stream.

Continue to the next section to find out more about streams.