Bento in a Nutshell

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Bento in a Nutshell

A Simple Page

To Bento, a web page is an object. An object has a type, a name and contents of some sort. The purpose of Bento is to define objects such as web pages. Here is a very simple object definition in Bento:



    page hello [|
        <h1>Hello, world.</h1>
    |]

The type of this object is page, its name is hello, and its content is a block of HTML. The [| and |] are static delimiters, indicating text which is to be sent to the browser.

Once an object has been defined in Bento, it may be constructed by a Bento compiler or a Bento-enabled server. Constructing an object yields HTML (or text in any other desired format) which may either be saved in a file (by a Bento compiler) or sent directly to a client (by a Bento-enabled server).

To see the actual page for yourself, go to hello.

Inheritance, Polymorphism and Composition

There's more to the hello object than just <h1>Hello, world</h1> however. Because hello is an object of type page, it inherits the contents of page as well. These contents include the boilerplate HTML that is a part of every web page, such as all the standard tags found on every proper HTML page (<html>, <head>, <title> and so on).

Inheritance is a key concept in object-oriented languages, and a key source of their power. It lets you define things as special cases of other things. In the case of hello, we defined a specific web page as a special case of a generic page. The concrete benefits of inheritance include making it easier to reuse existing code (reducing development costs), keep shared code in a single place (reducing maintenance costs) and keep content and presentation separate (the Holy Grail of web development).

Every object in Bento definition in Bento automatically also defines a type, which you can use to define new objects. For example, now that we've defined a hello object, we can define a subtype of hello called hello_too:



    hello hello_too [|
        <h1>Hello, world too.</h1>
    |]

The contents of hello_too override those of hello. Yet a hello2 can be used anywhere a hello object is expected (as a typed argument, for example), because a hello_too object is a hello object. This standard feature of object-oriented languages is called polymorphism.

In addition to overriding the contents of a type, a subtype may override the type's child definitions. A child definition is definition contained in another definition (the child's parent definition):



    hello hello3 [=
            title [| Hello World |]
            color bgcolor [| #EEDDBB |]
    =]

In this definition, title is a child of hello3. Bento definitions comprise a tree, with a special kind of definition called core at its root.

Note that the contents of hello3 are enclosed in [= and =] instead of [| and |] . [= and =] are Bento delimiters and mark a block of Bento statements; [| and |] are static delimiters and mark a block of static text.

A Dynamic Page

A Family of Pages

Integrating with External Objects

Levaraging the Power of Objects

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