Datasheet

Part I ✦ Curl Content Language Fundamentals

Curl was specifically designed to have a “gentle slope” learning curve. This means

that no matter what your current knowledge of Curl, learning the next level of func-

tionality is only slightly harder.

At one end of the learning curve, Curl is a simple markup language that you can use

in place of HTML. Authors can learn this aspect of Curl in a few minutes. Sliding up

the curve a notch, you can create simple interface elements such as buttons and

drop-down menus, with variables and local data validation. At the higher end of the

learning curve, you can have object-oriented client/server applications with 3D

graphics and other advanced tools.

Borrowing from Dylan, an object-oriented language, Curl combines the flexibility of

dynamic languages (Smalltalk, Scheme) with the speed of static-typed languages

(C++, Eiffel). This combination also provides a gentle slope for development styles.

When prototyping, Curl’s support of typeless variables and class variables provides

flexibility and speed of development. For commercial code, you can add more static

typing to improve correctness and execution speed.

Surge Lab IDE

The Surge Lab provides all the tools an author or developer needs to create Curl

content. In theory, Curl content could be written in any text editor, but the Surge

Lab provides much more functionality and it’s free.

The Surge Lab includes its own syntax-aware Source Editor, API Viewer, Debugger,

Object Inspector, and Release Tool for packaging Curl code. The Lab also allows

you to run applets locally without needing a Web server. See Chapter 3 for a tutorial

on the Surge Lab.

Surge plug-in

The Surge plug-in provides a sophisticated runtime environment for running Curl

code securely. The plug-in includes a just-in-time (JIT) compiler and a unique

security model that protects the user’s computer from the issues that have

plagued mobile code in the past. Developers can affect the executable code by

sending directives to the JIT compiler. These directives can control the trade-offs

between the freedom of typeless programming versus code-safety and speed.

The Surge plug-in also permits a single user to compile and run multiple versions

of Curl. If the applet needs a newer version of Curl, the plug-in gives the user the

option of downloading the newer module. This solves the thorny problem of

backward compatibility that haunts many other plug-ins.

Finally, the plug-in acts as the traffic cop that enforces many of Curl’s security

features. These include

✦ Verifying an applet’s right to

include or import Curl files from the host and

comparing package versions to ensure compatibility

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