Scripting Flash apps: design the language

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  • The language must be extremely http://fionadalwood.com/texting-and-driving-essay/ Texting And Driving Essay simple to design and implement (it is a didactic stuff indeed!);
  • The language must be Social Science Phd Thesis as simple as possible to learn and use: we won’t be an alternative to Pixel Bender (because we can’t … yet ;P)
  • The language must be quick to compile and execute.
  • A script must accept some parmeters to control its behaviour.
  • We must support comments!

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  • The first implementation of the language will support a sigle data type: Numbers. We will move further adding more data types later – I don’t want to focus on type checking yet.
  • We will add support for basic expression operators, basic control flow. No support for functions yet.
  • The language will provide some useful operators or builtin functions to manage common operations like packing/unpacking color components and peform some mathematical operations.
  • Arguments to a script will be only Numbers at first.
  • A script will be defined as a simple sequence of arguments followed by a function definition. This function will be applied sequentially to every pixel of one or more source images.
  • We will provide to implementations for the language: a simple (and slow) interpreter at first, http://www.evacias.com/?apa-style-research-paper-for-sale Apa Style Research Paper For Sale then we will generate native SWF code to speedup the performances.

Now that we defined those basic pointers, let’s see how the language will look like:

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// Simple crossfade filter
// The crossfade intensity
argument intensity;
/**
* A quick explanation of the used builtins:
*  - in( id, x, y ): gets the ARGB color at x and y of the image identified by id (there can be more than one image as input);
*  - out( id, x, y, color ): sets the ARGB color at x and y for the output image identified by id;
*  - argb( a, r, b, b ): build an ARGB color from its components (clamping and rounding the values as required);
*/
evaluatePixel( x, y )
{
// this kind of assignment is similar to the python unpack assignment
// but extracts the 4 components (ARGB) from a color.
a1, r1, g1, b1 = in( 0, x, y );
a2, r2, g2, b2 = in( 1, x, y );
out( 0, x, y, argb(
( 1 - intensity ) * a1 + intensity * a2,
( 1 - intensity ) * r1 + intensity * r2,
( 1 - intensity ) * g1 + intensity * g2,
( 1 - intensity ) * b1 + intensity * b2 ));
}

As a side not, I must say that the language may change during implementation because of unexpected limitations we will find during development.

Next week we will move forward start implementing the language. Stay tuned!

Scripting your Flash applications …

As someone of you may know, I really like studying programming languages and sometimes implement for fun (or for work) simple http://edgarvieira.com/roman-entertainment-primary-homework-help/ Roman Entertainment Primary Homework Help scripting languages that help me out during development.

The fight between scripting and programming languages will probably never end. Well, it is not really a fight but more an infinite race where the first position is exchanged continuosly between the two participants.
We need Custom Apparel Business Plan flexibility first, and so we add to our complex applications a way to support scripting to be able to easilly perform changes without the need to run the long time taking compilation process a low level language might take; then, the more the scripts became complex, the more we need an Diving School Business Plan Bundle increase in performances, and so we rapidly move to compiled plugin egines; plugins offer a bit of flexibility and usually a good speed. Then we grant other users the permission to write plugins and so we need a sandbox to run the plugins in and to be sure every single line of code that is executed doesn’t harm our application. And so we revert back to scripting … and so on.
The race will never end but the technologies will continue to increase in speed and sometimes in complexity.

All the introduction is to say that its not the point to choose if scripting is useful or not for Flash applications, but to say that http://www.beaconpoint.net/?essay-for-college-admission-social-work Essay For College Admission Social Work someone might need it for reasons we cannot think about right now, and someone else might not need it because they are fine with recompiling everything from scratch at each single small change.

I don’t think there are some many Flash applications that support scripting. I built myself a few of them for my company but they are for a particular purpose and probably the same motivations that made me decide to implement a scripting language are hard to find for other kind of applications.

As far as I know, the most of the applications that need to be flexible use a plugin system (more or less complicated – as Aviary for instance and Hobnox) and are fine with it because – we must say that – ActionScript is itself a scripting language and a SWF file is nothing more than a bunch of instructions (more or less) generated by compiled ActionScript.

But sometimes http://www.otradny.org/?find-someone-write-my-college-paper Find Someone Write My College Paper security comes into account, and it is hard (even if possible) to limit the funcionalities used by a plugin if this plugin is created by a 3rd party developer.

And so it comes into account scripting. With scripting we have Ghostwriter Gute full control over what a developer can do an how he can do that. We can limit it, provide builtin functionalities … But everything costs something, and building a fast/flexible/powerful/useful scripting languages is not that easy as it might seem.

This is why I decided to spend a bit of time in explaining the basics to implement a scripting language in actionscript to be able to script our applications. I’ll walk through all the passes – from lexing to bytecode generation and maybe a quick look into Virtual Machines – with the aim to provide someone (maybe in the far future) a bunch of documents to use as reference to build their own scripting language.

I’ll try to give an in depth look, but as far as the argument is quite complicated and full of facets, you may not find here the right solution for you. Nor the fastest or the most flexible. But it is better then nothing so if you are interested in that keep reading the blog 🙂

Expressions evaluation at (almost) native speed

Finally I found a bit of time this weekend to do some other tests with http://serc.eng.usm.my/?online-phd-thesis-library-science Online Phd Thesis Library Science expressions evaluation.

The results are pretty interesting, even if obvious from some point of view. I took the ExpressionEvaluator I wrote as example for the first post about this topic, and then I edited a bit the code adding just in time Help With Creating A Business Plan AS Bytecode compilation.
Thanks to that, expressions evaluation is much more fast and always safe because it runs in its own ApplicationDomain.

You can download the sources here, that includes the edited code and a test file. Develop Research Proposal Phd The test file runs 1 milion of iterations and may hang your browser or at worst case your system. Reduce the value of the ITERATIONS constant if you are not sure about the power of you machine.

If you want to read a bit more details about that, click on the link below to continue reading.

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