[fpc-devel] Pascal to Javascript - Call for Help

Marcos Douglas md at delfire.net
Sat Apr 5 20:26:05 CEST 2014

On Sat, Apr 5, 2014 at 6:48 AM, Michael Van Canneyt
<michael at freepascal.org> wrote:
> Hello,
> After many years of dreaming of an open source version of Morfik
> Appsbuilder,
> (and more recently Smart Mobile Studio), I've finally committed a first
> version of the pascal-to-javascript conversion engine.
> The unit and the associated unit tests are in
> packages/pastojs
> and a sample converter program in
> utils/pas2js
> This is a limited initial commit. It will convert plain pascal to
> javascript, almost verbatim.
> It will not yet convert everything, objects are not yet supported, for
> instance, neither are var arguments. Scope is also an issue. In fact, it can
> convert things that do not need a lot of context - plain syntactical
> conversion, if you want.
> However the engine is IMHO ready for the more serious work. At least it
> shows the ideas underpinning the project.
> This is potentially a big project, which I cannot handle alone (FPC is a
> circle of volunteers, after all). Therefor I'd like to invite people to have
> a look at the code, give remarks, submit patches.
> That said:
> There will also be an effort to let the Free Pascal compiler itself output
> Javascript (using asm.js or plain javascript), to which I will - to the best
> of my abilities - also contribute.
> Why 2 efforts ? The goals of these efforts are not the same:
> - The goal of the compiler is to compile all of pascal.
>   This will result in unreadable javascript, simulating heap memory etc.
>   It will be more comparable to assembler than to hand-written javascript.
> - The goal of this project is to generate understandable Javascript.
>   The idea is not to convert all existing code to work in the browser
> (depends on the code),
>   but rather to be able to program the browser in Object Pascal.
>   As a consequence, not all pascal constructs will be supported (pointers,
>   direct memory access jump to mind).
>   Another matter is that the treshold for understanding the compiler is
> rather
>   high (I myself don't claim to understand the compiler fully).
>   Whereas I believe that understanding this project should be within reach
> of everyone
>   that knows object pascal  (I may be wrong in this belief, of course ;) )
> Both efforts will use the same backend for writing javascript, so the
> javascript writer
> and the javascript syntax tree have been kept low-key, meaning that they can
> be compiled to
> depend almost exclusively on the system unit (no classes unit, to name but
> one).
> Feel free to discuss here or mail me in private with more questions.
> Michael.

Hi Michael,

A first little patch.
In line 1101 -- Function TPasToJSConverter.ConvertRepeatStatement --
you need to put a "raise"

    raise; <<<<

Marcos Douglas

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