Writing a rules parser in ActionScript/JavaScript

[Note to compiler types: Flex is Adobe's development framework,
not the lexer generator. -John]


We're trying to find the best approach to write/create a fairly simple
rules parser for the Flex 2 environment. The idea is to create a sort
of advanced validation engine that can process Drools-like notation,
specifically the left hand side (conditional) part, eg:


Cheese( type == "stilton" && price < 10, age == "mature" )


This would then be used for writing dynamic input validation. However,
because the running environment will be the Flex (Flash) engine, we
need to create something in ActionScript. (yes, I know, don't shoot
the messenger)


I have had some successes with the javacc parser before, but I can't
seem to find a precompiler that has ActionScript as the target
language (or something close enough like JavaScript). Does this exist?


Failing that, what would be the best approach to write a parser like
that from scratch? My guess is to follow a simple design pattern for
it, keeping the target environment in mind. Since I don't want to
reinvent the wheel, a simple but proven idea would be best.


Kind regards,
Thomas Goorden


PS: Interestingly, the rules engine we're going to (partly) emulate
has its parser written with javacc and those sources are available.

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