Re: how to (slightly) modify the Lua parser

[KHMan <keinhong@...>]

steve donovan wrote:
> On Mon, Oct 12, 2009 at 6:08 PM, Francesco Abbate
> <francesco.bbt@gmail.com> wrote:
> > |x| sin(x)/x
> > or
> > |x, y| sin(x) * cos(y)
>
> You're not the first to want this ;)
>
> http://lua-users.org/wiki/ShortAnonymousFunctions
>
> No direct clues there to patch the parser, however.

If you trace the call tree of the recursive descent parser in 
lparser.c (starting from luaY_parser), I think it is do-able, the 
call tree is pretty straightforward.

For function definitions:

statement() -> funcstat() -> funcname() -> body()

body() is where the parameter list is parsed.

So for |x,y|, you need to check for the first '|', then call out 
to its own 'stat' (statement handler) function, where you follow 
the style of the parameter parsing in body(), but check for '|' 
instead of a closing ')'.

For the body, which is a expression (or can it be a list of 
expressions?), you can look at the flow of explist1(). The 
expression handling stuff is pretty compact code, so take your 
time to follow the call tree.

HTH,
--
Cheers,
Kein-Hong Man (esq.)
Kuala Lumpur, Malaysia