Re: Finally a PIC32 with FPU for embedded Lua on MIPS

["John Hind" <john.hind@...>]

> I believe a chip with 512k of RAM is good for a lot of real world eLua
applications. <Bogdan Marinescu>

Have you considered doing a Kickstarter like the Python and JavaScript
examples I referenced?

> I don't think Lua is taking lot of RAM, all dynamic languages that I know
of need a lot of RAM (for good reasons) . <Bogdan Marinescu>

There is an idea that has been rattling about in my mind for a few years
now, but it may still be a little half-baked. This is that it should be
possible to allocate the bytecodes of functions/closures separately from any
required volatile storage (for example upvalues). The latter would be stored
in RAM, while the bytecodes would be stored as immutable strings (strings in
Lua already being  byte-safe and immutable). Then all you'd need is the
ability to compile the memory allocation functions to allocate strings in
EPROM. Not only does this take the bytecodes (and the strings) out of the
RAM budget, but it also allows string fragment compression/deduplication to
be used on bytecode sequences as well. If source is recompiled and generates
the same bytecode sequence, the deduplication automatically eliminates it
using no more memory. On von Neumann architectures everything would be
allocated from RAM but still benefit from compression, while on
microcontrollers the memory allocation function could be replaced by one
with access to both EPROM and RAM. Garbage collection would also need to be
modified so strings/bytecodes (if allocated in non-volatile memory) are only
collected on demand.

I'm still waiting for the JavaScript kickstarter chip to be delivered so
time will tell how useful it is. JavaScript has the big advantage that being
intrinsically event-driven it fits well with interrupt-driven
microcontroller applications, but compared to Lua it is an ugly, bloated
language, and Python is barely better without even the advantage of being
event-driven. But I think it would be relatively easy to write an
event/interrupt driven scheduler for Lua coroutines.

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