Tuesday, 19 January 2010

The saga continues ...

Well to answer the question posed two articles ago - nobody uses those old things anymore. Just had the sparkie around and he wired the a/c on a separate breaker (probably as it should have been in the first place) and moved the kitchen/laundry to a breaker too. He said they only come across those fuses when dismantling old fuse boxes.

So all that done, time for a hot coffee.

But the a/c didn't work either - panel did all the right things, pump too, just no air being pushed ... then it blew the breaker. So another visit from the installation guys basically just to confirm it's just broken and now a call's been lodged with the manufacturer for a 'service call'. Hopefully it's just a bung controller.

The insulation guy eventually rocked up yesterday too - and I had it installed by the end of the day. I suspect there's an awful lot of roofs in Adelaide that fall within the 100sqm limit of the 'average house' (hah, asif). Quite painless, although who knows how effective it is - they split some of the bats up to lay over the old stuff.


Mucked about with the FORTH some more, with all the interruptions and comings and goings that didn't happen till the evening - and then about 9pm I noticed it was dark. Not sure if that's a good thing or a bad thing (I definitely know that the 2 packets of chips and beer I had for lunchdinner[sic] was a bad thing though!). But as you'd expect given that it was a new processor to me, and that I was too tired and interrupted most of the time I was working on it - almost everything was wrong. Wrong registers in places, wrong order of registers, incorrect memory calculations and so on and so forth. But after many many iterations of fixing one function at a time I finally got something that compiled basic functions ok.

: a 42 EMIT ;

Well, "yay".

The current INTERPRET loop processes every character as it receives it - with no line editing and so on, so I thought about improving that. Didn't feel like writing that in assembly, so I fell back to C (TBH the compiler does a very good job with ARM code for the most part - but the core FORTH works better in assembly). I wrote a simple little 'readline' function with basic editing for single line input (cursor keys, delete, backspace etc) using terminal escape codes. That should do the job to start with once I hook it in.

As an exercise I thought i'd port it to FORTH instead. I was quite surprised - it (well, on paper - I don't have enough bootstrapped to build it yet) came out smaller (well no surprise there) and easier to read than the C equivalent. There's a few ugly bits but they can be hidden (or written better - no expert here). That's really what makes FORTH an interesting language, because you actively extend the language or add trivial functions to hide details without any penalty (in runtime or source baggage) for doing so. And it is real language extension including syntax, not just the run-time library. In-fact, since a threaded-interpreted run-time is so small I imagine the original powerful concept was that you could even radically alter that if need-be, although I think standardisation efforts muted the use of that `feature' to some extent.

I do think it falls down a bit on the variable front - they all work as explicit pointers, although I noticed there are now 'newer' concepts like 'values' that abstract some of messiness (and inefficiencies) away. And generally this stuff can be hidden away from most of the code.

Anyway, I'm quite enjoying this, so I'll see where it takes me, i've already got some ideas for tweaking the implementation and so on. Tho I'd better get outside and fill the bin with rubbish today as well, or it'll never get moved.

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