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Forum Index : Microcontroller and PC projects : CMM2: why no CHAIN?
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| nattacca Newbie  Joined: 29/07/2020 Location: United KingdomPosts: 2 |
Hi! The manual states, that CHAIN is not supported on the CMM2 because "The Colour Maximite 2 has an exceptionally large program memory space so this feature is not necessary." This sounds like the infamous Bill Gates quote "640K ought to be enough for anybody." :/ Even if memory itself is not the immediate problem, what about some means of dynamically loading program code, depending on whatever conditions one might see necessary? I.e. using some sort of library functions that are loaded during run time, depending on user choices. Is there any chance we can get CHAIN or similar commands for the CMM2? Or are there other ways to accomplish something similar? |
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thwill Guru  Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Hello "nattaca", What do you want to achieve (in BASIC) that storage (if not performance) wise cannot be achieved in 0.5 MB of program memory and 5 MB of data memory all backed by a fast storage device with 128 GB capacity? If you want to run one program from another then you can call RUN on a new program if it's location and arguments are fixed. If you need to create them dynamically then use EXECUTE to call RUN. If you need programs to share variables then stream them in and out of a file. Genuinely curious to know what you have planned, Tom Edited 2020-10-30 05:59 by thwill MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| nattacca Newbie Joined: 29/07/2020 Location: United KingdomPosts: 2 |
I seem to have misinterpreted the intended behaviour of CHAIN ... it basically just loads and runs another program, similar to RUN, but with a bit more options to configure it's behaviour, right? What I really want is a way to dynamically load code at runtime, pass the control flow to it, but then return to the original code and continue from there. I just want to dynamically load some sort of library with a bunch of subroutines that I then can call from my main program. I want different implementations of a sub routine in different (library)files, that I can load and call at run time. #INCLUDE seems to do that for me, but it lacks the dynamic part where I could decide at run time which file I want to include. |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10310 |
You can't do this and you won't ever be able to do this. MMBasic does quite a lot of manipulation of the program when it loads it to improve performance this is completely incompatible with being able to dynamically load new elements |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4311 |
Different platforms may have had different interpretations of CHAIN. If memory serves then on the BBC Micro it would load and run a new program whilst keeping the variables (and probably other non-program memory) intact. On your main topic you've described a desired solution without describing a concrete use-case. The CMM2 has sufficient program memory to store 10,000+ lines of BASIC which is probably enough to store multiple implementations of any given subroutine in a single monolith and use a SELECT CASE to dispatch requests to the desired one. I believe it is enough to knock off most, if not all, 8 and 16-bit video games plus the productivity applications that were available on those platforms. If you really do need more program memory then depending on your application you could either: Use a chain of multiple programs each operating on the outputs of the previous one, or Have a master/launcher program that dynamically writes the "real" program with the correct #INCLUDEs for the specific subroutine implementations required for a given execution. In a crazy future some insane genius might (even without further firmware extensions) concoct a mechanism to load machine code into integer arrays and then use a CSUB to pass control into that code. Such arrays could be dynamically loaded and swapped. @matherp may now point out some hardware limitation that means this is impossible, or he might just stand back and say that the "engine's cannae' take it!" Best wishes, Tom Edited 2020-10-30 21:44 by thwill MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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