Re: [PIC] Learning C

I must stress that I want to learn C as a desktop language before
converting to PIC use..
Recommendations for a good book would be appreciated
__________________________________________
David C Brown
43 Bings Road
Whaley Bridge
High Peak                           Phone: 01663 733236
Derbyshire                eMail: [email protected]
SK23 7ND          web: www.bings-knowle.co.uk/dcb
<http://www.jb.man.ac.uk/~dcb>



*Sent from my etch-a-sketch*


On Mon, 11 Nov 2024 at 00:26, Isaac Marino Bavaresco <
[email protected]> wrote:

> I rarely use other people's code, unless it is deemed to be of very high
> quality. I prefer to study the code and write my own version based on
> it. It is slow but has proven to save a lot of problems in the long run.
>
> I write the absolute majority of my code in C (C99 if possible) and try
> to keep with GCC. If a platform doesn't have a GCC port it is very
> likely that I won't adopt it. That's not the case for PICs, which I use
> for so many years that it predates the GCC wide availability.
>
> My LCD routines were written in C in the early 1990s for 8051 MCUs and I
> still use them for ARM and MIPS (PIC32). If they were written in
> assembly language I would have needed to recreate them at least five
> times (AVR, PIC, PIC18F, PIC32, ARM).
>
> I rewrote a large part of FATFS, because the code was so complicated and
> obscure that I could not understand it. I think that I found a few
> mistakes in the implementation during the process.
>
> I also wrote my own RTOS because I was not satisfied with the code of
> FreeRTOS.
>
>
> Cheers,
>
> Isaac
>
>
> Em 10/11/2024 21:36, smplx escreveu:
> > Hi Isaac,
> > The point isn't really what I could or should do, it's more to do with
> > what someone else has written and the rest of us have to use. How
> > often have you come across some code that was abandoned by the
> > original author many years ago and has been hacked by uncareing
> > individuals to fix an immediate problem. How often have you come
> > across comments that no longer reflect what the code actually does.
> >
> > And to make the NaN situation even more interesting a floating point
> > library might implement NaNs correctly (or not) where the "noddy" MCU
> > compiler doesn't. This is another reason why it's best to learn C in a
> > proven high quality dev environment like a PC. Look at the early PIC C
> > compilers - I dare you not to laugh.
> >
> > Another way to express a NaN's character is to say "it is unordered".
> >
> > Friendly Regards
> > Sergio Masci
> >
> > On Sun, 10 Nov 2024, Isaac Marino Bavaresco wrote:
> >
> >> But you could use also the function 'isnan', which is easier to
> >> understand for someone reading your code.
> >>
> >> There are also other functions like 'isinf', etc.
> >>
> >>
> >> Interestingly, a NaN is not greater, nor smaller nor equal to
> >> anything, not even itself. It is only different than everything.
> >>
> >>
> >> Cheers,
> >>
> >> Isaac
> >>
> >>
> >> Em 10/11/2024 20:09, smplx escreveu:
> >>> Hi Colin,
> >>>
> >>> You might be intested to know that to check for floating point
> >>> errors / exceptions in C you would use:
> >>>
> >>> if (x == x)...
> >>> or
> >>> if (x != x)...
> >>>
> >>> where x is a float
> >>>
> >>> e.g.
> >>>     float    x
> >>>
> >>>     x = 1.0 / 0.0;
> >>>
> >>>     if (x != x)
> >>>     {    // x is a NaN which is an error
> >>>     }
> >>>
> >>> Here clearly "x 'is the same as' x" but the test is "x 'is a NaN'".
> >>>
> >>> Friendly Regards
> >>> Sergio
> >>>
> >>> On Sun, 10 Nov 2024, CDB wrote:
> >>>
> >>>> I have always separated the difference of =  and == in C by
> >>>> referring to the latter as 'is the same as'
> >>>>
> >>>> if (X is the same as Y) then ......  if (X == Y) then
> >>>> x = y       x now contains the value of Y.
> >>>>
> >>>> Colin
> >>>>
> >>>>
> >>>> --
> >>>>
> >>>> [email protected]  11 November 2024
> >>>>
> >>>> Hosted by: www.superdomains.com.au
> >>>>
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> >>>> individual or Personnel Department, and public if addressed to a
> >>>> blog,  forum or news article.
> >>>>
> >>>>
> >>>>
> >>>> __________________________________
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> >>>>
> >>>>
> >>>> On 11/11/2024 08:24:15, "smplx" <[email protected]> wrote:
> >>>>
> >>>>>
> >>>>>
> >>>>> On Sun, 10 Nov 2024, Neil wrote:
> >>>>>
> >>>>>> Agree with a couple things from other comments such as C being
> >>>>>> high-level assembler and using a PC at first (you can just use
> >>>>>> gcc already on Linux).
> >>>>>>
> >>>>>> Already knowing a structured language is very helpful.
> >>>>>> But IMO you'll have to wrap your head around pointers, which can
> >>>>>> get confusing. I find this C visualizer very helpful for figuring
> >>>>>> out some algorithm... https://pythontutor.com/c.html
> >>>>>>
> >>>>>> One more note: = != ==
> >>>>>> Or in other words, the equal sign ( = ) and the double equal size
> >>>>>> ( == ) are very different things in C. The first assigns a value
> >>>>>> and the other compares values. But people new to C will
> >>>>>> invariably use a single equal for a comparison and the code is
> >>>>>> true every time, as C will compile it as valid code, do the
> >>>>>> assignment, then the comparison. You have been warned ;P
> >>>>>
> >>>>> Sorry to wade in here but:
> >>>>>
> >>>>> if (y = x)...
> >>>>>
> >>>>> assigns x to y then compares the result to 0. 0 is nomally taken to
> >>>>> mean false and "not 0" as true. So it is almost alway true except
> >>>>> in the case where x is 0.
> >>>>>
> >>>>> I'm not sure what happens if x and y are floats and x is a NaN or
> >>>>> if x and y are structures.
> >>>>>
> >>>>> if you're looking for a real headache try debugging a program that
> >>>>> contains:
> >>>>>
> >>>>> if (! x == y)...
> >>>>>
> >>>>> Trying to learn C on bare metal is like trying to learn to fly by
> >>>>> crashing a lot. It's a lot quicker and easier if you learn on a
> >>>>> simulator.
> >>>>>
> >>>>> Friendly Regards
> >>>>> Sergio Masci
> >>>>>
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> >>
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