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The picture shows:
void echo_infinite(UART *in, UART *out)
{
while (1)
{
while (!data_available(in))
{
// wait
}
char ch;
ch = read_byte(in);
while (!ready_for_sending(out))
{
// wait
}
write_byte(out, ch);
}
}
The above function will never terminate. That is no problem if that is the only thing your device has to do, but totally not acceptable, if your device has to do something else as well, for example, have a blinking LED. The traditional solution is to use a state machine and call the function implementing the state machine from the (never terminating) main loop. In case there is just one such task, one can make use of static define variables for the local variables. Otherwise, one has to define a struct for each such task and pass this as an argument. (See the page Machine independent implementation of Cooperative Multi-threading in C for how this could be done.) If you want to implement the above function echo_infinite as a state machine, you get something like::
void echo_state_machine(UART *in, UART *out)
{
static char ch;
static int state = 0;
switch (state)
{
case 0:
if (data_available(in))
{
ch = read_byte(in);
state = 1;
}
break;
case 1:
if (ready_for_sending(out))
{
write_byte(out, ch);
state = 0;
}
break;
}
}
This code looks rather different from the above code. For this simple case, with only two states, it is probably not that difficult, but in case you have something like ten states, it can quickly turn into Spagetti code, that is difficult to follow, could have dupplicated code, and could have subtile bugs. In case the function implementing your task had no switch-statements and there is but one instance of your task, one could write the following code using some defines that are going to be explained below:
void echo_async(UART *in, UART *out)
{
START_ASYNC
while (1)
{
while (!data_available(in))
{
WAIT
}
static char ch;
ch = read_byte(in);
while (!ready_for_sending(out))
{
WAIT
}
write_byte(out, ch);
}
END_ASYNC
}
Notice that this code looks very much like the initial version. Note the use of static before the definition of the local variable ch. The defines one has to use, are the following:
#define START_ASYNC static int state = 0; switch (state) { case 0:
#define WAIT state = __LINE__; return; case __LINE__:
#define END_ASYNC }
These defines make use of the fact that the 'case' statements belonging to 'switch' statement may occur everywhere in the block following the 'switch'. In a sense, the 'switch' statement acts like a kind of 'goto' that can jump everywhere in the code belonging to it. It also makes use of the fact that the '__LINE__' macro returns the number of the current line. Note that they are replaced with the line number of the line where 'WAIT' is used, not where it is defined, according to the standard rules of how the C-preprocessor works. See the program D241005.c for an example that uses the above functions, where the functions echo_stm and echo_async are called a hunderd times, which is not always enough to print the string "Hello World!". The programs accepts a number as an argument to be used for initializing the random generator. (Find a number that makes all the functions print the whole text.) After the above two functions are called from main, the function echo_infinite is called, which never terminates, meaning that the program has to be terminated for it to end.
If one does want to use a 'switch'-statement in the code, one could use a combination of a switch statement at the start of the function and 'goto'-statements to labels matching the various places to wait. This does recuire one to number the states explicitly, which requires some additional work and bookkeeping, but it could help when implementing unit tests. When using C++, one can replace the static variables with private members of the class the method belongs to. This technique can be used to define iterators that are implemented as co-routines that yield results whenever needed. For a example, see the next method of the class InlineIncludesIterator in the program kaem_parser.cpp. For a more detailed description of all the possible ways to implement co-routines, see also: Coroutines in C.
I am thinking about when to harvest them. If I harvest them now, the seeds might not be mature enough. It looks like the fruits have not come out yet. If I wait too long, the seeds might be eaten by some birds and I will not be able to harvest the seeds. In 2013, it was on November 25 that we harvested the berries. I think, I am going to keep an eye on it for the coming week.
At 13:44:26, I bought the booklet AKI Schilderlichting 2008 written by Joris Geurts, Kars Persoon, Kees Smits, and Elly Strik in Dutch and German, and published by AKI-ArtEZ Enschede in 2008 from Het Goed for € 0.50.
At TETEM art space, I saw the Model Collapse exhibition by Cyanne van den Houten and Ymer Marinus, who are part of the Telemagic collective. Before I entered the immersive exhibition, I was told that the exhibition is not about AI, as the title of it refers to concept of model collapse, but about how to get an AI like ChatGPT, but about how to get there. According to the description it 'depict the landscape from which generative AI emerges. Revealing its self-consuming origins in extraction of the earth's resources and data through relics, artifacts and stories from the past.' I was anticipating to learn some more about how these Large Language Models are created, but when I entered the exhibition I was a bit confused about it. There was a large screen with some text and about ten statue like objects with lights, buttons and displays. On was covered with a small displays that I found quite interesting.
At Fotogalerie Objectief, I saw the exhibition People Matter with photographs by Peter van Tuil and Frans Rentlink. From Peter van Tuil there were photographs from his books Ergens: Malaga 2023 and HUIS & HABITAT: Pieter en WillyPeter. The later is about the reclusive artist Pieter Derksen. Ingrid Hendriksen also took pictures of him with some text in English, which can be viewed at: (At home with Pieter Derksen: The reclusive artist. Frans Rentlink had a series of portrets of the surrealistic painter Charles du Bois and a friend of him called Johan.
At Concordia, it was quite busy with people visiting the Sustainable Fashion Experience Enschede. I first looked in the front room, where the exhibition Joystick by Madison Bycroft (on Instagram) was held. Next, I walked around the area where Kira Fröse and Marthe Zink are working on the Doublet #6 exhibition and then I went upstairs to have a second look at the Triangle in Square, but there was someone making some recording, so I did not walk around. I felt like the video's being displayed looked different. Then I heard some singing downstairs and it turned out that the gay men's chorus Soorten & Maten were practice singing the song 'Hotel California' (if I am not mistaken) as a warm-up for the performance they were going to give later. I presume as part of the opening of the exhibition It gets better by Tim Vischer, which is part of the Rainbow Days event. I left before the opening (also not being aware when it was).
