Meta commands

jens55

@dans79, agreed, that is the way I am used to program a loop and yes, nested loops will be a nightmare.

alankilian

nested loops will be a nightmare.

Why?

Each loop gets its own iterator (which is what iterators ARE) so everything works out.

m118 s"Starting the loop"
while iterations < 3
      m118 s"hello world first"
      while iterations < 3
        m118 s"hello world second"
        while iterations < 3
          m118 s"hello world third"
m118 s"Done with the loop"

8/12/2021, 2:57:50 PM 	M98 P"0:/macros/000_test"
Starting the loop
hello world first
hello world second
hello world third
hello world third
hello world third
hello world second
hello world third
hello world third
hello world third
hello world second
hello world third
hello world third
hello world third
hello world first
hello world second
hello world third
hello world third
hello world third
hello world second
hello world third
hello world third
hello world third
hello world second
hello world third
hello world third
hello world third
hello world first
hello world second
hello world third
hello world third
hello world third
hello world second
hello world third
hello world third
hello world third
hello world second
hello world third
hello world third
hello world third
Done with the loop

DanS79

@alankilian said in Meta commands:

@jens55 said in Meta commands:

nested loops will be a nightmare.

Why?

Each loop gets its own iterator (which is what iterators ARE) so everything works out.

They are all called iterations.

If use want to use multiple of them to set a variable, the code would be very hard to read (assuming scoping even allows you to access all of them).

The following would be real confusing to follow if you replaced a, b, and c with iterations .

var x = 0
var a = 0
var b = 0
var c = 0
while a < 10
    set var.b = 0
    while b < 20
        set var.c = 0
        while c < 40
            set var.x = (a * b) - c
            set var.c = c + 1
         set var.b = b + 1
    set var.a = a + 1

alankilian

@dans79 Yeah, there are a thousand wrong ways to use a programming feature for every right way to use them.

jens55

I think we are drifting away from the part that I am having problems with which is why the particular construct I was using was having issues. Yes, there is a way to change things but WHY is it needed.

Here is a different way of going:

This works:

while iterations < 10
  m118 s{"hello world " ^ iterations}
  g4 s2
  continue

This gives:
Error: in file macro line 6 column 11: meta command: 'continue' was not inside a loop

while iterations < 10
  m118 s{"hello world " ^ iterations}
;  m118 s{"hello world " ^ iterations}
  g4 s2
  continue

The commented out line seems to dump the 'continue' statement outside of the loop and seems to me to be a bug in interpretation.

alankilian

@jens55 You don't need to add a 'continue' statement at the end of a loop.

alankilian

@jens55 said in Meta commands:

The commented out line seems to dump the 'continue' statement outside of the loop and seems to me to be a bug in interpretation.

You need to be very particular with the left-side whitespace to keep things working.

The interpreter is going to look at how many tab (or space)?) characters you have at the beginning of every line to know where the end of the loops are.

Your commented-out line starts with a semicolon in column one which tells the interperter that's the end of your while loop.

So, the 'continue' statement is not outside of the loop.

jens55

@alankilian, I realize that .... but what I am getting at is that something is fishy about how this is interpreted. While I don't need the 'continue', there should be nothing barring me from using it. It isn't inherently wrong.

alankilian

@jens55 That semicolon in column-1 causes the interpeter to end the while loop.

This works:

while iterations < 10
  m118 s{"hello world " ^ iterations}
  ;  m118 s{"hello world " ^ iterations}
  g4 s2
  continue

jens55

@alankilian, I will test that but the semicolon is there to comment out the line and should not cause this reaction.

alankilian

@jens55 This works to keep the whitespace:

while iterations < 10
  m118 s{"hello world " ^ iterations}
  ;  m118 s{"hello world " ^ iterations}
  g4 s2
  continue

jens55

@alankilian
@dc42
Ahhhh, I need the spaces before the comment .... ok but that s a bug in the interpreter

alankilian

This post is deleted!

alankilian

@jens55 said in Meta commands:

Ahhhh, I need the spaces before the comment .... ok but that s a bug in the interpreter

From the documentation:

The body ends just before the first line that is not indented.

So, it could be argued that the interpreter is working fine.

It's not up to me to decide.

I'm happy you're getting going on your project again.

And I learned some things from this discussion, so thank you for that also.

jens55

@dc42
Here is another example of strange behaviour:

while true
  if iterations < 10
    m118 s"hello world"
    g4 s2
    continue
break

This executes but leaves the printer in a 'busy' state
Without the 'break' command it does the same
If I move the 'break' command to the right by two spaces, everything finishes ok - it breaks out of the loop
Point is, there is no such thing as an 'endif' to clearly identify where the 'if' statement ends. IMHO there should be (optional maybe) an 'endif' for readability but in any case, the 'break' should break out of the loop no matter what.

Edit: On re-reading this, there is a flaw in my thinking here, and unless the 'break' is indented two spaces over, the 'while' loop has no exit. Interesting note here is that the iteration variable apparently isn't reset until after exiting the 'while' loop because it only prints 'hello world' for one 'if' loop.
That to me seems rather odd ....

OwenD

@jens55
Nothing strange about it.
Using "while true" creates an infinite loop
This is a dangerous practice for the uninitiated as you must ensure that at some point you have a conditional that triggers a break command.
You have not done so. Therefore the loop continues.
Once it gets to iteration 10 it just stops sending the echo.

You should have put

'if iterations < 10
     Echo "blah blah"
else
      break

Your continue command is useless as it's not part of the while construct.
The point of continue is to skip an iteration.

'if iterations < 10
     if iterations = 5
            continue 
     Echo "blah blah" ; won't happen on #5
else
      break  ;  required to end loop

It's safer to use
while iterations < 10
blah blah

EDIT
Sorry. Doing this on my phone so I could not see your code
Your BREK is outside the whole loop, but the comments stand

jens55

Here is another thing that strikes me as odd:

while true
  if iterations < 10
    m118 s"hello world"
    g4 s2
    continue
  if iterations < 11
    m118 s"hello north america"
	g4 s2
	continue
  break

This code will execute the first 'if' for 10 times but will not reset 'iterations' as I would have expected and because of that will only execute the second 'if' loop once.

jens55

@owend said in Meta commands:

Your continue command is useless as it's not part of the while construct.
The point of continue is to skip an iteration.

To skip an iteration ???? Where did you see this in the documentation ???
I look at 'continue' as a command that strictly exists as a means to improve readability of the code since the command itself seems to do diddly squat and can be left out.

alankilian

@jens55 said in Meta commands:

@owend said in Meta commands:

Your continue command is useless as it's not part of the while construct.
The point of continue is to skip an iteration.

To skip an iteration ???? Where did you see this in the documentation ???

'continue' jumps back to the BEGINNING of a loop.

So if you have the following story: (COMPLETELY useless, but trying to illuminate how 'continue' is used)

while iterations < 10
  m118 s{"This is iteration " ^ iterations}
  if iterations > 5
    continue  ; Don't do this stuff after the first 5 iterations
  m118 s{"Perform this action on " ^ iterations}

This is iteration 0
Perform this action on 0
This is iteration 1
Perform this action on 1
This is iteration 2
Perform this action on 2
This is iteration 3
Perform this action on 3
This is iteration 4
Perform this action on 4
This is iteration 5
Perform this action on 5
This is iteration 6
This is iteration 7
This is iteration 8
This is iteration 9

alankilian

@jens55 said in Meta commands:

Here is another thing that strikes me as odd:
while true
  if iterations < 10
    m118 s"hello world"
    g4 s2
    continue
  if iterations < 11
    m118 s"hello north america"
	g4 s2
	continue
  break
This code will execute the first 'if' for 10 times but will not reset 'iterations' as I would have expected and because of that will only execute the second 'if' loop once.

Why do you think 'iterations' will get reset to zero?
'iterations' counts the number of times through the loop.

Your 'if' statements will not affect the iteration count at all.