Feedback wanted: conditional GCode without indentation

bot

I think removing all indentation/whitespace from the syntax is a good idea. I also think a single END keyword is best. Multiple end keywords is just unnecessary. Keep track of the ENDs the same way one keeps track of the }s.

fcwilt

@garyd9 said in Feedback wanted: conditional GCode without indentation:

That doesn't answer the question. Without an example of the problem, it's difficult to give a reasonable opinion on a proposed solution.

As dc42 said in his opening post:

However, the need to indent the body of a conditional or loop makes it impractical to use a while-loop to create a looping GCode file, for example for a belt printer.

That seems clear enough.

Frederick

dc42

@garyd9 said in Feedback wanted: conditional GCode without indentation:

@fcwilt said in Feedback wanted: conditional GCode without indentation:

@garyd9 said in Feedback wanted: conditional GCode without indentation:

Can you please give an example of a gcode sequence that would impractical with the current space delimiting blocks?

The issue is gcode files as generated by a slicer - not the files you would create yourself on the duet.

That doesn't answer the question. Without an example of the problem, it's difficult to give a reasonable opinion on a proposed solution.

Suppose you generate a GCode file using a slicer. But you have a belt printer and you want to print it 10 times, with a belt movement between each iteration.

Using existing slicers, there is no way to use the slicer start and end scripts to achieve this.

You could achieve it by editing the GCode file, but then you would have to indent almost the whole GCode file so that it became the body of the while-loop.

If we offer the option to delimit if- and while-commands explicitly, then you could insert one line near the start of the file (the 'while' line), and one near the end (the 'end' line). You might even be able to put the 'while' line in your slicer start script, and the 'end' line in the end script, so that you don't need to edit the file at all.

Does that make the reason for this proposal clearer?

fcwilt

@bot said in Feedback wanted: conditional GCode without indentation:

Keep track of the ENDs the same way one keeps track of the }s.

'}' symbols are evil incarnate.

Frederick

bot

@fcwilt } // they don't seem so bad to me

tekkydave

@dc42 curly braces for me every time. I don't see the point of adding extra keywords that just take up space.

tekkydave

@fcwilt I once used a language called pl/9 that had a repeat...until. I miss it from every other language I've used since.

fcwilt

@tekkydave said in Feedback wanted: conditional GCode without indentation:

@fcwilt I once used a language called pl/9 that had a repeat...until. I miss it from every other language I've used since.

I never heard of PL/9 - I used PL/1 for a bit - it's looping syntax was flexible and consistent.

My programming language of choice is Delphi.

Frederick

fcwilt

@tekkydave said in Feedback wanted: conditional GCode without indentation:

@dc42 curly braces for me every time. I don't see the point of adding extra keywords that just take up space.

Keywords have a mnemonic value that isolated arbitrary symbols lack.

Frederick

garyd9

@dc42 said in Feedback wanted: conditional GCode without indentation:

Does that make the reason for this proposal clearer?

Yes, much clearer. Thank you.

I'm not familiar with belt printers and how this might be used - which left (and still leaves) my understanding lacking.

That being said, can the problem be addressed using macros? Can a print job's gcode use M28/M29 to create new files?

; ----- start gcode
;
; inital printer setup
; 
M28 job.gcode ; cause the actual gcode to be written to job.gcode
;
; ------- actual print gcode generated by slicer
;
; --------- end gcode
M29  ; stop/save job.gcode
;
;  -- here would be the loop for running the print job
while (some_condition)
       ; belt movement
       M32 job.gcode

<eof>

(I have no idea if a gcode file can use M28/m29 to create another gcode file, but if it can...)

theruttmeister

@dc42 said in Feedback wanted: conditional GCode without indentation:

@garyd9 said in Feedback wanted: conditional GCode without indentation:

@fcwilt said in Feedback wanted: conditional GCode without indentation:

@garyd9 said in Feedback wanted: conditional GCode without indentation:

Can you please give an example of a gcode sequence that would impractical with the current space delimiting blocks?

The issue is gcode files as generated by a slicer - not the files you would create yourself on the duet.

That doesn't answer the question. Without an example of the problem, it's difficult to give a reasonable opinion on a proposed solution.

Suppose you generate a GCode file using a slicer. But you have a belt printer and you want to print it 10 times, with a belt movement between each iteration.

Using existing slicers, there is no way to use the slicer start and end scripts to achieve this.

You could achieve it by editing the GCode file, but then you would have to indent almost the whole GCode file so that it became the body of the while-loop.

If we offer the option to delimit if- and while-commands explicitly, then you could insert one line near the start of the file (the 'while' line), and one near the end (the 'end' line). You might even be able to put the 'while' line in your slicer start script, and the 'end' line in the end script, so that you don't need to edit the file at all.

Does that make the reason for this proposal clearer?

That could be simplified down to a gcode command that executed a specific .gcode file multiple times:
Mxxx thisprintjob.gcode S10
For example.
That has the advantage of not needing anything like the complexity of conditionals.

I think the fact that it is a programming loop is making people think that the solution is to create the ability in g-code to code loops. Where as in fact for the described use case at least, its not really a loop, its just a way to not have the file be 10 times longer than it needs to be.

At there other things that actually are conditional and not just 'do x, y number of times'?

(in fact, all this could be done in DWC... which in some ways makes more sense).

zapta

@fcwilt said in Feedback wanted: conditional GCode without indentation:

'}' symbols are evil incarnate.

The Duet's firmware is full of them, don't bring it into your home.

https://github.com/Duet3D/RepRapFirmware/blob/dev/src/Movement/DriveMovement.cpp

garethky

end is fine
I would pick just 1 way to do it, even if that way breaks existing code. Now is the time to make breaking changes. I don't want to imagine a) what tricky things users will think up to fool themselves b) what implementation bugs will arise due to the complexity of having 2 ways to do it.
As a software engineer, this question makes my skin crawl. I really wouldn't do anything for whole files, just blocks. But if you really want to mix both styles, I would do this: require unintended blocks to have a begin and end keywords, on their own lines, to delimit the block. That way begin/end can be used with all of the existing block types without renaming them (the names are perfectly good as-is).

if foo == bar
    begin  
; begin unruly slicer generated gcode
G10
G1 X50 Y50 F5000
; and so on ...
    end

This is basically a friendlier versions of parens{<block>}. You could also postfix the if statement with python's : to indicate an unintended block start but this is so subtle and easy to miss that I think it is visiting an evil on the intended audience.

Visual Basic has "OrElse" and "AndAlso", because they refused to re-define the meaning of "or" and "and". Don't be Visual Basic.

fcwilt

@zapta said in Feedback wanted: conditional GCode without indentation:

The Duet's firmware is full of them, don't bring it into your home.

That's why I perform a ritual "cleansing" of the boards before I use them in a printer.

Better safe than sorry.

Frederick

fcwilt

@theruttmeister said in Feedback wanted: conditional GCode without indentation:

That could be simplified down to a gcode command that executed a specific .gcode file multiple times:
Mxxx thisprintjob.gcode S10

That would still require editing the slicer generated file to separate out the pre-print/post-print code from the main body of the code.

With a While and End you add two lines to the file and your done.

Frederick

BoA

Should the keywork be 'end', or something else?
I think I would use

if condition
           then
                       if given condition true
                       execute all commands up to else statement
                       or to fi if there is no else statement

           else
                       if given condition false 
                       execute all commands up to fi
           fi

and

while condition
do
   command1
   command2
   command3
done

Should it be permitted to mix keywork-delimiting and indentation-delimiting in the same file? If so, what problems might arise, and what restrictions should be enforced?

IMO indentations should be allowed just to keep it more readable, but ignored in processing code

How should the user indicate to the firmware that a loop or conditional is to be delimited by a keyword instead of by indentation? One option is to have a new command keyword (e.g. 'noblockindent') that means that for the remainder of the file, keywork-delimiting will be used. Using that keyword when already inside a block would probably have to be banned. Another option is to use different variations of 'if' and 'while' (e.g. a different keyword or some extra character) to indicate keywork delimiting for that command.

I would drop indentations for indicating clode blocks

MJLew

The coding language that I use most of the time (Livecode) uses "end repeat" to end a repeat loop, "end if" to end a conditional et cetera. It is very nice in that it does not depend on indents and it is entirely unambiguous. I commend it as a model to follow.
No. Do not allow mixtures. They will be confusing.
Ideally you would make the delimiting by keyword and do not support indentation. However, I'm guessing that indentation is already in use, and in that case your idea of something like 'noblockindent' would work rather like M82 and M83 (absolute and relative extruder). Perhaps it should have two keywords 'blockindent' and 'blockwords'.

MikeS

@fcwilt +1 from me but at the moment {} brackets are used for putting variables from object model into gcode commands.

Anyway i think that more similiar the conditional code is to c++ and less to python is for me a big yes....i have no problem with this type of language but i hate having indentation to determine the loop/function start/end.

I would give a function its proper "ender" so for example "loop" for while loop and so on.

OwenD

Having come from a Delphi programming background (based on pascal) I'd be inclined to lean towards a similar syntax
Pascal was designed to be easy to read/teach.
Blocks are typically surrounded by begin/end and use the keyword "do"
Indentation is not required but usually used for clarity.

while iterations < 10 do
begin
// do stuff
end

For if statements

if move.axes[0].homed do
begin
echo "axis homed"
end
else
begin
echo "axis is not homed"
end

line ends are usually terminated with a semi colon ; except in nested begin/end blocks as if if else (the outer block must have a ; and the inner must not) but I don't think that is necessary here.
Likewise the do keyword is purely for human readability.

I would not allow mixing of indentation and whatever block format is chosen.

bot

I don't see the need for a begin keyword. If is the keyword that starts the block.

Perhaps if a keyword is required at the beginning, we could borrow some LUA parlance and use THEN, so that the parser knows when the conditional is over.