[jbzy324]

Hey all; So I'm working on my senior Mechanical Engineering project, a mechatronic/robotic painting table. A control system basically interprets a language called g-code, which is more or less a glorified dot-to-dot that tells the control system a series of points to drive the brush head to. I run into an issue with re-dipping the brush - it needs to be done on certain intervals, that are different for every drawing, and requires insertion of extra g-code lines into the original g-code, which just maps the pathways of the lines to be drawn. G-code runs from start to finish, so I need t

My programming knowledge is limited and only in C, so I hope this is a good place to start looking for help. Essentially I need to make a program that goes line by line through this g-code, and when it recognizes a certain character (Z, for instance), inserts some predisposed lines of g-code, and continues. I'll also need to be recognizing and storing different numbers along the way for calculations. Unfortunately, the scope of my small knowledge base is limited to the more math side of the language. My question is, is C a good language to code this type of program, or is there another that may be more streamlined/convenient/user friendly? And more or less, what does the structure of a code that reads through a text file line by line look like? I'm definitely not asking anyone for code, just help getting pointed in the right direction, and maybe some of the useful commands you guys think I'll have to implement. Thank you VERY much in advance.

jbzy

[Oler1s]

Quote

My question is, is C a good language to code this type of program

Probably not. Your requirements sound like nothing more than basic text parsing and manipulating, and C is a terrible language for that.

I know Python, so that's what I would use. Python, Ruby, Perl, all three would work. Or shell scripts if that's your thing? But not C.

Quote

And more or less, what does the structure of a code that reads through a text file line by line look like?

I have no idea what kind of meaningful answer would be given here. It's basically a repeated call to read a line from the file, with appropriate parsing and handling afterwards.

[JackOfAllTrades]

Moved to Software Development.

You might be better off with a higher-level language like Python for something like this.

[jbzy324]

Thanks Oler1s, like I said, that at least points me in the right direction.

Oler1s, on 08 May 2012 - 03:23 PM, said:

I have no idea what kind of meaningful answer would be given here. It's basically a repeated call to read a line from the file, with appropriate parsing and handling afterwards.

I know this was a weird question in the style of "Here's an all-too-vague description of what I need to do, but could you give me a basic skeleton?" But I was more thinking how I would implement it in C, as most of the commands I know are math based and have no idea how to effectively analyze text. I've heard from others that python would be the best way to go as well, so I'll start in that direction, and hopefully will have more pointed questions as some code gets written. I'm working off of a (very) loose pseudo code that I have written up, but unfortunately I don't know how "Look through the text until you see the letter 'z'" and "If you see an 'x' character, store the number directly after it, but that number could be any character length so keep reading numbers until you see a space" translate into python commands. So, I was hoping someone might offer a useful command/combination of commands in C that I might try; however, hopefully looking into parsing with python will help with some of that. I'm sure I'll have some more specific questions through the coding process. Thank you again for the help!

jbzy

[JackOfAllTrades]

Here's a place to start.

You're interested in input/output and string functions.

I also have some C entries in my blog, and we have tutorials.

[turboscrew]

Sedwould do that quite easily too.
There is also a windows version of sed.

This is a starting point.

Awk is probably a bit heavy.

[jon.kiparsky]

Quote

Sed would do that quite easily too. ...Awk is probably a bit heavy.

It's like they say: when all is sed and awk, there's a lot more sed than awk.


I'd reach for perl in this situation, myself, but perl-style regular expressions (which is what you need) are available in just about any language now, so you could do this in pretty much any modern language.

This post has been edited by jon.kiparsky: 08 May 2012 - 10:48 PM

[Python_4_President]

Hey Jbzy, I'm really interested in machining and G is pretty popular in the areas I'm interested in.

I'd love to help you work something out (I'm actually looking for a new project to jump into having completed my from-scratch(motor controllers/light controllers/etc) PC driven arduino/Xbee powered RC car).

I'm good with Python, and I have a pretty good idea how to whip something like you're talking about up, but obviously I'll need to see the g-code to know what to parse and when.

If you're capable of writing code in some language, I can definitely get you going in Python in short order.

This post has been edited by Python_4_President: 15 May 2012 - 01:40 PM

[Python_4_President]

Forgot to ask.....

What's your prefered way to communicate with people that may or may not live anywhere near you?



Also, some starting points...

Here's a complete python program and the command that executes it:

Program! (filename=myfirst.py)

print "This is my first Python program... holy crap, no includes."

COMMAND (for Window$!)

c:\python[version?]\python.exe myfirst.py

COMMAND (For Linux!)

python myfirst.py

WHAT STRINGS LOOK LIKE:

"Double quoted string"
'Single quoted string'
"""triple quoted string"""
type("") == type('') == type("""""")

HOW TO THINK ABOUT STRINGS LIKE ARRAYS IN C:

MyString = "This is my string"
MyString[0] == "T" or 'T' or """T"""
MyString[1] == "h" or 'h' or """h"""
MyString[2] == "i" or 'i' or """i"""

WHY PYTHON IS MORE AWESOMER:

MyString = "Yes, that is pretty cool."
MyString[-1] == "." or '.' or """."""
MyString[-2] == "l" or 'l' or """l"""

HOW DO I ACCOUNT FOR ' in a string, then?
You could be lame and do:

'Yes, I like being lame. It\'s fun.'

BUT,

"This is much better. ' != \""
"""This way is also possible. It's cool with 's or "s."""

HERE'S SOME RAW POWER:

"This string can be indexed and SLICED!, because it is a string object..."[5:11] == "string" 
"This string starts with This... as seen here ->".startswith("This") == True
"This string ends with -> as seen here ->".endswith("->") == True

WHAT YOU'LL USE A LOT, BECAUSE IT WINS:

gcodez_i_care_about = "some gcodez"
gcodez_i_am_looking_at = open("gcodez.gext", 'r').read()
if gcodez_i_care_about in gcodez_i_am_looking_at:
    print "I foundz useful gcodez!"

^ The in operator is just awesome. It tells you if the thing you're looking for is in the thing you're looking through.

Case sensitivity can be managed with the string method lower().

yay = "I LIKE CAPSLOCK, IT MAKES ME LOOK SMART."
stop_yelling_at_me = yay.lower()

^ There's also an upper(), which does what you'd expect.

This post has been edited by Python_4_President: 15 May 2012 - 02:13 PM

[peace_fixation]

In C you can read/write a text file like this, the syntax is loose but you should get the gist:

input_file = fopen("your_file.txt");
output_file = fopen("new_file.txt");
int ch;
while ((ch = fgetc(input_file)) != EOF)
{
  // read char by char until you hit End Of File
  // write each char to a new file, unless it's a special char
  // in which case, write the matching G-Code

  if (replacement_char(ch) == FALSE)
  {
    fputc(output_file); // put single char
  }
  else // replacement_char(ch) == TRUE
  {
    switch(c)
    {
    case 'Z':
      fprintf(output_file, "some G-Code"); // put G-Code string
      break;
    case 'A':
      fprintf(output_file, "some other G-Code");
      break;
    }
  }
}

fclose(input_file);
fclose(output_file); // now output_file == input_file with G-Codes replaced

This post has been edited by peace_fixation: 14 June 2012 - 02:33 AM