[REBOL] Re: REBOL Newbie tries to convert C source to REBOL (long posting)
From: antonr:iinet:au at: 21-Nov-2003 17:05
Hi,
What does the application do and why does it do it?
What does the data describe?
Handling blocks:
my-block: copy [] ; initialize the big block of data
; now within your parse rule
parse-rule: [
...
; at this point you have extracted section-name (eg. "sec1")
append my-block reduce [section-name copy []]
...
; at this point you have extracted some section data
; into data1 data2 data3 etc.. so store it
append last my-block reduce [data1 data2 data3]
]
That should have extracted all the data into my-block, which
should look like this:
my-block: [
"sec1" [
"dataline1" "111.11" "N012.11.029" "E034.31.110"
"dataline3" "111.11" "N015.11.099" "E034.31.110"
]
"sec2" [
"datalinex" "HFD" "111.11" "N012.11.099" "E034.31.114"
"dataliney" "LKA 131.41" "N011.11.049" "E031.31.116"
"datalinez" "JIH 111.11" "N012.11.019" "E032.31.114"
]
]
I've got all values as strings, but depending what they are you
could use numbers, words and issues for easier handling later.
I don't know - what do you want to do with the data?
After finishing the extraction, you can get to the block of lines
for each section like this:
section1-data: select my-block "sec2"
;== ["dataline1" "111.11" "N012.11.029" "E034.31.110" ...
To step through each line you could do this:
foreach [line-title data1 data2 data3] section1-data [
print [line-title data3]
]
I am assuming, for each section, that each line has the same number of
elements. If not, then I recommend putting each line into a block of
its own, so it looks like this:
my-block: [
"sec1" [
["dataline1" "111.11" "N012.11.029" "E034.31.110"]
["dataline3" "111.11" "N015.11.099" "E034.31.110"]
]
...
]
To get that data now, you can do this:
foreach line section1-data [
?? line ; show the contents of the block
print [line/1 line/4]
line/3: copy "N012.11.028" ; change third item
]
Read more comments interspersed below:
> Hi everybody !
>
> I am currently trying to port an ANSI C application over to REBOL.
> I am pretty much a newbie to REBOL - and was pretty impressed by
> its capabilities.
>
> My problem now is, porting looked a lot easier than it actually
> turns out to
> be for me.
>
> I seem to lack some fundamental things in REBOL - maybe I just think too
> "one-dimensional"
> because of my ASM/C - background, indeed, in C I do parse the whole data
> BYTE by BYTE - something that
> doesn't seem effective with REBOL - as there seem to be more efficient
> methods available,
> as I understand it.
>
> Actually, I would think the application should be fairly easy to
> be implemented with REBOL - it's bascially only 'simple' string
> processing -
>
> not much more. That's why I thought I should give it a try - also
> to be able
> to compare REBOL performance with my compiled C-application.
>
> basically, this is what my C source does:
>
> 1) open a data file (approx. 1 MB data)
>
> filename: "test.dat"
> data: read filename
>
> 2) parse the file for sections - every section is indicated by square
> brackets
> and is valid to the next (new) section
>
> like this: (example data)
> --------------------------------------------
> [sec1]
> dataline1 111.11 N012.11.029 E034.31.110
> dataline2 131.11 N012.11.099 E034.31.110
> dataline3 111.11 N015.11.099 E034.31.110
>
> [sec2]
> datalinex HFD 111.11 N012.11.099 E034.31.114
> dataliney LKA 131.41 N011.11.049 E031.31.116
> datalinez JIH 111.11 N012.11.019 E032.31.114
> --------------------------------------------
> So each sections contains several hundreds of lines with data,
> the data syntax is different with each section. That's why I initially
> separate the data only by whitespaces in C and take care of the
> exact syntax
> at
> a later time, using parsing rules specified in another array.
>
> 3) In C I would now simply determine each section's offsets within the
> memory
> and then store (memcpy) each section into its own multi-dimensional array
> using the offsets
> I determined in the previous loop, where each line of data is directly
> accessible
> - but also every part of the data line (separated by whitespaces).
>
> At first I would go and compute every section's beginning like this:
> ________________________________________
> sections: make block! 40
>
> parse data [
> any [to "[" copy sec indx: thru "]"
> (append sections index? indx)
> {/*
> For debugging purposes I also emit the name of
> each section
> that's found.
> */}
> (print sec)
> ]
> ]
> ________________________________________
>
> Then I got the position of each section in the data-series and compute
> the offset of each section by calculating the difference between
> 2 adjacent
> sections.
> Accordingly, in C I would then go to extract/copy the data within the two
> offsets
> and put it all in another array to work with.
>
> That's exactly where my problems start to overwhelm me.
> While reading the file in, and parsing it for sections does seem to
> work fairly well (and with MUCH less code !), I am having difficulties to
> create the
> multi-dimensional arrays for each section where all data is individually
> accessible stored.
>
> So as an example, having parsed [sec1] I want every element in
> each line to
> be individually
> accessible to simplify conversion.
>
> 4) Although the arrays don't work yet I tried to port the parsing routines
> over -
> In C I take the "parent" array that contains all sub-arrays and parse each
> section individually. Parsing is done in C with a certain set of
> rules (also
> stored in an array)
> - using regular expressions, I 'expect' a certain data format for
> particular
> sections.
> If a rule is matched I parse with that rule and separate the data into
> sub-arrays.
>
> In REBOL the latter seems fairly easy using the parse command:
>
> 5) when all data has been processed and separated by its
> corresponding rule
> I need to
> convert the data for each section into a different format.
> With C I am again using regular expressions to implement
> conversion. That's
> why I
> stored the recognition-rule and the conversion-rule in the same array
>
> 6) Final conversion of the original data will be to CSV-format - including
> most data that was
> read, but occasionally not all data is needed or an abbreviated form is
> sufficient.
>
> Maybe you guys got some thoughts on my problem - I don't want/need actual
> code - rather some
> hints how to accomplish my goals in REBOL. As you may be able to tell from
> the way I describe
> the problem, I might indeed be too heavily thinking in C. By the way: are
> you aware of any
> tutorials or books, particularly targeted at C-programmers. This seems
> really to be a situation
> where previous programming-experience limits my way of thinking.
> I did read
> a lot of stuff on
> the REBOL webpages, but still do have problems, grasping the
> inner concepts
> within in REBOL.
Did you do any Java? "Everything is a pointer" is kind of more
like rebol. Ask any questions here you want. We'll help you.
> Another question that just came to my mind: is there any decent REBOL code
> editor available?
> Simple syntax highlighting would be one thing - but I am thinking
> more of a
> supportive
> editor that also supports syntax completion or smart tooltips, helping a
> newbie like me.
>
> I guess, the power of REBOL is also some kind of problem for such
> an editor,
> as single
> objects/words can mean different things and dialects can easily
> be extended.
> Maybe some really good REBOL-programmer should go and program an editor
> for REBOL IN REBOL (view) ;-)
>
> I'd really love to see a REBOL-editor being implemented in REBOL
> - it could
> easily be
> enhanced by everybody, there might even be some kind of "plugin" concept
> considered -
> using rebol scripts, that are executed on demand.
> Using REBOL/VIEW it would also be available on pretty much all platforms.
This has often been wished for already.
I think it's a bit of a waste of time at the moment.
There are plenty of good text editors out there, and rebol syntax
highlighting for them too.
See my page on text editors:
http://www.lexicon.net/anton/FreeEditors.html
> Thanks for any help and comments - and sorry for this rather long
> eMail ;-)
> P.S.: Is there any kind of REBOL-specific FORUM available on the web ? If
> not: why not ? I would be willing to
> create one - if there's demand.
> Mike
There is RebolFrance.net - if you can read French it helps.
and Vanilla
http://www.compkarori.com/cgi-local/vanilla.r?selector=display&snip=start
and Agora-Dev
http://rebol.agora-dev.org/
Anton.
