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[Rebol School] Rebol School

PatrickP61
6-Jul-2007
[547x3]
This is my pseudocode approach:


New page is identified by a page header text that is the same on 
each page and the word PAGE at the end of the line

New section is identified by a section header text that is the same 
within the page and the text "NAME . . . . :"

Members lines do not have an identifying mark on the line but are 
always preceeded by the NAME line.

Member line continue until a new page is found, or the words "END 
OF NAME" is found (which I didnt show in my example above).


Initialize capture fields to -null-     like PAGE, NAME
Initialize OUTPUT-FLAG to OFF.

Loop through each line of the input file until end of file EOF.
/|\	If at a New-page line
 |	or at end of Name section
 |		Set OUTPUT-FLAG  OFF
 |	If OUTPUT-FLAG  ON

 |		Format output record from captured fields and current line (MEMBER)
 |		Write output record
 |	IF at New Name line
 |		Set OUTPUT-FLAG ON
 |	IF OUTPUT-FLAG OFF
 |		Get capture fields like PAGE-NUMBER when at a PAGE line
 |		Get NAME when at a NAME line.
 |____	Next line in the file.
Note to all -- Please realize this is a simplified version of the 
real report -- There are many more fields and other things to code 
for, but they are all similar items to the example PAGE, NAME, and 
MEMBER fields.
Oops -- I should put the IF at New Name line at the end of the loop, 
or put the capture of the name in that part.
Tomc
7-Jul-2007
[550]
Yes Patrick you have it right. The rules I gave would fail 
since you have multiple names/members

I would try to get away from the line by line mentality 
and try to break it into your conceptual record groupings
file, pages, sections, and details...

One trick I use is to replace a string delimiter for a record 
with a single char so parse returns a block of that record type. 

this is good because then when you work on each item in the block 
in turn
you know any fields you find do belong to this record and that 

you have not accidently skipped to a similar field in a later record.

something like this 


pages: read %file
replace/all/case pages "PAGE" "^L"
pages: parse/all pages "^L"

foreach page pages[
	p: first page
	page: find page newline
	replace/all/case page "NAME" "^L"
	sections: parse page "^L"
	foreach sec section [
		s: first section
		sec: find sec newline
		parse sec [
			any [thru "Member" copy detail to newline 
				newline (print [p tab s tab detail])
			]
		]
	]
]
PatrickP61
18-Jul-2007
[551x4]
I am a little confused about PORTS.  I want to control how much information 
is loaded into a block but I am not sure how to determine if data 
remains in a port.  Example:
In-port:	open/lines In-file
 while [not tail? In-port] [
	print In-port
	In-port:	next In-port
	]

 close In-port
This is not doing what I want.  

I want it to continue to run through all  lines of a file and print 
it
My goal is to be able to control how much of a file is loaded into 
a block then process the block and then go after the next set of 
data.  That is why I am using PORT to do this function instead of 
reading everything into memory etc.
Geomol
18-Jul-2007
[555x2]
Change the print line to:
print first In-port
I think, your code print the port specs and everything.
PatrickP61
19-Jul-2007
[557]
Yes, It does dump a lot of stuff that I don't kow about!!!
btiffin
19-Jul-2007
[558x2]
Ports are nifty little objects.  :)  And if you just type
>> In-port
 you get back nothing, just another prompt.
>>

The interpreter does not display the internals of objects, but print 
does, so what you are seeing is the object! that is In-port.  Well, 
I'm lying...In-port is a port!  not an object!  Close but not the 
same.  ports emulate a series! wrapped in object! wrapped in enigma. 
 Or is it an object! wrapped in a series! disguised as a sphynx? 
 :)


first In-port is a REBOL reflective property feature that when you 
get it, you'll go "Ahhhh" as you step closer to the Zen of REBOL.

For fun with a really big object!  try >> print system
Oh, by the way...we added to the %form-date.r script in the library. 
  See I'm New for details.
PatrickP61
20-Jul-2007
[560]
Another question -- I know to use escape to insert things like a 
tab as in ^(tab) into a string.
What can I use to insert a newline?  ^(newline) doesn't work.
Geomol
20-Jul-2007
[561x3]
str: ""
insert str newline
If you just write NEWLINE in the prompt, you'll see how it's defined. 
You can specify a newline in a string as
str: "a string with a newline: ^/"
A tab can also be specified as: "^-"
PatrickP61
20-Jul-2007
[564]
Perfect!   ^/ works just great!
Geomol
20-Jul-2007
[565]
It's a bit strange, that ^(newline) doesn't work, now that ^(tab) 
does. Maybe it was just forgotten.
PatrickP61
20-Jul-2007
[566]
As a newbie, it seemed natural to try ^(newline), but the shortcut 
^/ works for me too.
Geomol
20-Jul-2007
[567]
Unfortunately there are some strange things in the corners of REBOL, 
but you'll learn to live with it.
PatrickP61
20-Jul-2007
[568]
:-)
Geomol
20-Jul-2007
[569]
Now you're at it, check http://www.rebol.com/docs/core23/rebolcore-16.html#section-2.11
and http://www.rebol.com/docs/core23/rebolcore-8.html
for info about strings in REBOL.
PatrickP61
20-Jul-2007
[570]
Just what I needed!!!
Geomol
20-Jul-2007
[571]
Ah, there's the explanation, a newline can be specified as ^(line)
(for some reason)
PatrickP61
20-Jul-2007
[572]
Ahhhhh
Gregg
20-Jul-2007
[573]
More reference info here: http://www.rebol.com/docs/core23/rebolcore-16.html#section-3.1

And you also have the words CR, LF, and CRLF available.
PatrickP61
26-Jul-2007
[574]
My teachers,  I have an array ( block (of "lines") within a block 
(of values) ) that I would like to convert to a block (of "lines") 
with all values joined with an embedded tab.  What is the best way 
to achieve this?  See example: 


In-array:      [   [   {Col A1}     {Col B1}   ]        <-- I have 
this
                          [   {2}              {3}             ]
                          [   {line "3"}    {col "b"}    ]   ]


Out-block:   [   {Col A1^(tab)Col B1}             <-- I want this 
                         {2^(tab)3}
                         {line "3"^(tab)col "b"}         ]
Rebolek
26-Jul-2007
[575]
>> out-block: copy []
== []

>> foreach line in-array [append out-block rejoin [line/1 "^-" line/2]]
== ["Col A1^-Col B1" "2^-3" {line "3"^-col "b"}]
Anton
26-Jul-2007
[576x2]
in-array: [["Col A1" "Col B1"]["2" "3"][{line "3"} {col "b"}]]

out-block: copy [] 
foreach blk in-array [
	line: copy "" 
	repeat n -1 + length? blk [append append line blk/:n tab]
	if not empty? blk [append line last blk]
	append out-block line
]
new-line/all out-block on
== [
    "Col A1^-Col B1"
    "2^-3"
    {line "3"^-col "b"}
]
PatrickP61
26-Jul-2007
[578]
Anton, what does the new-line/all do.  I gather it inserts newlines 
after each value.  Is that right?
Volker
26-Jul-2007
[579]
it cleans up rebol-listings
PatrickP61
26-Jul-2007
[580]
Forgive me,  how does it do that?
Volker
26-Jul-2007
[581x2]
else all strings would be on one line. only interesting for probing 
rebol-code, does not change the strings itself
there is a hidden markerin values, for newline
PatrickP61
26-Jul-2007
[583]
So if i read you right, then if I didn't do new-line/all, and tried 
to probe Out-block, it would show the entire contents as one large 
string, whereas new-line/all will allow probe to show each value 
as a spearate line.  Right?
Volker
26-Jul-2007
[584x2]
as lots of strings in one line
and with the new-line all strings in own lines
PatrickP61
26-Jul-2007
[586x4]
I see how it works now  -- Thank you Anton and Volker!!
Thank you Reblek  -- didn't see your answer at first!
My teachers, Anton and Rebolek have submitted two answers.  The difference 
between them is that Anton's answer will insert a tab between varying 
numbers of  values per line, where Rebolek will insert a tab in-between 
col 1 and col2 (assuming only 2 columns in the array).  Is that a 
correct interpretation?
Anton, I understand Rebolek answer, but I want to understand your 
answer too.

 I'm wondering about the line: repeat N -1 + length? Blk [append append 
 Line Blk/:N tab]  

does Rebol do the inner append first  (in math expressions) like 
this:  [append ( append Line Blk/:N ) tab]
and then do this for the number of "lines" in the array
N	Out-block
0	[]
1	"Col A1^-Col B1"
2	"Col A1^-Col B1"	"2^-3"
3	"Col A1^-Col B1"	"2^-3"	{line "3"^-col "b"}


I think I see the above progression, but not sure about Blk [append 
Line last Blk]  Is this advancing the starting position within In-array?
Gregg
27-Jul-2007
[590]
...insert a tab between varying numbers of  values per line <versus> 
... insert a tab in-between col 1 and col2
 -- Correct.


On new-line, it's kind of advanced because it doesn't insert a newline 
(CR/LF), but rather a hidden marker between values that REBOL uses 
when molding blocks.
PatrickP61
27-Jul-2007
[591]
Hi Gregg -- Is that primarily for display purposes, or could it be 
used for other things?
Gregg
27-Jul-2007
[592x2]
On "append append", yes. You could also do it like this: "append 
line join blk/:n tab", the difference being that APPEND modifies 
its series argument, and JOIN does not.


REPEAT is 1-based, not zero, Anton is using "-1 + length? blk" rather 
than "(length? blk) - 1" or "subtract length? blk 1". The first of 
those cases requires the paren because "-" is an op! which will be 
evaluated before the length? func, so REBOL would see it like this 
"length? (blk - 1)", which doesn't work.
For display or formatted output. It's *very* useful when generating 
code for example.
PatrickP61
27-Jul-2007
[594]
Sounds like more advanced stuff than I'm understanding right now. 
 I'll read up on the terms. 

When I get REBOL code solution, I'd like to understand how Rebol 
is processing the code.  What it does logically first, and logically 
second... I think I get confused about when Rebol does the evaluations.
Gregg
27-Jul-2007
[595x2]
You shouldn't have to worry about new-line at all. It's actually 
relatively new, so we all lived without it for a long time.
It can be confusing at times, and even once you know what you're 
doing, you sometimes have to think about it a bit. The up-side is 
that you have a great deal of control once you know how to use it.