I know how to copy records from one pf to another by reading one file in dow loop and writing into another file like below. Files are PF1 and PF2 having record format rec1 and rec2 respectively where each file have only one field named fld1 and #fld1 respectively-
READ PF1
DOW not %eof(PF1) and not %error
eval fld1 = #fld1
write Rec2
READ PF1
ENDDO
As the comments in Buck's answer mention, your team mate is alluding to using the RPG cycle to process the file. The cycle is basically an implicit read loop of files declared as 'P'rimary.
http://www-01.ibm.com/support/knowledgecenter/ssw_ibm_i_71/rzasc/sc09250726.htm%23wq121
Originally, even RPG IV programs included code to used as part of the cycle, such as automatically opening files, even if you didn't actually declare any input primary files. Now however, you can create "Linear Main" programs using the MAIN() h-spec and your program will be cycle free.
Using the cycle is frowned upon in modern RPG. Primarily because the implicit nature of what's going on makes it tricky to understand non-trivial code. Additionally, cycle code doesn't perform any better than non-cycle code; it's just less to write. The I/Os being done remain exactly the same.
Finally, again as mentioned in the comments. If you want to optimize performace, use SQL. The set based nature of SQL beats RPG's one row at a time. I haven't benchmarked it recently, but way back on v5r2 or so, copying 100 or more rows was faster with SQL than RPG.
For reference only, FWiW; i.e. not recommendations, just examples of what can be done, esp. in cases alluded but for which no specifics were given:
My team mate told me that he can write code for this problem only in 4 lines including declaration of both files in F-spec. He will also not use read, move or dow loop. I don't know how can he do this. That's why I am eager to know this.
The following source is an example Cycle-program; my FLD1 of REC1 had a 10-byte field but I described my output for 20-bytes, so to avoid failed compile per sev-20 RNF7501 "Length of data structure in Result-Field does not equal the record length of Factor 2.", I specified GENLVL(20) on the CRTBNDRPG:
FPF1 IP E DISK rename(rec1:rcd1)
FPF2 O F 20 DISK
DINOUT E DS EXTNAME(PF1)
C WRITE PF2 INOUT
I don't want to use CL program. I just want to do it with a single program either in RPG3 or RPG4
A similar RPG Cycle-program could perform effectively the same thing, similarly copying the data from PF1 to PF2 despite different column name and [thus inherently also] the different record format, using the CL command without a CL program and almost as few lines. The following example depends on the must-always-be-one-row table called QSQPTABL in QSYS2 that would typically be in the system Library List, and the second argument could reflect the actual length of the command string, but just as easily codes the max prototyped length per the Const definition assuring the blank-padding up to that length without actually having to count the [~53] bytes of the concatenated string expression:
FQSQPTABL IP E DISK rename(qsqptabl:qsqptable)
DQcmdExc PR ExtPgm('QSYS/QCMDEXC')
D 200A const
D 15P05 const
c callp QcmdExc('cpyf pf1 pf2 mbropt(*add)'
c +' fmtopt(*nochk) crtfile(*no)':200)
Whereas both of the above sources are probably an enigma to anyone unfamiliar with the Cycle, the overall effects of the latter are quite likely to be inferred correctly [¿perhaps more appropriately described as guessed correctly?], by just about anyone with an understanding of the CL command string, despite their lack of understanding of the Cycle.
And of course, as was also noted, with the SQL the program is probably arguably even easier\simpler; possibly even more readable to the uninitiated [although the WITH NONE clause, shown as WITH NC, added just in case the COMMIT(*NONE) was overlooked on the compile request, probably is not easily intuited]:
C/Exec SQL
C+ insert into pf2 select * from pf1 WITH NC
C/End-Exec
C SETON LR
P.S. The source-code from the OP was originally [at least was, prior to my comment added here] incorrectly coded with eval fld1 = #fld1 when surely what was intended was eval #fld1 = fld1 according to the setup\given.
If you need to use RPG, use embedded SQL. Look up INSERT INTO.
If you aren't limited to RPG, consider CPYF... MBROPT(*ADD).
What business problem are you trying to solve by doing it another way?
Related
I'm trying to get a "retro-computing" class open and would like to give people the opportunity to finish projects at home (without carrying a 3kb monstrosity out of 1980 with them) I've heard that repl.it has every programming language, does it have QuickBasic and how do I use it online? Thanks for the help in advance!
You can do it (hint: search for QBasic; it shares syntax with QuickBASIC), but you should be aware that it has some limitations as it's running on an incomplete JavaScript implementation. For completeness, I'll reproduce the info from the original blog post:
What works
Only text mode is supported. The most common commands (enough to run
nibbles) are implemented. These include:
Subs and functions
Arrays
User types
Shared variables
Loops
Input from screen
What doesn't work
Graphics modes are not supported
No statements are allowed on the same line as IF/THEN
Line numbers are not supported
Only the built-in functions used by NIBBLES.BAS are implemented
All subroutines and functions must be declared using DECLARE
This is far from being done. In the comments, AC0KG points out that
P=1-1 doesn't work.
In short, it would need another 50 or 100 hours of work and there is
no reason to do this.
One caveat that I haven't been able to determine is a statement like INPUT or LINE INPUT... They just don't seem to work for me on repl.it, and I don't know where else one might find qb.js hosted.
My recommendation: FreeBASIC
I would recommend FreeBASIC instead, if possible. It's essentially a modern reimplementation coded in C++ (last I knew) with additional functionality.
Old DOS stuff like the DEF SEG statement and VARSEG function are no longer applicable since it is a modern BASIC implementation operating on a 32-bit flat address space rather than 16-bit segmented memory. I'm not sure what the difference between the old SADD function and the new StrPtr function is, if there is any, but the idea is the same: return the address of the bytes that make up a string.
You could also disable some stuff and maintain QB compatibility using #lang "qb" as the first line of a program as there will be noticeable differences when using the default "fb" dialect, or you could embrace the new features and avoid the "qb" dialect, focusing primarily on the programming concepts instead; the choice is yours. Regardless of the dialect you choose, the basic stuff should work just fine:
DECLARE SUB collatz ()
DIM SHARED n AS INTEGER
INPUT "Enter a value for n: ", n
PRINT n
DO WHILE n <> 4
collatz
PRINT n
LOOP
PRINT 2
PRINT 1
SUB collatz
IF n MOD 2 = 1 THEN
n = 3 * n + 1
ELSE
n = n \ 2
END IF
END SUB
A word about QB64
One might argue that there is a much more compatible transpiler known as QB64 (except for some things like DEF FN...), but I cannot recommend it if you want a tool for students to use. It's a large download for Windows users, and its syntax checking can be a bit poor at times, to the point that you might see the QB code compile only to see a cryptic message like "C++ compilation failed! See internals\temp\compile.txt for details". Simply put, it's usable and highly compatible, but it needs some work, like the qb.js script that repl.it uses.
An alternative: DOSBox and autorun
You could also find a way to run an actual copy of QB 4.5 in something like DOSBox and simply modify the autorun information in the default DOSBox.conf (or whatever it's called) to automatically launch QB. Then just repackage it with the modified DOSBox.conf in a nice installer for easy distribution (NSIS, Inno Setup, etc.) This will provide the most retro experience beyond something like a FreeDOS virtual machine as you'll be dealing with the 16-bit segmented memory, VGA, etc.—all emulated of course.
I'm gradually working my way up the perl learning curve (with thanks to contributors to this REALLY helpful site), but am struggling with how to approach this particular issue.
I'm building a perl utility which utilises three (c++) third party programmes. Normally these are run: A $file_list | B -args | C $file_out
where process A reads multiple files, process B modifies each individual file and process C collects all input files in the pipe and produces a single output file, with a null input file signifying the end of the input stream.
The input files are large(ish) at around 100Mb and around 10 in number. The processes are CPU intensive and the whole process need to be applied to thousands of groups of files each day, so the simple solution of reading and writing intermediate files to disk is simply too inefficient. In addition, the process above is only part of a processing sequence, where the input files are already in memory and the output file also needs to be in memory for further processing.
There are a number of solutions to this already well documented and I have a prototype version utilising IPC::Open3(). So far, so good. :)
However - when piping each file to process A through process B I need to modify the arguments in process B for each input file without interrupting the forward flow to process C. This is where I come unstuck and am looking for some suggestions.
As further background:
Running in Ubuntu 16.04 LTS (currently within Virtual box)and perl v5.22.1
The programme will run on (and within) a single machine by one user (me !), i.e. no external network communication or multi user or public requirement - so simplicity of programming is preferred over strong security.
Since the process must run repeatedly without interruption, robust/reliable I/O handling is required.
I have access to the source code of each process, so that could be modified (although I'd prefer not to).
My apologies for the lack of "code to date", but I thought the question is more one of "How do I approach this?" rather than "How do I get my code to work?".
Any pointers or help would be very much appreciated.
You need a fourth program (call it D) that determines what the arguments to B should be and executes B with those arguments and with D's stdin and stdout connected to B's stdin and stdout. You can then replace B with D in your pipeline.
What language you use for D is up to you.
If you're looking to feed output from different programs into the pipes, I'd suggest what you want to look at is ... well, pipe.
This lets you set up a pipe - that works much like the ones you get from IPC::Open3 but have a bit more control over what you read/write into it.
I'd like to use knitr to produce a document which includes numbers, tables, and figures defined separately in R. I have a separate .R script within which I define the variables of interest, and I have executed this script and verified the variables are in memory. Then, within a .Rmd file I have the R markup code, within which I attempt to display the variables I've defined in R. I keep getting error messages whenever I attempt to knit, stating something like:
Error in unique(c("AsIs", oldClass(x))) : object "lamdaQ6" not found...
Clearly the knitr process initiates a new environment which excludes already defined variables. I have rather extensive R code to define the variables I want to include in the document, which I want to keep separate from the R markup code (both for clarity, and because R markup is not a good development environment for R).
Is there some means of preserving awareness of existing variables in R memory within knitr? I have searched extensively and not found a solution, probably because I don't know the correct term.
The solution offered by Paul Roub worked -- I thought it didn't, but this turned-out to be due to my own typo.
A cleaner solution for my needs, rather than source the whole R file, was to use "save" to save just the objects I needed to create the document. I added a line to save the objects at the end of the .R file, then used "load" to load the objects at the top of the .Rmd script.
So, at the end of the .R file, to save objects XX and YY, I have:
save(XX,YY,file="Data4Rmd.RData")
Then, near the beginning of the .Rmd file, to import these objects, I have:
```
{r,echo=FALSE}
setwd("c:\CurrentProjectDirectory")
load(file="Data4Rmd.RData")
```
This allows me to later use statements like:
Decay rate is lambda = `r XX`, and mean lifetime is `r YY`.
Yet another alternative might have been to save and load the whole workspace, but this seemed excessive.
Thanks for the assistance Paul, much appreciated :)
I am defining a variable in the beginning of my source code in MATLAB. Now I would like to know at which lines this variable effects something. In other words, I would like to see all lines in which that variable is read out. This wish does not only include all accesses in the current function, but also possible accesses in sub-functions that use this variable as an input argument. In this way, I can see in a quick way where my change of this variable takes any influence.
Is there any possibility to do so in MATLAB? A graphical marking of the corresponding lines would be nice but a command line output might be even more practical.
You may always use "Find Files" to search for a certain keyword or expression. In my R2012a/Windows version is in Edit > Find Files..., with the keyboard shortcut [CTRL] + [SHIFT] + [F].
The result will be a list of lines where the searched string is found, in all the files found in the specified folder. Please check out the options in the search dialog for more details and flexibility.
Later edit: thanks to #zinjaai, I noticed that #tc88 required that this tool should track the effect of the name of the variable inside the functions/subfunctions. I think this is:
very difficult to achieve. The problem of running trough all the possible values and branching on every possible conditional expression is... well is hard. I think is halting-problem-hard.
in 90% of the case the assumption that the output of a function is influenced by the input is true. But the input and the output are part of the same statement (assigning the result of a function) so looking for where the variable is used as argument should suffice to identify what output variables are affected..
There are perverse cases where functions will alter arguments that are handle-type (because the argument is not copied, but referenced). This side-effect will break the assumption 2, and is one of the main reasons why 1. Outlining the cases when these side effects take place is again, hard, and is better to assume that all of them are modified.
Some other cases are inherently undecidable, because they don't depend on the computer states, but on the state of the "outside world". Example: suppose one calls uigetfile. The function returns a char type when the user selects a file, and a double type for the case when the user chooses not to select a file. Obviously the two cases will be treated differently. How could you know which variables are created/modified before the user deciding?
In conclusion: I think that human intuition, plus the MATLAB Debugger (for run time), and the Find Files (for quick search where a variable is used) and depfun (for quick identification of function dependence) is way cheaper. But I would like to be wrong. :-)
When working with unpack, I had hoped that b3 would return a bitstring, 3 bits in length.
The code that I had hoped to be writing (for parsing a websocket data packet) was:
my($FIN,$RSV1, $RSV2, $RSV3, $opcode, $MASK, $payload_length) = unpack('b1b1b1b1b4b1b7',substr($read_buffer,0,2));
I noticed that this doesn't do what I had hoped.
If I used b16 instead of the template above, I get the entire 2 bytes loaded into first variable as "1000000101100001".
That's great, and I have no problem with that.
I can use what I've got so far, by doing a bunch of substrings, but is there a better way of doing this? I was hoping there would be a way to process that bit string with a template similar to the one I attempted to make. Some sort of function where I can pass the specification for the packet on the right hand side, and a list of variables on the left?
Edit: I don't want to do this with a regex, since it will be in a very tight loop that will occur a lot.
Edit2: Ideally it would be nice to be able to specify what the bit string should be evaluated as (Boolean, integer, etc).
If I have understood correctly, your goal is to split the 2-bytes input to 7 new variables.
For this purpose you can use bitwise operations. This is an example of how to get your $opcode value:
my $b4 = $read_buffer & 0x0f00; # your mask to filter 9-12 bits
$opcode = $b4 >> 8; # rshift your bits
You can do the same manipulations (maybe in a single statement, if you want) for all your variables and it should execute at a resonable good speed.