I have several pressure sensors in my setup and I read the data into labview. Is it possible to do this without writing the initialization code for each device seperately? It is exactly the same for each sensor...
#Adrian already answered to your question but I'd like to provide some more details.
I'd suggest that you create a subVI. Basically, you will have a piece of code where you define inputs and outputs and how to manipulate them. Then you can re-use whenever you need (similar to a function in other programming languages). Here is the official NI guide, where you can find all you need.
Related
Can someone guide me as googling does not send me to the right places.
I want to adapt netlogo to include players real or simulated with other technologies. I need to interface the netlogo core (running an established game) and have the moves and choices determined by the external entities, which may be human or automania.
In searching for the API to allow this, I can find is the controlling API which is seems to be for running NetLogo muitiple runs of a model and not what I want.
And please before you close this again suggest how I can make this more focused as the problem is finding the starting point....
Can anyone assist.
Regards
Robert
There are two main ways to interface between NetLogo and the "outside world":
The extensions API.
The controlling API.
Which one to use depends on what you're trying to achieve.
You say that you:
need to interface the netlogo core (running an established game) and have the moves and choices determined by the external entities, which may be human or automania.
That, to me, sounds very much like a job for the extensions API, which is what has been suggested to you on the netlogo-devel group. Extensions allow to add new "primitives" to NetLogo, and those primitives can be written in any language that runs on the JVM (Java, Scala, Clojure, etc.)
So if you have a game written in NetLogo and a bot written in some other language that the JVM can interface with (possibly by using the JNI), you could write a new NetLogo extension command that calls out to the bot (e.g., something like bot:play game-state). A game written in NetLogo could then use that command to let the bot play its turn.
If that is indeed what you want to do, then Jeremy has already given you a good starting point in his netlogo-devel answer, and there is not much we can add to this until you have more specific questions.
You also said, however, that you looked at using the controlling API, so maybe what you had in mind is to have a game written in some other language, and use a NetLogo model to generate the behaviour of a particular player in that game. The controlling API allows you to do that. (It's not just for running a model multiple times!) If you look at the examples in the controlling guide, you'll see that you can use the API to send commands to a NetLogo model and to report the results back to your external program. The only constraint is that this external program needs to be able to talk to the JVM.
If you don't think this answers you question, please try to give us a concrete example of a precise thing that you want to do but do not think can be achieve in one of these two ways. We might be able to help you better than.
Is there something similar to a standard library for modern ABAP (maybe even OO-Abap)? For example a curated list of objects that address some of the most common programming tasks like
high-level data structures (not just plain internal tables)
working with file paths and directories
working with files (reading, saving, ...)
working with different file types (text, csv, xml, ...)
regular expressions
working with the environment (client, application server)
...
My current workflow is to stumble upon a problem like getting the extension of a file from a filename (or something fairly similar and easy). Then I have three options:
Dig through a ton of (mostly old and lacking) posts on SDN until i maybe find a pointer to solve the problem
Hack away and create a one-off solution to the problem
Take my time and implement a good and well documented solution
Many times I feel a bit lost. A lot of the available information is old, bad or both. Is there a more structured approach to tackle the problem of finding a suitable abstraction in the ABAP-world?
To answer your first question no, unlike C, C#, Java, there is no need to include a library since all the functions are always available to you, so in that regards it might be simpler. What you are asking though is a great question, I am sure you probably see tons of queries in SDN for "Is there a Function module for?" etc.
There isn't an easy answer but In SAP ABAP I think the easiest way might be to find this is by looking at packages. Similar to a library by looking at a package for the type of function your looking for might get you there. For example if I am looking for handling files I might look for the control framework package and there I can see all the available functions/classes/methods/BAPIs etc. that are related to front end controls/file handling etc. and might be able to find what I am looking for. Note its not perfect as the way packages are used has changed from time to time so its actually better for finding functions related to for example purchasing or sales etc. but its one way that we use.
Like other languages in that we still need to know what library to link in to get the function you need, in ABAP you just have to find the related package. Hope it helps a little, I know its not perfect. Example package for front end controls
For working with the environment:
If you have access to SAP there is a transaction code called BAPI
Here you could find a hierarchical list of all the main objects in SAP (i.e. Material, Purchase Order, etc)
In this list you could find documentation, the function modules used for the object (i.e. créate/get detail/update etc)
And digging into the function modules could take a look to the structures, receiving parameters, etc
The other questions are a little bit complex, I am not aware of any comprehensive list but digging into SCN usually is easy to find a solution for the most common things like handling files, etc
In the particular case of regular expressions, SAP native language, ABAP, has keywords for handling them, but you also have a class in SAP called CL_JAVA_SCRIPT which you could use for doing thigs in "JavaScript way"
For example I used this class in the past to evaluate a simple formula provided in a string (i.e 3 + 2 * 5 )
This is an operation really complex to do in ABAP but easy to do in JS.
Hope it helps
SAP Reuse Library (SE83) is the most close thing to what you are looking for. It provides common development tasks grouped in hierarchy (UI controls, standard dialogs, confirmation prompts) and contains code snippets for each with commonly used classes/modules:
Though, it is incomplete and lacks many popular things.
Consider also DWDM, BIBS, LIBS transactions and other packages in this link.
This question is related to diagraming a software process. As an electrical engineer, much of the software I do is for embedded micro-controllers. In school, we learned to illustrate our algorithm using a flowchart. However, nowadays, many of my embedded projects are heavily interrupt-driven where the main process runs some basic algorithm a variety of interrupt sources provide its stimulus. So, my question is, what are some diagramming techniques that I can use to illustrate my process such that future developers can understand what I am doing easily and get involved in development?
Here are some key features that I am looking for:
Shows data structures and how data is passed between processes & interrupts
Shows conditions that cause each interrupt
Shows how data is gathered and passed through a downlink
Shows how command messages are received, parsed, and executed
Ideally is well suited for hierarchical breakdown into smaller processes with greater levels of detail
I've always seen interrupt timing drawn as follows:
Or inline line so:
But I prefer the former as it gives more room for annotation.
In response to your comment, perhaps a UML state machine diagram (with some adaptation) may be closer suited to your purpose:
There are many of interesting approaches you can find in diagram drawing. I will post a few here. You will find a lot of Operation System and Architecture scpecific names in there such as register , event, function names and etc. It is more for representation so far, right? So he we are.
Use UML class diagrams for showing data structures. Use sequence diagrams to show interactions between classes and interrupt service routines (showing function calls only). Use activity diagrams to show how interrupts interact with processes (signals are good for this). An activity diagram can also be used to show the process of receiving data, parsing it, and dispatching it. This can also be represented in a static view by a package diagram where the command handler is in one package and the command parser is in another, connected by a dependency line. Use cases are good for a high level view of functionality.
The main point is that UML supports many different views (static, dynamic, logical, deployment) into your system. Don't try to express everything at once.
The diagram below shows an example of an interrupt to a process.
I now have sufficent exposure to the Objective-C that if i'm stuck with anything, I know how to think of the problem in terms of a likely tool I need and go look for it. Simple really. There's A Method For That. So nothings a real problem anymore.
Now I'm looking deeper at the language in broader terms. We write stuff. The compiler hews out all the code to execute it. From a simple flashlight app thats a if/then decision to turn on, to a highly complex accelerometer driven 3D shoot 'em up with blood 'n guts and body parts following all sorts of physics, the compiler prepares the code ready to be executed like a giant railway layout. No matter how random it appears on the screen, everything possible can be generically described and prepared for.
So here's the question:
Are there cases where something completely unexpected to the software designer can still be handled without an execution halt? Maybe I'd better re-frame the question a few different ways: Can a ( objective-C ) program meta-compile within itself in response to an unplanned-for user request? or to re-put my opening remark, are there tools or methods for unlikely descriptions of unlikely problems?
I think #kfb has the right comment about metaprogramming. Check out the Runtime docs in conjunction with metaprogramming tutorials.
Parts of your last question might be in the realm of this doc.
If your looking for ways to reduce the size of your code base for the lesser used features, one idea might be to make the features internet based (assuming connectivity is not a problem).
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Is there any real use for self modifying code?
I know that they can be used to build worms/viruses, but I was wondering whether there is some good reason that a programmer may have to use self modifying code.
Any ideas? Hypothetical situations are welcome too.
Turns out that the Wikipedia entry on "self-modifying code" has a great list:
Semi-automatic optimization of a state dependent loop.
Runtime code generation, or specialization of an algorithm in
runtime or loadtime (which is popular,
for example, in the domain of
real-time graphics) such as a general
sort utility preparing code to perform
the key comparison described in a
specific invocation.
Altering of inlined state of an object, or simulating the high-level
construction of closures.
Patching of subroutine address calling, as done usually at load time
of dynamic libraries, or, on each
invocation patching the subroutine's
internal references to its parameters
so as to use their actual addresses.
Whether this is regarded as
'self-modifying code' or not is a case
of terminology.
Evolutionary computing systems such as genetic programming.
Hiding of code to prevent reverse engineering, as through use of a
disassembler or debugger.
Hiding of code to evade detection by virus/spyware scanning software and
the like.
Filling 100% of memory (in some architectures) with a rolling pattern
of repeating opcodes, to erase all
programs and data, or to burn-in
hardware.
Compression of code to be decompressed and executed at runtime,
e.g., when memory or disk space is
limited.
Some very limited instruction sets leave no option but to use
self-modifying code to achieve certain
functionality. For example, a "One
Instruction Set Computer" machine that
uses only the
subtract-and-branch-if-negative
"instruction" cannot do an indirect
copy (something like the equivalent of
"*a = **b" in the C programming
language) without using self-modifying
code.
Altering instructions for fault-tolerance
On the point about thwarting hackers using self-modifying code:
Over the course of several firmware updates, DirectTV slowly assembled a program on their smart card to destroy cards that have been hacked to illegally receive unpaid channels. See Jeff's Coding Horror article on the Black Sunday Hack for more information.
I've seen self-modifying code used for:
speed optimisation, by having the program write more code for itself on the fly
obsfucation, to make reverse engineering much harder
In former times where RAM was limited, self modifying code was used to save memory. Nowadays for example application compression utilities like UPX are used to decompress/modify the own code after loading a compressed image of the application.
Because the Commodore 64 doesn't have many registers and has a 1Mhz processor. When you need to read a memory address offset by a value it is easier to modify the source.
#Reader:
LDA $C000
STA $D020
INC Reader+1
JMP Reader
That's the last time I wrote self-modifying code anyway :-)
Artificial Intelligence?
Because it's really really cool, and sometimes that's reason enough.
1960s-era assembly languages used self-modifying code to implement function calls without a stack.
Knuth, v1, 1ed p.182:
MAX100 STJ EXIT ;Subroutine linkage
ENT3 100 ;M1. Initialize
JMP 2F
1H CMPA X,3 ;M3. Compare
JGE *+3
2H ENT2 0,3 ;M4. Change m
LDA X,3 ;(New maximum found)
DEC3 1 ;M5. Decrease k
J3P 1B ;M2. All tested?
EXIT JMP * ;Return to main program
In a larger program containing this coding as a subroutine, the single instruction "JMP MAX100" would cause register A to be set to the current maximum value of locations X + 1 through X + 100, and the position of the maximum would appear in rI2. Subroutine linkage in this case is achieved by the instructions "MAX100 STJ EXIT" and, later, "EXIT JMP *". Because of the way the J-register operates, the exit instruction will then jump to the location following the place where the original reference to MAX100 was made.
Edit: It may be hard to see what's going on, even with the brief explanation here. In the line MAX100 STJ EXIT, MAX100 is a label for the instruction (and thus for the procedure as a whole), STJ means STORE the jump register (where we just came from), EXIT means the memory location labeled 'EXIT' is the target of the STORE. EXIT, we see later is the label for the last instruction. So it's overwriting code! But, many instructions (including STJ here) implicitly overwrite only the operand portion of the instruction word. So the JMP remains untouched, and the * is a dummy token, since there's really nothing meaningful to put there, it'd only get overwritten.
Self-modifying code is also used where register-indirect addressing is not available, and yet the address you need is sitting right there in the register. PDP-1 LISP:
dap .+1 ;deposit address part of accumulator in (IP+1)
lac xy ;load accumulator with (ADDRESS) [xy is a dummy symbol, just like * above]
These two instructions perform ACC := (ACC) by modifying the operand of the load instruction.
Modifications like these are relatively safe, and on antique architectures, they are necessary.
Lots of reasons. Off the top of my head:
Runtime class construction and meta programming. For example, having a class factory that takes a connection to an SQL table and generates a client class specialized for that table (with accessors for the columns, find methods, etc.).
Then of course there's the famous bitblt example, and the regexp analogs.
Dynamically optimizing based on RT information a la tracing JITs
Subtype specialization of ada style generic functions in an accretive environment.
-- MarkusQ
Dynamic linking is a kind of self-modification (patching absolute and/or relative jump locations) ... that's normally done by the O/S's program loader, though.
Neural networks are kind of self-modifying code.
Then there are evolutionary algorithms which modify themselves.
Mike Abrash described the Pixomatic code generator for Dr. Dobb's Journal a while back: http://www.ddj.com/architect/184405807 . That's a software 3d dx7(?) compatible rasterizer.
LOL - i've written self-modifying code on two occasions:
when first learning assembly language, before i understood indirect indexed access
accidentally, as pointer bugs in assembly language and C
i can imagine that there may be scenarios where self-modifying code would be more efficient than alternatives, but nothing obvious leaps to mind. In general, this is something to avoid - debugging nightmare, etc. - unless you are deliberately trying to obfuscate as mentioned above.
Applications which implement their own scripting languages often do this. For example, database servers often compile stored procedures (or queries) this way.
Dynamic code generation in SwiftShader is a form of self modifying code that enables it to efficiently implement Direct3D 9 on the CPU.
Modern example:
I have a script that needs JWT token to work. To request a token interactive login is needed or use a refresh token that is issued with new JWT token. Would be nice to store refresh token in the script and update it each time it is being executed