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  • Tricking a Unix Commandline Program into Accepting a File Stream

    - by Alan Storm
    Hypothetical situation. I have a command line program in *nix (linux, BSD, etc.). It was written so that you pass it a text file as an argument $ program file.txt Run the program, it looks at the text in file.txt. Is it possible to "trick" this program into accepting input from a file stream rather than reading a file via disk? I'm pretty comfortable using unix pipes to do stuff, but there's still something a little mysterious about their internals that make it so I can't say (definitively) yes or not to the above question.

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  • Sending multiline message via sockets without closing the connection

    - by Yasir Arsanukaev
    Hello folks. Currently I have this code of my client-side Haskell application: import Network.Socket import Network.BSD import System.IO hiding (hPutStr, hPutStrLn, hGetLine, hGetContents) import System.IO.UTF8 connectserver :: HostName -- ^ Remote hostname, or localhost -> String -- ^ Port number or name -> IO Handle connectserver hostname port = withSocketsDo $ do -- withSocketsDo is required on Windows -- Look up the hostname and port. Either raises an exception -- or returns a nonempty list. First element in that list -- is supposed to be the best option. addrinfos <- getAddrInfo Nothing (Just hostname) (Just port) let serveraddr = head addrinfos -- Establish a socket for communication sock <- socket (addrFamily serveraddr) Stream defaultProtocol -- Mark the socket for keep-alive handling since it may be idle -- for long periods of time setSocketOption sock KeepAlive 1 -- Connect to server connect sock (addrAddress serveraddr) -- Make a Handle out of it for convenience h <- socketToHandle sock ReadWriteMode -- Were going to set buffering to LineBuffering and then -- explicitly call hFlush after each message, below, so that -- messages get logged immediately hSetBuffering h LineBuffering return h sendid :: Handle -> String -> IO String sendid h id = do hPutStr h id -- Make sure that we send data immediately hFlush h -- Retrieve results hGetLine h The code portions in connectserver are from this chapter of Real World Haskell book where they say: When dealing with TCP data, it's often convenient to convert a socket into a Haskell Handle. We do so here, and explicitly set the buffering – an important point for TCP communication. Next, we set up lazy reading from the socket's Handle. For each incoming line, we pass it to handle. After there is no more data – because the remote end has closed the socket – we output a message about that. Since hGetContents blocks until the server closes the socket on the other side, I used hGetLine instead. It satisfied me before I decided to implement multiline output to client. I wouldn't like the server to close a socket every time it finishes sending multiline text. The only simple idea I have at the moment is to count the number of linefeeds and stop reading lines after two subsequent linefeeds. Do you have any better suggestions? Thanks.

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  • Derivative of a Higher-Order Function

    - by Claudiu
    This is in the context of Automatic Differentiation - what would such a system do with a function like map, or filter - or even one of the SKI Combinators? Example: I have the following function: def func(x): return sum(map(lambda a: a**x, range(20))) What would its derivative be? What will an AD system yield as a result? (This function is well-defined on real-number inputs).

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  • scripts on Cshell

    - by lego69
    hello, I've got some problem, I have list of data in the file: 053-37878 03828008 Moskovitch James 500 052-34363 01234567 Mendelson Kippi 450 053-32322 03828008 Jameson Shula 350 054-39238 03333333 Merden Moshe 300 is it possible rewrite this list in the same file (without using temporary file) but without last number thanks in advance for any help (I'm talking about C-Shell scripts)

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  • How to return the output of a recursive function in Clojure

    - by Silanglaya Valerio
    Hi everyone! I'm new to functional languages and clojure, so please bear with me... I'm trying to construct a list of functions, with either random parameters or constants. The function that constructs the list of functions is already working, though it doesn't return the function itself. I verified this using println. Here is the snippet: (def operations (list #(- %1 %2) #(+ %1 %2) #(* %1 %2) #(/ %1 %2))) (def parameters (list \u \v \w \x \y \z)) (def parameterlistcount 6) (def paramcount 2) (def opcount 4) (defn generateFunction "Generates a random function list" ([] (generateFunction 2 4 0.5 0.6 '())) ([pc maxdepth fp pp function] (if (and (> maxdepth 0) (< (rand) fp)) (dotimes [i 2] (println(conj (generateFunction pc (dec maxdepth) fp pp function) {:op (nth operations (rand-int opcount))}))) (if (and (< (rand) pp) (> pc 0)) (do (dec pc) (conj function {:param (nth parameters (rand-int parameterlistcount))})) (conj function {:const (rand-int 100)}))))) Any help will be appreciated, thanks!

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  • Efficient algorithm to generate all solutions of a linear diophantine equation with ai=1

    - by Ben
    I am trying to generate all the solutions for the following equations for a given H. With H=4 : 1) ALL solutions for x_1 + x_2 + x_3 + x_4 =4 2) ALL solutions for x_1 + x_2 + x_3 = 4 3) ALL solutions for x_1 + x_2 = 4 4) ALL solutions for x_1 =4 For my problem, there are always 4 equations to solve (independently from the others). There are a total of 2^(H-1) solutions. For the previous one, here are the solutions : 1) 1 1 1 1 2) 1 1 2 and 1 2 1 and 2 1 1 3) 1 3 and 3 1 and 2 2 4) 4 Here is an R algorithm which solve the problem. library(gtools) H<-4 solutions<-NULL for(i in seq(H)) { res<-permutations(H-i+1,i,repeats.allowed=T) resum<-apply(res,1,sum) id<-which(resum==H) print(paste("solutions with ",i," variables",sep="")) print(res[id,]) } However, this algorithm makes more calculations than needed. I am sure it is possible to go faster. By that, I mean not generating the permutations for which the sums is H Any idea of a better algorithm for a given H ?

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  • Interacting with system commands using a web dev language

    - by Jamie
    Hi all, First of all, sorry for the vague title. Let me explain. At work we're currently using SunGrid I've been assigned a project to create a web interface wrapper for interacting with the engine. i.e. displaying users jobs, submitting jobs via a nice GUI etc. (most of the sgrid commands output xml which is nice) My question for you chaps is the following: What web dev language would you use to interact with the system? i.e. use the language to do a system call and evaluate the response. I'm not after an argument on which language is best, I just would like to know which language is specifically good for interacting with the system and is also good for web dev.

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  • Naming Suggestions For A Function Providing Method Chaining In A Different Way

    - by sid3k
    I've coded an experimental function which makes passed objects chainable by using high order functions. It's name is "chain" for now, and here is a usage example; chain("Hello World") (print) // evaluates print function by passing "Hello World" object. (console.log,"Optional","Parameters") (returnfrom) // returns "Hello World" It looks lispy but behaves very different since it's coded in a C based language, I don't know if there is a name for this idiom and I couldn't any name more suitable than "chain". Any ideas, suggestions?

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  • Is Haskell "mainstream", or is it mainly used by hobbyists and academics?

    - by Asher
    I came across a post where someone wrote something inaccurate about Haskell (won't go into it) and he got flammed for it. Which (pleasantly) surprised me. About 3 years ago I read this joke about Haskell: All the haskell programmers in the world can fit into a 747 and if that plane were to crash no one would care... or something along those lines. Which brings me to my question: how healthy is the Haskell community, anyway? Is Haskell "mainstream"? Is it mainly used by hobbiest and academics or someone making some serious money from it (which is the true yardstick of how good a language is - just kidding, geez!)?

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  • Multiple Socket Connections

    - by BSchlinker
    I need to write a server which accepts connections from multiple client machines, maintains track of connected clients and sends individual clients data as necessary. Sometimes, all clients may be contacted at once with the same message, other times, it may be one individual client or a group of clients. Since I need confirmation that the clients received the information and don't want to build an ACK structure for a UDP connection, I decided to use a TCP streaming method. However, I've been struggling to understand how to maintain multiple connections and keep them idle. I seem to have three options. Use a fork for each incoming connection to create a separate child process, use pthread_create to create an entire new thread for each process, or use select() to wait on all open socket IDs for a connection. Recommendations as to how to attack this? I've begun working with pthreads but since performance will likely not be an issue, multicore processing is not necessary and perhaps there is a simpler way.

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  • how/resources to compile a procedural language into [sql]

    - by Philip
    I am looking into the possibility/feasibility/resources for building a cross compiler which takes a procedural or Object Oriented language like C, or Java and compiling it into SQL. I understand that the advantage of SQL code is performing set operations which is fundamentally different from procedural languages which generally process 1 at a time. If anyone has done this before, or if it is thought of as too complicated to do or any other ideas/concerns/suggestions would be greatly appreciated. Thanks in advance Philip

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  • How to call schedule method in NSObject?

    - by Tattat
    It is my Object.... -(id)init{ if(self = [super init]){ [self schedule:@selector(testCalled:) interval:1.0]; } } -(void)testCalled{ NSLog(@"Called from my Object"); } I already add this line in the .h...: -(void)testCalled; It prompt me that "MyObject" may not respond to -'schedule:interval:', but in my scene, which have a super class CCLayer can call this method,so, I think it is a method from CCLayer, how can I replace it with NSObject default method?

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  • How do I compile a module in User Mode Linux

    - by Zach
    Having a tough time compiling a module for User Mode Linux. I just need a basic way to compile a very basic module in user mode linux and cannot seem to get it to work. I checked out the how-to on sourceforge for UML but had no luck. Anyone have a working example of what it takes? Thanks!

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  • getting started with lex

    - by cambr
    I need to format some hexdump like this: 00010: 02 03 04 05 00020: 02 03 04 08 00030: 02 03 04 08 00010: 02 03 04 05 00020: 02 03 04 05 02 03 04 05 02 03 04 08 to 02 03 04 05 02 03 04 08 02 03 04 02 03 04 05 02 03 04 05 02 03 04 05 02 03 04 a) remove the address fields, if present b) remove any 08 at the end of a paragraph (followed by an empty line) c) remove any empty lines How can this be done using lex? thanks!

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  • Collapsible controls in MFC (example included)

    - by John
    In the WindowsXP Control panel, you can see a nice collapsible panel control on the left: These are not just collapsible, but animated too. I wondered if these are any kind of control accessible to a developer, specifically in MFC? Or are they custom/bespoke functionality?

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  • What is the right approach to checksumming UDP packets

    - by mr.b
    I'm building UDP server application in C#. I've come across a packet checksum problem. As you probably know, each packet should carry some simple way of telling receiver if packet data is intact. Now, UDP already has 2-byte checksum as part of header, which is optional, at least in IPv4 world. Alternative method is to have custom checksum as part of data section in each packet, and to verify it on receiver. My question boils down to: is it better to rely on (optional) checksum in UDP packet header, or to make a custom checksum implementation as part of packet data section? Perhaps the right answer depends on circumstances (as usual), so one circumstance here is that, even though code is written and developed in .NET on Windows, it might have to run under platform-independent Mono.NET, so eventual solution should be compatible with other platforms. I believe that custom checksum algorithm would be easily portable, but I'm not so sure about the first one. Any thoughts? Also, shouts about packet checksumming in general are welcome.

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  • BASH Script to Check if a number is Armstrong or Not

    - by atif089
    Hi, I was writing a script to check if a number is Armstrong or not. This is my Code echo "Enter Number" read num sum=0 item=$num while [ $item -ne 0 ] do rem='expr $item % 10' cube='expr $rem \* $rem \* $rem' sum='expr $sum + $cube' item='expr $item / 10' done if [ $sum -eq $num ] then echo "$num is an Amstrong Number" else echo "$num is not an Amstrong Number" fi After I run this script, $ ./arm.sh I always get this error ./arm.sh: line 5: [: too many arguments ./arm.sh: line 12: [: too many arguments I am on cygwin.

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  • What could be the Java successor Oracle wants to invest in?

    - by deamon
    I've read that Oracle wants to invest into another language than Java: "On the other hand, Oracle has been particularly supportive of alternative JVM languages. Adam Messinger ( http://www.linkedin.com/in/adammessinger ) was pretty blunt at the JVM Languages Summit this year about Java the language reaching it's logical end and how Oracle is looking for a 'higher level' language to 'put significant investment into.'" But what language could be the one Oracle wants to invest in? Is there another candidate than Scala?

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  • Linux Kernel - programmatically retrieve block numbers as they are written to

    - by SpdStr
    I want to maintain a list of block numbers as they are physically written to using the linux kernel source. I plan to modify the kernel source to do this. I just need to find the structure and functions in the kernel source that handle writing to physical partitions and get the block numbers as they write to the physical partition. Any way of doing this? Any help is appreciated. If I can find where the kernel is actually writing to the partitions and returning the block numbers, that'd work.

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