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  • Can you dynamically combine multiple conditional functions into one in Python?

    - by erich
    I'm curious if it's possible to take several conditional functions and create one function that checks them all (e.g. the way a generator takes a procedure for iterating through a series and creates an iterator). The basic usage case would be when you have a large number of conditional parameters (e.g. "max_a", "min_a", "max_b", "min_b", etc.), many of which could be blank. They would all be passed to this "function creating" function, which would then return one function that checked them all. Below is an example of a naive way of doing what I'm asking: def combining_function(max_a, min_a, max_b, min_b, ...): f_array = [] if max_a is not None: f_array.append( lambda x: x.a < max_a ) if min_a is not None: f_array.append( lambda x: x.a > min_a ) ... return lambda x: all( [ f(x) for f in f_array ] ) What I'm wondering is what is the most efficient to achieve what's being done above? It seems like executing a function call for every function in f_array would create a decent amount of overhead, but perhaps I'm engaging in premature/unnecessary optimization. Regardless, I'd be interested to see if anyone else has come across usage cases like this and how they proceeded. Also, if this isn't possible in Python, is it possible in other (perhaps more functional) languages?

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  • Collaborative kernel development

    - by Raffo
    Hi, I have to develop a patch for the linux kernel (2.6) for an university course I'm attending. I have to develop this patch with a friend of mine and we need to edit the same files on our computers (2-3 PCs). So, we want to use something like a collaborative editor and/or a version control system. The problem is that we never used something like that and that we cannot release our software as open source till we take the exam. Obviously, we're using linux. I'm here to ask you suggestions in order to manage our work in the best way. Thank you

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  • Hold a network connection although IP address change

    - by rursw1
    Hi, Is it possible to hold an open TCP connection with a client, while the IP address of the client is externally changed? For example, the connection is establishes against address X, but somewhen while the connection is open, the client-side user asks for IP renew and gets another IP address. Can the connection remains alive in this case? Thanks in advance.

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  • What libraries provide cross-platform 3D and P2P support?

    - by uckelman
    I'm trying to find a constellation of libraries which, taken together, meet the following requirements: Smooth scaling, rotation, panning (in two dimensions). I'll have a large bitmap (or SVG, in some cases), maybe up to 10000x10000 pixels, which serves as map, with some middling number of small bitmaps (or, again, possibly SVG) that can be dragged around over it. I need to be able to zoom, rotate, and pan this scene; however, the view will always be normal to (i.e., looking head-on at) the large bitmap, so I'm not really using the depth dimension. Peer-to-peer. I'd like for multiple users to be able to connect in order to share one of the scenes mentioned above, preferably peer-to-peer, without much configuration by the user. I'm intending to have a server running for cases where users are unable to connect P2P; I'd like to have the failover happen automatically, or possibly have some way of promoting clients who are capable to be servers themselves. Synchronization. Once a user has started dragging one of the small bitmaps (a piece), no other user should be able to drag that piece until the drag stops. I haven't thought of exactly how to do this---there might be a simple solution, or this kind of synchronization might be something that a library provides. Cross(ish)-platform. I need to be able to run on Linux, Windows, and Mac OS. It would be nice to also be able to run on tablets. Having mostly the same code for all platforms is a plus, but not absolutely necessary. (L)GPL compatible. I'm planning to release under the LGPL or GPL, preferably the latter, so I need libraries which have compatible licenses. I'm not set on any particular language, I'd like to use the library or libraries which make the work easiest, though my preference is to work in at most two languages for the project. (The Model could potentially be in one language and the View in another, so they could talk to each other via some protocol I define, if that would get me a better selection of libraries to use.) Can anyone offer suggestions for what to use?

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  • Raw socket implementation in windows?

    - by krishnakumar
    I need to create TCP/IP headers manually for my application. For that i used Raw socket. My system os is win xp (SP3). My code compiles fine :) but it throws a run time error: Initialising Winsock...Initialised successfully. Creating Raw TCP Socket...Raw TCP Socket Created successfully. Setting the socket in RAW mode...Successful. Enter hostname : 192.168.1.152 Resolving Hostname...Resolved. Enter Source IP : 192.168.1.151 Sending packet... Error sending Packet : 10022 I have set IP_HDRINCL to 1. What am i doing wrong? I switched off the firewall too but still get the same result.

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  • Avoiding dependency carrying

    - by dotnetdev
    When coding, I often come across the following pattern: -A method calls another method (Fine), but the method being called/callee takes parameters, so in the wrapping method, I pass in parameters. Problem is, this dependency carrying can go on and on. How could I avoid this (any sample code appreciated)? Thanks

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  • Using excel, how can I count the number of cells in a column containing the text "true" or "false"?

    - by Jay Elston
    I have a spreadsheet that has a column of cells where each cell contains a single work. I would like to count the occurrences of some words. I can use the COUNTIF function for most words, but if the word is "true" or "false", I get 0. A B 1 apples 2 2 true 0 3 false 0 4 oranges 1 5 apples In the above spreadsheet table, I have these formulas in cells B1, B2, B3 and B4: =COUNTIF(A1:A5,"apples") =COUNTIF(A1:A5,"true") =COUNTIF(A1:A5,"false") =COUNTIF(A1:A5,"oranges) As you can see, I can count apples, but not true or false. I have also tried this: =COUNTIF(A1:A5,TRUE) But that does not work either. Note -- I am using Excel 2007.

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  • PHP: prepared statement, IF statement help needed

    - by JGreig
    I have the following code: $sql = "SELECT name, address, city FROM tableA, tableB WHERE tableA.id = tableB.id"; if (isset($price) ) { $sql = $sql . ' AND price = :price '; } if (isset($sqft) ) { $sql = $sql . ' AND sqft >= :sqft '; } if (isset($bedrooms) ) { $sql = $sql . ' AND bedrooms >= :bedrooms '; } $stmt = $dbh->prepare($sql); if (isset($price) ) { $stmt->bindParam(':price', $price); } if (isset($sqft) ) { $stmt->bindParam(':price', $price); } if (isset($bedrooms) ) { $stmt->bindParam(':bedrooms', $bedrooms); } $stmt->execute(); $result_set = $stmt->fetchAll(PDO::FETCH_ASSOC); What I notice is the redundant multiple IF statements I have. Question: is there any way to clean up my code so that I don't have these multiple IF statements for prepared statements?

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  • What language is .NET Framework written in?

    - by chester89
    The question I always wanted to ask and was afraid to, actually - what language is .NET Framework written in? I mean library itself. It seems to me that it was C and C++ mostly. (I hope Jon Skeet is reading this one, it`ll be very interesting to hear what he thinks about it)

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  • Function Overloading

    - by Sanju
    Let us suppose i have these three methods defined: int F1(int, int); int F1(float, float); Float F1(int, int); and i am calling method F1 here: Console.writeline(F1(5,6).ToString())); Which method it will call and why?

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  • Additional concerns when compiling for x64

    - by dotnetdev
    I know that the additional consideratiosn when compiling for x64 is that some data types, like ints, can hold larger values. Are there any concerns? VS2010, released a few days ago, can support compiling for x64 and x32, just like VS2008. The app is x32/86 only. I keep thinking that the app needs to be 64 bit however. What am I missing? Obviously this is not the case. Thanks

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  • Generating a python file

    - by fema
    Hi! I'm havin issues with python (imo python itself is an issue). I have a txt file, it contains a custom language and I have to translate it to a working python code. The input: import sys n = int(sys.argv[1]) ;;print "Beginning of the program!" LOOP i in range(1,n) {print "The number:";;print i} BRANCH n < 5 {print n ;;print "less than 5"} The wanted output looks exactly like this: import sys n = int(sys.argv[1]) print "Beginning of the program!" for i in range(1,n) : print "The number:" print i if n < 5 : print n print "less than 5" The name of the input file is read from parameter. The out file is out.py. In case of a wrong parameter, it gives an error message. The ;; means a new line. When I tried to do it, I made an array, I read all the lines into it, split by " ". Then I wanted to strip it from the marks I don't need. I made 2 loops, one for the lines, one for the words. So then I started to replace the things. Everything went fine until it came to the } mark. It finds it, but it can not replace or strip it. I have no more idea what to do. Could someone help me, please? Thanks in advance!

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  • Waiting for data via select not working

    - by BSchlinker
    I'm currently working on a project which involves multiple clients connected to a server and waiting for data. I'm using select and monitoring the connection for incoming data. However, the client just continues to print nothing, acting as if select has discovered incoming data. Perhaps I'm attacking this wrong? For the first piece of data the server does send, it is displayed correctly. However, the server then disconnects and the client continues to spew blank lines. FD_ZERO(&readnet); FD_SET(sockfd, &readnet); while(1){ rv = select(socketdescrip, &readnet, NULL, NULL, &timeout); if (rv == -1) { perror("select"); // error occurred in select() } else if (rv == 0) { printf("Connection timeout! No data after 10 seconds.\n"); } else { // one or both of the descriptors have data if (FD_ISSET(sockfd, &readnet)) { numbytes = recv(sockfd, buf, sizeof buf, 0); printf("Data Received\n"); buf[numbytes] = '\0'; printf("client: received '%s'\n",buf); sleep(10); } } }

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  • Kernel module for /proc

    - by sb2367
    How to write a kernel module that creates a directory in /proc named mymod and a file in it name is mymodfile. This file should accept a number ranged from 1 to 3 when written into it and return the following messages when read based on the number already written into it: • 1: Current system time (in microseconds precision) • 2: System uptime • 3: Number of processes currently in the system “The Output” root@Paradise# echo 1 > /proc/mymod/mymodfile root@Paradise# cat /proc/mymod/mymodfile 08:30:24 342us root@Paradise# echo 2 > /proc/mymod/mymodfile root@Paradise# cat /proc/mymod/mymodfile up 1 day, 8 min root@Paradise# echo 3 > /proc/mymod/mymodfile root@Paradise# cat /proc/mymod/mymodfile process count: 48 please give me some hint how to write a kernel modules and how to compile and install it .

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  • How to filter and intercept Linux packets by using net_dev_add() API?

    - by Khajavi
    I'm writing ethernet network driver for linux. I want to receive packets, edit and resend them. I know how to edit the packet in packet_interceptor function, but how can I drop incoming packets in this function?? #include <linux/netdevice.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <net/sock.h> struct packet_type my_proto; int packet_interceptor(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) { // I dont want certain packets go to upper in net_devices for further processing. // How can I drop sk_buff here?! return 0; } static int hello_init( void ) { printk(KERN_INFO "Hello, world!\n"); my_proto.type = htons(ETH_P_ALL); my_proto.dev = NULL; my_proto.func = packet_interceptor; dev_add_pack(&my_proto); return 0; } static void hello_exit(void) { dev_remove_pack(&my_proto); printk(KERN_INFO "Bye, world\n"); } module_init(hello_init); module_exit(hello_exit);

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  • How to cast a character to int in Clojure?

    - by Learning Clojure
    How to cast a character to int in Clojure? I am trying to write a rot 13 in clojure, so I need to have something to cast my char to int. I found something called (int), so I put: (int a) Get: CompilerException java.lang.RuntimeException: Unable to resolve symbol: a in this context, compiling:(NO_SOURCE_PATH:13:1) Then I put: (int 'a) Get: ClassCastException clojure.lang.Symbol cannot be cast to java.lang.Character clojure.lang.RT.intCast (RT.java:1087) Then: (rot13 ''a') Get: ClassCastException clojure.lang.PersistentList cannot be cast to java.lang.Character clojure.lang.RT.intCast (RT.java:1087) And: (rot13 "a") Get: ClassCastException java.lang.String cannot be cast to java.lang.Character clojure.lang.RT.intCast (RT.java:1087) So what is the right way to do it? btw, I always get confused with all these clojure syntax. But I can never find any source only help me with my problem. Any suggestions? Thank you!!

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  • Best ways to write a method that updates two objects in a multithreaded java environment?

    - by DanielHonig
    Suppose we have a class called AccountService that manages the state of accounts. AccountService is defined as interface AccountService{ public void debit(account); public void credit(account); public void transfer(Account account, Account account1); } Given this definition, what is the best way to implement transfer() so that you can guarantee that transfer is an atomic operation. I'm interested in answers that reference Java 1.4 code as well as answers that might use resources from java.util.concurrent in Java 5

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  • Is it faster to count down than it is to count up?

    - by Bob
    Our computer science teacher once said that for some reason it is more efficient to count down that count up. For example if you need to use a FOR loop and the loop index is not used somewhere (like printing a line of N * to the screen) I mean that code like this : for (i=N; i>=0; i--) putchar('*'); is better than: for (i=0; i<N; i++) putchar('*'); Is it really true? and if so does anyone know why?

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  • Composing adaptors in Boost::range

    - by bruno nery
    I started playing with Boost::Range in order to have a pipeline of lazy transforms in C++]1. My problem now is how to split a pipeline in smaller parts. Suppose I have: int main(){ auto map = boost::adaptors::transformed; // shorten the name auto sink = generate(1) | map([](int x){ return 2*x; }) | map([](int x){ return x+1; }) | map([](int x){ return 3*x; }); for(auto i : sink) std::cout << i << "\n"; } And I want to replace the first two maps with a magic_transform, i.e.: int main(){ auto map = boost::adaptors::transformed; // shorten the name auto sink = generate(1) | magic_transform() | map([](int x){ return 3*x; }); for(auto i : sink) std::cout << i << "\n"; } How would one write magic_transform? I looked up Boost::Range's documentation, but I can't get a good grasp of it.

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  • What are the benefits of `while(condition) { //work }` and `do { //work } while(condition)`?

    - by Shaharyar
    I found myself confronted with an interview question where the goal was to write a sorting algorithm that sorts an array of unsorted int values: int[] unsortedArray = { 9, 6, 3, 1, 5, 8, 4, 2, 7, 0 }; Now I googled and found out that there are so many sorting algorithms out there! Finally I could motivate myself to dig into Bubble Sort because it seemed pretty simple to start with. I read the sample code and came to a solution looking like this: static int[] BubbleSort(ref int[] array) { long lastItemLocation = array.Length - 1; int temp; bool swapped; do { swapped = false; for (int itemLocationCounter = 0; itemLocationCounter < lastItemLocation; itemLocationCounter++) { if (array[itemLocationCounter] > array[itemLocationCounter + 1]) { temp = array[itemLocationCounter]; array[itemLocationCounter] = array[itemLocationCounter + 1]; array[itemLocationCounter + 1] = temp; swapped = true; } } } while (swapped); return array; } I clearly see that this is a situation where the do { //work } while(cond) statement is a great help to be and prevents the use of another helper variable. But is this the only case that this is more useful or do you know any other application where this condition has been used?

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  • What experience is the most valued in a programmer?

    - by Christo
    I've been coding application level software for a while now. I've had some experience with internet (server/client based) applications, but that has been fairly scant. The field doesn't scare although I know that experience can be almost be measured in gold. I see myself as a highly qualified and experienced programmer, but I also see my short comings in these fields. Does this count against me (and others like me?) and would this cut anyone from obtaining the shortlist or are there other factors which bear more weight?

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