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  • what is main focus for a developer when coding?

    - by ajsie
    i read a lot of books about how to code right and usually the are talking about all these techniques from a point of view i can't understand. eg. lets consider the singleton pattern. i'm restricting so the class can only be instantiated once. but since it's only me creating the application, if i know that the class only should be instantiated once, then why would i create it a second time? i feel like missing the big picture. what is my main goal when coding an application? how should i think? thanks

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  • List filtering: list comprehension vs. lambda + filter

    - by Agos
    I happened to find myself having a basic filtering need: I have a list and I have to filter it by an attribute of the items. My code looked like this: list = [i for i in list if i.attribute == value] But then i thought, wouldn't it be better to write it like this? filter(lambda x: x.attribute == value, list) It's more readable, and if needed for performance the lambda could be taken out to gain something. Question is: are there any caveats in using the second way? Any performance difference? Am I missing the Pythonic Way™ entirely and should do it in yet another way (such as using itemgetter instead of the lambda)? Thanks in advance

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  • error in script

    - by lego69
    can somebody please help, I'm working with C-Shell, I'm trying to run this script set callsTo = "`cut -d" " -f2 ${1}`" echo $callsTo cut receives data from the file which is the first parameter > ./myscript data I need only second field from every row -f2 after that I want to check if the data was stored, but I receive or an error unmatched `. or empty row, what is wrong with my script, thanks in advance for any help

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  • wireless networks c program

    - by Nave
    i wud like to create a wireless network from a laptop. if some laptops come within this range, i wud like to send them a welcome message and when they leave the wifi range, i send them a bye message. is it possible to code such a thing in C? please help me out with this.

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  • Can anyone help me find why this C program work on VS2005 but not on DEV-C++

    - by user333771
    Hello to everybody..and greetings from Greece I have a C program for an exercise and it has a strange issue The program runs just fine on VS 2005 but it crashes on DEV-C++ and the problem that the problem is that the exercise is always evaluated against DEV-C++ The program is about inserting nodes to a BST and this is where the problem lies... Well i would really appreciate some help. enter code here #include <stdio.h> #include <stdlib.h> #include <malloc.h> typedef struct tree_node { int value; int weight; struct tree_node *left; struct tree_node *right; } TREE_NODE; /* The Following function creates a Binary Search Treed */ TREE_NODE *create_tree(int list[], int size); TREE_NODE *search_pos_to_insert(TREE_NODE *root, int value, int *left_or_right); /* this is the problematic function */ void inorder(TREE_NODE *root); /* Inorder Traversing */ TREE_NODE *temp; int main() { TREE_NODE *root; /* Pointer to the root of the BST */ int values[] = {10, 5, 3, 4, 1, 9, 6, 7, 8, 2}; /* Values for BST */ int size = 10, tree_weight; root = create_tree(values, 10); printf("\n"); inorder(root); /* Inorder BST*/ system("PAUSE"); } TREE_NODE *search_pos_to_insert(TREE_NODE *root, int value, int *left_or_right) { if(root !=NULL) { temp = root; if(value >root->value) { *left_or_right=1; *search_pos_to_insert(root->right, value, left_or_right); } else { *left_or_right=0; *search_pos_to_insert(root->left, value, left_or_right); } } else return temp;/* THIS IS THE PROBLEM (1) */ } TREE_NODE *create_tree(int list[], int size) { TREE_NODE *new_node_pntr, *insert_point, *root = NULL; int i, left_or_right; /* First Value of the Array is the root of the BST */ new_node_pntr = (TREE_NODE *) malloc(sizeof(TREE_NODE)); new_node_pntr->value = list[0]; /* ¸íèåóå ôçí ðñþôç ôéìÞ ôïõ ðßíáêá. */ new_node_pntr->weight = 0; new_node_pntr->left = NULL; new_node_pntr->right = NULL; root = new_node_pntr; /* Now the rest of the arrat. */ for (i = 1; i < size; i++) { insert_point = search_pos_to_insert(root, list[i], &left_or_right); /* THIS IS THE PROBLEM (2) */ /* insert_point just won't get the return from temp */ new_node_pntr = (TREE_NODE *) malloc(sizeof(TREE_NODE)); new_node_pntr->value = list[i]; new_node_pntr->weight = 0; new_node_pntr->left = NULL; new_node_pntr->right = NULL; if (left_or_right == 0) insert_point->left = new_node_pntr; else insert_point->right = new_node_pntr; } return(root); } void inorder(TREE_NODE *root) { if (root == NULL) return; inorder(root->left); printf("Value: %d, Weight: %d.\n", root->value, root->weight); inorder(root->right); }

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  • Applet networking patterns

    - by Kristoffersen
    Hi SO. I have an applet that connects to a server, it receives some commands and based on that it haves to draw (or move) different things. Which patterns should I use? I assume that the network connection and applet should run in two different threads? Thanks, Kristoffer

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  • Using LINQ, need help splitting a byte array on data received from Silverlight sockets

    - by gcadmes
    The message packats received contains multiple messages deliniated by a header=0xFD and a footer=0xFE // sample message packet with three // different size messages List<byte> receiveBuffer = new List<byte>(); receiveBuffer.AddRange(new byte[] { 0xFD, 1, 2, 0xFE, 0xFD, 1, 2, 3, 4, 5, 6, 7, 8, 0xFE, 0xFD, 33, 65, 25, 44, 0xFE}); // note: this sample code is without synchronization, // statements, error handling...etc. while (receiveBuffer.Count > 0) { var bytesInRange = receiveBuffer.TakeWhile(n => n != 0xFE); foreach (var n in bytesInRange) Console.WriteLine(n); // process message.. // 1) remove bytes read from receive buffer // 2) construct message object... // 3) etc... receiveBuffer.RemoveRange(0, bytesInRange.Count()); } As you can see, (including header/footer) the first message in this message packet contains 4 bytes, and the 2nd message contains 10 bytes,a and the 3rd message contains 6 bytes. In the while loop, I was expecting the TakeWhile to add the bytes that did not equal the footer part of the message. Note: Since I am removing the bytes after reading them, the header can always be expected to be at position '0'. I searched examples for splitting byte arrays, but non demonstrated splitting on arrays of unknown and fluctuating sizes. Any help will be greatly appreciated. thanks much!

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  • Haskell: How to compose `not` with a function of arbitrary arity?

    - by Hynek -Pichi- Vychodil
    When I have some function of type like f :: (Ord a) => a -> a -> Bool f a b = a > b I should like make function which wrap this function with not. e.g. make function like this g :: (Ord a) => a -> a -> Bool g a b = not $ f a b I can make combinator like n f = (\a -> \b -> not $ f a b) But I don't know how. *Main> let n f = (\a -> \b -> not $ f a b) n :: (t -> t1 -> Bool) -> t -> t1 -> Bool Main> :t n f n f :: (Ord t) => t -> t -> Bool *Main> let g = n f g :: () -> () -> Bool What am I doing wrong? And bonus question how I can do this for function with more and lest parameters e.g. t -> Bool t -> t1 -> Bool t -> t1 -> t2 -> Bool t -> t1 -> t2 -> t3 -> Bool

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  • Testing for a closed socket

    - by Robert S. Barnes
    I'm trying to test for a closed socket that has been gracefully closed by the peer without incurring the latency hit of a double send to induce a SIGPIPE. One of the assumptions here is that the socket if closed was gracefully closed by the peer immediately after it's last write / send. Actual errors like a premature close are dealt with else where in the code. If the socket is still open, there will be 0 or more bytes data which I don't actually want to pull out of the socket buffer yet. I was thinking that I could call int ret = recv(sockfd, buf, 1, MSG_DONTWAIT | MSG_PEEK); to determine if the socket is still connected. If it's connected but there's no data in the buffer I'll get a return of -1 with errno == EAGAIN and return the sockfd for reuse. If it's been gracefully closed by the peer I'll get ret == 0 and open a new connection. I've tested this and it seems to work. However, I suspect there is a small window between when I recv the last bit of my data and when the peer FIN arrives in which I could get a false-positive EAGAIN from my test recv. Is this going to bite me, or is there a better way of doing this?

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  • How can I programmatically get the connection status of OSX network services?

    - by BigBrainz
    In the OS X System Preferences, when I click on 'Network' I see a green dot by 'Ethernet', and red dots by 'AirPort' and 'FireWire'. This is because I turned off AirPort and FireWire, as I access networks and the Internet via Ethernet. I need to programmatically determine which of these network services displayed in System Preferences have green dots and which have red dots. For Ethernet and FireWire the displayed status is 'Connected' or 'Not Connected', and for AirPort the displayed status is 'On' or 'Off'. Perhaps other network services have other status labels. I have picked through all the plist files in '/Library/Preferences/SystemConfiguration', particularly 'preferences.plist' and 'NetworkInterfaces.plist'. I can get all sorts of information there, such as the Location set, network service order, proxy information (which is also important to my task), but I cannot find how to determine whether a given network service is on or off--the equivalent of having the green dot displayed. I have also tried using System Configuration framework, specifically the SCNetworkConnectionGetStatus function, but all I get are invalid connection statuses. Does anyone know how to actually retrieve this connection status information? Thanks.

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  • Call/Return feature of classic C++(C with Classes), what modern languages have it?

    - by AraK
    Hi, On page 57 of The Design and Evolution of C++, Dr. Stroustrup talks about a feature that was initially part of C with Classes, but it isn't part of modern C++(standard C++). The feature is called call/return. This is an example: class myclass { call() { /* do something before each call to a function. */ } return() { /* do something else after each call to a function. */ } ... }; I find this feature very interesting. Does any modern language have this particular feature?

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  • Choosing a Job based on languages?

    - by Alan
    How often is language the deciding factor for selecting a job? Many of us here are well versed in many languages, C++, Java, C#, and likely have many other languages under our belt for the right occassion (really any occasion is the right occasion for Python, AMIRITE?), so this isn't so much a question of choosing a job that is a good fit based on your skill set. Rather, if you are skilled with most languages, do you pick your favorite, or do you follow the money (given the tight economy). I'm considering coming out of retirement, and have started to look around and what's available. Over the years, I've moved towards C# and Python; many jobs in the area are looking for .NET developers, but there are plenty of them that do not. I cut my teef on C++, consider myself adept at the language, and know my way around a Java. But I find myself really digging what they're doing to C#, and I have always loved python. So when I see an interesting job req that is looking for C++ developers; it gives me 2nd thoughts. Not because I can't cut it, but because I don't know if I want to go back to C++. Even if the work will be interesting, how important is the language to you?

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  • how to access child instances in a vector in c++

    - by tsubasa
    I have a parent class and child class (inherited from parent). In the child class, I have a member function named function_blah(); I used vector<parent*> A to store 5 parent instances, 3 child instances. So the total number of elements in the vector is 8. I can easily access to member functions of element A[0] to A[4], which are parent instances. But whenever I try to have access to member functions of element A[5] to A[7], the compiler complains that class parent has no member named 'function_blah' The way I access to elements is using index. e.x A[i] with i = 0..7. Is it correct? if not, how?

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  • Simple way to print value of a register in x86 assembly.

    - by Bob
    I need to write a program in 8086 Assembly that receives data from the user, does some mathematical calculations and prints the answer on the screen, I have written all parts of the program and all work fine but I don't know how to print the number to the screen. At the end of all my calculation the answer is AX and it is treated as an unsigned 16 bit integer. How do I print the decimal (unsigned) value of the AX register?

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  • Need complete picture of virtual adress space

    - by claws
    Hello, This image gives a good picture about Virtual Adress space. But it only says half of the story. It only gives complete picture of User Adress space ie.. lower 50% (or 75% in some cases). What about the rest 50% (or 25%) which is occupied by the kernel. I know kernel also has so many different things like kernel modules , device drivers, core kernel itself. There must be some kind of layout right? What is its layout? If you say its Operating System dependent. I would say, there are two major operating systems Windows & Linux. Please give answer for any one these.

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  • Get the number of packages transmitted per connection

    - by Daniel
    How do I get the number of packages transmitted per TCP connection? I am using Java, but i know I will have to fetch the number from the underlying OS, so this quastion applies to Linux and Windows operating systems and will have different answers for each of them, I assume. I need this information to profile the network load of an application which seems to send too many small packages by flushing the socket streams too often.

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