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  • Is there an "opposite" to the null coalescing operator? (…in any language?)

    - by Jay
    null coalescing translates roughly to return x, unless it is null, in which case return y I often need return null if x is null, otherwise return x.y I can use return x == null ? null : x.y; Not bad, but that null in the middle always bothers me -- it seems superfluous. I'd prefer something like return x :: x.y;, where what follows the :: is evaluated only if what precedes it is not null. I see this as almost an opposite to null coalescence, kind of mixed in with a terse, inline null-check, but I'm [almost] certain that there is no such operator in C#. Are there other languages that have such an operator? If so, what is it called? (I know that I can write a method for it in C#; I use return NullOrValue.of(x, () => x.y);, but if you have anything better, I'd like to see that too.)

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  • Visual Studio T4 vs CodeSmith

    - by Jake
    I've been using CodeSmith for the past 2 years and love what it does for me. However, I also know about T4 which is built in to Visual Studio and can do some pretty cool stuff too. Based on conversations with friends T4 in VS2010 T4 is going to be even better. So the question is: do I keep riding the CodeSmith bus or is it time to start converting all of my templates to T4?

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  • SIMPLE OpenSSL RSA Encryption in C/C++ is causing me headaches

    - by Josh
    Hey guys, I'm having some trouble figuring out how to do this. Basically I just want a client and server to be able to send each other encrypted messages. This is going to be incredibly insecure because I'm trying to figure this all out so I might as well start at the ground floor. So far I've got all the keys working but encryption/decryption is giving me hell. I'll start by saying I am using C++ but most of these functions require C strings so whatever I'm doing may be causing problems. Note that on the client side I receive the following error in regards to decryption. error:04065072:rsa routines:RSA_EAY_PRIVATE_DECRYPT:padding check failed I don't really understand how padding works so I don't know how to fix it. Anywho here are the relevant variables on each side followed by the code. Client: RSA *myKey; // Loaded with private key // The below will hold the decrypted message unsigned char* decrypted = (unsigned char*) malloc(RSA_size(myKey)); /* The below holds the encrypted string received over the network. Originally held in a C-string but C strings never work for me and scare me so I put it in a C++ string */ string encrypted; // The reinterpret_cast line was to get rid of an error message. // Maybe the cause of one of my problems? if(RSA_private_decrypt(sizeof(encrypted.c_str()), reinterpret_cast<const unsigned char*>(encrypted.c_str()), decrypted, myKey, RSA_PKCS1_OAEP_PADDING)==-1) { cout << "Private decryption failed" << endl; ERR_error_string(ERR_peek_last_error(), errBuf); printf("Error: %s\n", errBuf); free(decrypted); exit(1); } Server: RSA *pkey; // Holds the client's public key string key; // Holds a session key I want to encrypt and send //The below will hold the encrypted message unsigned char *encrypted = (unsigned char*)malloc(RSA_size(pkey)); // The reinterpret_cast line was to get rid of an error message. // Maybe the cause of one of my problems? if(RSA_public_encrypt(sizeof(key.c_str()), reinterpret_cast<const unsigned char*>(key.c_str()), encrypted, pkey, RSA_PKCS1_OAEP_PADDING)==-1) { cout << "Public encryption failed" << endl; ERR_error_string(ERR_peek_last_error(), errBuf); printf("Error: %s\n", errBuf); free(encrypted); exit(1); } Let me once again state, in case I didn't before, that I know my code sucks but I'm just trying to establish a framework for understanding this. I'm sorry if this offends you veteran coders. Thanks in advance for any help you guys can provide!

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  • question about pcap

    - by scatman
    hi, i have to do a sniffer as an assignment for the security course. i am using c and the pcap library. i got everything working well (since i got a code from the internet and changed it). but i have some questions about the code. u_int ip_len = (ih->ver_ihl & 0xf) * 4; ih is of type ip_header, and its currently pointing the to ip header in the packet. ver_ihl gives the version of the ip i can't figure out what is: & 0xf) * 4; any help?

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  • Do you guys recommend any business magazine? [closed]

    - by kunjaan
    I want to get a birds eye view of the computing industry, read about company profiles, management decisions, new upcoming software companies, learn more about our industry and about the business aspect of my profession. Do you guys read recommend any good business magazines for me to increase my business acumen?

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  • JVM (embarrasingly) parallel processing libraries/tools

    - by Winterstream
    I am looking for something that will make it easy to run (correctly coded) embarrassingly parallel JVM code on a cluster (so that I can use Clojure + Incanter). I have used Parallel Python in the past to do this. We have a new PBS cluster and our admin will soon set up IPython nodes that use PBS as the backend. Both of these systems make it almost a no-brainer to run certain types of code in a cluster. I made the mistake of using Hadoop in the past (Hadoop is just not suited to the kind of data that I use) - the latency made even small runs execute for 1-2 minutes. Is JPPF or Gridgain better for what I need? Does anyone here have any experience with either? Is there anything else you can recommend?

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  • Definition of the job titles involved in a software development process.

    - by Rafael Romão
    I have seen many job titles for people involved in a software development process, but never found a consensus about they mean. I know many of them are equivalent, and found some other questions about that here in SO, but I would like to know your definitions and comments about them. I want not only to know if there is really a consensus, but also to know if what I suppose to be a Software Architect, is really a Software Architect, and so on. The job titles I mean are: Developer; System Analyst; Programmer; Analyst Programmer; Software Engineer; Software Architect; Designer; Software Designer; Business Manager; Business Analyst; Program Manager; Project Manager; Development Manager; Tester; Support Analyst; Please, feel free to add more titles to this list in your answers. It would be very helpful.

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  • Query on Booleans in Lambda Calculus

    - by darkie15
    Hi All, I have following query on lambda calculus which am not able to understand: Here is the lambda calculus representation for the AND operator: lambda(m).lambda(n).lambda (a).lambda (b). m(n a b) b Can anyone help me in understanding this representation? Regards, darkie

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  • Genetic Algorithms applied to Curve Fitting

    - by devoured elysium
    Let's imagine I have an unknown function that I want to approximate via Genetic Algorithms. For this case, I'll assume it is y = 2x. I'd have a DNA composed of 5 elements, one y for each x, from x = 0 to x = 4, in which, after a lot of trials and computation and I'd arrive near something of the form: best_adn = [ 0, 2, 4, 6, 8 ] Keep in mind I don't know beforehand if it is a linear function, a polynomial or something way more ugly, Also, my goal is not to infer from the best_adn what is the type of function, I just want those points, so I can use them later. This was just an example problem. In my case, instead of having only 5 points in the DNA, I have something like 50 or 100. What is the best approach with GA to find the best set of points? Generating a population of 100, discard the worse 20% Recombine the remaining 80%? How? Cutting them at a random point and then putting together the first part of ADN of the father with the second part of ADN of the mother? Mutation, how should I define in this kind of problem mutation? Is it worth using Elitism? Any other simple idea worth using around? Thanks

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  • Scalaz: request for use case

    - by oxbow_lakes
    This question isn't meant as flame-bait! As it might be apparent, I've been looking at Scalaz recently. I'm trying to understand why I need some of the functionality that the library provides. Here's something: import scalaz._ import Scalaz._ type NEL[A] = NonEmptyList[A] val NEL = NonEmptyList I put some println statements in my functions to see what was going on (aside: what would I have done if I was trying to avoid side effects like that?). My functions are: val f: NEL[Int] => String = (l: NEL[Int]) => {println("f: " + l); l.toString |+| "X" } val g: NEL[String] => BigInt = (l: NEL[String]) => {println("g: " + l); BigInt(l.map(_.length).sum) } Then I combine them via a cokleisli and pass in a NEL[Int] val k = cokleisli(f) =>= cokleisli(g) println("RES: " + k( NEL(1, 2, 3) )) What does this print? f: NonEmptyList(1, 2, 3) f: NonEmptyList(2, 3) f: NonEmptyList(3) g: NonEmptyList(NonEmptyList(1, 2, 3)X, NonEmptyList(2, 3)X, NonEmptyList(3)X) RES: 57 The RES value is the character count of the (String) elements in the final NEL. Two things occur to me: How could I have known that my NEL was going to be reduced in this manner from the method signatures involved? (I wasn't expecting the result at all) What is the point of this? Can a reasonably simple and easy-to-follow use case be distilled for me? This question is a thinly-veiled plea for some lovely person like retronym to explain how this powerful library actually works.

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  • Create ntp time stamp from gettimeofday

    - by krunk
    I need to calculate an ntp time stamp using gettimeofday. Below is how I've done it with comments on method. Look good to you guys? (minus error checking). Also, here's a codepad link. #include <unistd.h> #include <sys/time.h> const unsigned long EPOCH = 2208988800UL; // delta between epoch time and ntp time const double NTP_SCALE_FRAC = 4294967295.0; // maximum value of the ntp fractional part int main() { struct timeval tv; uint64_t ntp_time; uint64_t tv_ntp; double tv_usecs; gettimeofday(&tv, NULL); tv_ntp = tv.tv_sec + EPOCH; // convert tv_usec to a fraction of a second // next, we multiply this fraction times the NTP_SCALE_FRAC, which represents // the maximum value of the fraction until it rolls over to one. Thus, // .05 seconds is represented in NTP as (.05 * NTP_SCALE_FRAC) tv_usecs = (tv.tv_usec * 1e-6) * NTP_SCALE_FRAC; // next we take the tv_ntp seconds value and shift it 32 bits to the left. This puts the // seconds in the proper location for NTP time stamps. I recognize this method has an // overflow hazard if used after around the year 2106 // Next we do a bitwise AND with the tv_usecs cast as a uin32_t, dropping the fractional // part ntp_time = ((tv_ntp << 32) & (uint32_t)tv_usecs); }

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  • Using HTMLAgility Pack to Extract Links

    - by Soham
    Hi Folks, Consider this simplest piece of code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using HtmlAgilityPack; namespace WebScraper { class Program { static void Main(string[] args) { HtmlDocument doc = new HtmlDocument(); doc.LoadHtml("http://www.google.com"); foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[@href]")) { } } } } This effectively doesnt do anything at all, and is copied/inspired from various other StackOverflow questions like this. When compiling this, there is a runtime error which says "Object reference not set to an instance of an object." highlighting the foreach line. I can't understand, why the environment has become irritable to this humble,innocent and useless piece of code. I would also like to know, does HTMLAgilityPack accept HTML classes as nodes?

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  • How to delete columns?

    - by Joey jie
    Hi all, I have generated the following text file below: fe120b99164f151b28bf86afa6389b22 -rw-r--r-- 1 joey joey 186 2010-03-14 19:26 Descript.txt 41705ea936cfc653f273b5454c1cdde6 -rw-r--r-- 1 joey joey 30 2010-03-14 20:29 listof.txt 0e25cca3222d32fff43563465af03340 -rw-r--r-- 1 joey joey 28 2010-03-14 23:35 sedexample.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test1.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test2.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test3.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test4.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test5.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-02-16 15:11 test6.txt f5c7f1856249d0526be10df5bd5b895a -rw-r--r-- 1 joey joey 26 2010-03-13 14:13 testingfile.txt d41d8cd98f00b204e9800998ecf8427e -rw-r--r-- 1 joey joey 0 2010-03-15 00:28 uniquelist.txt Basically I would like to get rid of the access, amount column, user and group columns. In other words, I want rid of columns 3,4,5. I have tried using cut to keep the columns that I do want and having " " as my delimiter however because of the file size figures, it messes up using "space" as a delimiter. Any advice would be much appreciated! Oh just to add, I would like to save the output as another text file. Many thanks!

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  • Web serivce time out errors in delphi

    - by JD
    Hi, I have a client application that makes SOAP requests. I have set the timeout to 20 minutes. However, sometimes I see the timeout error occurring after 10 seconds. I have the following in code: RIO.HTTPWebNode.ReceiveTimeout := 1200000 Do I need to set the ConnectTimeout and SendTimeOut? Currently they are set to the default values of 0. What difference would setting these make? I am using Delphi 2007. Looking further at the error message I see I get "The operation timed out....". So should I be setting my ReceiveTimeOut to zero since I really do not want any timeout at all?

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  • Where did the "Polymorphism" word come from?

    - by Alon
    I've always wondered where did the word "Polymorphism" word come from. I know what is polymorphism and I use it of course, but I just don't understand why this technique called polymorphism. Note that I'm not a native English speaker, and I will thank you if you'll use simple English in your answers. Thank you.

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  • Python equivalent of IDL's stop and .reset

    - by Jamie
    Hi there, I'm relatively new to python but have a bit of experience using IDL. I was wondering if anyone knows if there are equivalent commands in python for IDL's stop and .reset commands. If I'm running some IDL script I wrote that I put a stop command in, essentially what it does is stop the script there and give me access to the command line in the middle of the script. So I have access to all the functions and variables that I defined before the stop command, which I find really useful for debugging. The .reset command I find extremely useful too. What it does is reset the the IDL environment (clears all variables, functions, etc.). It's as if I closed that session and opened a new one, but without having to exit and restart IDL. I find that if I'm trying to debug a script I wrote it's useful sometimes to start from scratch and not have to reset IDL (or python now). It would be useful also in python to be able to un-import any modules I had previously imported. Any help with these issues would be greatly appreciated. Cheers Related Python Drop into REPL Is it possible to go into ipython from code?

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  • Generic Data Structure Description Language

    - by Jon Purdy
    I am wondering whether there exists any declarative language for arbitrarily describing the format and semantics of a data structure, that can be compiled to a specific implementation of that structure in any of a set of target languages. That is, something like a generic data definition language but geared toward describing arbitrary data structures such as vectors, lists, trees, etc., and the semantics of operations on those structures. I ask because I had an idea for a feasible implementation of this concept, and I'm just wondering whether it's worth it, and, consequently, whether it's been done before. Another, slightly more abstract question: is there any real difference between the normative specification of a data structure (what it does) and its implementation (how it does it)?

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