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• Linux Kernel - Socket file descriptor close location

  - by NTek

  Where in the linux kernel does the closing of a socket's file descriptor occur? I know for a file, the file's file descriptor is closed in fs/open.cs function sys_close(). However, for a socket file descriptor, is this the same location or somewhere else? Also, do sockets utilize the file.c alloc_fd to allocate the file descriptor or do they utilize some other function?

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• Most efficient way for testing links

  - by Burnzy

  I'm currently developping an app that is going through all the files on a server and checking every single hrefs to check wether they are valid or not. Using a WebClient or a HttpWebRequest/HttpWebResponse is kinda overkilling the process because it downloads the whole page each time, which is useless, I only need to check if the link do not return 404. What would be the most efficient way? Socket seems to be a good way of doing it, however I'm not quite sure how this works. Thanks for sharing your expertise!

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• Writing an auto-memoizer in Scheme. Help with macro and a wrapper.

  - by kunjaan

  I am facing a couple of problems while writing an auto-memoizer in Scheme. I have a working memoizer function, which creats a hash table and checks if the value is already computed. If it has been computed before then it returns the value else it calls the function. (define (memoizer fun) (let ((a-table (make-hash))) (?(n) (define false-if-fail (?() #f)) (let ((return-val (hash-ref a-table n false-if-fail))) (if return-val return-val (begin (hash-set! a-table n (fun n)) (hash-ref a-table n))))))) Now I want to create a memoize-wrapper function like this: (define (memoize-wrapper function) (set! function (memoizer function))) And hopefully create a macro called def-memo which defines the function with the memoize-wrapper. eg. the macro could expand to (memoizer (define function-name arguments body ...) or something like that. So that I should be able to do : (def-memo (factorial n) (cond ((= n 1) 1) (else (* n (factorial (- n 1)))))) which should create a memoized version of the factorial instead of the normal slow one. My problem is that the The memoize-wrapper is not working properly, it doesnt call the memoized function but the original function. I have no idea how to write a define inside of the macro. How do I make sure that I can get variable lenght arguments and variable length body? How do I then define the function and wrap it around with the memoizer? Thanks a lot.

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• Picking the right language

  - by simion

  I am a student at University so my experience is limited, hence the question. If someone says to you, here is a task to code, what are you looking at in order to choose the language or paradigm in which you will do it in? Hope the question makes sense?

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• How to receive packets on the MCU's serial port?

  - by itisravi

  Hello, Consider this code running on my microcontroller unit(MCU): while(1){ do_stuff; if(packet_from_PC) send_data_via_gpio(new_packet); //send via general purpose i/o pins else send_data_via_gpio(default_packet); do_other_stuff; } The MCU is also interfaced to a PC via a UART.Whenever the PC sends data to the MCU, the *new_packet* is sent, otherwise the *default_packet* is sent.Each packet can be 5 or more bytes with a pre defined packet structure. My question is: 1.Should i receive the entire packet from PC using inside the UART interrut service routine (ISR)? In this case, i have to implement a state machine inside the ISR to assemble the packet (which can be lengthy with if-else or switch-case blocks). 2.Detect a REQUEST command (one byte)from the PC in my ISR set a flag, diable UART interrupt alone and form the packet in my while(1) loop by polling the UART?

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• Static and Dynamic Scooping Problem

  - by Devyn

  Hi, I'm solving following code in Static and Dynamic Scooping. I got following answer but I need someone to confirm if I'm correct or not since I'm a bit confusing. I really appreciate if anyone can explain in simple way! Static => (1)8 (2)27 Dynamic => (1)10 (2)27 proc main var x,y,z; proc sub1 var x,z x := 6; z := 7; sub2; x := y*z + x; print(x); ---- (2) end; proc sub2 var x,y x := 1; y := x+z+2; print(y); ---- (1) end; begin x := 1; y:=3; z:=5; sub1; end

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• What's the purpose of the empty string?

  - by Max Toro

  To me, as a developer and as a user, I find the empty string ("") useless and the cause of much confusion, it's like saying string == char[] Maybe computers need the empty string, so I'd like to learn why.

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• Interview question: difference between object and object-oriented languages.

  - by Bar

  My friend was asked the following question: what's the difference between object language and object-oriented language? It's a little unintelligible question. What does term «object language» correspond to? Does that mean «pure» object-oriented language, like the Wikipedia article says: Languages called "pure" OO languages, because everything in them is treated consistently as an object, from primitives such as characters and punctuation, all the way up to whole classes, prototypes, blocks, modules, etc. They were designed specifically to facilitate, even enforce, OO methods. Examples: Smalltalk, Eiffel, Ruby, JADE, VB.NET.

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• Developing a project which is an implementation of an open standard/protocol

  - by dotnetdev

  Hi, A lot of interesting code/projects are implementations of protocols, eg SNMP. How are projects like these, which depend on implementing a certain format, developed? Is the process something like get the guidelines of the protocol and then implement code which follows it. For example, XML-RPC is about transmitting XML docs between client/server, so the documentation on this protocol must outline the structure of the XML documents and then the way the transportation between client and server works, so the coder will implement this sort of functionality (xml doc construction, networking between the client and server). Projects I am thinking of (not to develop) are C# libraries which can interpret .PSDs, make VHDs, etc. So if I was to develop a C# app to implement .AI files (Illustrator files), what would be the steps I would look at (such as contacting Adobe, etc)? Is this the way such projects are developed?

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• How do I use Declarations (type, inline, optimize) in Scheme?

  - by kunjaan

  How do I declare the types of the parameters in order to circumvent type checking? How do I optimize the speed to tell the compiler to run the function as fast as possible like (optimize speed (safety 0))? How do I make an inline function in Scheme? How do I use an unboxed representation of a data object? And finally are any of these important or necessary? Can I depend on my compiler to make these optimizations? thanks, kunjaan.

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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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• Connective of Android phone to Windows using Bluetooth

  - by Gururaja B O

  Hi , How to connect the android phone to Windows Laptop. I tried connecting. but it is showing pairing but never pair. Please let me know the steps to configure the same on windows laptop. Regards Gururaja b O

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• Setting the rank of a user-defined verb in J

  - by Gregory Higley

  Here's a function to calculate the digital sum of a number in J: digitalSum =: +/@:("."0)@": If I use b. to query the rank of this verb, I get _ 1 _, i.e., infinite. (We can ignore the dyadic case since digitalSum is not dyadic.) I would like the monadic rank of this verb to be 0, as reported by b.. The only way I know of to do this is to use a "shim", e.g., ds =: +/@:("."0)@": digitalSum =: ds"0 This works great, but I want to know whether it's the only way to do this, or if there's something else I'm missing.

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• Which is the best pick?

  - by Daniel

  Hi, considering I have experience with Java SE: which language should I learn(and is best for that purpose) in order to build web applications some day with it? I have been contemplating PHP and Java EE. The latter does indeed seems as an obvious choice given my Java SE knowledge. But how does it fares in comparison with PHP and how good is it for the aforementioned purpose? If there is a better language for this purpose, feel free to recommend it. Thank you.

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• How much one can trust the information published in the wikipedia? [closed]

  - by AKN

  Wikipedia has answers for many question almost in all categories. Let it be Technical Sports Personalities Important events (this day, that day) Scientific terms etc... I know the source of contents are from volunteers (Please correct me if I'm wrong here). But what measures they have to ensure that contents are properly written. Even if they have admin/moderator and all that, they may not be experts in all areas. So how do they validate the appropriateness of the content?

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• Using items in a list as arguments

  - by Travis Brown

  Suppose I have a function with the following type signature: g :: a -> a -> a -> b I also have a list of as—let's call it xs—that I know will contain at least three items. I'd like to apply g to the first three items of xs. I know I could define a combinator like the following: ($$$) :: (a -> a -> a -> b) -> [a] -> b f $$$ (x:y:z:_) = f x y z Then I could just use g $$$ xs. This makes $$$ a bit like uncurry, but for a function with three arguments of the same type and a list instead of a tuple. Is there a way to do this idiomatically using standard combinators? Or rather, what's the most idiomatic way to do this in Haskell? I thought trying pointfree on a non-infix version of $$$ might give me some idea of where to start, but the output was an abomination with 10 flips, a handful of heads and tails and aps, and 28 parentheses. (NB: I know this isn't a terribly Haskelly thing to do in the first place, but I've come across a couple of situations where it seems like a reasonable solution, especially when using Parsec. I'll certainly accept "don't ever do this in real code" if that's the best answer, but I'd prefer to see some clever trick involving the ((->) r) monad or whatever.)

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• Abstracting the adding of click events to elements selected by class using jQuery

  - by baroquedub

  I'm slowly getting up to speed with jQuery and am starting to want to abstract my code. I'm running into problems trying to define click events at page load. In the code below, I'm trying to run through each div with the 'block' class and add events to some of its child elements by selecting them by class: <script language="javascript" type="text/javascript"> $(document).ready(function (){ $('HTML').addClass('JS'); // if JS enabled, hide answers $(".block").each(function() { problem = $(this).children('.problem'); button = $(this).children('.showButton'); problem.data('currentState', 'off'); button.click(function() { if ((problem.data('currentState')) == 'off'){ button.children('.btn').html('Hide'); problem.data('currentState', 'on'); problem.fadeIn('slow'); } else if ((problem.data('currentState')) == 'on'){ button.children('.btn').html('Solve'); problem.data('currentState', 'off'); problem.fadeOut('fast'); } return false; }); }); }); </script> <style media="all" type="text/css"> .JS div.problem{display:none;} </style> <div class="block"> <div class="showButton"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem"> <p>Answer 1</p> </div> </div> <div class="block"> <div class="showButton"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem"> <p>Answer 2</p> </div> </div> Unfortunately using this, only the last of the divs' button actually works. The event is not 'localised' (if that's the right word for it?) i.e. the event is only applied to the last $(".block") in the each method. So I have to laboriously add ids for each element and define my click events one by one. Surely there's a better way! Can anyone tell me what I'm doing wrong? And how I can get rid of the need for those IDs (I want this to work on dynamically generated pages where I might not know how many 'blocks' there are...) <script language="javascript" type="text/javascript"> $(document).ready(function (){ $('HTML').addClass('JS'); // if JS enabled, hide answers // Preferred version DOESN'T' WORK // So have to add ids to each element and laboriously set-up each one in turn... $('#problem1').data('currentState', 'off'); $('#showButton1').click(function() { if (($('#problem1').data('currentState')) == 'off'){ $('#showButton1 > a').html('Hide'); $('#problem1').data('currentState', 'on'); $('#problem1').fadeIn('slow'); } else if (($('#problem1').data('currentState')) == 'on'){ $('#showButton1 > a').html('Solve'); $('#problem1').data('currentState', 'off'); $('#problem1').fadeOut('fast'); } return false; }); $('#problem2').data('currentState', 'off'); $('#showButton2').click(function() { if (($('#problem2').data('currentState')) == 'off'){ $('#showButton2 > a').html('Hide'); $('#problem2').data('currentState', 'on'); $('#problem2').fadeIn('slow'); } else if (($('#problem2').data('currentState')) == 'on'){ $('#showButton2 > a').html('Solve'); $('#problem2').data('currentState', 'off'); $('#problem2').fadeOut('fast'); } return false; }); }); </script> <style media="all" type="text/css"> .JS div.problem{display:none;} </style> <div class="block"> <div class="showButton" id="showButton1"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem" id="problem1"> <p>Answer 1</p> </div> </div> <div class="block"> <div class="showButton" id="showButton2"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem" id="problem2"> <p>Answer 2</p> </div> </div>

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• "entering link in browser" to "finding route to host" how it works?

  - by Algorist

  Hi, Is there a wiki or book, which explains what happens when user enters a link in the browser, and how the dns is resolved, how the router finds the route to the host etc.. I am mainly interested in routing the packets. Thank you

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• Passing a hostname of over 255 characters to getaddrinfo causes a getaddrinfo failed: memory allocat

  - by darrickc

  I am currently upgrading our software to support ipv6 and in the meantime I'm expanding hostname/ip fields to the max hostname size. In sun documentation it seems like this can be up to 1025 (netdb.h:#define NI_MAXHOST 1025 - this is the recommended hostname allocation define), but when I pass a hostname of over 255 to getaddrinfo I get "getaddrinfo failed: memory allocation failure". I am testing on a Sol10 box. Ideas?

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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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• Differneces between static class and instance class with private constructor

  - by dotnetdev

  Hi, Although a static class has only one instance and can't be instantiated, a class with a private constructor can't be instantiated (as the constructor can't be seen), so every time you call this class, this is the same one instance? Factory classes always follow the last convention (instance class with private constructor). Why is this? Thanks

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• PHP string to object name.

  - by Smickie

  Ok I have a string... $a_string = "Product"; and I want to use this string in a call to a object like this: $this->$a_string->some_function(); How the dickens do I dynamically call that object? (don't think Im on php 5 mind)

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• Pointers and Addresses in C

  - by Mohit

  #include "stdio.h" main() { int i=3,*x; float j=1.5,*y; char k='c',*z; x=&i; y=&j; z=&k; printf("\nAddress of x= %u",x); printf("\nAddress of y= %u",y); printf("\nAddress of z= %u",z); x++; y++;y++;y++;y++; z++; printf("\nNew Address of x= %u",x); printf("\nNew Address of y= %u",y); printf("\nNew Address of z= %u",z); printf("\nNew Value of i= %d",i); printf("\nNew Value of j= %f",j); printf("\nNew Value of k= %c\n",k); } Output: Address of x= 3219901868 Address of y= 3219901860 Address of z= 3219901875 New Address of x= 3219901872 New Address of y= 3219901876 New Address of z= 3219901876 New Value of i= 3 New Value of j= 1.500000 New Value of k= c The new address of variable y and z are same. How can two variables have same address and et have different values? Note: I used gcc compiler on Ubuntu 9.04

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• How to use PHP fgetcsv to create an array for each piece of data in csv file?

  - by Olivia

  I'm trying to import data from a csv file to some html code to use it in a graph I have already coded. I'm trying to use PHP and fgetcsv to create arrays for each separate piece of data to use PHP to put it into the html code. I know how to open the csv file and to print it using PHP, and how to print each separate row, but not each piece of data separated by a comma. Is there a way to do this? If this helps, this is the csv data I am trying to import. May 10,72,12,60 May 11,86,24,62 May 12,67,32,34 May 13,87,12,75 May 14,112,23,89 May 17,69,21,48 May 18,98,14,84 May 19,115,18,97 May 20,101,13,88 May 21,107,32,75 I hope that makes sense.

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• Pros and Cons of Proprietary Software

  - by Jon Purdy

  Proprietary software is about as good as open-source software. There are so many problems with proprietary technologies, however, that I'm beginning to think it's best to avoid them: The software will only be maintained as long as the company exists (and profits). The level of security of the application is as unknowable as the source code. Alterations and derivative works, however necessary and beneficial, are disallowed. I simply don't see any point in even learning to use such systems as those created by Microsoft and Apple. Of course I don't pretend that ignorance is the superior option: one has to have a certain working knowledge simply because of the ubiquity of these things. I just don't see any reason why, as an independent developer, I should ever consider it a remotely good idea to actually use them. So that's the question, or discussion topic, or what have you: In what ways do developers benefit at all from using closed-source development software?

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