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  • In SICP exercise 2.26 using DrScheme, why does cons return a list, instead of a pair of lists?

    - by limist
    In SICP exercise 2.26, this Scheme code is given: (define x (list 1 2 3)) (define y (list 4 5 6)) Then this cons call is given: (cons x y) I expected a pair of lists would result, ((1 2 3) (4 5 6)) but the interpreter gives, ((1 2 3) 4 5 6) ...a list with 4 elements, the first being a list. Why is y treated differently? I've tried looking up other SICP answers for an explanation, but couldn't find something satisfactory. So could any Scheme/Lisp experts please shed some light on this aspect of cons? Thanks in advance for any insight.

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  • .net 4 Chart Control - Hide labels in pie chart

    - by Ricardo Deano
    Hello all. Am I going mad/blind? Probably a combination of the two. How does one go about removing the data labels from a pie chart with the new chart control in .net 4? I can get these to display as tooltips absolutely fine, but ultiamtely I'd like the labels not to be present as it looks rather busy. I've searched previous answers and seen code behind resolutions but surely there must be some sort of code infront option to turn these labels off? Apologies for being thick/blind.

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  • What design pattern do you use the most?

    - by spoon16
    I'm interested in understanding what design patterns people find themselves using often. Hopefully this list will help other recognize common scenarios and the associated design pattern that can be used to solve them. Please describe a common problem you find yourself solving and the design pattern(s) you use to solve it. Links to blogs or documentation describing the pattern are also appreciated. Edit: Please expand on your answers a bit, I would like this to be a useful reference for someone who wants to learn more about design patterns and is curious on what situations a specific design pattern might be used. Nobody has linked to any "more learning" resources.

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  • JavaScript setInterval loop not holding variable

    - by Ryan
    Here is my code: var showNo = 1; window.setInterval(function() { console.log(showNo); if(showNo === 1) { var nextNo = 2; } else if(showNo === 2) { var nextNo = 3; } else if(showNo === 3) { var nextNo = 4; } else if(showNo === 4) { var nextNo = 5; } else if(showNo === 5) { var nextNo = 1; } else { var showNo = 1; var nextNo = 2; } var showNo = nextNo; }, 500); My question is, why is the showNo variable not holding when the setInterval loop starts? The console displays 'undefined' in the above example. This may be a simple question, but I am trying to teach myself query and this has me stuck.. Any answers would be great. Thanks.

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  • Ruby Methods: how to return an usage string when insufficient arguments are given

    - by Shyam
    Hi, After I have created a serious bunch of classes (with initialize methods), I am loading these into IRb to test each of them. I do so by creating simple instances and calling their methods to learn their behavior. However sometimes I don't remember exactly what order I was supposed to give the arguments when I call the .new method on the class. It requires me to look back at the code. However, I think it should be easy enough to return a usage message, instead of seeing: ArgumentError: wrong number of arguments (0 for 9) So I prefer to return a string with the human readable arguments, by example using "puts" or just a return of a string. Now I have seen the rescue keyword inside begin-end code, but I wonder how I could catch the ArgumentError when the initialize method is called. Thank you for your answers, feedback and comments!

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  • How to correctly calculate address spaces?

    - by user337308
    Below is an example of a question given on my last test in a Computer Engineering course. Anyone mind explaining to me how to get the start/end addresses of each? I have listed the correct answers at the bottom... The MSP430F2410 device has an address space of 64 KB (the basic MSP430 architecture). Fill in the table below if we know the following. The first 16 bytes of the address space (starting at the address 0x0000) is reserved for special function registers (IE1, IE2, IFG1, IFG2, etc.), the next 240 bytes is reserved for 8-bit peripheral devices, and the next 256 bytes is reserved for 16-bit peripheral devices. The RAM memory capacity is 2 Kbytes and it starts at the address 0x1100. At the top of the address space is 56KB of flash memory reserved for code and interrupt vector table. What Start Address End Address Special Function Registers (16 bytes) 0x0000 0x000F 8-bit peripheral devices (240 bytes) 0x0010 0x00FF 16-bit peripheral devices (256 bytes) 0x0100 0x01FF RAM memory (2 Kbytes) 0x1100 0x18FF Flash Memory (56 Kbytes) 0x2000 0xFFFF

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  • How do I use .NET to find an orange ball in an image?

    - by JohnS
    I'm getting images from a C328R camera attached to a small arduino robot. I want the robot to drive towards orange ping-pong balls and pick them up. I'm using the C# code supplied by funkotron76 at http://www.codeproject.com/KB/recipes/C328R.aspx. Is there a library I can use to do this, or do I need to iterate over every pixel in the image looking for orange? If so, what kind of tolerance would I need to compensate for various lighting conditions? I could probably test to figure out these numbers, but I'm hoping someone out there knows the answers.

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  • Zero division does not throw exception in nunit

    - by Boris
    Running the following C# code through NUnit yields Test.ControllerTest.TestSanity: Expected: <System.DivideByZeroException> But was: null So either no DivideByZeroException is thrown, or NUnit does not catch it. Similar to this question, but the answers he got, do not seem to work for me. This is using NUnit 2.5.5.10112, and .NET 4.0.30319. [Test] public void TestSanity() { Assert.Throws<DivideByZeroException>(new TestDelegate(() => DivideByZero())); } private void DivideByZero() { // Parse "0" to make sure to get an error at run time, not compile time. var a = (1 / Double.Parse("0")); } Any ideas?

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  • Is it possible to use WIndows Speech Recognition Engine in a word pronounciation game?

    - by XBasic3000
    I use to create an application that uses the windows speech recognition engine or the SAPI. its like a game for pronounciation that it give you score when you pronounce it correctly. but when i started experiments with SAPI, it has poor recognition unless if you load a grammar on it (XML) its give best recognition result. but the problem now is closest pronounciation from the input text will be recognize. for example: Database - dedebase - correct. even if you mispronounce it. it gives you correct answers. without using the xml grammar when you say database it give you "in the base/the base/data base/etc..." please post your answer,suggestion,clarication. votes for best answer. is it posible or not? by the way i use delphi compiler on the projects....

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  • getting mysql_insert_id() while using ON DUPLICATE KEY UPDATE with PHP

    - by julio
    Hi-- I've found a few answers for this using mySQL alone, but I was hoping someone could show me a way to get the ID of the last inserted or updated row of a mysql DB when using PHP to handle the inserts/updates. Currently I have something like this, where column3 is a unique key, and there's also an id column that's an autoincremented primary key: $query ="INSERT INTO TABLE (column1, column2, column3) VALUES (value1, value2, value3) ON DUPLICATE KEY UPDATE SET column1=value1, column2=value2, column3=value3"; mysql_query($query); $my_id = mysql_insert_id(); $my_id is correct on INSERT, but incorrect when it's updating a row (ON DUPLICATE KEY UPDATE). I have seen several posts with people advising that you use something like INSERT INTO table (a) VALUES (0) ON DUPLICATE KEY UPDATE id=LAST_INSERT_ID(id) to get a valid ID value when the ON DUPLICATE KEY is invoked-- but will this return that valid ID to the PHP "mysql_insert_id()" function? Thanks for any advice.

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  • web developer editor ubuntu

    - by madphp
    Hi, I know theres hundred of questions and answers out there, but cant find one to specifically answer this. I need a web editor that will let me choose a dark themed editor. I understand gvim is one, but im not totally ready to let go of my mouse. I would like something like sublime text editor for windows, but open to other suggestions. The less bloat the best. I dont need a full IDE like eclipse, but willing to compromise, as long as the themes can easily be added. I've tried bluefish, kompozer and not happy with them. Just need a basic text editor that will highlight php syntax on a dark background.

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  • jQuery fadeout a div that's revealed by php and not Javascript?

    - by songdogtech
    Seems like this might be easy, but from reading other SO answers there are a number of ways for it to possibly work: I have the "thanks" div below that shows when a php form is sucessfully submitted: <?php if(isset($emailSent) && $emailSent == true) { ?> <div class="thanks"></div> The page does not reload after the form is submitted; the php for the form is included in the page header, the php above is in <body>, and when the form is submitted, the "thanks" div appears. Question: How can the div be faded out (or simply removed) after a few seconds? Document ready doesn't seem like it would work because the page is not reloaded. Can jQuery detect the appearance of the div and then start the fadeout timer? If possible, I'd like to stay with the php form and not move to a jQuery form.

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  • How Do You Profile & Optimize CUDA Kernels?

    - by John Dibling
    I am somewhat familiar with the CUDA visual profiler and the occupancy spreadsheet, although I am probably not leveraging them as well as I could. Profiling & optimizing CUDA code is not like profiling & optimizing code that runs on a CPU. So I am hoping to learn from your experiences about how to get the most out of my code. There was a post recently looking for the fastest possible code to identify self numbers, and I provided a CUDA implementation. I'm not satisfied that this code is as fast as it can be, but I'm at a loss as to figure out both what the right questions are and what tool I can get the answers from. How do you identify ways to make your CUDA kernels perform faster?

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  • Detecting if Excel file has been closed

    - by Charlie
    Hi StackOverflow, I've spent the past 3 hours trawling the web for answers to no avail, so I hope you can help me. I'm writing an application which automates Excel. The application has an option to "show/hide the excel sheet" so you can look at it, make any final changes and so forth. Closing the application will naturally close the instance of Excel, however, there is a small chance that someone may exit out of Excel directly, without thinking. This breaks my application and I can't seem to find anyway of "checking if the same workbook is still open, and if not, re-opening it", before saving it I've tried all sorts of things: checking if the Excel Application is null (when it's !=null it will save correctly, but when it "is" null (or at least, something other than !=null it won't even hit the breakpoint so I'm completely lost :( Help please?

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  • Vectorizing sums of different diagonals in a matrix

    - by reve_etrange
    I want to vectorize the following MATLAB code. I think it must be simple but I'm finding it confusing nevertheless. r = some constant less than m or n [m,n] = size(C); S = zeros(m-r,n-r); for i=1:m-r for j=1:n-r S(i,j) = sum(diag(C(i:i+r-1,j:j+r-1))); end end The code calculates a table of scores, S, for a dynamic programming algorithm, from another score table, C. The diagonal summing is to generate scores for individual pieces of the data used to generate C, for all possible pieces (of size r). Thanks in advance for any answers! Sorry if this one should be obvious...

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  • Performance optimization strategies of last resort?

    - by jerryjvl
    There are plenty of performance questions on this site already, but it occurs to me that almost all are very problem-specific and fairly narrow. And almost all repeat the advice to avoid premature optimization. Let's assume: the code already is working correctly the algorithms chosen are already optimal for the circumstances of the problem the code has been measured, and the offending routines have been isolated all attempts to optimize will also be measured to ensure they do not make matters worse What I am looking for here is strategies and tricks to squeeze out up to the last few percent in a critical algorithm when there is nothing else left to do but whatever it takes. Ideally, try to make answers language agnostic, and indicate any down-sides to the suggested strategies where applicable. I'll add a reply with my own initial suggestions, and look forward to whatever else the SO community can think of.

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  • Text message (SMS) verification for signups

    - by Unknown
    I have seen a disturbing trend where websites are starting to require verification sent to cellphones by text message (SMS). Gmail and Facebook are two of them. What I want to know are the following: Is it a good idea to start requiring cellphones instead of emails now? How do I do it on my own website? Edit Here are some of my new questions on the topic in response to the answers: I see that most of you are saying that SMS registrations is ok. But what about the people who don't have cell phones? And why is it accepted to give out your cell phone information freely? Do those big providers really pay per message to a gateway service? Is it not possible to set up a server with the correct SMS software, or at least buy a subscription directly instead of having a middleman?

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  • compilation error: request member in something not a structure of union

    - by Fantastic Fourier
    Hi everybody, I'm having the above error request member rv in something not a structure of union. I've googled it and several answers told me it's when working with a pointer but tries to access it as a struct, where I should be using -> instead of . int foo(void * arg, struct message * msg) { struct fd_info * info = (struct something *) arg; int * socks[MAX_CONNECTION]; socks = &(info->_socks); // where int * _socks[MAX_CONNECTION] in struct info // do other things rv = sendto(socks[i], &msg, sizeof(&msg), NULL, &(csys->client_address), sizeof(csys->client_address)); ... } The problem is all of the arguments i have are pointers. i'm confused as to what is wrong. thanks to any comments/thoughts.

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  • Recommended way to manage persistent PHP script processes?

    - by BigglesZX
    First off - hello, this is my first Stack Overflow question so I'll try my best to communicate properly. The title of my question may be a bit ambiguous so let me expand upon it immediately: I'm planning a project which involves taking data inputs from several "streaming" APIs, Twitter being one example. I've got a basic script coded up in PHP which runs indefinitely from the command line, taking input from the Twitter streaming API and doing very basic things with it. My eventual objective is to have several such processes running (perhaps daemonized using the System Daemon PEAR class), and I would like to be able to manage them from some governing process (also a PHP script). By manage I mean basic operations such as stop/start and (most crucially) automatically restarting a process that crashes. I would appreciate any pointers on how best to approach this process management angle. Again, apologies if this question is too expansive - tips on more tightly focused lines of enquiry would be appreciated if necessary. Thanks for reading and I look forward to your answers.

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  • ZendFramework integration with other frameworks

    - by St.Woland
    I want to make this question a guide for those interested in ZendFramework integration with other libraries/frameworks. Searching over StackOverflow doesn't give a broad view on the subject. The question is: which libraries/frameworks do you use in your current ZF-based project? what are the best practices for ZF-based project architecture? I don't mean any components that are already a part of ZF. Please give a description of aditional frameworks you have integrated (like RuckUsing, Smarty, or Doctrine). It also applies to any GUI frameworks (perhaps you use a CSS framework), as well as JS frameworks (not just jQuery or prototype, but rather some advanced structures). The main requirement: it has to be a ZendFramework project. Additional bonus will be given to answers that describe performance optimization.

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  • (php) how to properly 'save' info in forms completed thus far

    - by hatorade
    So i have a form that on paper is 40 pages long. I was going to take the natural sections of this form, and make separate html forms for each section, with the idea that on the first page there would be a first form, then you hit 'Continue to next section' which essentially is the 'submit' button, which moves the user to section two, etc, until they hit the last section. i am not actually storing the results of the form in a database, but rather sending an email. the idea then is to store the separate form answers (one html form per section in the real form) as arrays or objects in the session, so that if they go back to a section in the form, it repopulates the values they entered since they are stored in the session. the result would be an array in the session storing the results for each of my forms, and i have one form for each section. my question is: is it secure to temporarily store things like SSNs or driver's license numbers as session variables? why or why not?

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  • Can you automatically create a mysqldump file that doesn't enforce foreign key constraints?

    - by Tai Squared
    When I run a mysqldump command on my database and then try to import it, it fails as it attempts to create the tables alphabetically, even though they may have a foreign key that references a table later in the file. There doesn't appear to be anything in the documentation and I've found answers like this that say to update the file after it's created to include: set FOREIGN_KEY_CHECKS = 0; ...original mysqldump file contents... set FOREIGN_KEY_CHECKS = 1; Is there no way to automatically set those lines or export the tables in the necessary order (without having to manually specify all table names as that can be tedious and error prone)? I could wrap those lines in a script, but was wondering if there is an easy way to ensure I can dump a file and then import it without manually updating it.

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  • Pros and Cons of Java HTML to XML cleaners

    - by cjavapro
    I am looking to allow HTML emails (and other HTML uploads) without letting in scripts and stuff. I plan to have a white list of safe tags and attributes as well as a whitelist of CSS tags and value regexes (to prevent automatic return receipt). I asked a question: Parse a badly formatted XML document (like an HTML file) I found there are many many ways to do this. Some systems have built in sanitizers (which I don't care so much about). I will post some answers and say Community Wiki. Please post any other options you like and say Community Wiki so they can be voted on. Also any comments or wiki edits on what part of a certain product is better and what is not would be greatly appreciated. This page is a very nice listing page but I get kinda lost http://java-source.net/open-source/html-parsers

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  • jQuery setInterval loop not holding variable

    - by Ryan
    Here is my code: var showNo = 1; window.setInterval(function() { if(showNo === 1) { var nextNo = 2; } else if(showNo === 2) { var nextNo = 3; } else if(showNo === 3) { var nextNo = 4; } else if(showNo === 4) { var nextNo = 5; } else if(showNo === 5) { var nextNo = 1; } else { var showNo = 1; var nextNo = 2; } var showNo = nextNo; }, 500); My question is, why is the showNo variable not holding when the setInterval loop starts? This may be a simple question, but I am trying to teach myself query and this has me stuck.. Any answers would be great. Thanks.

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  • Scala and the Java Memory Model

    - by Ben Lings
    The Java Memory Model (since 1.5) treats final fields differently to non-final fields. In particular, provided the this reference doesn't escape during construction, writes to final fields in the constructor are guaranteed to be visible on other threads even if the object is made available to the other thread via a data race. (Writes to non-final fields aren't guaranteed to be visible, so if you improperly publish them, another thread could see them in a partially constructed state.) Is there any documentation on how/if the Scala compiler creates final (rather than non-final) backing fields for classes? I've looked through the language specification and searched the web but can't find any definitive answers. (In comparison the @scala.volatile annotation is documented to mark a field as volatile)

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