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  • Call methods on native Javascript types without wrapping with ()

    - by Anurag
    In Javascript, we can call methods on string literals directly without enclosing it within round brackets. But not for other types such as numbers, or functions. It is a syntax error, but is there a reason as to why the Javascript lexer needs these other types to be enclosed in round brackets? For example, if we extend Number, String, and Function with an alert method and try calling this method on the literals, it's a SyntaxError for Number and Function, while it works for a String. function alertValue() { alert(this); } Number.prototype.alert = alertValue; String.prototype.alert = alertValue; Function.prototype.alert = alertValue; We can call alert directly on a string object: "someStringLiteral".alert() // alerts someStringLiteral but it's a SyntaxError on numbers, and functions. 7.alert(); function() {}.alert(); To work with these types, we have to enclose it within brackets: (7).alert(); // alerts "7" (function() {}).alert(); // alerts "function() {}"

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  • Device drivers and Windows

    - by b-gen-jack-o-neill
    Hi, I am trying to complete the picture of how the PC and the OS interacts together. And I am at point, where I am little out of guess when it comes to device drivers. Please, don´t write things like its too complicated, or you don´t need to know when using high programming laguage and winapi functions. I want to know, it´s for study purposes. So, the very basic structure of how OS and PC (by PC I mean of course HW) is how I see it is that all other than direct CPU commands, which can CPU do on itself (arithmetic operation, its registers access and memory access) must pass thru OS. Mainly becouse from ring level 3 you cannot use in and out intructions which are used for acesing other HW. I know that there is MMIO,but it must be set by port comunication first. It was not like this all the time. Even I am bit young to remember MSDOS, I know you could access HW directly, becouse there ws no limitation, no ring mode. So you could to write string to diplay use wheather DOS function, or directly acess video card memory and write it by yourself. But as OS developed, there is no longer this possibility. But it is fine, since OS now handles all the HW comunication, and frankly it more convinient and much more safe (I would say the only option) in multitasking environment. So nowdays you instead of using int instructions to use BIOS mapped function or DOS function you call dll which internally than handles everything you don´t need to know about. I understand this. I also undrstand that device drivers is the piece of code that runs in ring level 0, so it can do all the HW interactions. But what I don´t understand is connection between OS and device driver. Let´s take a example - I want to make a sound card make a sound. So I call windows API to acess sound card, but what happens than? Does windows call device drivers to do so? But if it does call device driver, does it mean, that all device drivers which can be called by winAPI function, must have routines named in some specific way? I mean, when I have new sound card, must its drivers have functions named same as the old one? So Windows can actually call the same function from its perspective? But if Windows have predefined sets of functions requored by device drivers, that it cannot use new drivers that doesent existed before last version of OS came out. Please, help me understand this mess. I am really getting mad. Thanks.

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  • How To Refactor If-else Code Segment?

    - by LostInLib
    I'm developing win8(metro style) application with Html5-js-jquery. I have this code segment; GetBoutiqueDetail: function (boutiqueId, options) { if (IsUserLogin()) { //different job A } else { ShowLoginPanel(undefined); } }, GetProductDetail: function (boutiqueId, productId, options) { if (IsUserLogin()) { //different job B } else { ShowLoginPanel(undefined); } }, AddBasket: function (productId, productVariantId, quantity, options) { if (IsUserLogin()) { //different job C } else { ShowLoginPanel(undefined); } },.... .And ~20 functions should check if user login or not. I should call functions like similar to "Library.GetBoutiqueDetail();" So my question is simple, how can I refactor that code to remove these if-else sections ?

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  • Missing something with Reader monad - passing the damn thing around everywhere

    - by Richard Huxton
    Learning Haskell, managing syntax, have a rough grasp of what monads etc are about but I'm clearly missing something. In main I can read my config file, and supply it as runReader (somefunc) myEnv just fine. But somefunc doesn't need access to the myEnv the reader supplies, nor do the next couple in the chain. The function that needs something from myEnv is a tiny leaf function. So - how do I get access to the environment in a function without tagging all the intervening functions as (Reader Env)? That can't be right because otherwise you'd just pass myEnv around in the first place. And passing unused parameters through multiple levels of functions is just ugly (isn't it?). There are plenty of examples I can find on the net but they all seem to have only one level between runReader and accessing the environment.

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  • Hashing a python function to regenerate output when the function is modified

    - by Seth Johnson
    I have a python function that has a deterministic result. It takes a long time to run and generates a large output: def time_consuming_function(): # lots_of_computing_time to come up with the_result return the_result I modify time_consuming_function from time to time, but I would like to avoid having it run again while it's unchanged. [time_consuming_function only depends on functions that are immutable for the purposes considered here; i.e. it might have functions from Python libraries but not from other pieces of my code that I'd change.] The solution that suggests itself to me is to cache the output and also cache some "hash" of the function. If the hash changes, the function will have been modified, and we have to re-generate the output. Is this possible or ridiculous? Updated: based on the answers, it looks like what I want to do is to "memoize" time_consuming_function, except instead of (or in addition to) arguments passed into an invariant function, I want to account for a function that itself will change.

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  • What is user gcc's purpose in requesting code possibly like this?

    - by James Morris
    In the question between syntax, are there any equal function the user gcc is requesting only what I can imagine to be the following code: #include <stdio.h> #include <string.h> /* estimated magic values */ #define MAXFUNCS 8 #define MAXFUNCLEN 3 int the_mainp_compare_func(char** mainp) { char mainp0[MAXFUNCS][MAXFUNCLEN] = { 0 }; char mainp1[MAXFUNCS][MAXFUNCLEN] = { 0 }; char* psrc, *pdst; int i = 0; int func = 0; psrc = mainp[0]; printf("scanning mainp[0] for functions...\n"); while(*psrc) { if (*psrc == '\0') break; else if (*psrc == ',') ++psrc; else { mainp0[func][0] = *psrc++; if (*psrc == ',') { mainp0[func][1] = '\0'; psrc++; } else if (*psrc !='\0') { mainp0[func][1] = *psrc++; mainp0[func][2] = '\0'; } printf("function: '%s'\n", mainp0[func]); } ++func; } printf("\nscanning mainp[1] for functions...\n"); psrc = mainp[1]; func = 0; while(*psrc) { if (*psrc == '\0') break; else if (*psrc == ',') ++psrc; else { mainp1[func][0] = *psrc++; if (*psrc == ',') { mainp1[func][1] = '\0'; psrc++; } else if (*psrc !='\0') { mainp1[func][1] = *psrc++; mainp1[func][2] = '\0'; } printf("function: '%s'\n", mainp1[func]); } ++func; } printf("\ncomparing functions in '%s' with those in '%s'\n", mainp[0], mainp[1] ); int func2; func = 0; while (*mainp0[func] != '\0') { func2 = 0; while(*mainp1[func2] != '\0') { printf("comparing %s with %s\n", mainp0[func], mainp1[func2]); if (strcmp(mainp0[func], mainp1[func2++]) == 0) return 1; /* not sure what to return here */ } ++func; } /* no matches == failure */ return -1; /* not sure what to return on failure */ } int main(int argc, char** argv) { char* mainp[] = { "P,-Q,Q,-R", "R,A,P,B,F" }; if (the_mainp_compare_func(mainp) == 1) printf("a match was found, but I don't know what to do with it!\n"); else printf("no match found, and I'm none the wiser!\n"); return 0; } My question is, what is it's purpose?

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  • jQuery. Treat a string as a HTML document?

    - by James Jeffery
    I'm not sure if I worded the title correctly. Basically is it possible to treat a string as HTML as if it was on the page? So I can use $("#elem") and all the other jQuery functions? The HTML is loaded into a string from an ajax request and stored in a string. Instead of using regular expressions to access the data needed is it possible to use jQuery functions? ajaxTextResponse.$("#telephone"); I know the above won't work, but you see what I am getting at. Thanks

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  • The ultimate c# file and directory utility library?

    - by Serge van den Oever
    I find myself writing file and directory utility functions all the time, and I was wondering if there is good file and directory library that already implements a more extensive set than available by default in System.IO. The kind of functions I'm looking for is things like: public static void GetTemporaryDirectory() { string tempDirectory = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName()); Directory.CreateDirectory(tempDirectory); return tempDirectory; } public static void CreateEmptyFile(string filename) { File.Create(filename).Dispose(); } public static void CreateEmptyFile(string path, string filename) { File.Create(Path.Combine(path, filename)).Dispose(); } public static void CreateDirectory(string path) { Directory.CreateDirectory(path); } public static void CreateDirectory(string path, string childpath) { Directory.CreateDirectory(Path.Combine(path, childpath)); }

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  • Multiple connections to a MySQL database in a single PHP script.

    - by st3
    There are multiple times in one page where I need to connect and subsequently query a MySQL database, yet my code won't let me. I think it might be something to do with how my files are nested but it makes no sense. I am opening the SQL connection in the header file. The top of the offending page looks like the following: <?php $page_title = 'Dashboard'; include('templates/header.inc'); // includes a 'require_once('mysqli_connect.php') and a small query to the database; require_once('includes/functions.php'); require_once('includes/dashboard_sql.php'); // Contains functions which connect to database (which are failing.) ?> I get the PHP error Notice: Undefined variable: dbc in /Library/WebServer/Documents/pediatory_site/includes/dashboard_sql.php Where $dbc is the database connection defined in mysqli_connect.php. If anyone could help me out that would be great.

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  • backgroundworkers or threadpools

    - by vbNewbie
    I am trying to create an app that allows multiple search requests to occur whilst maintaining use of the user interface to allow interaction. For the multiple search requests, I initially only had one search request running with user interaction still capable by using a backgroundworker to do this. Now I need to extend these functions by allowing more search functions and basically just queueing them up. I am not sure whether to use multiple backgroundworkers or use the threadpool since I want to be able to know the progress of each search job at any time.

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  • Memory error, access violation.

    - by Ordo
    Hello! I'm learning C on my own and as a exercise i have written a program but it does not work. The program is splitted into 3 parts. A header file, a main file for executing the program a file to define the functions. I'm not using all the functions yet but that shouldn't be the problem. Here is my header file, nothing special in it. #ifndef EMPLOYEE_H #define EMPLOYEE_H struct Employee { char first[21]; char last[21]; char title[21]; int salary; }; struct Employee* createEmployee(char*, char*, char*, int); // Creates a struct Employee object on the heap. char* getfirstname (struct Employee*); char* getlastname (struct Employee*); char* gettitle (struct Employee*); int getsalary (struct Employee*); void setfirstname (struct Employee*, char*); void setlastname (struct Employee*, char*); void settitle (struct Employee*, char*); void setsalary (struct Employee*, int); void printEmployee(struct Employee*); #endif In this file i define the functions and how they work: #include "7.1.h" #include <stdio.h> #include <stdlib.h> #include <string.h> struct Employee* createEmployee(char* first, char* last, char* title, int salary) // Creates a struct Employee object on the heap. { struct Employee* p = (struct Employee*) malloc(sizeof(struct Employee)); if (p != NULL) { strcpy(p->first, first); strcpy(p->last, last); strcpy(p->title, title); p->salary, salary; } return p; } char* getfirstname (struct Employee* p) { if (p != NULL) return p ? p->first : ""; } char* getlastname (struct Employee* p) { if (p != NULL) return p ? p->last : ""; } char* gettitle (struct Employee* p) { if (p != NULL) return p ? p->title : ""; } int getsalary (struct Employee* p) { if (p != NULL) return p ? p->salary : 0; } void setfirstname (struct Employee* p, char* first) { if (p != NULL) strcpy(p->first, first); } void setlastname (struct Employee* p, char* last) { if (p != NULL) strcpy(p->last, last); } void settitle (struct Employee* p, char* title) { if (p != NULL) strcpy(p->title, title); } void setsalary (struct Employee* p, char* salary) { if (p != NULL) p->salary, salary; } void printEmployee(struct Employee* p) { if (p != NULL) { printf("%s, %s, %s, %d", p->first, p->last, p->salary, p->salary ); } } And the last file is used to executed the program/functions: #include "7.1.h" #include <stdio.h> #include <stdlib.h> int main () { char decision; struct Employee emp; struct Employee* emps[3]; for ( int i = 0; i < 1; i ++) { printf("Please type in the emplooyes data.\nFirstname:"); scanf("%s", emp.first); printf("Lastname:"); scanf("%s", emp.last); printf("Title:"); scanf("%s", emp.title); printf("Salary:"); scanf("%d", &emp.salary); emps[i] = createEmployee(emp.first, emp.last, emp.title, emp.salary); } printf("Do you want to print out your information? (Y/N):"); scanf("%c", &decision); if (decision == 'y' || decision == 'Y') { printEmployee(emps[1]); } } I don't know what the problem is. I 'm always getting the following error message after typing in first, last, title and salary for the first time. The error is written in german. It means: Unhandled exception at 0x102de42e (msvcr100d.dll) in 7.1.exe: 0xC0000005: Access violation when writing to 0xCCCCCCCC position. I could fix the first problem with the hints given below. Now when i want to print out the employee data using the function:printEmployee(emps[1]);, I get the same kind of error with access violation.

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  • Is it possible to remove all event handlers of a given element in javascript?

    - by MartyIX
    Hi, I would like to remove ALL handlers for a given event type. Let's say I've added twice "onclick event" to a button and now I would like to return back to the original state where no event handler was set to the button. How can I do that? P.S.: I've found removeEventListener (non-IE)/detachEvent (IE) methods but the functions want me to pass as a parameter the function that handles the event which seems to me quite clumsy because I would have to store the functions somewhere. EDIT: http://ejohn.org/blog/flexible-javascript-events/ - I'm now using this code Thank you!

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  • Data binding in gridview column using eval

    - by ROBIN
    I hava grid containing a column for displaying countrynames. I need to display value in that column as contrycode-first 10 letters of country name (in-India) .I tried it using Eval functions with in the item template: <asp:TemplateField> <ItemTemplate> <asp:Label ID="CountryNameLabe" runat="server" Text='<%# Eval("CorporateAddressCountry").SubString(0,6) %>' ></asp:Label> </ItemTemplate> </asp:TemplateField> But it shows error. Can i use custom functions in eval? please help

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  • Visual Studio 2010 deploys views too late in deploy process

    - by Markus
    I have a database project in my VS2010 solution. I recently changed a view and and changed a number of functions to use this view instead of going directly against a table. But now when I deploy I get errors on most of these functions because the column asked for does not exists in the view yet. The update of the view happends later than the update of UDF's. Is there any way to change this behaviour? Wouldn't the best thing be if the deploy script updated in this order: tables, views, SP and UDF. It seems like tables is updated first, but the views are just thrown in somewhere in the middle of the deploy script.

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  • How can I write faster JavaScript?

    - by a paid nerd
    I'm writing an HTML5 canvas visualization. According to the Chrome Developer Tools profiler, 90% of the work is being done in (program), which I assume is the V8 interpreter at work calling functions and switching contexts and whatnot. Other than logic optimizations (e.g., only redrawing parts of the visualization that have changed), what can I do to optimize the CPU usage of my JavaScript? I'm willing to sacrifice some amount of readability and extensibility for performance. Is there a big list I'm missing because my Google skills suck? I have some ideas but I'm not sure if they're worth it: Limit function calls When possible, use arrays instead of objects and properties Use variables for math operation results as much as possible Cache common math operations such as Math.PI / 180 Use sin and cos approximation functions instead of Math.sin() and Math.cos() Reuse objects when passing around data instead of creating new ones Replace Math.abs() with ~~ Study jsperf.com until my eyes bleed Use a preprocessor on my JavaScript to do some of the above operations

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  • Adding the text area input to a list with jquery

    - by amylynn83
    I am making a shopping list app. When an item is added to the text input, it should be converted into a list item with a class of "tile" and added to the beginning of the list with a class of ".shopping_item_list". Here is my HTML: <section> <h1 class="outline">Shopping List Items</h1> <ul class="shopping_item_list"> <li class="tile">Flowers<span class="delete">Delete</span></li> </ul> </section> My jQuery: $("input[name='shopping_item']").change(function() { var item = $(this).val(); $("<li class='tile'>+ item +</li>").prependTo(".shopping_item_list"); $(".tile").removeClass("middle"); $(".shopping_item_list li:nth-child(3n+2)").addClass("middle"); }); This isn't working, and I can't figure out why. I'm new to jQuery. Also, I need to add the "delete" span to the list item and am not sure how. Thanks for any help you can offer! Edited to add: Thanks to the feedback here, I was able to make it work with: $("input[name='shopping_item']").change(function() { var item = $(this).val(); $("<li class='tile'>" + item + "<span class='delete'>Delete</span>" + " </li>").prependTo(".shopping_item_list"); $(".tile").removeClass("middle"); $(".shopping_item_list li:nth-child(3n+2)").addClass("middle"); }); However, in my jquery, I have functions for the classes "tile" and "delete" that are not working for newly added items. // hide delete button $(".delete").hide(); // delete square $(".tile").hover(function() { $(this).find(".delete").toggle(); }); $(".tile").on("click", ".delete", function() { $(this).closest("li.tile").remove(); $(".tile").removeClass("middle"); $(".shopping_item_list li:nth-child(3n+2)").addClass("middle"); }); // cross off list $(".tile").click(function() { $(this).toggleClass("deleteAction"); }); The new items, which have these classes applied aren't using these functions at all. Do I need to add the functions below the add item? Does the order in which they appear in my js file matter? Do I need to add some kind of function?

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  • C++ wrapper for C library

    - by Maximilien
    Hi, Recently I found a C library that I want to use in my C++ project. This code is configured with global variables and writes it's output to memory pointed by static pointers. When I execute my project I would like 2 instances of the C program to run: one with configuration A and one with configuration B. I can't afford to run my program twice, so I think there are 2 options: Make a C++ wrapper: The problem here is that the wrapper-class should contain all global/static variables the C library has. Since the functions in the C library use those variables I will have to create very big argument-lists for those functions. Copy-paste the C library: Here I'll have to adapt the name of every function and every variable inside the C library. Which one is the fastest solution? Are there other possibilities to run 2 instances of the same C source? Thanks, Max

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  • boost scoped_lock mutex crashes

    - by JahSumbar
    hello, I have protected a std::queue's access functions, push, pop, size, with boost::mutexes and boost::mutex::scoped_lock in these functions from time to time it crashes in a scoped lock the call stack is this: 0 0x0040f005 boost::detail::win32::interlocked_bit_test_and_set include/boost/thread/win32/thread_primitives.hpp 361 1 0x0040e879 boost::detail::basic_timed_mutex::timed_lock include/boost/thread/win32/basic_timed_mutex.hpp 68 2 0x0040e9d3 boost::detail::basic_timed_mutex::lock include/boost/thread/win32/basic_timed_mutex.hpp 64 3 0x0040b96b boost::unique_lock<boost::mutex>::lock include/boost/thread/locks.hpp 349 4 0x0040b998 unique_lock include/boost/thread/locks.hpp 227 5 0x00403837 MyClass::inboxSize - this is my inboxSize function that uses this code: MyClass::inboxSize () { boost::mutex::scoped_lock scoped_lock(m_inboxMutex); return m_inbox.size(); } and the mutex is declared like this: boost::mutex m_inboxMutex; it crashes at the last pasted line in this function: inline bool interlocked_bit_test_and_set(long* x,long bit) { long const value=1<<bit; long old=*x; and x has this value: 0xababac17 Thanks for the help

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  • problem with live function

    - by Dirty Bird Design
    I had this working to spec, until the specs changed. This function is now brought in via ajax .load. Easy enough to bring it in and I have all my other functions on the page that is brought in working in the parent page except this one: $("#CME").hide(); $(function() { $("#CME1, #CMEQL, #CBT1, #CBTQL, #NYM1, #CMX1").live("change", function(){ var checkBoxes = $("#CME1, #CMEQL, #CBT1, #CBTQL, #NYM1, #CMX1").filter(":not(:checked)"); if(checkBoxes.length == 0){ $("#CME").slideDown("fast"); } else { $("#CME").slideUp("fast"); } }); the div "#CME" is not hidden and the .live('change', function () { isn't working. I have other similar .live functions that are working and structured the same. How do I bind the initial $(function() with .live and why isn't the .hide() working? });//CME

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  • SWIG: Throwing exceptions from Python to C++

    - by wheaties
    We've got an interface we've defined in C++ (abstract class, all functions pure virtual) which will be extended in Python. To overcome the cross-language polymorphism issues we're planning on using SWIG directors. I've read how to catch exceptions thrown from C++ code in our Python code here, here, here, and even on SO. It's fairly straight forward and I'm not expecting issues with handling our library's own exceptions. What I'd like to know and can't seem to find in the documentation is how to have our Python implementation of the extended C++ interface throw those C++ exceptions in a way that makes them visible to the C++ code. We could make small functions within the *.i files such that each function throws our exceptions: void throw_myException(){ throw MyException; } but I'm wondering how it will interact with the Python code. Anyone have any experience with throwing C++ exceptions from Python code?

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