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  • Sqlite View : Add a column based on some other column

    - by NightCoder
    Hi, I have two tables Employee ID | Name | Department ---------------------- 121 |Name1 | dep1 223 |Name2 | dep2 Assignment ID | EID| --------- 1 |121 2 |223 3 |121 [other columns omitted for brevity] The table assignment indicates which is work is assigned to whom.EID is a foriegn key to the table Employee.Also it is possible to have two work assigned to the same employee. Now i want to create a view like this EID | Assigned -------------- 121 |true 333 |false Assigned column should be calculated based on the entries in the Assignment table. So far i am only successful in creating a view like this EID | Assigned -------------- 121 |2 333 |0 using the command CREATE VIEW "AssignmentView" AS SELECT distinct ID ,(select Count(*) from Assignment where Assignment.EID = Employee.ID) as Assigned FROM Employee; Thanks

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  • Building Reducisaurus URLs

    - by Alix Axel
    I'm trying to use Reducisaurus Web Service to minify CSS and Javascript but I've run into a problem... Suppose I've two unminified CSS at: http:/domain.com/dynamic/styles/theme.php?color=red http:/domain.com/dynamic/styles/typography.php?font=Arial According to the docs I should call the web service like this: http:/reducisaurus.appspot.com/css?url=http:/domain.com/dynamic/styles/theme.php?color=red And if I want to minify both CSS files at once: http:/reducisaurus.appspot.com/css?url1=http:/domain.com/dynamic/styles/theme.php?color=red&url2=http:/domain.com/dynamic/styles/theme.php?color=red If I wanted to specify a different number of seconds for the cache (3600 for instance) I would use: http:/reducisaurus.appspot.com/css?url=http:/domain.com/dynamic/styles/theme.php?color=red&expire_urls=3600 And again for both CSS files at once: http:/reducisaurus.appspot.com/css?url1=http:/domain.com/dynamic/styles/theme.php?color=red&url2=http:/domain.com/dynamic/styles/theme.php?color=red&expire_urls=3600 Now my question is, how does Reducisaurus knows how to separate the URLs I want? How does it know that &expire_urls=3600 is not part of my URL? And how does it know that &url2=... is not a GET argument of url1? I'm I doing this right? Do I need to urlencode my URLs? I took a peek into the source code and although my Java is very poor it seems that the methods acquireFromRemoteUrl() and getSortedParameterNames() from the BaseServlet.java file hold the answers to my question - if a GET argument name contains - or _ they should be ignored?! What about multiple &url(n)s?

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  • Python 3, urllib ... Reset Connection Possible?

    - by Rhys
    In the larger scale of my program the goal of the below code is to filter out all dynamic html in a web-page source code code snippet: try: deepreq3 = urllib.request.Request(deepurl3) deepreq3.add_header("User-Agent","etc......") deepdata3 = urllib.request.urlopen(deepurl3).read().decode("utf8", 'ignore') The following code is looped 3 times in order to identify whether the target web-page is Dynamic (source code is changed at intervals) or not. If the page IS dynamic, the above code loops another 15 times and attempts to filter out the dynamic content. QUESTION: While this filtering method works 80% of the time, some pages will reload ALL 15 times and STILL contain dynamic code. HOWEVER. If I manually close down the Python Shell and re-execute my program, the dynamic html that my 'refresh-page method' could not shake off is no longer there ... it's been replaced with new dynamic html that my 'refresh-page method' cannot shake off. So I need to know, what is going on here? How is re-running my program causing the dynamic content of a page to change. AND, is there any way, any 'reset connection' command I can use to recreate this ... without manually restarting my app. Thanks for your response.

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  • PHP Warning: PHP Startup: Unable to load dynamic library php_mysql.dll, Mac 10.6, Apache 2.2, php 5

    - by munchybunch
    I'm trying to use the PHP CLI, and when I enter something like php test.php in the command line it returns: PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions/no-debug-non-zts-20090626/php_mysql.dll' - dlopen(/usr/lib/php/extensions/no-debug-non-zts-20090626/php_mysql.dll, 9): image not found in Unknown on line 0 something test.php contains: <?php echo 'something'; ?> I checked /usr/lib/php/extensions/no-debug-non-zts-20090626/, and as expected the .dll file isn't there. I'm a complete beginner when it comes to this - what is happening, and how can I fix it? A search of my system for "php_msyql.dll" reveals nothing. Does it have to do with how I compiled it? I don't have the original version of php that came with the mac, I think - I may have reinstalled it somewhere along the way. Any help would be appreciated!

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  • Does kern.hz still have any relevance in FreeBSD if "dynamic tick mode" is enabled?

    - by Frerich Raabe
    I'm running a FreeBSD 9.0 setup as a virtual machine in a KVM setup. In previous versions of FreeBSD it was common to force the kern.hz setting to a lower value so that the virtual machine does not keep the host busy because it's handling timer interrupts without having any work to do - the FreeBSD Handbook explains: The most important step is to reduce the kern.hz tunable to reduce the CPU utilization of FreeBSD under the Parallels environment. This is accomplished by adding the following line to /boot/loader.conf: kern.hz=100 Without this setting, an idle FreeBSD Parallels guest OS will use roughly 15% of the CPU of a single processor iMac®. After this change the usage will be closer to a mere 5%. However, in FreeBSD 9, the "dynamic tick mode" (aka "tickless mode") is the default, controlled by the kern.eventtimer.periodic setting which defaults to 0 (read: tickless mode). This makes me wonder - does the tip of lowering kern.hz still have any relevance for making FreeBSD 9 play nicely in a virtual machine setup?

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  • How to create dynamic Scatter Plot/Matrix with labels and categories on both axis in Excel 2010?

    - by user1581900
    Let us consider a following data set: Name | Age | Hair Color ----------------------------- John | Young | Brown Sophie | Old | Blond Adam | Mature| Blond Mark | Teen | Dark Jeremy | Old | Grey Alex | Young | Brown etc... Both Age and Hair Color, can take only defined values(Young/teen/mature/old and Blond/brown/Dark/Grey). Name is the only real variable here. I want to create a Scatter Plot / Matrix that will look something like that: I know that I schould use this tool to add labels to the scatter plot. I also found this youtube video that explains how to display categories on Y-axis Moreover I need the chart to be dynamic as explained in another youtube video. How do I combine all these approaches to get a Scatter Plot with categories as values on both axis?

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  • Recommended Free DNS hosting for my webserve on a dynamic IP? [closed]

    - by JSchwartz
    I have finished a webserver project (for school) and the professor wants to be able to "test it" from home whenever he is free - this means I need to provide his with the URL to my webserver (which is fine). The only issue is that my IP-Address is dynamic (changes almost everyday) and I would rather not have to email him everytime - nor do I want him to try when it isn't working ... So I was looking into alternative solutions like DNS hosting (I hope that is the right terminology), so I could provide something static for him to connect to ... problem is I have never done this before... Are there any recommeneded free ones? Does Google or someone provide something good? I found http://www.no-ip.com/ which seems like it does what I want... Any feedback would be appreciated. Thanks,

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  • Poor home office network performance and cannot figure out where the issue is

    - by Jeff Willener
    This is the most bizarre issue. I have worked with small to mid size networks for quite a long time and can say I'm comfortable connecting hardware. Where you will start to lose me is with managed switches and firewalls. To start, let me describe my network (sigh, shouldn't but I MUST solve this). 1) Comcast Cable Internet 2) Motorola SURFboard eXtreme Cable Modem. a) Model: SB6120 b) DOCSIS 3.0 and 2.0 support c) IPv4 and IPv6 support 3-A) Cisco Small Business RV220W Wireless N Firewall a) Latest firmware b) Model: RV220W-A-K9-NA c) WAN Port to Modem (2) d) vlan 1: work e) vlan 2: everything else. 3-B) D-Link DIR-615 Draft 802.11 N Wireless Router a) Latest firmware b) WAN Port to Modem (2) 4) Servers connected directly to firewall a) If firewall 3-A, then vlan 1 b) CAT5e patch cables c) Dell PowerEdge 1400SC w/ 10/100 integrated NIC (Domain Controller, DNS, former DHCP) d) Dell PowerEdge 400SC w/ 10/100/1000 integrated NIC (VMWare Server) 4) Linksys EZXS88W unmanaged Workgroup 10/100 Switch a) If firewall 3-A, then vlan 2 b) 25' CAT5e patch cable to firewall (3-A or 3-B) c) Connects xBox 360, Blu-Ray player, PC at TV 5) Office equipment connected directly to firewall a) If firewall 3-A, then vlan 1 b) ~80' CAT6 or CAT5e patch cable to firewall (3-A or 3-B) c) Connects 1) Dell Latitude laptop 10/100/1000 2) Dell Inspiron laptop 10/100 3) Dell Workstation 10/100/1000 (Pristine host, VMWare Workstation 7.x with many bridged VM's) 4) Brother Laser Printer 10/100 5) Epson All-In-One Workforce 310 10/100 5-A) NetGear FS116 unmanaged 10/100 switch a) I've had this switch for a long time and never had issues. 5-B) NetGear GS108 unmanaged 10/100/1000 switch a) Bought new for this issue and returned. 5-C) Linksys SE2500 unmanaged 10/100/1000 switch a) Bought new for this issue and returned. 5-D) TP-Link TL-SG10008D unmanaged 10/100/1000 a) Bought new for this issue and still have. 6) VLan 1 Wireless Connections (on same subnet if 3-B) a) Any of those at 5c b) HP Laptop 7) VLan 2 Wireless Connection (on same subnet if 3-B) a) IPad, IPod b) Compaq Laptop c) Epson Wireless Printer Shew, without hosting a diagram I hope that paints a good picture. The Issue The breakdown here is at item 5. No matter what I do I cannot have a switch at 5 and have to run everything wireless regardless of router. Issues related to using a switch (point 5 above) SpeedTest is good. Poor throughput to other devices if can communicate at all. Usually cannot ping other devices even on the same switch although, when able, ping times are good. Eventual lose of connectivity and can "sometimes" be restored by unplugging everything for several days, not minutes or hours but we're talking a week if at all. Directly connect to computer gives good internet connection however throughput to other devices connected to firewall is at best horrible. Yet printing doesn't seem to be an issue as long as they are connected via wireless. I have to force the RV220W to 1000Mb on the respective port if using a Gig Switch Issues related to using wireless in place of a switch (point 5 above) Poor throughput to other devices if can communicate. SpeedTest is good. Bottom line Internet speeds are awesome. By the way, Comcast went WAY above and beyond to make sure it was not them. They rewired EVERYTHING which did solve internet drops. Computer to computer connections are garbage Cannot get switch at 5 to work, yet other at 4 has never had an issue. Direct connection, bypass switch, is good for DHCP and internet. DNS must be on server, not firewall. Cisco insists its my switches but as you can see I have used four and two different cables with the same result. My gut feeling is something is happening with routing. But I'm not smart enough to know that answer. I run a lot of VM's at 5-c-3, could that cause it? What's different compared to my previous house is I have introduced Gigabit hardware (firewall/switches/computers). Some of my computers might have IPv6 turned on if I haven't turned it off already. I'm truly at a loss and hope anyone has some crazy idea how to solve this. Bottom line, I need a switch in my office behind the firewall. I've changed everything. The real crux is I will find a working solution and, again, after days it will stop working. So this means I cannot isolate if its a computer since I have to use them. Oh and a solution is not throwing more money at this. I'm well into $1k already. Yah, lame.

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  • ANSI C blackjack assignment, linux GCC compiler, i'm stuck...

    - by Bill Adams
    Here's what i have so far... I have yet to figure out how i'm going to handle the 11 / 1 situation with an ace, and when the player chooses an option for hit/stand, i get segfault. HELP!!! #include <stdio.h> #include <string.h> #include <stdlib.h> #include <time.h> #define DECKSIZE 52 #define VALUE 9 #define FACE 4 #define HANDSIZE 26 typedef struct { int value; char* suit; char* name; }Card; typedef struct { int value; char* suit; char* name; }dealerHand; typedef struct { int value; char* suit; char* name; }playerHand; Card cards[DECKSIZE]; dealerHand deal[HANDSIZE]; playerHand dealt[HANDSIZE]; char *faceName[]={"two","three", "four","five","six", "seven","eight","nine", "ten", "jack","queen", "king","ace"}; char *suitName[]={"spades","diamonds","clubs","hearts"}; void printDeck(){ int i; for(i=0;i<DECKSIZE;i++){ printf("%s of %s value = %d\n ",cards[i].name,cards[i].suit,cards[i].value); if((i+1)%13==0 && i!=0) printf("-------------------\n\n"); } } void shuffleDeck(){ srand(time(NULL)); int this; int that; Card temp; int c; for(c=0;c<10000;c++){ //c is the index for number of individual card shuffles should be set to c<10000 or more this=rand()%DECKSIZE; that=rand()%DECKSIZE; temp=cards[this]; cards[this]=cards[that]; cards[that]=temp; } } /*void hitStand(i,y){ // I dumped this because of a segfault i couldn't figure out. int k; printf(" Press 1 to HIT or press 2 to STAND:"); scanf("%d",k); if(k=1){ dealt[y].suit=cards[i].suit; dealt[y].name=cards[i].name; dealt[y].value=cards[i].value; y++; i++; } } */ int main(){ int suitCount=0; int faceCount=0; int i; int x; int y; int d; int p; int k; for(i=0;i<DECKSIZE;i++){ //this for statement builds the deck if(faceCount<9){ cards[i].value=faceCount+2; }else{ //assigns face cards as value 10 cards[i].value=10; } cards[i].suit=suitName[suitCount]; cards[i].name=faceName[faceCount++]; if(faceCount==13){ //this if loop increments suit count once cards[i].value=11; //all faces have been assigned, and also suitCount++; //assigns the ace as 11 faceCount=0; } //end building deck } /*printDeck(); //prints the deck in order shuffleDeck(); //shuffles the deck printDeck(); //prints the deck as shuffled This was used in testing, commented out to keep the deck hidden!*/ shuffleDeck(); x=0; y=0; for(i=0;i<4;i++){ //this for loop deals the first 4 cards, dealt[y].suit=cards[i].suit; //first card to player, second to dealer, dealt[y].name=cards[i].name; //as per standard dealing practice. dealt[y].value=cards[i].value; i++; y++; deal[x].suit=cards[i].suit; deal[x].name=cards[i].name; deal[x].value=cards[i].value; x++; } printf(" Dealer's hand is: %s of %s and XXXX of XXXX. (Second card is hidden!)\n",deal[0].name,deal[0].suit,deal[1].name,deal[1].suit); printf(" Player's hand is: %s of %s and %s of %s.\n",dealt[0].name,dealt[0].suit,dealt[1].name,dealt[1].suit); printf(" the current value of the index i=%d\n",i); //this line gave me the value of i for testing d=deal[0].value+deal[1].value; p=dealt[0].value+dealt[1].value; if(d==21){ printf(" The Dealer has Blackjack! House win!\n"); }else{ if(d>21){ printf(" The dealer is Bust! You win!\n"); }else{ if(d>17){ printf(" Press 1 to HIT or 2 to STAND"); scanf("%d",k); if(k==1){ dealt[y].suit=cards[i].suit; dealt[y].name=cards[i].name; dealt[y].value=cards[i].value; y++; i++; } }else{ if(d<17){ printf(" Dealer Hits!"); deal[x].suit=cards[i].suit; deal[x].name=cards[i].name; deal[x].value=cards[i].value; x++; i++; } } } } return 0; }

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  • Is there a name for a language feature that allows assignment/creation?

    - by Alex Mcp
    This is a bit hard for me to articulate, but in PHP you can say something like: $myArray['someindex'] = "my string"; and if there is no index named that, it will create/assign the value, and if there IS an index, it will overwrite the existing value. Compare this to Javascript where today I had to do checks like so: if (!myObject[key]) myObject[key] = "value"; I know this may be a bit of a picky point, but is there a name for the ability of PHP (and many other languages) to do these checks on their own as opposed to the more verbose (read: PITA) method of Javascript?

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  • How to control order of assignment for new identity column in SQL Server?

    - by alpav
    I have a table with CreateDate datetime field default(getdate()) that does not have any identity column. I would like to add identity(1,1) field that would reflect same order of existing records as CreateDate field (order by would give same results). How can I do that ? I guess if I create clustered key on CreateDate field and then add identity column it will work (not sure if it's guaranteed), is there a good/better way ? I am interested in SQL Server 2005, but I guess the answer will be the same for SQL Server 2008, SQL Server 2000.

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  • Index, assignment and increment in one statement behaves differently in C++ and C#. Why?

    - by Ivan Zlatanov
    Why is this example of code behaving differently in c++ and C#. [C++ Example] int arr[2]; int index = 0; arr[index] = ++index; The result of which will be arr[1] = 1; [C# Example] int[] arr = new int[2]; int index = 0; arr[index] = ++index; The result of which will be arr[0] = 1; I find this very strange. Surely there must be some rationale for both languages to implement it differently? I wonder what would C++/CLI output?

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  • How to control order of assignment for new identity column in mssql ?

    - by alpav
    I have a table with CreateDate datetime field default(getdate()) that does not have any identity column. I would like to add identity(1,1) field that would reflect same order of existing records as CreateDate field (order by would give same results). How can I do that ? I guess if I create clustered key on CreateDate field and then add identity column it will work (not sure if it's guaranteed), is there a good/better way ? I am interested in sql 2005, but I guess the answer will be the same for sql 2008, sql 2000.

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  • Python del() built-in can't be used in assignment?

    - by emcee
    I noticed a problem when I was trying to use del in a lambda to thin out a list of threads to just those running: map(lambda x: del(x) if not x.isAlive() else x, self.threads) Ignore for a second that this doesn't do anything, I'm just fooling around with map, reduce, and lambda. This fails with a syntax error at del(x). With some messing around, I think the problem is del() doesn't return a value. For example, this fails with the same error: b = 5 x = del(b) This doesn't, however: def rmThis(x): del(x) Which means I'm using this workaround: map(lambda x: rmThis(x) if not x.isAlive() else x, self.threads) So is the limitation just because del() doesn't return a value? Why not? I'm using python 2.6.2

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  • Is single float assignment an atomic operation on the iPhone?

    - by iter
    I assume that on a 32-bit device like the iPhone, assigning a short float is an atomic, thread-safe operation. I want to make sure it is. I have a C function that I want to call from an Objective-C thread, and I don't want to acquire a lock before calling it: void setFloatValue(float value) { globalFloat = value; }

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  • Is there a difference between Perl's shift versus assignment from @_ for subroutine parameters?

    - by cowgod
    Let us ignore for a moment Damian Conway's best practice of no more than three positional parameters for any given subroutine. Is there any difference between the two examples below in regards to performance or functionality? Using shift: sub do_something_fantastical { my $foo = shift; my $bar = shift; my $baz = shift; my $qux = shift; my $quux = shift; my $corge = shift; } Using @_: sub do_something_fantastical { my ($foo, $bar, $baz, $qux, $quux, $corge) = @_; } Provided that both examples are the same in terms of performance and functionality, what do people think about one format over the other? Obviously the example using @_ is fewer lines of code, but isn't it more legible to use shift as shown in the other example? Opinions with good reasoning are welcome.

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  • How can I override the attribute assignment in an active record object?

    - by ryeguy
    I know you can do this with virtual attributes, but what if the column actually exists? For example, my model has a raw_topic column. When raw_topic is set, I want artist and song_title to be set based off of raw_topic's contents. Ideally, I'd like to override the raw_topic= method, but rails doesn't seem to like that. What's the proper way of doing this? Is a callback the only way?

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  • How to use a object whose copy constructor and copy assignment is private?

    - by coanor
    In reading TCPL, I got a problem, as the title refered, and then 'private' class is: class Unique_handle { private: Unique_handle& operator=(const Unique_handle &rhs); Unique_handle(const Unique_handle &rhs); public: //... }; the using code is: struct Y { //... Unique_handle obj; }; and I want to execute such operations: int main() { Y y1; Y y2 = y1; } although, these code are come from TCPL, but I still can not got the solution... Can anybody help me, appreciate.

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  • Is it possible to raise an error if a variable assignment in a select returns multiple values?

    - by Brann
    I just found a bug on one of my softwares where I had forgotten a where clause. The code was something like that : declare @foo bigint declare @bar bigint select @foo = foo, @bar=bar from tbFooBar where (....a long list of condition goes there) (... and an extra condition should have went there but I forgot it) Unfortunately, the where clause I forgot was useful in very specific corner cases and the code went through testing successfully. Eventually, the query returned two values instead of one, and the resulting bug was a nightmare to track down (as it was very difficult to reproduce, and it wasn't obvious at all that this specific stored procedure was causing the issue we spotted) Debugging would have been a lot easier if the @foo=foo had raised an exception instead of silently assigning the first value out of multiple rows. Why is that this way? I can't think of a situation where one would actually want to do that without raising an error (bearing in mind the clauses 'distinct' and 'top' are there for a reason) And is there a way to make sql server 2008 raise an error if this situation occurs ?

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  • Want to Receive dynamic length data from a message queue in IPC?

    - by user1089679
    Here I have to send and receive dynamic data using a SysV message queue. so in structure filed i have dynamic memory allocation char * because its size may be varies. so how can i receive this type of message at receiver side. Please let me know how can i send dynamic length of data with message queue. I am getting problem in this i posted my code below. send.c /*filename : send.c *To compile : gcc send.c -o send */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> struct my_msgbuf { long mtype; char *mtext; }; int main(void) { struct my_msgbuf buf; int msqid; key_t key; static int count = 0; char temp[5]; int run = 1; if ((key = ftok("send.c", 'B')) == -1) { perror("ftok"); exit(1); } printf("send.c Key is = %d\n",key); if ((msqid = msgget(key, 0644 | IPC_CREAT)) == -1) { perror("msgget"); exit(1); } printf("Enter lines of text, ^D to quit:\n"); buf.mtype = 1; /* we don't really care in this case */ int ret = -1; while(run) { count++; buf.mtext = malloc(50); strcpy(buf.mtext,"Hi hello test message here"); snprintf(temp, sizeof (temp), "%d",count); strcat(buf.mtext,temp); int len = strlen(buf.mtext); /* ditch newline at end, if it exists */ if (buf.mtext[len-1] == '\n') buf.mtext[len-1] = '\0'; if (msgsnd(msqid, &buf, len+1, IPC_NOWAIT) == -1) /* +1 for '\0' */ perror("msgsnd"); if(count == 100) run = 0; usleep(1000000); } if (msgctl(msqid, IPC_RMID, NULL) == -1) { perror("msgctl"); exit(1); } return 0; } receive.c /* filename : receive.c * To compile : gcc receive.c -o receive */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> struct my_msgbuf { long mtype; char *mtext; }; int main(void) { struct my_msgbuf buf; int msqid; key_t key; if ((key = ftok("send.c", 'B')) == -1) { /* same key as send.c */ perror("ftok"); exit(1); } if ((msqid = msgget(key, 0644)) == -1) { /* connect to the queue */ perror("msgget"); exit(1); } printf("test: ready to receive messages, captain.\n"); for(;;) { /* receive never quits! */ buf.mtext = malloc(50); if (msgrcv(msqid, &buf, 50, 0, 0) == -1) { perror("msgrcv"); exit(1); } printf("test: \"%s\"\n", buf.mtext); } return 0; }

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  • PHP 5 functioning returning an array- interaction without assignment?

    - by Lee
    I'm wondering if this kind of thing will ever be possible in PHP (and whether it already is and I'm just missing something...) <?php function test() { return array( 'id'=>10, 'name'=>'John' ); } echo 'Your name is: '.test()['name']; ?> I'd really like to be able to use returned arrays directly instead of first assigning them to a var... possible?

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  • Why does gcc warn about incompatible struct assignment with a `self = [super initDesignatedInit];' c

    - by gavinbeatty
    I have the following base/derived class setup in Objective-C: @interface ASCIICodeBase : NSObject { @protected char code_[4]; } - (Base *)initWithASCIICode:(const char *)code; @end @implementation ASCIICodeBase - (ASCIICodeBase *)initWithCode:(const char *)code len:(size_t)len { if (len == 0 || len > 3) { return nil; } if (self = [super init]) { memset(code_, 0, 4); strncpy(code_, code, 3); } return self; } @end @interface CountryCode : ASCIICodeBase - (CountryCode *)initWithCode:(const char *)code; @end @implementation CountryCode - (CountryCode *)initWithCode:(const char *)code { size_t len = strlen(code); if (len != 2) { return nil; } self = [super initWithCode:code len:len]; // here return self; } @end On the line marked "here", I get the following gcc warning: warning: incompatible Objective-C types assigning 'struct ASCIICodeBase *', expected 'struct CurrencyCode *' Is there something wrong with this code or should I have the ASCIICodeBase return id? Or maybe use a cast on the "here" line?

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  • Adventures in MVVM &ndash; My ViewModel Base

    - by Brian Genisio's House Of Bilz
    More Adventures in MVVM First, I’d like to say: THIS IS NOT A NEW MVVM FRAMEWORK. I tend to believe that MVVM support code should be specific to the system you are building and the developers working on it.  I have yet to find an MVVM framework that does everything I want it to without doing too much.  Don’t get me wrong… there are some good frameworks out there.  I just like to pick and choose things that make sense for me.  I’d also like to add that some of these features only work in WPF.  As of Silveright 4, they don’t support binding to dynamic properties, so some of the capabilities are lost. That being said, I want to share my ViewModel base class with the world.  I have had several conversations with people about the problems I have solved using this ViewModel base.  A while back, I posted an article about some experiments with a “Rails Inspired ViewModel”.  What followed from those ideas was a ViewModel base class that I take with me and use in my projects.  It has a lot of features, all designed to reduce the friction in writing view models. I have put the code out on Codeplex under the project: ViewModelSupport. Finally, this article focuses on the ViewModel and only glosses over the View and the Model.  Without all three, you don’t have MVVM.  But this base class is for the ViewModel, so that is what I am focusing on. Features: Automatic Command Plumbing Property Change Notification Strongly Typed Property Getter/Setters Dynamic Properties Default Property values Derived Properties Automatic Method Execution Command CanExecute Change Notification Design-Time Detection What about Silverlight? Automatic Command Plumbing This feature takes the plumbing out of creating commands.  The common pattern for commands in a ViewModel is to have an Execute method as well as an optional CanExecute method.  To plumb that together, you create an ICommand Property, and set it in the constructor like so: Before public class AutomaticCommandViewModel { public AutomaticCommandViewModel() { MyCommand = new DelegateCommand(Execute_MyCommand, CanExecute_MyCommand); } public void Execute_MyCommand() { // Do something } public bool CanExecute_MyCommand() { // Are we in a state to do something? return true; } public DelegateCommand MyCommand { get; private set; } } With the base class, this plumbing is automatic and the property (MyCommand of type ICommand) is created for you.  The base class uses the convention that methods be prefixed with Execute_ and CanExecute_ in order to be plumbed into commands with the property name after the prefix.  You are left to be expressive with your behavior without the plumbing.  If you are wondering how CanExecuteChanged is raised, see the later section “Command CanExecute Change Notification”. After public class AutomaticCommandViewModel : ViewModelBase { public void Execute_MyCommand() { // Do something } public bool CanExecute_MyCommand() { // Are we in a state to do something? return true; } }   Property Change Notification One thing that always kills me when implementing ViewModels is how to make properties that notify when they change (via the INotifyPropertyChanged interface).  There have been many attempts to make this more automatic.  My base class includes one option.  There are others, but I feel like this works best for me. The common pattern (without my base class) is to create a private backing store for the variable and specify a getter that returns the private field.  The setter will set the private field and fire an event that notifies the change, only if the value has changed. Before public class PropertyHelpersViewModel : INotifyPropertyChanged { private string text; public string Text { get { return text; } set { if(text != value) { text = value; RaisePropertyChanged("Text"); } } } protected void RaisePropertyChanged(string propertyName) { var handlers = PropertyChanged; if(handlers != null) handlers(this, new PropertyChangedEventArgs(propertyName)); } public event PropertyChangedEventHandler PropertyChanged; } This way of defining properties is error-prone and tedious.  Too much plumbing.  My base class eliminates much of that plumbing with the same functionality: After public class PropertyHelpersViewModel : ViewModelBase { public string Text { get { return Get<string>("Text"); } set { Set("Text", value);} } }   Strongly Typed Property Getters/Setters It turns out that we can do better than that.  We are using a strongly typed language where the use of “Magic Strings” is often frowned upon.  Lets make the names in the getters and setters strongly typed: A refinement public class PropertyHelpersViewModel : ViewModelBase { public string Text { get { return Get(() => Text); } set { Set(() => Text, value); } } }   Dynamic Properties In C# 4.0, we have the ability to program statically OR dynamically.  This base class lets us leverage the powerful dynamic capabilities in our ecosystem. (This is how the automatic commands are implemented, BTW)  By calling Set(“Foo”, 1), you have now created a dynamic property called Foo.  It can be bound against like any static property.  The opportunities are endless.  One great way to exploit this behavior is if you have a customizable view engine with templates that bind to properties defined by the user.  The base class just needs to create the dynamic properties at runtime from information in the model, and the custom template can bind even though the static properties do not exist. All dynamic properties still benefit from the notifiable capabilities that static properties do. For any nay-sayers out there that don’t like using the dynamic features of C#, just remember this: the act of binding the View to a ViewModel is dynamic already.  Why not exploit it?  Get over it :) Just declare the property dynamically public class DynamicPropertyViewModel : ViewModelBase { public DynamicPropertyViewModel() { Set("Foo", "Bar"); } } Then reference it normally <TextBlock Text="{Binding Foo}" />   Default Property Values The Get() method also allows for default properties to be set.  Don’t set them in the constructor.  Set them in the property and keep the related code together: public string Text { get { return Get(() => Text, "This is the default value"); } set { Set(() => Text, value);} }   Derived Properties This is something I blogged about a while back in more detail.  This feature came from the chaining of property notifications when one property affects the results of another, like this: Before public class DependantPropertiesViewModel : ViewModelBase { public double Score { get { return Get(() => Score); } set { Set(() => Score, value); RaisePropertyChanged("Percentage"); RaisePropertyChanged("Output"); } } public int Percentage { get { return (int)(100 * Score); } } public string Output { get { return "You scored " + Percentage + "%."; } } } The problem is: The setter for Score has to be responsible for notifying the world that Percentage and Output have also changed.  This, to me, is backwards.    It certainly violates the “Single Responsibility Principle.” I have been bitten in the rear more than once by problems created from code like this.  What we really want to do is invert the dependency.  Let the Percentage property declare that it changes when the Score Property changes. After public class DependantPropertiesViewModel : ViewModelBase { public double Score { get { return Get(() => Score); } set { Set(() => Score, value); } } [DependsUpon("Score")] public int Percentage { get { return (int)(100 * Score); } } [DependsUpon("Percentage")] public string Output { get { return "You scored " + Percentage + "%."; } } }   Automatic Method Execution This one is extremely similar to the previous, but it deals with method execution as opposed to property.  When you want to execute a method triggered by property changes, let the method declare the dependency instead of the other way around. Before public class DependantMethodsViewModel : ViewModelBase { public double Score { get { return Get(() => Score); } set { Set(() => Score, value); WhenScoreChanges(); } } public void WhenScoreChanges() { // Handle this case } } After public class DependantMethodsViewModel : ViewModelBase { public double Score { get { return Get(() => Score); } set { Set(() => Score, value); } } [DependsUpon("Score")] public void WhenScoreChanges() { // Handle this case } }   Command CanExecute Change Notification Back to Commands.  One of the responsibilities of commands that implement ICommand – it must fire an event declaring that CanExecute() needs to be re-evaluated.  I wanted to wait until we got past a few concepts before explaining this behavior.  You can use the same mechanism here to fire off the change.  In the CanExecute_ method, declare the property that it depends upon.  When that property changes, the command will fire a CanExecuteChanged event, telling the View to re-evaluate the state of the command.  The View will make appropriate adjustments, like disabling the button. DependsUpon works on CanExecute methods as well public class CanExecuteViewModel : ViewModelBase { public void Execute_MakeLower() { Output = Input.ToLower(); } [DependsUpon("Input")] public bool CanExecute_MakeLower() { return !string.IsNullOrWhiteSpace(Input); } public string Input { get { return Get(() => Input); } set { Set(() => Input, value);} } public string Output { get { return Get(() => Output); } set { Set(() => Output, value); } } }   Design-Time Detection If you want to add design-time data to your ViewModel, the base class has a property that lets you ask if you are in the designer.  You can then set some default values that let your designer see what things might look like in runtime. Use the IsInDesignMode property public DependantPropertiesViewModel() { if(IsInDesignMode) { Score = .5; } }   What About Silverlight? Some of the features in this base class only work in WPF.  As of version 4, Silverlight does not support binding to dynamic properties.  This, in my opinion, is a HUGE limitation.  Not only does it keep you from using many of the features in this ViewModel, it also keeps you from binding to ViewModels designed in IronRuby.  Does this mean that the base class will not work in Silverlight?  No.  Many of the features outlined in this article WILL work.  All of the property abstractions are functional, as long as you refer to them statically in the View.  This, of course, means that the automatic command hook-up doesn’t work in Silverlight.  You need to plumb it to a static property in order for the Silverlight View to bind to it.  Can I has a dynamic property in SL5?     Good to go? So, that concludes the feature explanation of my ViewModel base class.  Feel free to take it, fork it, whatever.  It is hosted on CodePlex.  When I find other useful additions, I will add them to the public repository.  I use this base class every day.  It is mature, and well tested.  If, however, you find any problems with it, please let me know!  Also, feel free to suggest patches to me via the CodePlex site.  :)

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  • E-Business Suite : Role of CHUNK_SIZE in Oracle Payroll

    - by Giri Mandalika
    Different batch processes in Oracle Payroll flow have the ability to spawn multiple child processes (or threads) to complete the work in hand. The number of child processes to fork is controlled by the THREADS parameter in APPS.PAY_ACTION_PARAMETERS view. THREADS parameter The default value for THREADS parameter is 1, which is fine for a single-processor system but not optimal for the modern multi-core multi-processor systems. Setting the THREADS parameter to a value equal to or less than the total number of [virtual] processors available on the system may improve the performance of payroll processing. However on the down side, since multiple child processes operate against the same set of payroll tables in HR schema, database may experience undesired consequences such as buffer busy waits and index contention, which results in giving up some of the gains achieved by using multiple child processes/threads to process the work. Couple of other action parameters, CHUNK_SIZE and CHUNK_SHUFFLE, help alleviate the database contention. eg., Set a value for THREADS parameter as shown below. CONNECT APPS/APPS_PASSWORD UPDATE PAY_ACTION_PARAMETERS SET PARAMETER_VALUE = DESIRED_VALUE WHERE PARAMETER_NAME = 'THREADS'; COMMIT; (I am not aware of any maximum value for THREADS parameter) CHUNK_SIZE parameter The size of each commit unit for the batch process is controlled by the CHUNK_SIZE action parameter. In other words, chunking is the act of splitting the assignment actions into commit groups of desired size represented by the CHUNK_SIZE parameter. The default value is 20, and each thread processes one chunk at a time -- which means each child process inserts or processes 20 assignment actions at any time. When multiple threads are configured, each thread picks up a chunk to process, completes the assignment actions and then picks up another chunk. This is repeated until all the chunks are exhausted. It is possible to use different chunk sizes in different batch processes. During the initial phase of processing, CHUNK_SIZE number of assignment actions are inserted into relevant table(s). When multiple child processes are inserting data at the same time into the same set of tables, as explained earlier, database may experience contention. The default value of 20 is mostly optimal in such a case. Experiment with different values for the initial phase by +/-10 for CHUNK_SIZE parameter and observe the performance impact. A larger value may make sense during the main processing phase. Again experimentation is the key in finding the suitable value for your environment. Start with a large value such as 2000 for the chunk size, then increment or decrement the size by 500 at a time until an optimal value is found. eg., Set a value for CHUNK_SIZE parameter as shown below. CONNECT APPS/APPS_PASSWORD UPDATE PAY_ACTION_PARAMETERS SET PARAMETER_VALUE = DESIRED_VALUE WHERE PARAMETER_NAME = 'CHUNK_SIZE'; COMMIT; CHUNK_SIZE action parameter accepts a value that is as low as 1 or as high as 16000. CHUNK SHUFFLE parameter By default, chunks of assignment actions are processed sequentially by all threads - which may not be a good thing especially given that all child processes/threads performing similar actions against the same set of tables almost at the same time. By saying not a good thing, I mean to say that the default behavior leads to contention in the database (in data blocks, for example). It is possible to relieve some of that database contention by randomizing the processing order of chunks of assignment actions. This behavior is controlled by the CHUNK SHUFFLE action parameter. Chunk processing is not randomized unless explicitly configured. eg., Set chunk shuffling as shown below. CONNECT APPS/APPS_PASSWORD UPDATE PAY_ACTION_PARAMETERS SET PARAMETER_VALUE = 'Y' WHERE PARAMETER_NAME = 'CHUNK SHUFFLE'; COMMIT; Finally I recommend checking the following document out for additional details and additional pay action tunable parameters that may speed up the processing of Oracle Payroll.     My Oracle Support Doc ID: 226987.1 Oracle 11i & R12 Human Resources (HRMS) & Benefits (BEN) Tuning & System Health Checks Also experiment with different combinations of parameters and values until the right set of action parameters and values are found for your deployment.

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