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  • Why did Dylan lose to Objective-C

    - by Adam Gent
    I have played/worked with many different programming languages and Dylan is still one of my favorites. My question is why did Dylan fail when Objective-C, Ruby and even Scheme have had more success? Was Dylans performance that much worse than Objective-C that Apple went with it or was purely for social/political reasons. Hopefully someone from apple will see this question :) BTW if you have no idea what Dylan is please google Dylan Progrmaming Language.

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  • Why did Dylan loose to Objective-C

    - by Adam Gent
    I have played/worked with many different programming languages and Dylan is still one of my favorites. My question is why did Dylan fail when Objective-C, Ruby and even Scheme have had more success? Was Dylans performance that much worse than Objective-C that Apple went with it or was purely for social/political reasons. Hopefully someone from apple will see this question :) BTW if you have no idea what Dylan is please google Dylan Progrmaming Language.

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  • mysqladmin - Unknown MySQL server host

    - by ert
    I'm trying to connect to a mysql server over a local network. The server is running and listening to post 41322. dylan~$ netstat -ln | s mysql unix 2 [ ACC ] STREAM LISTENING 41322 /var/run/mysqld/mysqld.sock My user is granted all rights from all addresses, and I can log in locally. dylan~$ mysqladmin -P 41322 -h [email protected] create database test mysqladmin: connect to server at '[email protected]' failed error: 'Unknown MySQL server host '[email protected]' (1)' Check that mysqld is running on [email protected] and that the port is 41322. You can check this by doing 'telnet [email protected] 41322' Adding a --verbose flag gives no additional output. I've commented out bind-address=127.0.0.1 in /etc/mysql/my.cnf on the server. I can ssh into the server without a problem. dylan~$ ps a | grep mysql 11131 pts/3 S 0:00 /bin/sh /usr/bin/mysqld_safe 11170 pts/3 Sl 0:03 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock 11171 pts/3 S 0:00 logger -p daemon.err -t mysqld_safe -i -t mysqld 13710 pts/1 S+ 0:00 grep mysq Any help or thoughts are appreciated.

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  • WSAECONNRESET (10054) error using WebDrive to map to a Subversion/Apache WebDAV share

    - by Dylan Beattie
    Hello, I'm using WebDrive to map a drive letter to a WebDAV share running on Subversion with the SVNAutoversioning flag enabled. The Subversion server is running CollabNet Subversion Edge with LDAP authentication. When trying to connect using WebDrive, I get: Connecting to site myserver Connecting to http://myserver/webdrive/ Resolving url myserver to an IP address Url resolved to IP address 192.168.0.12 Connecting to 192.168.0.12 on port 80 Connected successfully to the server on port 80 Testing directory listing ... Connecting to 192.168.0.12 on port 80 Connected successfully to the server on port 80 Unable to connect to server, error information below Error: Socket receive failure (4507) Operation: Connecting to server Winsock Error: WSAECONNRESET (10054) The httpd.conf file running on the server contains the following section: <Location /webdrive/> DAV svn SVNParentPath "C:\Program Files\Subversion\data\repositories" SVNReposName "My Subversion WebDrive" AuthzSVNAccessFile "C:\Program Files\Subversion\data/conf/svn_access_file" SVNListParentPath On Allow from all AuthType Basic AuthName "My Subversion Repository" AuthBasicProvider csvn-file-users ldap-users Require valid-user ModMimeUsePathInfo on SVNAutoversioning on </Location> and in the Apache error_yyyy_mm_dd.log file on the server, I'm seeing this when I try to connect via WebDAV: [Mon Jan 10 14:53:22 2011] [debug] mod_authnz_ldap.c(379): [client 192.168.0.50] [5572] auth_ldap authenticate: using URL ldap://mydc/dc=mydomain,dc=com?sAMAccountName?sub [Mon Jan 10 14:53:22 2011] [debug] mod_authnz_ldap.c(484): [client 192.168.0.50] [5572] auth_ldap authenticate: accepting dylan.beattie [Mon Jan 10 14:53:22 2011] [info] [client 192.168.0.50] Access granted: 'dylan.beattie' OPTIONS webdrive:/ [Mon Jan 10 14:53:22 2011] [debug] mod_authnz_ldap.c(379): [client 192.168.0.50] [5572] auth_ldap authenticate: using URL ldap://mydc/dc=mydomain,dc=com?sAMAccountName?sub [Mon Jan 10 14:53:22 2011] [debug] mod_authnz_ldap.c(484): [client 192.168.0.50] [5572] auth_ldap authenticate: accepting dylan.beattie [Mon Jan 10 14:53:22 2011] [info] [client 192.168.0.50] Access granted: 'dylan.beattie' PROPFIND webdrive:/ [Mon Jan 10 14:53:25 2011] [notice] Parent: child process exited with status 3221225477 -- Restarting. [Mon Jan 10 14:53:25 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xcd0f18 rmm=0xcd0f48 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:25 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xcd0f18 rmm=0xcd0f48 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:25 2011] [info] APR LDAP: Built with Microsoft Corporation. LDAP SDK [Mon Jan 10 14:53:25 2011] [info] LDAP: SSL support unavailable: LDAP: CA certificates cannot be set using this method, as they are stored in the registry instead. [Mon Jan 10 14:53:25 2011] [notice] Apache/2.2.16 (Win32) DAV/2 SVN/1.6.13 configured -- resuming normal operations [Mon Jan 10 14:53:25 2011] [notice] Server built: Oct 4 2010 19:55:36 [Mon Jan 10 14:53:25 2011] [notice] Parent: Created child process 4368 [Mon Jan 10 14:53:25 2011] [debug] mpm_winnt.c(487): Parent: Sent the scoreboard to the child [Mon Jan 10 14:53:25 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xca2bb0 rmm=0xca2be0 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:25 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xca2bb0 rmm=0xca2be0 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:25 2011] [info] APR LDAP: Built with Microsoft Corporation. LDAP SDK [Mon Jan 10 14:53:25 2011] [info] LDAP: SSL support unavailable: LDAP: CA certificates cannot be set using this method, as they are stored in the registry instead. [Mon Jan 10 14:53:25 2011] [error] python_init: Python version mismatch, expected '2.5', found '2.5.4'. [Mon Jan 10 14:53:25 2011] [error] python_init: Python executable found 'C:\\Program Files\\Subversion\\bin\\httpd.exe'. [Mon Jan 10 14:53:25 2011] [error] python_init: Python path being used 'C:\\Program Files\\Subversion\\Python25\\python25.zip;C:\\Program Files\\Subversion\\Python25\\\\DLLs;C:\\Program Files\\Subversion\\Python25\\\\lib;C:\\Program Files\\Subversion\\Python25\\\\lib\\plat-win;C:\\Program Files\\Subversion\\Python25\\\\lib\\lib-tk;C:\\Program Files\\Subversion\\bin'. [Mon Jan 10 14:53:25 2011] [notice] mod_python: Creating 8 session mutexes based on 0 max processes and 64 max threads. [Mon Jan 10 14:53:25 2011] [notice] Child 4368: Child process is running [Mon Jan 10 14:53:25 2011] [debug] mpm_winnt.c(408): Child 4368: Retrieved our scoreboard from the parent. [Mon Jan 10 14:53:25 2011] [info] Parent: Duplicating socket 288 and sending it to child process 4368 [Mon Jan 10 14:53:25 2011] [info] Parent: Duplicating socket 276 and sending it to child process 4368 [Mon Jan 10 14:53:25 2011] [debug] mpm_winnt.c(564): Child 4368: retrieved 2 listeners from parent [Mon Jan 10 14:53:25 2011] [notice] Child 4368: Acquired the start mutex. [Mon Jan 10 14:53:25 2011] [notice] Child 4368: Starting 64 worker threads. [Mon Jan 10 14:53:25 2011] [debug] mpm_winnt.c(605): Parent: Sent 2 listeners to child 4368 [Mon Jan 10 14:53:25 2011] [notice] Child 4368: Starting thread to listen on port 49159. [Mon Jan 10 14:53:25 2011] [notice] Child 4368: Starting thread to listen on port 80. [Mon Jan 10 14:53:25 2011] [debug] mod_authnz_ldap.c(379): [client 192.168.0.50] [4368] auth_ldap authenticate: using URL ldap://mydc/dc=mydomain,dc=com?sAMAccountName?sub [Mon Jan 10 14:53:25 2011] [debug] mod_authnz_ldap.c(484): [client 192.168.0.50] [4368] auth_ldap authenticate: accepting dylan.beattie [Mon Jan 10 14:53:25 2011] [info] [client 192.168.0.50] Access granted: 'dylan.beattie' PROPFIND webdrive:/ [Mon Jan 10 14:53:28 2011] [notice] Parent: child process exited with status 3221225477 -- Restarting. [Mon Jan 10 14:53:28 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xcd4f90 rmm=0xcd4fc0 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:28 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xcd4f90 rmm=0xcd4fc0 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:28 2011] [info] APR LDAP: Built with Microsoft Corporation. LDAP SDK [Mon Jan 10 14:53:28 2011] [info] LDAP: SSL support unavailable: LDAP: CA certificates cannot be set using this method, as they are stored in the registry instead. [Mon Jan 10 14:53:28 2011] [notice] Apache/2.2.16 (Win32) DAV/2 SVN/1.6.13 configured -- resuming normal operations [Mon Jan 10 14:53:28 2011] [notice] Server built: Oct 4 2010 19:55:36 [Mon Jan 10 14:53:28 2011] [notice] Parent: Created child process 5440 [Mon Jan 10 14:53:28 2011] [debug] mpm_winnt.c(487): Parent: Sent the scoreboard to the child [Mon Jan 10 14:53:28 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xda2bb0 rmm=0xda2be0 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:28 2011] [debug] util_ldap.c(1990): LDAP merging Shared Cache conf: shm=0xda2bb0 rmm=0xda2be0 for VHOST: myserver.mydomain.com [Mon Jan 10 14:53:28 2011] [info] APR LDAP: Built with Microsoft Corporation. LDAP SDK [Mon Jan 10 14:53:28 2011] [info] LDAP: SSL support unavailable: LDAP: CA certificates cannot be set using this method, as they are stored in the registry instead. [Mon Jan 10 14:53:28 2011] [error] python_init: Python version mismatch, expected '2.5', found '2.5.4'. [Mon Jan 10 14:53:28 2011] [error] python_init: Python executable found 'C:\\Program Files\\Subversion\\bin\\httpd.exe'. [Mon Jan 10 14:53:28 2011] [error] python_init: Python path being used 'C:\\Program Files\\Subversion\\Python25\\python25.zip;C:\\Program Files\\Subversion\\Python25\\\\DLLs;C:\\Program Files\\Subversion\\Python25\\\\lib;C:\\Program Files\\Subversion\\Python25\\\\lib\\plat-win;C:\\Program Files\\Subversion\\Python25\\\\lib\\lib-tk;C:\\Program Files\\Subversion\\bin'. [Mon Jan 10 14:53:28 2011] [notice] mod_python: Creating 8 session mutexes based on 0 max processes and 64 max threads. [Mon Jan 10 14:53:28 2011] [notice] Child 5440: Child process is running [Mon Jan 10 14:53:28 2011] [debug] mpm_winnt.c(408): Child 5440: Retrieved our scoreboard from the parent. [Mon Jan 10 14:53:28 2011] [info] Parent: Duplicating socket 288 and sending it to child process 5440 [Mon Jan 10 14:53:28 2011] [info] Parent: Duplicating socket 276 and sending it to child process 5440 [Mon Jan 10 14:53:28 2011] [debug] mpm_winnt.c(564): Child 5440: retrieved 2 listeners from parent [Mon Jan 10 14:53:28 2011] [notice] Child 5440: Acquired the start mutex. [Mon Jan 10 14:53:28 2011] [notice] Child 5440: Starting 64 worker threads. [Mon Jan 10 14:53:28 2011] [debug] mpm_winnt.c(605): Parent: Sent 2 listeners to child 5440 [Mon Jan 10 14:53:28 2011] [notice] Child 5440: Starting thread to listen on port 49159. [Mon Jan 10 14:53:28 2011] [notice] Child 5440: Starting thread to listen on port 80. Browsing http://myserver/webdrive/ from a web browser is working fine, and I have a similar set-up working perfectly on a different SVN server that isn't running Collabnet but has had Subversion and Apache installed and configured separately. Any ideas? The python version error might be red herring - I've seen it in a couple of places in the log files and in other scenarios it doesn't appear to be breaking anything...

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  • File permissions with FileSystemObject - CScript.exe says one thing, Classic ASP says another...

    - by Dylan Beattie
    I have a classic ASP page - written in JScript - that's using Scripting.FileSystemObject to save files to a network share - and it's not working. ("Permission denied") The ASP page is running under IIS using Windows authentication, with impersonation enabled. If I run the following block of code locally via CScript.exe: var objNet = new ActiveXObject("WScript.Network"); WScript.Echo(objNet.ComputerName); WScript.Echo(objNet.UserName); WScript.Echo(objNet.UserDomain); var fso = new ActiveXObject("Scripting.FileSystemObject"); var path = "\\\\myserver\\my_share\\some_path"; if (fso.FolderExists(path)) { WScript.Echo("Yes"); } else { WScript.Echo("No"); } I get the (expected) output: MY_COMPUTER dylan.beattie MYDOMAIN Yes If I run the same code as part of a .ASP page, substituting Response.Write for WScript.Echo I get this output: MY_COMPUTER dylan.beattie MYDOMAIN No Now - my understanding is that the WScript.Network object will retrieve the current security credentials of the thread that's actually running the code. If this is correct - then why is the same user, on the same domain, getting different results from CScript.exe vs ASP? If my ASP code is running as dylan.beattie, then why can't I see the network share? And if it's not running as dylan.beattie, why does WScript.Network think it is?

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  • Javascript Rookie Question: Define Variables Inline

    - by Dylan Kinnett
    I'm proficient with HTML and CSS but I'm still pretty shaky when it comes to Javascript. That said, I've been able to build a site using the Internet Archive Book Reader, which relies on reader.js Here's a copy of one of my versions of reader.js https://gist.github.com/dylan-k/ed4efed2384e221d46cc It's a good site, but I find I have to repeat things a lot. Basically, I have one copy of reader.js for every page/book featured on the site. It seems there must be a better way. I re-use the script, making copies, just so that I can change lines 28, 80, 83, 84. Is there a way I could include just one copy of reader.js and then use a <script> tag to define these 4 lines for the individual pages?

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  • SDL_image & OpenGL Problem

    - by Dylan
    i've been following tutorials online to load textures using SDL and display them on a opengl quad. but ive been getting weird results that no one else on the internet seems to be getting... so when i render the texture in opengl i get something like this. http://www.kiddiescissors.com/after.png when the original .bmp file is this: http://www.kiddiescissors.com/before.bmp ive tried other images too, so its not that this particular image is corrupt. it seems like my rgb channels are all jumbled or something. im pulling my hair out at this point. heres the relevant code from my init() function if ( SDL_Init(SDL_INIT_VIDEO) != 0 ) { return 1; } SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1); SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 ); SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 ); SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 ); SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 ); SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1); SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 4); SDL_SetVideoMode(WINDOW_WIDTH, WINDOW_HEIGHT, 32, SDL_HWSURFACE | SDL_GL_DOUBLEBUFFER | SDL_OPENGL); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(50, (GLfloat)WINDOW_WIDTH/WINDOW_HEIGHT, 1, 50); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glEnable(GL_DEPTH_TEST); glEnable(GL_MULTISAMPLE); glEnable(GL_TEXTURE_2D); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_BLEND); heres the code that is called when my main player object (the one with which this sprite is associated) is initialized texture = 0; SDL_Surface* surface = IMG_Load("i.bmp"); glGenTextures(1, &texture); glBindTexture(GL_TEXTURE_2D, texture); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, surface->w, surface->h, 0, GL_RGB, GL_UNSIGNED_BYTE, surface->pixels); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); SDL_FreeSurface(surface); and then heres the relevant code from my display function glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); glColor4f(1, 1, 1, 1); glPushMatrix(); glBindTexture(GL_TEXTURE_2D, texture); glTranslatef(getCenter().x, getCenter().y, 0); glRotatef(getAngle()*(180/M_PI), 0, 0, 1); glTranslatef(-getCenter().x, -getCenter().y, 0); glBegin(GL_QUADS); glTexCoord2f(0, 0); glVertex3f(getTopLeft().x, getTopLeft().y, 0); glTexCoord2f(0, 1); glVertex3f(getTopLeft().x, getTopLeft().y + size.y, 0); glTexCoord2f(1, 1); glVertex3f(getTopLeft().x + size.x, getTopLeft().y + size.y, 0); glTexCoord2f(1, 0); glVertex3f(getTopLeft().x + size.x, getTopLeft().y, 0); glEnd(); glPopMatrix(); let me know if i left out anything important... or if you need more info from me. thanks a ton, -Dylan

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  • What's causing Remote Access error 807 using rasdial.exe to connect to a PPTP VPN?

    - by Dylan Beattie
    I'm using rasdial.exe to connect an offsite server to our VPN. Remote box is a Windows 2008 x64 server; the VPN host at this end is a Watchguard Firebox x750e running Fireware 10.2 It connects fine about 20-30% of the time. The rest of the time I get: Remote Access error 807 - The network connection between your computer and the VPN server was interrupted. This can be caused by a problem in the VPN transmission and is commonly the result of internet latency or simply that your VPN server has reached capacity. Please try to reconnect to the VPN server. If this problem persists, contact the VPN administrator and analyze quality of network connectivity. For more help on this error: Type 'hh netcfg.chm' In help, click Troubleshooting, then Error Messages, then 807 The VPN isn't full, and it's 100Mb dedicated fibre on both ends so I can't believe it's a connectivity issue - especially since I'm RDP'ed into the remote box whilst trying to do this! Any bright ideas as to what might be causing the problem? Thanks, Dylan

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  • PHP Summarize any URL

    - by Dylan Taylor
    Hey guys, How can I, in PHP, get a summary of any URL? By summary, I mean something similar to the URL descriptions in Google web search results. Is this possible? Is there already some kind of tool I can plug in to so I don't have to generate my own summaries? I don't want to use metadata descriptions if possible. -Dylan

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  • Using PHP, how to parse the title and meta tags from a HTML page?

    - by Dylan Taylor
    Hey guys, I need to be able to get the TITLE and DESCIPTION metadata out of a page. I've been trying to do this but I've been getting more errors than actual results. (I have an array of about 10 URLS, usually only about 2 of them give me the descrption. I have yet to get the title). So how do I, in PHP, get the Desc and Title from a remote page, and if there is none or if there's an error, ignore it? -Dylan

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  • PHP array taking up too much memory

    - by Dylan Taylor
    I have a multidimensional array. The array itself is fine. My problem is that the script takes up monster amounts of memory, and since I'm running this on my MAMP install on my iBook G4, my computer freezes up. Below is the full script. $query = "SELECT * FROM posts ORDER BY id DESC LIMIT 10"; $result = mysql_query($query); $posts = array(); while($row = mysql_fetch_array($result)){ $posts[$row["id"]]['post_id'] = $row["id"]; $posts[$row["id"]]['post_title'] = $row["title"]; $posts[$row["id"]]['post_text'] = $row["text"]; $posts[$row["id"]]['post_tags'] = $row["tags"]; $posts[$row["id"]]['post_category'] = $row["category"]; foreach ($posts as $post) { echo $post["post_id"]; } Is there a workaround that still achieves my goal (to export the MySQL query rows to an array)? -Dylan

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  • PHP array taking up to much memory

    - by Dylan Taylor
    I have a multidimensional array. The array itself is fine. My problem is that the script takes up monster amounts of memory, and since I'm running this on my MAMP install on my iBook G4, my computer freezes up. Below is the full script. $query = "SELECT * FROM posts ORDER BY id DESC LIMIT 10"; $result = mysql_query($query); $posts = array(); while($row = mysql_fetch_array($result)){ $posts[$row["id"]]['post_id'] = $row["id"]; $posts[$row["id"]]['post_title'] = $row["title"]; $posts[$row["id"]]['post_text'] = $row["text"]; $posts[$row["id"]]['post_tags'] = $row["tags"]; $posts[$row["id"]]['post_category'] = $row["category"]; foreach ($posts as $post) { echo $post["post_id"]; } Is there a workaround that still achieves my goal (to export the MySQL query rows to an array)? -Dylan

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  • Customizing TabWidget in SDK 1.5, API 3

    - by Dylan McClung
    I'm aware that API 3 doesn't allow a view to be set for a tab, but I still need to modify the TextView displayed as the indicator. I'd also like to change the Drawable for the tab, but I don't see a way to do it without a custom tab view as allowed in 1.6, API 4. Working with this generic example below, is there way to retrieve the TextView and modify its properties or change the drawable? TabHost tabHost = getTabHost(); TabHost.TabSpec spec; spec = tabHost.newTabSpec("nearby") .setIndicator("Nearby Activity") .setContent(R.id.nearby_list); tabHost.addTab(spec); spec = tabHost.newTabSpec("friends") .setIndicator("Friends & Favorites") .setContent(R.id.friends_list); tabHost.addTab(spec); tabHost.setCurrentTabByTag("nearby"); Thanks for any help.

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  • What's a good AJAX Autocomplete Plugin for jQuery?

    - by Murat Ayfer
    I usually use jQuery as my JS library on my sites, and I would like to stick with it since I'm familiar with it. I need to implement an AJAX autocomplete, mainly for suggesting search results. Here are a few I have found: Dylan Verheul's version Jörn Zaefferer's version A modification of Dylan Verheul's version If you have tried any of these plugins, were you happy with them? Which one do you think is the most (and easily) customizable?

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  • CQRS &ndash; Questions and Concerns

    - by Dylan Smith
    I’ve been doing a lot of learning on CQRS and Event Sourcing over the last little while and I have a number of questions that I haven’t been able to answer. 1. What is the benefit of CQRS when compared to a typical DDD architecture that uses Event Sourcing and properly captures intent and behavior via verb-based commands? (other than Scalability) 2. When using CQRS what do you do with complex query-based logic? I’m going to elaborate on #1 in this blog post and I’ll do a follow-up post on #2. I watched through Greg Young’s video on the business benefits of CQRS + Event Sourcing and first let me say that I thought it was an excellent presentation that really drives home a lot of the benefits to this approach to architecture (I watched it twice in a row I enjoyed it so much!). But it didn’t answer some of my questions fully (I wish I had been there to ask these of Greg in person!). So let me pick apart some of the points he makes and how they relate to my first question above. I’m completely sold on the idea of event sourcing and have a clear understanding of the benefits that it brings to the table, so I’m not going to question that. But you can use event sourcing without going to a CQRS architecture, so my main question is around the benefits of CQRS + Event Sourcing vs Event Sourcing + Typical DDD architecture Architecture with Event Sourcing + Commands on Left, CQRS on Right Greg talks about how the stereotypical architecture doesn’t support DDD, but is that only because his diagram shows DTO’s coming up from the client. If we use the same diagram but allow the client to send commands doesn’t that remove a lot of the arguments that Greg makes against the stereotypical architecture? We can now introduce verbs into the system. We can capture intent now (storing it still requires event sourcing, but you can implement event sourcing without doing CQRS) We can create a rich domain model (as opposed to an anemic domain model) Scalability is obviously a benefit that CQRS brings to the table, but like Greg says, very few of the systems we create truly need significant scalability Greg talks about the ability to scale your development efforts. He says CQRS allows you to split the system into 3 parts (Client, Domain/Commands, Reads) and assign 3 teams of developers to work on them in parallel; letting you scale your development efforts by 3x with nearly linear gains. But in the stereotypical architecture don’t you already have 2 separate modules that you can split your dev efforts between: The client that sends commands/queries and receives DTO’s, and the Domain which accepts commands/queries, and generates events/DTO’s. If this is true it’s not really a 3x scaling you achieve with CQRS but merely a 1.5x scaling which while great doesn’t sound nearly as dramatic (“I can do it with 10 devs in 12 months – let me hire 5 more and we can have it done in 8 months”). Making the Query side “stupid simple” such that you can assign junior developers (or even outsource it) sounds like a valid benefit, but I have some concerns over what you do with complex query-based logic/behavior. I’m going to go into more detail on this in a follow-up blog post shortly. He also seemed to focus on how “stupid-simple” it is doing queries against the de-normalized data store, but I imagine there is still significant complexity in the event handlers that interpret the events and apply them to the de-normalized tables. It sounds like Greg suggests that because we’re doing CQRS that allows us to apply Event Sourcing when we otherwise wouldn’t be able to (~33:30 in the video). I don’t believe this is true. I don’t see why you wouldn’t be able to apply Event Sourcing without separating out the Commands and Queries. The queries would just operate against the domain model instead of the database. But you’d still get the benefits of Event Sourcing. Without CQRS the queries would only be able to operate against the current state rather than the event history, but even in CQRS the domain behaviors can only operate against the current state and I don’t see that being a big limiting factor. If some query needs to operate against something that is not captured by the current state you would just have to update the domain model to capture that information (no different than if that statement were made about a Command under CQRS). Some of the benefits I do see being applicable are that your domain model might end up being simpler/smaller since it only needs to represent the state needed to process commands and not worry about the reads (like the Deactivate Inventory Item and associated comment example that Greg provides). And also commands that can be handled in a Transaction Script style manner by the command handler simply generating events and not touching the domain model. It also makes it easier for your senior developers to focus on the command behavior and ignore the queries, which is usually going to be a better use of their time. And of course scalability. If anybody out there has any thoughts on this and can help educate me further, please either leave a comment or feel free to get in touch with me via email:

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  • CQRS - Benefits

    - by Dylan Smith
    Thanks to all the comments and feedback from the last post I think I have a better understanding now of the benefits of CQRS (separate from the benefits of Event Sourcing). I’m going to try and sum it up here, and point out some areas where I could still use some advice: CQRS Benefits Sounds like the primary benefit of CQRS as an architecture is it allows you to create a simpler domain model by sucking out everything related to queries. I can definitely see the benefit to this, in general the domain logic related to commands is the high-value behavior in the software, but the logic required to service the queries would add a lot of low-value “noise” to the domain model that would dilute the high-value (command) behavior – sorting, paging, filtering, pre-fetch paths, etc. Also the most appropriate domain structure for implementing commands might not be the most optimal for implementing queries. To paraphrase Greg, this usually results in a domain model that is mediocre at both, piss-poor at one, or more likely piss-poor at both commands and queries. Not only will you be able to simplify your domain model by pulling out all the query logic, but at least a handful of commands in most systems will probably be “pass-though” type commands with little to no logic that just generate events. If these can be implemented directly in the command-handler and never touch the domain model, this allows you to slim down the domain model even more. Also, if you were to do event sourcing without CQRS, you no longer have a database containing the current state (only the domain model would) which makes it difficult (or impossible) to support ad-hoc querying and/or reporting that is common in most business software. Of course CQRS provides some great scalability benefits, not only scalability but I have to assume that it provides extremely low latency for most operations, especially if you have an asynchronous event bus. I know Greg says that you get a 3x scaling (Commands, Queries, Client) of your ability to perform parallel development, but IMHO, it seems like it only provides 1.5x scaling since even without CQRS you’re going to have your client loosely coupled to your domain - which is still a great benefit to be able to realize. Questions / Concerns If all the queries against an aggregate get pulled out to the Query layer, what if the only commands for that aggregate can be handled in a “pass-through” manner with the command handler directly generating events. Is it possible to have an aggregate that isn’t modeled in the domain model? Are there any issues or downsides to this? I know in the feedback from my previous posts it was suggested that having one domain model handling both commands and queries requires implementing a lot of traversals between objects that wouldn’t be necessary if it was only servicing commands. My question is, do you include traversals in your domain model based on the needs of the code, or based on the conceptual domain model? If none of my Commands require a Customer.Orders traversal, but the conceptual domain includes the concept of a set of orders belonging to a customer – should I model that in my domain model or not? I like the idea of using the Query side of the architecture as a place to put junior devs where the risk of them screwing something up has minimal impact. But I’m not sold on the idea that you can actually outsource it. Like I said in one of my comments on my previous post, the code to handle a query and generate DTO’s is going to be dead simple, but the code to process events and apply them to the tables on the query side is going to require a significant amount of domain knowledge to know which events to listen for to update each of the de-normalized tables (and what changes need to be made when each event is processed). I don’t know about everybody else, but having Indian/Russian/whatever outsourced developers have to do anything that requires significant domain knowledge has never been successful in my experience. And if you need to spec out for each new query which events to listen to and what to do with each one, well that’s probably going to be just as much work to document as it would be to just implement it. Greg made the point in a comment that doing an aggregate query like “Total Sales By Customer” is going to be inefficient if you use event sourcing but not CQRS. I don’t understand why that would be the case. I imagine in that case you’d simply have a method/property on the Customer object that calculated total sales for that customer by enumerating over the Orders collection. Then the application services layer would generate DTO’s off of the Customers collection that included say the CustomerID, CustomerName, TotalSales, or whatever the case may be. As long as you use a snapshotting implementation, I don’t see why that would be anymore inefficient in a DDD+Event Sourcing implementation than in a typical DDD implementation. Like I mentioned in my last post I still have some questions about query logic that haven’t been answered yet, but before I start asking those I want to make sure I have a strong grasp on what benefits CQRS provides.  My main concern with the query logic was that I know I could just toss it all into the query side, but I was concerned that I would be losing the benefits of using CQRS in the first place if I did that.  I want to elaborate more on this though with some example situations in an upcoming post.

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  • Software Engineering Practices &ndash; Different Projects should have different maturity levels

    - by Dylan Smith
    I’ve had a lot of discussions at the office lately about the drastically different sets of software engineering practices used on our various projects, if what we are doing is appropriate, and what factors should you be considering when determining what practices are most appropriate in a given context. I wanted to write up my thoughts in a little more detail on this subject, so here we go: If you compare any two software projects (specifically comparing their codebases) you’ll often see very different levels of maturity in the software engineering practices employed. By software engineering practices, I’m specifically referring to the quality of the code and the amount of technical debt present in the project. Things such as Test Driven Development, Domain Driven Design, Behavior Driven Development, proper adherence to the SOLID principles, etc. are all practices that you would expect at the mature end of the spectrum. At the other end of the spectrum would be the quick-and-dirty solutions that are done using something like an Access Database, Excel Spreadsheet, or maybe some quick “drag-and-drop coding”. For this blog post I’m going to refer to this as the Software Engineering Maturity Spectrum (SEMS). I believe there is a time and a place for projects at every part of that SEMS. The risks and costs associated with under-engineering solutions have been written about a million times over so I won’t bother going into them again here, but there are also (unnecessary) costs with over-engineering a solution. Sometimes putting multiple layers, and IoC containers, and abstracting out the persistence, etc is complete overkill if a one-time use Access database could solve the problem perfectly well. A lot of software developers I talk to seem to automatically jump to the very right-hand side of this SEMS in everything they do. A common rationalization I hear is that it may seem like a small trivial application today, but these things always grow and stick around for many years, then you’re stuck maintaining a big ball of mud. I think this is a cop-out. Sure you can’t always anticipate how an application will be used or grow over its lifetime (can you ever??), but that doesn’t mean you can’t manage it and evolve the underlying software architecture as necessary (even if that means having to toss the code out and re-write it at some point…maybe even multiple times). My thoughts are that we should be making a conscious decision around the start of each project approximately where on the SEMS we want the project to exist. I believe this decision should be based on 3 factors: 1. Importance - How important to the business is this application? What is the impact if the application were to suddenly stop working? 2. Complexity - How complex is the application functionality? 3. Life-Expectancy - How long is this application expected to be in use? Is this a one-time use application, does it fill a short-term need, or is it more strategic and is expected to be in-use for many years to come? Of course this isn’t an exact science. You can’t say that Project X should be at the 73% mark on the SEMS and expect that to be helpful. My point is not that you need to precisely figure out what point on the SEMS the project should be at then translate that into some prescriptive set of practices and techniques you should be using. Rather my point is that we need to be aware that there is a spectrum, and that not everything is going to be (or should be) at the edges of that spectrum, indeed a large number of projects should probably fall somewhere within the middle; and different projects should adopt a different level of software engineering practices and maturity levels based on the needs of that project. To give an example of this way of thinking from my day job: Every couple of years my company plans and hosts a large event where ~400 of our customers all fly in to one location for a multi-day event with various activities. We have some staff whose job it is to organize the logistics of this event, which includes tracking which flights everybody is booked on, arranging for transportation to/from airports, arranging for hotel rooms, name tags, etc The last time we arranged this event all these various pieces of data were tracked in separate spreadsheets and reconciliation and cross-referencing of all the data was literally done by hand using printed copies of the spreadsheets and several people sitting around a table going down each list row by row. Obviously there is some room for improvement in how we are using software to manage the event’s logistics. The next time this event occurs we plan to provide the event planning staff with a more intelligent tool (either an Excel spreadsheet or probably an Access database) that can track all the information in one location and make sure that the various pieces of data are properly linked together (so for example if a person cancels you only need to delete them from one place, and not a dozen separate lists). This solution would fall at or near the very left end of the SEMS meaning that we will just quickly create something with very little attention paid to using mature software engineering practices. If we examine this project against the 3 criteria I listed above for determining it’s place within the SEMS we can see why: Importance – If this application were to stop working the business doesn’t grind to a halt, revenue doesn’t stop, and in fact our customers wouldn’t even notice since it isn’t a customer facing application. The impact would simply be more work for our event planning staff as they revert back to the previous way of doing things (assuming we don’t have any data loss). Complexity – The use cases for this project are pretty straightforward. It simply needs to manage several lists of data, and link them together appropriately. Precisely the task that access (and/or Excel) can do with minimal custom development required. Life-Expectancy – For this specific project we’re only planning to create something to be used for the one event (we only hold these events every 2 years). If it works well this may change (see below). Let’s assume we hack something out quickly and it works great when we plan the next event. We may decide that we want to make some tweaks to the tool and adopt it for planning all future events of this nature. In that case we should examine where the current application is on the SEMS, and make a conscious decision whether something needs to be done to move it further to the right based on the new objectives and goals for this application. This may mean scrapping the access database and re-writing it as an actual web or windows application. In this case, the life-expectancy changed, but let’s assume the importance and complexity didn’t change all that much. We can still probably get away with not adopting a lot of the so-called “best practices”. For example, we can probably still use some of the RAD tooling available and might have an Autonomous View style design that connects directly to the database and binds to typed datasets (we might even choose to simply leave it as an access database and continue using it; this is a decision that needs to be made on a case-by-case basis). At Anvil Digital we have aspirations to become a primarily product-based company. So let’s say we use this tool to plan a handful of events internally, and everybody loves it. Maybe a couple years down the road we decide we want to package the tool up and sell it as a product to some of our customers. In this case the project objectives/goals change quite drastically. Now the tool becomes a source of revenue, and the impact of it suddenly stopping working is significantly less acceptable. Also as we hold focus groups, and gather feedback from customers and potential customers there’s a pretty good chance the feature-set and complexity will have to grow considerably from when we were using it only internally for planning a small handful of events for one company. In this fictional scenario I would expect the target on the SEMS to jump to the far right. Depending on how we implemented the previous release we may be able to refactor and evolve the existing codebase to introduce a more layered architecture, a robust set of automated tests, introduce a proper ORM and IoC container, etc. More likely in this example the jump along the SEMS would be so large we’d probably end up scrapping the current code and re-writing. Although, if it was a slow phased roll-out to only a handful of customers, where we collected feedback, made some tweaks, and then rolled out to a couple more customers, we may be able to slowly refactor and evolve the code over time rather than tossing it out and starting from scratch. The key point I’m trying to get across is not that you should be throwing out your code and starting from scratch all the time. But rather that you should be aware of when and how the context and objectives around a project changes and periodically re-assess where the project currently falls on the SEMS and whether that needs to be adjusted based on changing needs. Note: There is also the idea of “spectrum decay”. Since our industry is rapidly evolving, what we currently accept as mature software engineering practices (the right end of the SEMS) probably won’t be the same 3 years from now. If you have a project that you were to assess at somewhere around the 80% mark on the SEMS today, but don’t touch the code for 3 years and come back and re-assess its position, it will almost certainly have changed since the right end of the SEMS will have moved farther out (maybe the project is now only around 60% due to decay). Developer Skills Another important aspect to this whole discussion is around the skill sets of your architects and lead developers. When talking about the progression of a developers skills from junior->intermediate->senior->… they generally start by only being able to write code that belongs on the left side of the SEMS and as they gain more knowledge and skill they become capable of working at a higher and higher level along the SEMS. We all realize that the learning never stops, but eventually you’ll get to the point where you can comfortably develop at the right-end of the SEMS (the exact practices and techniques that translates to is constantly changing, but that’s not the point here). A critical skill that I’d love to see more evidence of in our industry is the most senior guys not only being able to work at the right-end of the SEMS, but more importantly be able to consciously work at any point along the SEMS as project needs dictate. An even more valuable skill would be if you could make the conscious decision to move a projects code further right on the SEMS (based on changing needs) and do so in an incremental manner without having to start from scratch. An exercise that I’m planning to go through with all of our projects here at Anvil in the near future is to map out where I believe each project currently falls within this SEMS, where I believe the project *should* be on the SEMS based on the business needs, and for those that don’t match up (i.e. most of them) come up with a plan to improve the situation.

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  • Meta package / quick reference for string manipulation commands?

    - by Dylan McCall
    The latest version of the Scribes text editor lets us select some text, hit Alt+X, and then run an arbitrary command. For example, I can run the sort command and the selected text is replaced appropriately. This is quite useful but I am also not very well-versed in awk and the like. Is there something I can grab that will provide more of these commands like sort? Maybe a package with a whole bunch of handy, task-specific string manipulation commands?

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  • Running Unity 2d - Does not work on actual system but works fine in VM

    - by Dylan
    So I'm running Ubuntu 10.10 and I cannot get Unity 2d to work with my system. This is particularly frustrating as it works just fine in all the VMs I've tested it on. I actually really like Unity and I want to get to know it (in part) before Ubuntu 11.04. I checked Synaptic and it looks like everything's there. The only thing not installed are dev libs and so on. Should I install those as well? Obviously the difference between my system and a VM is that the VM is running off a basically brand new OS. I only use VMs to test new stuff out and remake them often, so my only guess is that I have something installed on my system that is preventing Unity from running. Any thoughts?

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  • PrairieDevCon &ndash; Slide Decks

    - by Dylan Smith
    PrairieDevCon 2010 was an awesome time.  Learned a lot, and had some amazing conversations.  You guys even managed to convince me that NoSQL databases might actually be useful after all.   For those interested here’s my slide decks from my two sessions: Agile In Action Database Change Management With Visual Studio

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  • How can I get something like Nautilus's "spatial" behaviour in 11.10 and later?

    - by Dylan McCall
    Until recently, Nautilus had an optional "spatial" mode as an alternative to its usual browser mode. Users could enable it by opening Nautilus's preferences and selecting "Open each folder in its own window." Choosing this option resulted in a stripped down interface, and folders would always open in the same place on the screen. It looked something like this: That checkbox is still there, but it doesn't do the same thing: while every folder opens in a new window, those windows are all the same size and positioned the same way. Nautilus doesn't restore the size and position of each folder, which is what spatial mode was all about. This difference really shows if someone opens a folder in a new window, and then opens the same folder again. Nautilus will create another window instead of focusing the existing window. I help someone who is currently using Ubuntu 10.04, and he will be upgrading to 12.04 in the future. He is very comfortable with Nautilus's spatial behaviour and I think he would be disappointed to lose it. Is there an alternative file manager, or perhaps some less obvious option, that will give him an interface similar to the one he is comfortable with?

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  • Rawr Code Clone Analysis&ndash;Part 0

    - by Dylan Smith
    Code Clone Analysis is a cool new feature in Visual Studio 11 (vNext).  It analyzes all the code in your solution and attempts to identify blocks of code that are similar, and thus candidates for refactoring to eliminate the duplication.  The power lies in the fact that the blocks of code don't need to be identical for Code Clone to identify them, it will report Exact, Strong, Medium and Weak matches indicating how similar the blocks of code in question are.   People that know me know that I'm anal enthusiastic about both writing clean code, and taking old crappy code and making it suck less. So the possibilities for this feature have me pretty excited if it works well - and thats a big if that I'm hoping to explore over the next few blog posts. I'm going to grab the Rawr source code from CodePlex (a World Of Warcraft gear calculator engine program), run Code Clone Analysis against it, then go through the results one-by-one and refactor where appropriate blogging along the way.  My goals with this blog series are twofold: Evaluate and demonstrate Code Clone Analysis Provide some concrete examples of refactoring code to eliminate duplication and improve the code-base Here are the initial results:   Code Clone Analysis has found: 129 Exact Matches 201 Strong Matches 300 Medium Matches 193 Weak Matches Also indicated is that there was a total of 45,181 potentially duplicated lines of code that could be eliminated through refactoring.  Considering the entire solution only has 109,763 lines of code, if true, the duplicates lines of code number is pretty significant. In the next post we’ll start examining some of the individual results and determine if they really do indicate a potential refactoring.

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  • Calculating instantaneous speed and acceleration for a simple Car software model

    - by Dylan
    I am trying to model a speedometer and tachometer for a simple software model of a car dashboard. I want this to be relatively simple, so for my purposes I won't likely simulate variables such as drag (or, assume that drag is a constant). But I would like to know the general formulas for: 1) Calculating the RPM, depending on a position of a graphical slider representing the accelerator. 2) Using this information to find the instantaneous speed (or, magnitude of instantaneous velocity?). I am not sure, in the case of 2), what other independent variables I need to consider. Do I need to consider the frequency of rotation of the wheels (assuming a fixed radius), in addition to the RPM? If anyone can give me a rough explanation plus relevant formulas, or alternatively direct me to other trusted resources online (I have had a hard time sifting through info and determining the accuracy), it would be much appreciated.

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  • How do I theme the maximized window buttons with Unity?

    - by Dylan McCall
    I use a custom Gtk theme along with the default Ambiance window controls. Using my theme, the Unity panel shows its very ugly default buttons when my window is maximized. Since I have the same window theme, I am assuming this comes from the Gtk theme. I tried copying and pasting a few things from Ambiance's gtkrc, but nothing has stuck so far. What must a theme author do to gain pretty looking window buttons in Unity's panel?

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