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• Correct way to protect a private API key when versioning a python application on a public git repo

  - by systempuntoout

  I would like to open-source a python project on Github but it contains an API key that should not be distributed. I guess there's something better than removing the key each time a "push" is committed to the repo. Imagine a simplified foomodule.py : import urllib2 API_KEY = 'XXXXXXXXX' urllib2.urlopen("http://example.com/foo?id=123%s" % API_KEY ).read() What i'm thinking is: Move the API_KEY in a second key.py module importing it on foomodule.py; i would then add key.py on .gitignore file. Same as 1 but using ConfigParser Do you know a good programmatic way to handle this scenario?

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• how to querry on the database without accessing the tables, correct the database but not the tables

  - by user287745

  used is c# sql vs 08 sql server 2005 express whenever and where ever an sql select statement is used, its always like select * from tablename or count statement is alsi like select count something from table name for selecting or doing anything on the tables, i would like to know which tables exits in my the database i am connected to! so like select alltablenames from database_name. please guide.

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• I make this for balancing paranthesis of equation but i think it is wrong check and correct it

  - by muhammadlodhi

  int main(){ char i,input[30],close,open; for(i=0;i<='.';i++){ printf("enter equation"); scanf("%c",input[i]); if(input[i]=='(') input++; input[i]=open; else if(input[i]==')') input[i]--; input[i]=close; else if(open[i]==close[i]) { printf("paranthesis are balance"); } else printf("paranthesis are not balance"); } getch(); return 0; }

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• Is my code a correct implementation of insertion sort?

  - by user1657171

  This code sorts correctly. Is this an insertion sort? import java.util.Scanner; public class InsertionSort { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter the number of elements: "); int count; count = sc.nextInt(); int[] a = new int[count]; System.out.println("Enter elements: "); for(int i = 0 ; i<count;i++){ a[i] = sc.nextInt(); } int j,temp; System.out.println("aftr insertion sort :"); for(int i = 1 ; i<count;i++){ j=i; while(j>0 && a[j-1] > a[j] ){ temp = a[j]; a[j] = a[j-1]; a[j-1] = temp; j--; } } for(int i = 0 ; i<count;i++){ System.out.print(a[i]+" "); } } }

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• Is this the correct way to set up has many with multiple associations?

  - by user323763

  I'm trying to set up a new project for a music site. I'm learning ROR and am a bit confused about how to make join models/tables. Does this look right? I have users, playlists, songs, and comments. Users can have multiple playlists. Users can have multiple comments on their profile. Playlists can have multiple songs. Playlists can have comments. Songs can have comments. class CreateTables < ActiveRecord::Migration def self.up create_table :users do |t| t.string :login t.string :email t.string :firstname t.string :lastname t.timestamps end create_table :playlists do |t| t.string :title t.text :description t.timestamps end create_table :songs do |t| t.string :title t.string :artist t.string :album t.integer :duration t.string :image t.string :source t.timestamps end create_table :comments do |t| t.string :title t.text :body t.timestamps end create_table :users_playlists do |t| t.integer :user_id t.integer :playlist_id t.timestamps end create_table :playlists_songs do |t| t.integer :playlist_id t.integer :song_id t.integer :position t.timestamps end create_table :users_comments do |t| t.integer :user_id t.integer :comment_id t.timestamps end create_table :playlists_comments do |t| t.integer :playlist_id t.integer :comment_id t.timestamps end create_table :songs_comments do |t| t.integer :song_id t.integer :comment_id t.timestamps end end def self.down drop_table :playlists drop_table :comments drop_table :songs_comments drop_table :users_comments drop_table :users_playlists drop_table :users drop_table :playlists drop_table :songs drop_table :playlists end end

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• Need help with tweaking a Dropdown with three options, user selects one - a hidden div appears with correct fields

  - by Jack

  Hello Again, I posted a question on here and got an answer within minutes I'm hoping the wizards on here can help me again. Okay so I'm using a script I found online to try and add this function to a shopping cart form. Here's the setup. I have a payment method dropdown with Visa, Mastercard and Bank Withdrawal as the options. For the credit cards I have one hidden div with a certain set of fields, and for the bank I have another hidden div. Each of the divs have named ID's - #payCredit and #payBank The css for both have margin: 0px and display: none; Here's a peice of javascript I used successfuly on a shipping address checkbox `function toggleLayer( whichLayer ) { var elem, vis; if( document.getElementById ) // this is the way the standards work elem = document.getElementById( whichLayer ); else if( document.all ) // this is the way old msie versions work elem = document.all[whichLayer]; else if( document.layers ) // this is the way nn4 works elem = document.layers[whichLayer]; vis = elem.style; // if the style.display value is blank we try to figure it out here if(vis.display==''&&elem.offsetWidth!=undefined&&elem.offsetHeight!=undefined) vis.display = (elem.offsetWidth!=0&&elem.offsetHeight!=0)?'block':'none'; vis.display = (vis.display==''||vis.display=='block')?'none':'block'; }` I was hoping I could change it slightly to meet my needs. Here's the dropdown <label>Payment Method:</label> <select name="payment" id="payment" class="dropdown3" style="width:8em"> <option selected="selected">Select</option> <option value="Visa" onclick="javascript:toggleLayer('payCredit');">Visa</option> <option value="MasterCard" onclick="javascript:toggleLayer('payCredit');">Mastercard</option> <option value="Direct" onclick="javascript:toggleLayer('payBank');">Direct Withdraw</option> </select></li> The current result is that it kinda works. I can open the dropdown and select Visa and it appears, if I select Visa again it disappears, if I select Visa and then select bank, both appear. You can see what i'm working on here - http://test.sharevetcare.com/bestfriends/cart3.html

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• Is this Leftist Tree piece of code from Wikipedia correct?

  - by they changed my name

  Link public Node merge(Node x, Node y) { if(x == null) return y; if(y == null) return x; // if this was a max height biased leftist tree, then the // next line would be: if(x.element < y.element) if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } x.rightChild = merge(x.rightChild, y); if(x.leftChild == null) { // left child doesn't exist, so move right child to the left side x.leftChild = x.rightChild; x.rightChild = null; x.s = 1; } else { // left child does exist, so compare s-values if(x.leftChild.s < x.rightChild.s) { Node temp = x.leftChild; x.leftChild = x.rightChild; x.rightChild = temp; } // since we know the right child has the lower s-value, we can just // add one to its s-value x.s = x.rightChild.s + 1; } return x; } What makes me ask this question is: if(x.element.compareTo(y.element) > 0) { // x.element > y.element Node temp = x; x = y; y = temp; } Isn't that just not gonna work, since the references are only switched inside the method?

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• Is this a correct syntax (c code found on wikipedia)?

  - by m4design

  I just found this code on wikipedia. Link: http://en.wikipedia.org/wiki/Sizeof#Use The code: /* the following code illustrates the use of sizeof * with variables and expressions (no parentheses needed), * and with type names (parentheses needed) */ char c; printf("%zu,%zu", sizeof c, sizeof(int)); It states that: "The z prefix should be used to print it, because the actual size can differ on each architecture." I tried it on my compiler, but it gives the following result: 'zu,zu'

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• .Net: Is this correct: objSample.dispose() means objSample = null ?

  - by odiseh

  Hi Just wanna to know objSample.dispose() is equal to objSample = null Indeed, can I get answer to such these questions from disassemblers? how? Thank you

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• How to get correct children ids using fields_for "parents[]", parent do |f| using f.fields_for :children, child ?

  - by Anatortoise House

  I'm editing multiple instances of a parent model in an index view in one form, as in Railscasts #198. Each parent has_many :children and accepts_nested_attributes_for :children, as in Railscasts #196 and #197 <%= form_tag %> <% for parent in @parents %> <%= fields_for "parents[]", parent do |f| <%= f.text_field :job %> <%= f.fields_for :children do |cf| %> <% cf.text_field :chore %> <% end %> <% end %> <% end %> <% end %> Given parent.id==1 f.text_field :job correctly generates <input id="parents_1_job" type="text" value="coding" size="30" name="parents[1][job]"> But cf.text_field :chore generates ids and names that don't have the parent index. id="parents_children_attributes_0_chore" name="parents[children_attributes][0][chore]" If I try passing the specific child object to f.fields_for like this: <% for child in parent.children %> <%= f.fields_for :children, child do |cf| %> <%= cf.text_field :chore %> <% end %> <% end %> I get the same. If I change the method from :children to "[]children" I get id="parents_1___children_chore" which gets the right parent_index but doesn't provide an array slot for the child index. "[]children[]" isn't right either: id="parents_1__children_3_chore" as I was expecting attributes_0_chore instead of 3_chore. Do I need to directly modify an attribute of the FormBuilder object, or subclass FormBuilder to make this work, or is there a syntax that fits this situation? Thanks for any thoughts.

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• How to submit the correct div elements (not the div that's hidden)?

  - by user356651

  Hello, I have the following code working fine but the problem is that it always submits the first div (article) even though it's hidden. My question is how do I submit the form and the elements in the form in the div that's shown? (if I select Music radiobutton, I want to submit the input elements of the Music Div not the Article div. Thanks. $(document).ready(function(){ $("input[name$='itemlist']").click(function() { var selection = $(this).val(); $("div.box").hide(); $("#"+selection).show(); }); }); <!--radio buttons--> <div id="articleselection"><input name="itemlist" type="radio" value="article" /> Article/Book </div> <div id="musicselection"><input name="itemlist" type="radio" value="music" /> Music</div> <!--article div starts--> <div id="article" class="box"> <table class="fieldgroup"> <tr><td>Journal Title: <input id="JournalTitle" name="JournalTitle" type="text" size="60" class="f-name" tabindex="1" value="JournalTitle"> </table> <table class="fieldgroup"> <tr><td>Article Author: <input id="ArticleAuthor" name="ArticleAuthor" type="text" size="40" class="f-name" tabindex="2" value="<"ArticleAuthor"></td></tr> </table> </div> <!--music div starts--> <div id="music" class="box"> <table class="fieldgroup"> <tr><td>Music Title: <input id="Music Title" name="Music Title" type="text" size="60" class="f-name" tabindex="1" value="Music Title"> </table> <table class="fieldgroup"> <tr><td> Music Author: <input id="MusicAuthor" name="Music Author" type="text" size="40" class="f-name" tabindex="2" value="<"MusicAuthor"></td></tr> </table> </div>

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• Databound Label text displays old data upon save. Re-open record and data is correct?

  - by Mike Hestness

  I have a windows forms application. I have a main form and I have a button on this form to set a "Qualified" date/time stamp. I have a Databound label control that I set the value when the user clicks the button. This date/time stamp is working as far as displaying but when you click the save button it either shows blank or the previous date/time. If you then then close the record and re-open it the new date/time value is displayed so the data is getting to the database it's just not persisting in the dataset as new data?? Not sure why the databinding isn't refreshing the value. I have noticed this behavior even if I use a textbox, same thing if I do it programatically. If I manually type in a value it persists?? Here is the code I'm using in the click event of my button: string result = string.Empty; string jobOrderID = UnitOfWork.MasterDSBS.MJOBO[0].JC_IDNO.ToString(); string timeNow = DateTime.Now.ToString(); //Call Web service to make the update RadServices.Service1 rsWeb = new RadServices.Service1(); result = rsWeb.SetQualifiedDate(timeNow, jobOrderID ); //Changed the qualified label text. _btnQualify.Text = "Qualified"; rlQualifiedDate.Text = timeNow;

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• C# getpixels() gets the correct value on xp and vista but is slightly off when used on windows 7

  - by user352288

  I have a C# program that works correctly on xp and vista but it needs to be used on windows 7, I have not been able to come up with a solution, it appears that getpixels just doesn't work right on windows 7, thanks.

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• What is the correct way to set size of elements of GUI?

  - by Roman

  I am using swing to create my GUI. J have a JFrame containing one main JPanel which, in its turn contain several JPanels which, in their turn, contain buttons. I would like to set certain sizes to mu buttons and JPanels. How does it work? Should I set sizes of my buttons and then the size of the JPanel and the JFrame will be set according to the buttons sizes? Or it works in the opposite direction? I set size for the JPanel and the size of the buttons will be set automatically?

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• Is this the correct syntax for 'array_unique()' in PHP?

  - by patrick

  I want to get rid of duplicates in my array but I'm still printing duplicates with this: $getuser = ltrim($top10['url'], " users/" ); //trim url to get user id $array[$i++] = $getuser; $dirty = $array; $clean = array_unique($dirty); print_r($clean)."<br />";

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• Wireless is detected, but not connecting. Ethernet works. How to correct the wireless address?

  - by Lucas

  I am running Ubuntu 14.04 with cable internet, and my wireless is detected and connected, but I cannot connect to the internet. I know the problem is with my machine because other machines are connecting to the same router just fine. I can connect via ethernet just fine as well. Here are some notable tests: ping 192.168.0.105 works with 0% packet loss, but ping 192.168.0.1 has 100% packet loss. When I plug in my ethernet, ping 192.168.0.1 works with 0% packet loss. My wireless name is tg, and the router ip is 192.168.0.1 (where I can enter username and password). I suspect that I need to change my wireless address from 192.168.0.105 to 192.168.0.1. Any suggestions on how to proceed? extra info: [lucas@lucas-ThinkPad-W520]/home/lucas$ iwconfig eth0 no wireless extensions. lo no wireless extensions. wlan0 IEEE 802.11abgn ESSID:"tg" Mode:Managed Frequency:2.462 GHz Access Point: 00:02:6F:83:F8:F4 Bit Rate=1 Mb/s Tx-Power=15 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=62/70 Signal level=-48 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:52 Invalid misc:166 Missed beacon:0 [lucas@lucas-ThinkPad-W520]/home/lucas$ ifconfig eth0 Link encap:Ethernet HWaddr f0:de:f1:b2:53:53 inet addr:192.168.0.100 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::f2de:f1ff:feb2:5353/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:980003 errors:0 dropped:0 overruns:0 frame:0 TX packets:498384 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1320506168 (1.3 GB) TX bytes:59780591 (59.7 MB) Interrupt:20 Memory:f3a00000-f3a20000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:21927 errors:0 dropped:0 overruns:0 frame:0 TX packets:21927 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:1781719 (1.7 MB) TX bytes:1781719 (1.7 MB) wlan0 Link encap:Ethernet HWaddr 24:77:03:29:8f:dc inet addr:192.168.0.105 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::2677:3ff:fe29:8fdc/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:11828 errors:0 dropped:0 overruns:0 frame:0 TX packets:15444 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:4855662 (4.8 MB) TX bytes:2250585 (2.2 MB) [lucas@lucas-ThinkPad-W520]/home/lucas$ lspci -nn | grep 0280 03:00.0 Network controller [0280]: Intel Corporation Centrino Ultimate-N 6300 [8086:4238] (rev 3e) [lucas@lucas-ThinkPad-W520]/home/lucas$ rfkill list 0: hci0: Bluetooth Soft blocked: no Hard blocked: no 1: tpacpi_bluetooth_sw: Bluetooth Soft blocked: no Hard blocked: no 2: phy0: Wireless LAN Soft blocked: no Hard blocked: no with ethernet unplugged: [lucas@lucas-ThinkPad-W520]/home/lucas$ route -n | grep UG 0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 wlan0 with ethernet plugged in: [lucas@lucas-ThinkPad-W520]/home/lucas$ route -n | grep UG 0.0.0.0 192.168.0.1 0.0.0.0 UG 0 0 0 eth0 [lucas@lucas-ThinkPad-W520]/home/lucas$ nm-tool NetworkManager Tool State: connected (global) - Device: wlan0 [tg] ---------------------------------------------------------- Type: 802.11 WiFi Driver: iwlwifi State: connected Default: no HW Address: 24:77:03:29:8F:DC Capabilities: Speed: 52 Mb/s Wireless Properties WEP Encryption: yes WPA Encryption: yes WPA2 Encryption: yes Wireless Access Points (* = current AP) tatum: Infra, 40:8B:07:D8:A5:04, Freq 2437 MHz, Rate 54 Mb/s, Strength 42 W PA WPA2 ums: Infra, 00:20:A6:72:52:BF, Freq 2437 MHz, Rate 54 Mb/s, Strength 59 Alpha 40: Infra, 28:CF:E9:86:59:5D, Freq 5260 MHz, Rate 54 Mb/s, Strength 30 W PA WPA2 thepromiselan: Infra, 58:6D:8F:51:E5:54, Freq 2452 MHz, Rate 54 Mb/s, Strength 34 $ PA WPA2 xfinitywifi: Infra, 06:1D:D5:84:27:A0, Freq 2437 MHz, Rate 54 Mb/s, Strength 52 *tg: Infra, 00:02:6F:83:F8:F4, Freq 2462 MHz, Rate 54 Mb/s, Strength 73 W PA2 ums: Infra, 00:20:A6:A1:9F:25, Freq 2452 MHz, Rate 54 Mb/s, Strength 44 BRIAN-PC_Network:Infra, 20:AA:4B:DD:93:D6, Freq 2462 MHz, Rate 54 Mb/s, Strength 35 W PA2 HOME-C0F8: Infra, 44:32:C8:D2:C0:F8, Freq 2412 MHz, Rate 54 Mb/s, Strength 40 W PA WPA2 abcsexy: Infra, 28:28:5D:27:5D:85, Freq 2412 MHz, Rate 54 Mb/s, Strength 27 W PA WPA2 IPv4 Settings: Address: 192.168.0.105 Prefix: 24 (255.255.255.0) Gateway: 192.168.0.1 DNS: 192.168.0.1 - Device: eth0 [Wired connection 1] ------------------------------------------- Type: Wired Driver: e1000e State: connected Default: yes HW Address: F0:DE:F1:B2:53:53 Capabilities: Carrier Detect: yes Speed: 100 Mb/s Wired Properties Carrier: on IPv4 Settings: Address: 192.168.0.100 Prefix: 24 (255.255.255.0) Gateway: 192.168.0.1 DNS: 192.168.0.1

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• I have done everything correct on my asp.net website, re: SEO; why aren't google backlinks showing?

  - by Jason Weber

  I recently implemented many SEO techniques for a company on their asp.net website; in 6 months, we jumped from a PR1 to a PR3. But I'm having issues with google backlinking. Here are some of the things I've done: Not only did I set up their own Google+ page 6 months ago, I update it pretty much daily with links, pictures, etc., and I blog about it on my own personal Google+ page and post links, etc. ... They have their own Twitter, Facebook, YouTube, and all are updated almost daily. I've listed in as many quality, relevant directories as possible 6 months ago; I've avoided link farms. The site is solid SEO-wise. Key-phrase rich URLs, schema.org & rich snippets. No duplicate content ... www or non-www 301's, trailing slashes, etc. ... all taken care of. Probably a ton of other things, but basically, the site is all set, SEO-wise. Here's what's confounding: When I do a link:www.example.com in Bing/Yahoo, it shows many backlinks. When I do a link:www.example.com in google, it shows up 0 links. Or when I use a site-ranker like Web Site Rank Tool it's showing 0 backlinks from Google. Any suggestions would be appreciated!

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• (12.04 vm/server) Dist-upgrade to 3.2.0-63 wants to remove git (1.9.2) and git-core - is that the correct behavior?

  - by YellowShark

  was wondering if anyone knows dist-upgrade wants to remove git. FWIW, this is a pretty simple box, mainly used for web dev. $ uname -a Linux precise64 3.2.0-61-generic #93-Ubuntu SMP Fri May 2 21:31:50 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux $ git --version git version 1.9.2 $ sudo apt-get dist-upgrade Reading package lists... Done Building dependency tree Reading state information... Done Calculating upgrade... Done The following packages will be REMOVED: git git-core The following NEW packages will be installed: linux-headers-3.2.0-63 linux-headers-3.2.0-63-generic linux-image-3.2.0-63-generic The following packages will be upgraded: git-man linux-headers-server linux-image-server linux-server phpmyadmin 5 upgraded, 3 newly installed, 2 to remove and 0 not upgraded. Need to get 58.8 MB of archives. After this operation, 199 MB of additional disk space will be used. Do you want to continue [Y/n]?

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• Stop Excel from changing cell contents, ever

  - by Enable Manual-Correct

  I work with card numbers, like credit card and ID numbers. We do not do any calculations with card numbers, obviously. They are "text." I format them as text, I type them like text. I know how that works. Excel doesn't care. 16 digit card numbers get their last digit turned into a zero, changed into scientific notation, stupid stuff that I did not tell Excel to do. I need to do things like Find/Remove spaces from cells in files downloaded from our currently imperfect web-system. The system sends me files with 16 digit numbers, cells formatted as text, but due to bugs there are spaces at the end. I do Find/Remove all spaces and all my card numbers are transformed into scientific notation and the last digit turned into a 0. THEY ARE TEXT, they are formatted as text, I yelled into the screen that they are text, why does Excel refuse to acknowledge that they are text? (I would rather find a way to stop Excel's action than find a way to tell our programmers to put an apostrophe in every cell) How do I make it so that Excel just STOPS doing anything that I didn't tell it to do? Or at least stop it from doing anything to numbers it doesn't like. Maybe I can write a macro for whenever it discovers "Uhoh I should change that number to something different!" I'll make it format that cell to text a thousand times instead. Give me an error when I try calculating with a number larger than 15 digits, make my computer explode violently, that's fine. Just stop changing the numbers. Is it possible? I have many thousands of numbers that need changing in many different scenarios. I just want to stop it from trying to help. I can't understand why that would be difficult. I have 2007, but answers for other versions would be great as well. Thank you!

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• Available Coroutine Libraries in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7? Edited to add: Just to ensure that confusion is contained, this is a related question to my other one, but not the same. This one is looking for an existing implementation in a bid to avoid reinventing the wheel unnecessarily. The other one is a question relating to how one would go about implementing coroutines in Java should this question prove unanswerable. The intent is to keep different questions on different threads.

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• What does the `forall` keyword in Haskell/GHC do?

  - by JUST MY correct OPINION

  I've been banging my head on this one for (quite literally) years now. I'm beginning to kinda/sorta understand how the foreach keyword is used in so-called "existential types" like this: data ShowBox = forall s. Show s => SB s (This despite the confusingly-worded explanations of it in the fragments found all around the web.) This is only a subset, however, of how foreach is used and I simply cannot wrap my mind around its use in things like this: runST :: forall a. (forall s. ST s a) -> a Or explaining why these are different: foo :: (forall a. a -> a) -> (Char,Bool) bar :: forall a. ((a -> a) -> (Char, Bool)) Or the whole RankNTypes stuff that breaks my brain when "explained" in a way that makes me want to do that Samuel L. Jackson thing from Pulp Fiction. (Don't follow that link if you're easily offended by strong language.) The problem, really, is that I'm a dullard. I can't fathom the chicken scratchings (some call them "formulae") of the elite mathematicians that created this language seeing as my university years are over two decades behind me and I never actually had to put what I learnt into use in practice. I also tend to prefer clear, jargon-free English rather than the kinds of language which are normal in academic environments. Most of the explanations I attempt to read on this (the ones I can find through search engines) have these problems: They're incomplete. They explain one part of the use of this keyword (like "existential types") which makes me feel happy until I read code that uses it in a completely different way (like runST, foo and bar above). They're densely packed with assumptions that I've read the latest in whatever branch of discrete math, category theory or abstract algebra is popular this week. (If I never read the words "consult the paper whatever for details of implementation" again, it will be too soon.) They're written in ways that frequently turn even simple concepts into tortuously twisted and fractured grammar and semantics. (I suspect that the last two items are the biggest problem. I wouldn't know, though, since I'm too much a dullard to comprehend them.) It's been asked why Haskell never really caught on in industry. I suspect, in my own humble, unintelligent way, that my experience in figuring out one stupid little keyword -- a keyword that is increasingly ubiquitous in the libraries being written these days -- are also part of the answer to that question. It's hard for a language to catch on when even its individual keywords cause years-long quests to comprehend. Years-long quests which end in failure. So... On to the actual question. Can anybody completely explain the foreach keyword in clear, plain English (or, if it exists somewhere, point to such a clear explanation which I've missed) that doesn't assume I'm a mathematician steeped in the jargon?

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• Coroutines in Java

  - by JUST MY correct OPINION

  I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7?

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• Implementing coroutines in Java

  - by JUST MY correct OPINION

  This question is related to my question on existing coroutine implementations in Java. If, as I suspect, it turns out that there is no full implementation of coroutines currently available in Java, what would be required to implement them? As I said in that question, I know about the following: You can implement "coroutines" as threads/thread pools behind the scenes. You can do tricksy things with JVM bytecode behind the scenes to make coroutines possible. The so-called "Da Vinci Machine" JVM implementation has primitives that make coroutines doable without bytecode manipulation. There are various JNI-based approaches to coroutines also possible. I'll address each one's deficiencies in turn. Thread-based coroutines This "solution" is pathological. The whole point of coroutines is to avoid the overhead of threading, locking, kernel scheduling, etc. Coroutines are supposed to be light and fast and to execute only in user space. Implementing them in terms of full-tilt threads with tight restrictions gets rid of all the advantages. JVM bytecode manipulation This solution is more practical, albeit a bit difficult to pull off. This is roughly the same as jumping down into assembly language for coroutine libraries in C (which is how many of them work) with the advantage that you have only one architecture to worry about and get right. It also ties you down to only running your code on fully-compliant JVM stacks (which means, for example, no Android) unless you can find a way to do the same thing on the non-compliant stack. If you do find a way to do this, however, you have now doubled your system complexity and testing needs. The Da Vinci Machine The Da Vinci Machine is cool for experimentation, but since it is not a standard JVM its features aren't going to be available everywhere. Indeed I suspect most production environments would specifically forbid the use of the Da Vinci Machine. Thus I could use this to make cool experiments but not for any code I expect to release to the real world. This also has the added problem similar to the JVM bytecode manipulation solution above: won't work on alternative stacks (like Android's). JNI implementation This solution renders the point of doing this in Java at all moot. Each combination of CPU and operating system requires independent testing and each is a point of potentially frustrating subtle failure. Alternatively, of course, I could tie myself down to one platform entirely but this, too, makes the point of doing things in Java entirely moot. So... Is there any way to implement coroutines in Java without using one of these four techniques? Or will I be forced to use the one of those four that smells the least (JVM manipulation) instead?

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• How difficult is it for an old-school programmer to pick up an FPGA kit and make something useful wi

  - by JUST MY correct OPINION

  I'm an old, old, old coder. (How old? I've used paper tape in anger.) I've programmed in a lot of languages and under a lot of paradigms (spaghetti, structured, object-oriented, functional and a smattering of logical). I'm getting bored. FPGAs look interesting to me. I have the crazy notion of resurrecting some of the ancient hardware I worked on in the days using FPGAs. I know this can be done because I've seen PDP-10 and PDP-11 implementations in FPGAs. I'd like to do the same for a few machines that are perhaps not as popular as those two, however. While I am an old, old coder, what I am not is an electronics or computer systems engineer. I'll be learning from scratch if I go down this path. My question, therefore, is two-fold: How difficult will it be for this old dinosaur to pick up and learn FPGAs to the point that interesting (not necessarily practical -- more from a hobbyist perspective) projects can be made? What should I start with learning-wise to go down this path? I know where to get FPGA kits, but I haven't found anything like "FPGAs for Complete Dinosaurs" yet anywhere out there.

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• Wine is no longer able to initialize OpenGL

  - by nebukadnezzar

  Since a while, wine is no longer able to initialize OpenGL on my 64bit Linux. This is by no means a unique problem to me- Lots of people with nvidia cards running 64bit linux seem to have this problem with wine on oneiric: http://forum.winehq.org/viewtopic.php?p=66856&sid=9d6e5ad628ee6fb6e5ef04577275daed http://forum.pinguyos.com/Thread-Wine-OpenGl-Problem https://bbs.archlinux.org/viewtopic.php?id=137696 And while some launchpad bug reports say one should use this workaround: LD_PRELOAD=/usr/lib32/nvidia-current/libGL.so.1 wine <app> It unfortunately does not solve the problem at all for me; That is, if i'd run CS:S, the game will run just fine for a while, but will abort after some time, including a range of GLSL-related errors. Here the startup errors from simply running steam: + wine steam.exe fixme:process:GetLogicalProcessorInformation ((nil),0x33e488): stub [.. snip ...] fixme:dwmapi:DwmSetWindowAttribute (0x1009a, 3, 0x33d384, 4) stub fixme:dwmapi:DwmSetWindowAttribute (0x1009a, 4, 0x33d374, 4) stub err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! [... this error is being reported a few dozen times, so snip again ...] err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! err:wgl:is_extension_supported No OpenGL extensions found, check if your OpenGL setup is correct! fixme:iphlpapi:NotifyAddrChange (Handle 0x47cdba8, overlapped 0x45dba80): stub fixme:winsock:WSALookupServiceBeginW (0x47cdbc8 0x00000ff0 0x47cdbc4) Stub! [... snip ...] Here are the errors reported while running, and after running (because the log is huge-ish, it's pasted elsewhere): http://paste.ubuntu.com/901925/ Now, 32bit OpenGL works just fine; The 32bit executables of Nexuiz, for example, work just fine. That being said, I'm suspecting that this is a problem of wine itself. I've already manually built the git version of wine, to no avail. So what's going on? Is something broken? How do I check (correctly) whether something is broken? How do I solve this?

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