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• MODx character encoding

  - by Piet

  Ahhh character encodings. Don’t you just love them? Having character issues in MODx? Then probably the MODx manager character encoding, the character encoding of the site itself, your database’s character encoding, or the encoding MODx/php uses to talk to MySQL isn’t correct. The Website Encoding Your MODx site’s character encoding can be configured in the manager under Tools/Configuration/Site/Character encoding. This is the encoding your website’s visitors will get. The Manager’s Encoding The manager’s encoding can be changed by setting $modx_manager_charset at manager/includes/lang/<language>.inc.php like this (for example): $modx_manager_charset = 'iso-8859-1'; To find out what language you’re using (and thus was file you need to change), check Tools/Configuration/Site/Language (1 line above the character encoding setting). This needs to be the same encoding as your site. You can’t have your manager in utf8 and your site in iso-8859-1. Your Database’s Encoding The charset MODx/php uses to talk to your database can be set by changing $database_connection_charset in manager/includes/config.inc.php. This needs to be the same as your database’s charset. Make sure you use the correct corresponding charset, for iso-8859-1 you need to use ‘latin1′. Utf8 is just utf8. Example: $database_connection_charset = 'latin1'; Now, if you check Reports/System info, the ‘Database Charset’ might say something else. This is because the mysql variable ‘character_set_database’ is displayed here, which contains the character set used by the default database and not the one for the current database/connection. However, if you’d change this to display ‘character_set_connection’, it could still say something else because the ’set character set’ statement used by MODx doesn’t change this value either. The ’set names’ statement does, but since it turns out my MODx install works now as expected I’ll just leave it at this before I get a headache. If I saved you a potential headache or you think I’m totally wrong or overlooked something, let me know in the comments. btw: I want to be able to use a real editor with MODx. Somehow.

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• Deleting elements from stl set while iterating through it does not invalidate the iterators.

  - by pedromanoel

  I need to go through a set and remove elements that meet a predefined criteria. This is the test code I wrote: #include <set> #include <algorithm> void printElement(int value) { std::cout << value << " "; } int main() { int initNum[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }; std::set<int> numbers(initNum, initNum + 10); // print '0 1 2 3 4 5 6 7 8 9' std::for_each(numbers.begin(), numbers.end(), printElement); std::set<int>::iterator it = numbers.begin(); // iterate through the set and erase all even numbers for (; it != numbers.end(); ++it) { int n = *it; if (n % 2 == 0) { // wouldn't invalidate the iterator? numbers.erase(it); } } // print '1 3 5 7 9' std::for_each(numbers.begin(), numbers.end(), printElement); return 0; } At first, I thought that erasing an element from the set while iterating through it would invalidate the iterator, and the increment at the for loop would have undefined behavior. Even though, I executed this test code and all went well, and I can't explain why. My question: Is this the defined behavior for std sets or is this implementation specific? I am using gcc 4.3.3 on ubuntu 10.04 (32-bit version), by the way. Thanks!

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• Creating Property Set Expression Trees In A Developer Friendly Way

  - by Paulo Morgado

  In a previous post I showed how to create expression trees to set properties on an object. The way I did it was not very developer friendly. It involved explicitly creating the necessary expressions because the compiler won’t generate expression trees with property or field set expressions. Recently someone contacted me the help develop some kind of command pattern framework that used developer friendly lambdas to generate property set expression trees. Simply putting, given this entity class: public class Person { public string Name { get; set; } } The person in question wanted to write code like this: var et = Set((Person p) => p.Name = "me"); Where et is the expression tree that represents the property assignment. So, if we can’t do this, let’s try the next best thing that is splitting retrieving the property information from the retrieving the value to assign o the property: var et = Set((Person p) => p.Name, () => "me"); And this is something that the compiler can handle. The implementation of Set receives an expression to retrieve the property information from and another expression the retrieve the value to assign to the property: public static Expression<Action<TEntity>> Set<TEntity, TValue>( Expression<Func<TEntity, TValue>> propertyGetExpression, Expression<Func<TValue>> valueExpression) The implementation of this method gets the property information form the body of the property get expression (propertyGetExpression) and the value expression (valueExpression) to build an assign expression and builds a lambda expression using the same parameter of the property get expression as its parameter: public static Expression<Action<TEntity>> Set<TEntity, TValue>( Expression<Func<TEntity, TValue>> propertyGetExpression, Expression<Func<TValue>> valueExpression) { var entityParameterExpression = (ParameterExpression)(((MemberExpression)(propertyGetExpression.Body)).Expression); return Expression.Lambda<Action<TEntity>>( Expression.Assign(propertyGetExpression.Body, valueExpression.Body), entityParameterExpression); } And now we can use the expression to translate to another context or just compile and use it: var et = Set((Person p) => p.Name, () => name); Console.WriteLine(person.Name); // Prints: p => (p.Name = “me”) var d = et.Compile(); d(person); Console.WriteLine(person.Name); // Prints: me It can even support closures: var et = Set((Person p) => p.Name, () => name); Console.WriteLine(person.Name); // Prints: p => (p.Name = value(<>c__DisplayClass0).name) var d = et.Compile(); name = "me"; d(person); Console.WriteLine(person.Name); // Prints: me name = "you"; d(person); Console.WriteLine(person.Name); // Prints: you Not so useful in the intended scenario (but still possible) is building an expression tree that receives the value to assign to the property as a parameter: public static Expression<Action<TEntity, TValue>> Set<TEntity, TValue>(Expression<Func<TEntity, TValue>> propertyGetExpression) { var entityParameterExpression = (ParameterExpression)(((MemberExpression)(propertyGetExpression.Body)).Expression); var valueParameterExpression = Expression.Parameter(typeof(TValue)); return Expression.Lambda<Action<TEntity, TValue>>( Expression.Assign(propertyGetExpression.Body, valueParameterExpression), entityParameterExpression, valueParameterExpression); } This new expression can be used like this: var et = Set((Person p) => p.Name); Console.WriteLine(person.Name); // Prints: (p, Param_0) => (p.Name = Param_0) var d = et.Compile(); d(person, "me"); Console.WriteLine(person.Name); // Prints: me d(person, "you"); Console.WriteLine(person.Name); // Prints: you The only caveat is that we need to be able to write code to read the property in order to write to it.

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• Running a Mongo Replica Set on Azure VM Roles

  - by Elton Stoneman

  Originally posted on: http://geekswithblogs.net/EltonStoneman/archive/2013/10/15/running-a-mongo-replica-set-on-azure-vm-roles.aspxSetting up a MongoDB Replica Set with a bunch of Azure VMs is straightforward stuff. Here’s a step-by-step which gets you from 0 to fully-redundant 3-node document database in about 30 minutes (most of which will be spent waiting for VMs to fire up). First, create yourself 3 VM roles, which is the minimum number of nodes you need for high availability. You can use any OS that Mongo supports. This guide uses Windows but the only difference will be the mechanism for starting the Mongo service when the VM starts (Windows Service, daemon etc.) While the VMs are provisioning, download and install Mongo locally, so you can set up the replica set with the Mongo shell. We’ll create our replica set from scratch, doing one machine at a time (if you have a single node you want to upgrade to a replica set, it’s the same from step 3 onwards): 1. Setup Mongo Log into the first node, download mongo and unzip it to C:. Rename the folder to remove the version – so you have c:\MongoDB\bin etc. – and create a new folder for the logs, c:\MongoDB\logs. 2. Setup your data disk When you initialize a node in a replica set, Mongo pre-allocates a whole chunk of storage to use for data replication. It will use up to 5% of your data disk, so if you use a Windows VM image with a defsault 120Gb disk and host your data on C:, then Mongo will allocate 6Gb for replication. And that takes a while. Instead you can create yourself a new partition by shrinking down the C: drive in Computer Management, by say 10Gb, and then creating a new logical disk for your data from that spare 10Gb, which will be allocated as E:. Create a new folder, e:\data. 3. Start Mongo When that’s done, start a command line, point to the mongo binaries folder, install Mongo as a Windows Service, running in replica set mode, and start the service: cd c:\mongodb\bin mongod -logpath c:\mongodb\logs\mongod.log -dbpath e:\data -replSet TheReplicaSet –install net start mongodb 4. Open the ports Mongo uses port 27017 by default, so you need to allow access in the machine and in Azure. In the VM, open Windows Firewall and create a new inbound rule to allow access via port 27017. Then in the Azure Management Console for the VM role, under the Configure tab add a new rule, again to allow port 27017. 5. Initialise the replica set Start up your local mongo shell, connecting to your Azure VM, and initiate the replica set: c:\mongodb\bin\mongo sc-xyz-db1.cloudapp.net rs.initiate() This is the bit where the new node (at this point the only node) allocates its replication files, so if your data disk is large, this can take a long time (if you’re using the default C: drive with 120Gb, it may take so long that rs.initiate() never responds. If you’re sat waiting more than 20 minutes, start another instance of the mongo shell pointing to the same machine to check on it). Run rs.conf() and you should see one node configured. 6. Fix the host name for the primary – *don’t miss this one* For the first node in the replica set, Mongo on Windows doesn’t populate the full machine name. Run rs.conf() and the name of the primary is sc-xyz-db1, which isn’t accessible to the outside world. The replica set configuration needs the full DNS name of every node, so you need to manually rename it in your shell, which you can do like this: cfg = rs.conf() cfg.members[0].host = ‘sc-xyz-db1.cloudapp.net:27017’ rs.reconfig(cfg) When that returns, rs.conf() will have your full DNS name for the primary, and the other nodes will be able to connect. At this point you have a working database, so you can start adding documents, but there’s no replication yet. 7. Add more nodes For the next two VMs, follow steps 1 through to 4, which will give you a working Mongo database on each node, which you can add to the replica set from the shell with rs.add(), using the full DNS name of the new node and the port you’re using: rs.add(‘sc-xyz-db2.cloudapp.net:27017’) Run rs.status() and you’ll see your new node in STARTUP2 state, which means its initializing and replicating from the PRIMARY. Repeat for your third node: rs.add(‘sc-xyz-db3.cloudapp.net:27017’) When all nodes are finished initializing, you will have a PRIMARY and two SECONDARY nodes showing in rs.status(). Now you have high availability, so you can happily stop db1, and one of the other nodes will become the PRIMARY with no loss of data or service. Note – the process for AWS EC2 is exactly the same, but with one important difference. On the Azure Windows Server 2012 base image, the MongoDB release for 64-bit 2008R2+ works fine, but on the base 2012 AMI that release keeps failing with a UAC permission error. The standard 64-bit release is fine, but it lacks some optimizations that are in the 2008R2+ version.

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• How to get correct Set-Cookie headers for NSHTTPURLResponse?

  - by overboming

  I want to use the following code to login to a website which returns its cookie information in the following manner: Set-Cookie: 19231234 Set-Cookie: u2am1342340 Set-Cookie: owwjera I'm using the following code to log in to the site, but the print statement at the end doesn't output anything about "set-cookie". On Snow leopard, the library seems to automatically pick up the cookie for this site and later connections sent out is set with correct "cookie" headers. But on leopard, it doesn't work that way, so is that a trigger for this "remember the cookie for certain root url" behavior? NSMutableURLRequest *request = [[[NSMutableURLRequest alloc] init] autorelease]; [request setURL:[NSURL URLWithString:uurl]]; [request setHTTPMethod:@"POST"]; [request setValue:postLength forHTTPHeaderField:@"Content-Length"]; [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"]; [request setValue:@"keep-live" forHTTPHeaderField:@"Connection"]; [request setValue:@"300" forHTTPHeaderField:@"Keep-Alive"]; [request setHTTPShouldHandleCookies:YES]; [request setHTTPBody:postData]; [request setTimeoutInterval:10.0]; NSData *urlData; NSHTTPURLResponse *response; NSError *error; urlData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error]; NSLog(@"response dictionary %@",[response allHeaderFields]);

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• Fastest way to put contents of Set<String> to a single String with words separated by a whitespace?

  - by Lars Andren

  I have a few Set<String>s and want to transform each of these into a single String where each element of the original Set is separated by a whitespace " ". A naive first approach is doing it like this Set<String> set_1; Set<String> set_2; StringBuilder builder = new StringBuilder(); for (String str : set_1) { builder.append(str).append(" "); } this.string_1 = builder.toString(); builder = new StringBuilder(); for (String str : set_2) { builder.append(str).append(" "); } this.string_2 = builder.toString(); Can anyone think of a faster, prettier or more efficient way to do this?

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• how to compare each other elements in std set?

  - by vinnitu

  i mean i have set set from "one", "two", "three" how to get all pairs from it one - two one - three two - three ?

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• How to remove an element from set using Iterator?

  - by ankit

  I have a scenario that I am iterating over a set using iterator. Now I want to remove 1st element while my iterator is on 2nd element. How can I do it. I dont want to convert this set to list and using listIterator. I dont want to collect all objects to be removed in other set and call remove all sample code. Set<MyObject> mySet = new HashSet<MyObject>(); mySet.add(MyObject1); mySet.add(MyObject2); ... Iterator itr = mySet.iterator(); while(itr.hasNext()) { // Now iterator is at second element and I want to remove first element }

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• how to set different wallpapers in ubuntu workspaces

  - by Steve

  I'm having an issues trying to customize ubuntu workspaces in the gnome environment. Assuming the default four workspaces aka desktops, how can one have a different wallpaper for each one? When I go to an individual workspace to set its wallpaper, all of the workspaces use it. So if I set: wallpaper B on workspace 2 wallpaper C on workspace 3 What will happen is that all the workspaces will default to the last wallpaper set no matter which workspace it was set in. What's even weirder is that the very first wallpaper set upon using it for the very first time is what shows up when i call up the Workspaces tool. Even though once I settle upon a workspace, no matter which one, the original wallpaper disappears and the last wallpaper set is the one that always shows up.

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• Bin packing part 6: Further improvements

  - by Hugo Kornelis

  In part 5 of my series on the bin packing problem, I presented a method that sits somewhere in between the true row-by-row iterative characteristics of the first three parts and the truly set-based approach of the fourth part. I did use iteration, but each pass through the loop would use a set-based statement to process a lot of rows at once. Since that statement is fairly complex, I am sure that a single execution of it is far from cheap – but the algorithm used is efficient enough that the entire...(read more)

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• Don Knuth and MMIXAL vs. Chuck Moore and Forth -- Algorithms and Ideal Machines -- was there cross-pollination / influence in their ideas / work?

  - by AKE

  Question: To what extent is it known (or believed) that Chuck Moore and Don Knuth had influence on each other's thoughts on ideal machines, or their work on algorithms? I'm interested in citations, interviews, articles, links, or any other sort of evidence. It could also be evidence of the form of A and B here suggest that Moore might have borrowed or influenced C and D from Knuth here, or vice versa. (Opinions are of course welcome, but references / links would be better!) Context: Until fairly recently, I have been primarily familiar with Knuth's work on algorithms and computing models, mostly through TAOCP but also through his interviews and other writings. However, the more I have been using Forth, the more I am struck by both the power of a stack-based machine model, and the way in which the spareness of the model makes fundamental algorithmic improvements more readily apparent. A lot of what Knuth has done in fundamental analysis of algorithms has, it seems to me, a very similar flavour, and I can easily imagine that in a parallel universe, Knuth might perhaps have chosen Forth as his computing model. That's the software / algorithms / programming side of things. When it comes to "ideal computing machines", Knuth in the 70s came up with the MIX computer model, and then, collaborating with designers of state-of-the-art RISC chips through the 90s, updated this with the modern MMIX model and its attendant assembly language MMIXAL. Meanwhile, Moore, having been using and refining Forth as a language, but using it on top of whatever processor happened to be in the computer he was programming, began to imagine a world in which the efficiency and value of stack-based programming were reflected in hardware. So he went on in the 80s to develop his own stack-based hardware chips, defining the term MISC (Minimal Instruction Set Computers) along the way, and ending up eventually with the first Forth chip, the MuP21. Both are brilliant men with keen insight into the art of programming and algorithms, and both work at the intersection between algorithms, programs, and bare metal hardware (i.e. hardware without the clutter of operating systems). Which leads me to the headlined question... Question:To what extent is it known (or believed) that Chuck Moore and Don Knuth had influence on each other's thoughts on ideal machines, or their work on algorithms?

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• How to set a Static Route on a Storage Node

  - by csoto

  To set up a host route to an IP address, here are the procedures for BUI and CLI. You need to know the destination, mask, interface and network. Note that, in this case, the values are just examples. CLI - Log into CLI and run the commands below: configuration net routing create set family=IPv4 set destination=203.246.186.80 set mask=32 set gateway=192.168.100.230 set interface=igb0 commit BUI - Log in to the web ui of the ZFSSA NAS head - Click Configuration - Network - Routing - (+) - In the popup window that will be displayed, enter the values accordingly on the popup window shown on the screenshot below: Any of the two above procedures should get your desired route in place.

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• Ray-box Intersection Theory

  - by Myx

  Hello: I wish to determine the intersection point between a ray and a box. The box is defined by its min 3D coordinate and max 3D coordinate and the ray is defined by its origin and the direction to which it points. Currently, I am forming a plane for each face of the box and I'm intersecting the ray with the plane. If the ray intersects the plane, then I check whether or not the intersection point is actually on the surface of the box. If so, I check whether it is the closest intersection for this ray and I return the closest intersection. The way I check whether the plane-intersection point is on the box surface itself is through a function bool PointOnBoxFace(R3Point point, R3Point corner1, R3Point corner2) { double min_x = min(corner1.X(), corner2.X()); double max_x = max(corner1.X(), corner2.X()); double min_y = min(corner1.Y(), corner2.Y()); double max_y = max(corner1.Y(), corner2.Y()); double min_z = min(corner1.Z(), corner2.Z()); double max_z = max(corner1.Z(), corner2.Z()); if(point.X() >= min_x && point.X() <= max_x && point.Y() >= min_y && point.Y() <= max_y && point.Z() >= min_z && point.Z() <= max_z) return true; return false; } where corner1 is one corner of the rectangle for that box face and corner2 is the opposite corner. My implementation works most of the time but sometimes it gives me the wrong intersection. I was wondering if the way I'm checking whether the intersection point is on the box is correct or if I should use some other algorithm. Thanks.

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• Database theory - relationship between two tables

  - by iansinke

  I have a database with two tables - let's call them Foo and Bar. Each foo may be related to any number of bars, and each bar may be related to any number of foos. I want to be able to retrieve, with one query, the foos that are associated with a certain bar, and the bars that are associated with a certain foo. My question is, what is the best way of recording these relationships? Should I have a separate table with records of each relationship (e.g. two columns, foo and bar)? Should the foo table have a column for a list of bars, and vice versa? Is there another option that I'm overlooking? I'm using SQL Server, if that makes a difference.

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• Traceroute Theory

  - by Hamza Yerlikaya

  I am toying with trace route, my application send a ICMP echo request with a ttl of 0 every time i receive a time exceeded message i increment the ttl by one and resent the package, but what happens is I have 2 routers on my network i can trace the route through these router but third hop always ends up being one of the open dns servers same ip every time no matter where i traceroute to. AFAIK this is the correct traceroute implementation, can anyone tell me what i am doing wrong?

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• Discrete mathematics problem - Probability theory and counting

  - by Mohammad

  Hello All, I'm taking a discrete mathematics course, and I encountered a question and I need your help. I don't know if this is the right place for that though :) It says: Each user on a computer system has a password, which is six to eight characters long, where each character is an uppercase letter or a digit. Each password must contain at least one digit. How many possible passwords are there? The book solves this by adding the probabilities of having six,seven and eight characters long password. However, when he solves for probability of six characters he does this P6 = 36^6 - 26^6 and does P7 = 36^7 - 26^7 and P8 = 36^8 - 26^8 and then add them all I understand the solution, but my question is why doesn't calculating, P6 = 10*36^5 and the same for P7 and P8, work? 10 for the digit and 36 for the alphanumeric? Also, if anyone could give me another solution, other than the one in the book. Thank you very much :)

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• Theory of Game Interface Design

  - by anon

  Anyone know of a good book on Game Interface Design (not game play mechanics; the actual UI). I'm particular interested in theories of cognition, and how game interfaces are designed to allow the enduser efficient communication with the game (whether it in FPS, RTS, or so on). In a modern game, the amount of information conveyed to the user, the amount of choices the user can make; and the support for the user to make said decisions is simply astounding (think UIs for Starcraft II / WoW). Any insights into this would be greatly appreciated.

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• How to put theory into practise

  - by Dave greg

  I like to read alot of IT books e.g programming / functional. But the problem is that after reading I cannot find reasons to put it into practise and I soon forget what I read. Any advise?

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• Permutations distinct under given symmetry (Mathematica 8 group theory)

  - by Yaroslav Bulatov

  Given a list of integers like {2,1,1,0} I'd like to list all permutations of that list that are not equivalent under given group. For instance, using symmetry of the square, the result would be {{2, 1, 1, 0}, {2, 1, 0, 1}}. Approach below (Mathematica 8) generates all permutations, then weeds out the equivalent ones. I can't use it because I can't afford to generate all permutations, is there a more efficient way? Update: actually, the bottleneck is in DeleteCases. The following list {2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 0, 0, 0} has about a million permutations and takes 0.1 seconds to compute. Apparently there are supposed to be 1292 orderings after removing symmetries, but my approach doesn't finish in 10 minutes removeEquivalent[{}] := {}; removeEquivalent[list_] := ( Sow[First[list]]; equivalents = Permute[First[list], #] & /@ GroupElements[group]; DeleteCases[list, Alternatives @@ equivalents] ); nonequivalentPermutations[list_] := ( reaped = Reap@FixedPoint[removeEquivalent, Permutations@list]; reaped[[2, 1]] ); group = DihedralGroup[4]; nonequivalentPermutations[{2, 1, 1, 0}]

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• Goldbach theory in C

  - by nofe

  I want to write some code which takes any positive, even number (greater than 2) and gives me the smallest pair of primes that sum up to this number. I need this program to handle any integer up to 9 digits long. My aim is to make something that looks like this: Please enter a positive even integer ( greater than 2 ) : 10 The first primes adding : 3+7=10. Please enter a positive even integer ( greater than 2 ) : 160 The first primes adding : 3+157=160. Please enter a positive even integer ( greater than 2 ) : 18456 The first primes adding : 5+18451=18456. I don't want to use any library besides stdio.h. I don't want to use arrays, strings, or anything besides for the most basic toolbox: scanf, printf, for, while, do-while, if, else if, break, continue, and the basic operators (<,, ==, =+, !=, %, *, /, etc...). Please no other functions especially is_prime. I know how to limit the input to my needs so that it loops until given a valid entry. So now I'm trying to figure out the algorithm. I thought of starting a while loop like something like this: #include <stdio.h> long first, second, sum, goldbach, min; long a,b,i,k; //indices int main (){ while (1){ printf("Please enter a positive integer :\n"); scanf("%ld",&goldbach); if ((goldbach>2)&&((goldbach%2)==0)) break; else printf("Wrong input, "); } while (sum!=goldbach){ for (a=3;a<goldbach;a=(a+2)) for (i=2;(goldbach-a)%i;i++) first = a; for (b=5;b<goldbach;b=(b+2)) for (k=2;(goldbach-b)%k;k++) sum = first + second; } }

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• SQL Query Theory Question...

  - by Keng

  I have a large historical transaction table (15-20 million rows MANY columns) and a table with one row one column. The table with one row contains a date (last processing date) which will be used to pull the data in the trasaction table ('process_date'). Question: Should I inner join the 'process_date' table to the transaction table or the transaction table to the 'process_date' table?

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• C: theory on how to extract files from an archived file

  - by donok

  In C I have created a program which can archive multiple files into an archive file via the command line. e.g. $echo 'file1/2' > file1/2.txt $./archive file1.txt file2.txt arhivedfile $cat archivedfile file1 file2 How do I create a process so that in my archivedfile I have: header file1 end header file2 end They are all stored in the archive file one after another after another. I know that perhaps a header file is needed(containing filename, size of filename, start and end of file) for extracting these files back out into their original form, but how would I go about doing this. I am stuck on where and how to start. Please could someone help me on some logic as to how to approach extracting files back out of an archived file.

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• Is there a way to intersect/diff a std::map and a std::set?

  - by Jack

  I'm wondering if there a way to intersect or make the differences between two structures defined as std::set<MyData*> and std::map<MyData*, MyValue> with standard algorithms (like std::set_intersect) The problem is that I need to compute the difference between the set and the keyset of the map but I would like to avoid reallocating it (since it's something that is done many times per second with large data structures). Is there a way to obtain a "key view" of the std::map? After all what I'm looking is to consider just the keys when doing the set operation so from an implementation point it should be possible but I haven't been able to find anything.

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• Do game-theoretic considerations stand in the way of this market-based game-mechanic achieving its goals?

  - by BerndBrot

  Mechanic The mechanic is called "market manipulation" and is supposed to work like this: Players can enter the London Stock Exchange (LSE) LSE displays the stock prices of 8 to 10 companies and derivatives. This number is relatively small to ensure that players will collide in their efforts to manipulate the market in their favor. The prices are calculated based on real world prices of these companies and derivatives (in real time) any market manipulations that were conducted by the players any market corrections of the system Players can buy and sell shares with cash, a resource in the game, at current in-game market value Players can manipulate the market, i.e. let the price of a share either rise or fall, by some amount, over a certain period of time. Manipulating the market requires spending certain in-game resources and is therefore limited. The system continuously corrects market manipulations by letting the in-game prices converge towards their real world counterparts at a rate of 2% of the difference between the two per hour. Because of this market correction mechanism, pushing up prices (and screwing down prices) becomes increasingly difficult the higher (lower) the price already is. Goals Players are supposed to collide (and have incentives to collide) in their efforts to manipulate the market in their favor, especially when it comes to manipulation efforts by different groups. Prices should not resolve around any equilibrium points. The more variance the better. Band-wagoning should always involve risk (recognizing that prices start rising should not be a sure sign that they will keep rising so that everybody can make easy profits even when they don't manipulate the market themselves) Question Are there any game-theoretic considerations that prevent the mechanic from achieving these goals?

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• Cuppa Corner talk "A trip to First Normal Form" available - Domains, Functional Dependencies, Repeat

  - by tonyrogerson

  It's 15 minutes, I talk about Domains, Functional Dependencies, Repeating Groups, Relational Valued Attributes and of course First Normal Form. http://sqlcontent.sqlblogcasts.com/video/cctr20100507dbdesign1nf/cctr20100507dbdesign1nf.html For questions just ask on the http://sqlserverfaq.com chat control or Twitter using #sqlfaq tag. Slides are also availble here: http://sqlcontent.sqlblogcasts.com/video/cctr20100507dbdesign1nf/cc_tr20100507_dbdesign1nf.pptx...(read more)

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