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• Algorithm for finding the best routes for food distribution in game

  - by Tautrimas

  Hello, I'm designing a city building game and got into a problem. Imagine Sierra's Caesar III game mechanics: you have many city districts with one market each. There are several granaries over the distance connected with a directed weighted graph. The difference: people (here cars) are units that form traffic jams (here goes the graph weights). Note: in Ceasar game series, people harvested food and stockpiled it in several big granaries, whereas many markets (small shops) took food from the granaries and delivered it to the citizens. The task: tell each district where they should be getting their food from while taking least time and minimizing congestions on the city's roads. Map example Sample diagram Suppose that yellow districts need 7, 7 and 4 apples accordingly. Bluish granaries have 7 and 11 apples accordingly. Suppose edges weights to be proportional to their length. Then, the solution should be something like the gray numbers indicated on the edges. Eg, first district gets 4 apples from the 1st and 3 apples from the 2nd granary, while the last district gets 4 apples from only the 2nd granary. Here, vertical roads are first occupied to the max, and then the remaining workers are sent to the diagonal paths. Question What practical and very fast algorithm should I use? I was looking at some papers (Congestion Games: Optimization in Competition etc.) describing congestion games, but could not get the big picture. Any help is very appreciated! P. S. I can post very little links and no images because of new user restriction.

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• Delphi access violation assigning local variable

  - by Justin

  This seems like the simplest thing in the world and I'm ready to pull my hair out over it. I have a unit that looks like this ; Unit myUnit; // ... //normal declarations //... Public //bunch of procedures including Procedure myProcedure; const //bunch of constants var //bunch of vars including myCounter:integer; Implementation Uses //(all my uses) // All of my procedures including Procedure myProcedure; try // load items from file to TListBox - this all works except on EReadError do begin // handle exception end; end; //try myCounter:=0; // <-- ACCESS VIOLATION HERE while myCounter //...etc It's a simple assignment of a variable and I have no idea why it is doing this. I've tried declaring the variable local to the unit, to the procedure, globally - no matter where I try to do it I can't assign a value of zero to an integer, declared anywhere, within this procedure without it throwing an access violation. I'm totally stumped. I'm calling the procedure from inside a button OnClick handler from within the same unit, but no matter where I call it from it throws the exception. The crazy thing is that I do the exact same thing in a dozen other places in units all over the program without problems. Why here? I'm at a total loss.

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• How to modulate every texture unit in OpenGL ES 1.1?

  - by Jesse Beder

  I have two textures and a "blend factor", and I'd like to mix them, modulated by the current color; in effect, I want to use the following shader: gl_FragColor = gl_Color * mix(tex0, tex1, blendFactor); I'm using OpenGL ES 1.1, targeting all versions of the iPhone, so I can't use shaders, and I have two texture units. My best attempt is: // texture 0 glActiveTexture(GL_TEXTURE0); image1.Bind(); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); // texture 1 glActiveTexture(GL_TEXTURE1); image2.Bind(); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE); glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_INTERPOLATE); glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_RGB, GL_PREVIOUS); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR); glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_RGB, GL_TEXTURE); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR); glTexEnvi(GL_TEXTURE_ENV, GL_SRC2_RGB, GL_CONSTANT); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND2_RGB, GL_SRC_ALPHA); glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_ALPHA, GL_INTERPOLATE); glTexEnvi(GL_TEXTURE_ENV, GL_SRC0_ALPHA, GL_PREVIOUS); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND0_ALPHA, GL_SRC_ALPHA); glTexEnvi(GL_TEXTURE_ENV, GL_SRC1_ALPHA, GL_TEXTURE); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND1_ALPHA, GL_SRC_ALPHA); glTexEnvi(GL_TEXTURE_ENV, GL_SRC2_ALPHA, GL_CONSTANT); glTexEnvi(GL_TEXTURE_ENV, GL_OPERAND2_ALPHA, GL_SRC_ALPHA); const float factor[] = { 0, 0, 0, blendFactor }; glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, factor); This has the effect of the shader: gl_FragColor = mix(gl_Color * tex0, tex1, blendFactor); but I don't see how to module texture 1 by the color. Is there any way to have the color provided by a texture unit automatically modulated by the incoming primary color? Or any other way to do what I want that I'm missing? Multiple passes are definitely allowed, but they have to have the proper blend effect; I have glBlend(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); enabled, so it can be tricky to get right with multiple passes.

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• Ruby Doesn't Recognize Alias Method

  - by Jesse J

  I'm trying to debug someone else's code and having trouble figuring out what's wrong. When I run rake, one of the errors I get is: 2) Error: test_math(TestRubyUnits): NoMethodError: undefined method `unit_sin' for CMath:Module /home/user/ruby-units/lib/ruby_units/math.rb:21:in `sin' This is the function that calls the method: assert_equal Math.sin(pi), Math.sin("180 deg".unit) And this is what the class looks like: module Math alias unit_sin sin def sin(n) Unit === n ? unit_sin(n.to('radian').scalar) : unit_sin(n) end alias unit_cos cos def cos(n) Unit === n ? unit_cos(n.to('radian').scalar) : unit_cos(n) end ... module_function :unit_sin module_function :sin module_function :unit_cos module_function :cos ... end (The ellipsis means "more of the same"). As far as I can see, this is valid Ruby code. Is there something I'm missing here that's causing the error, or could the error be coming from something else? Update: I'm wondering if the problem has to do with namespaces. This code is attempting to extend CMath, so perhaps the alias and/or module_function isn't actually getting into CMath, or something like that....

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• Raw types and subtyping

  - by Dmitrii

  We have generic class SomeClass<T>{ } We can write the line: SomeClass s= new SomeClass<String>(); It's ok, because raw type is supertype for generic type. But SomeClass<String> s= new SomeClass(); is correct to. Why is it correct? I thought that type erasure was before type checking, but it's wrong. From Hacker's Guide to Javac When the Java compiler is invoked with default compile policy it performs the following passes: parse: Reads a set of *.java source files and maps the resulting token sequence into AST-Nodes. enter: Enters symbols for the definitions into the symbol table. process annotations: If Requested, processes annotations found in the specified compilation units. attribute: Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. flow: Performs data ow analysis on the trees from the previous step. This includes checks for assignments and reachability. desugar: Rewrites the AST and translates away some syntactic sugar. generate: Generates Source Files or Class Files. Generic is syntax sugar, hence type erasure invoked at 6 pass, after type checking, which invoked at 4 pass. I'm confused.

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• Implementing a 1 to many relationship with SQLite

  - by Patrick

  I have the following schema implemented successfully in my application. The application connects desk unit channels to IO unit channels. The DeskUnits and IOUnits tables are basically just a list of desk/IO units and the number of channels on each. For example a desk could be 4 or 12 channel. CREATE TABLE DeskUnits (Name TEXT, NumChannels NUMERIC); CREATE TABLE IOUnits (Name TEXT, NumChannels NUMERIC); CREATE TABLE RoutingTable (DeskUnitName TEXT, DeskUnitChannel NUMERIC, IOUnitName TEXT, IOUnitChannel NUMERIC); The RoutingTable 'table' then connects each DeskUnit channel to an IOUnit channel. For example the DeskUnit called "Desk1" channel 1 may route to IOunit name "IOUnit1" channel 2, etc. So far I hope this is pretty straightforward and understandable. The problem is, however, this is a strictly 1 to 1 relationship. Any DeskUnit channel can route to only 1 IOUnit channel. Now, I need to implement a 1 to many relationship. Where any DeskUnit channel can connect to multiple IOUnit channels. I realise I may have to rearrange the tables completely, but I am not sure the best way to go about this. I am fairly new to SQLite and databases in general so any help would be appreciated. Thanks Patrick

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• Group variables in a boxplot in R

  - by tao.hong

  I am trying to generate a boxplot whose data come from two scenarios. In the plot, I would like to group boxes by their names (So there will be two boxes per variable). I know ggplot would be a good choice. But I got errors which I could not figure out. Can anyone give me some suggestions? sensitivity_out1 structure(c(0.0522902104339716, 0.0521369824334004, 0.0520240345973737, 0.0519818337359876, 0.051935071418996, 0.0519089404325544, 0.000392698277338341, 0.000326135474295325, 0.000280863338343747, 0.000259631566041935, 0.000246594043996332, 0.000237923540393391, 0.00046732650331544, 0.000474448907808135, 0.000478287273678457, 0.000480194683464109, 0.000480631753078668, 0.000481760272726273, 0.000947965771207979, 0.000944821699830455, 0.000939631071343889, 0.000937186900570605, 0.000936007346568281, 0.000934756220144141, 0.00132442589501872, 0.00132658367774979, 0.00133334696220742, 0.00133622384928092, 0.0013381577476241, 0.00134005741746304, 0.0991622968751298, 0.100791399440082, 0.101946808417405, 0.102524244727408, 0.102920085260477, 0.103232984259916, 0.0305219507186844, 0.0304635269233494, 0.0304161055015213, 0.0303742106794513, 0.0303381888169022, 0.0302996157711171, 1.94268588634518e-05, 2.23991225564447e-05, 2.5756135487907e-05, 2.79997917298194e-05, 3.00753967077715e-05, 3.16270817369878e-05, 0.544701146678523, 0.542887331601984, 0.541632986366816, 0.541005610554556, 0.540617004208336, 0.540315690692195, 0.000453386694666078, 0.000448473414508756, 0.00044692043197248, 0.000444826296854332, 0.000445747996014684, 0.000444764303682453, 0.000127569551159321, 0.000128422491392669, 0.00012933662856487, 0.000129941842982939, 0.000129578971489026, 0.000131113075233758, 0.00684610571790029, 0.00686349387897349, 0.00687468164010565, 0.00687880720347743, 0.00688275579317197, 0.00687822247621936), .Dim = c(6L, 12L)) out2 structure(c(0.0189965816735366, 0.0189995096225103, 0.0190099362589894, 0.0190033523148514, 0.01900896721937, 0.0190099427513381, 0.00192043989797585, 0.00207303208721059, 0.00225931163225165, 0.0024049969048389, 0.00252310364086785, 0.00262940166568126, 0.00195164921633517, 0.00190079923515755, 0.00186139563778548, 0.00184188171395076, 0.00183248544676564, 0.00182492970673969, 1.83038731485927e-05, 1.98252671720347e-05, 2.14794764479231e-05, 2.30713122969332e-05, 2.4484220713564e-05, 2.55958833705284e-05, 0.0428066864455102, 0.0431686808647809, 0.0434411033615353, 0.0435883377765726, 0.0436690169266633, 0.0437340464360965, 0.145288252474567, 0.141488776430307, 0.138204532539654, 0.136281799717717, 0.134864952272761, 0.133738386148036, 0.0711728636959696, 0.072031388688795, 0.0727536853228245, 0.0731581966147734, 0.0734424337399303, 0.0736637270702609, 0.000605277151497094, 0.000617268349064968, 0.000632975679951382, 0.000643904422677427, 0.000653775268094148, 0.000662225067910141, 0.26735354610469, 0.267515415990146, 0.26753155165617, 0.267553498616325, 0.267532284594615, 0.267510330320289, 0.000334158771646756, 0.000319032383145857, 0.000306074699839994, 0.000299153278494114, 0.000293956197852583, 0.000290171804454218, 0.000645975219899115, 0.000637548672578787, 0.000632375486965757, 0.000629579821884212, 0.000624956458229123, 0.000622456283217054, 0.0645188290106884, 0.0651539609630352, 0.0656417364889907, 0.0658996698322889, 0.0660715073023965, 0.0662034341510152), .Dim = c(6L, 12L)) Melt data: group variable value 1 1 PLDKRT 0 2 1 PLDKRT 0 3 1 PLDKRT 0 4 1 PLDKRT 0 5 1 PLDKRT 0 6 1 PLDKRT 0 Code: #Data_source 1 sensitivity_1=rbind(sensitivity_out1,sensitivity_out2) sensitivity_1=data.frame(sensitivity_1) colnames(sensitivity_1)=main_l #variable names sensitivity_1$group=1 #Data_source 2 sensitivity_2=rbind(sensitivity_out1[3:4,],sensitivity_out2[3:4,]) sensitivity_2=data.frame(sensitivity_2) colnames(sensitivity_2)=main_l sensitivity_2$group=2 sensitivity_pool=rbind(sensitivity_1,sensitivity_2) sensitivity_pool_m=melt(sensitivity_pool,id.vars="group") ggplot(data = sensitivity_pool_m, aes(x = variable, y = value)) + geom_boxplot(aes( fill= group), width = 0.8) Error: "Error in unit(tic_pos.c, "mm") : 'x' and 'units' must have length > 0" Update Figure out the error. I should use geom_boxplot(aes( fill= factor(group)), width = 0.8) rather than fill= group

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• Extending the .NET type system so the compiler enforces semantic meaning of primitive values in cert

  - by Drew Noakes

  I'm working with geometry a bit at the moment and am converting a lot between degrees and radians. Unfortunately, both of these are represented by double, so there's compile time warning/error if I try to pass a value in degrees where radians are expected. I believe F# has a compile-time solution for this (called units of measure.) I'd like to do something similar in C#. As another example, imagine a SQL library that accepts various query parameters as strings. It'd be good to have a way of enforcing that only clean strings were allowed to be passed in at runtime, and the only way to get a clean string was to pass through some SQL injection attack preventing logic. The obvious solution is to wrap the double/string/whatever in a new type to give it the type information the compiler needs. I'm curious if anyone has an alternative solution. If you do think wrapping is the only/best way, then please go into some of the downsides of the pattern (and any upsides I haven't mentioned too.) I'm especially concerned about the performance of abstracted primitive numeric types on my calculations at runtime.

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• parsing xml using dom4j

  - by D3GAN

  My XML structure is like this: <rss> <channel> <yweather:location city="Paris" region="" country="France"/> <yweather:units temperature="C" distance="km" pressure="mb" speed="km/h"/> <yweather:wind chill="-1" direction="40" speed="11.27"/> <yweather:atmosphere humidity="87" visibility="9.99" pressure="1015.92" rising="0"/> <yweather:astronomy sunrise="8:30 am" sunset="4:54 pm"/> </channel> </rss> when I tried to parse it using dom4j SAXReader xmlReader = createXmlReader(); Document doc = null; doc = xmlReader.read( inputStream );//inputStream is input of function log.info(doc.valueOf("/rss/channel/yweather:location/@city")); private SAXReader createXmlReader() { Map<String,String> uris = new HashMap<String,String>(); uris.put( "yweather", "http://xml.weather.yahoo.com/ns/rss/1.0" ); uris.put( "geo", "http://www.w3.org/2003/01/geo/wgs84_pos#" ); DocumentFactory factory = new DocumentFactory(); factory.setXPathNamespaceURIs( uris ); SAXReader xmlReader = new SAXReader(); xmlReader.setDocumentFactory( factory ); return xmlReader; } But I got nothing in cmd but when I print doc.asXML(), my XML structure print correctly!

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• VS 2008 C++ build output?

  - by STingRaySC

  Why when I watch the build output from a VC++ project in VS do I see: 1Compiling... 1a.cpp 1b.cpp 1c.cpp 1d.cpp 1e.cpp [etc...] 1Generating code... 1x.cpp 1y.cpp [etc...] The output looks as though several compilation units are being handled before any code is generated. Is this really going on? I'm trying to improve build times, and by using pre-compiled headers, I've gotten great speedups for each ".cpp" file, but there is a relatively long pause during the "Generating Code..." message. I do not have "Whole Program Optimization" nor "Link Time Code Generation" turned on. If this is the case, then why? Why doesn't VC++ compile each ".cpp" individually (which would include the code generation phase)? If this isn't just an illusion of the output, is there cross-compilation-unit optimization potentially going on here? There don't appear to be any compiler options to control that behavior (I know about WPO and LTCG, as mentioned above). EDIT: The build log just shows the ".obj" files in the output directory, one per line. There is no indication of "Compiling..." vs. "Generating code..." steps. EDIT: I have confirmed that this behavior has nothing to do with the "maximum number of parallel project builds" setting in Tools - Options - Projects and Solutions - Build and Run. Nor is it related to the MSBuild project build output verbosity setting. Indeed if I cancel the build before the "Generating code..." step, the ".obj" files will not exist for the most recent set of "compiled" files. E.g., if I cancel the build during "c.cpp" above, I will see only "a.obj" and "b.obj".

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• floating point equality in Python and in general

  - by eric.frederich

  I have a piece of code that behaves differently depending on whether I go through a dictionary to get conversion factors or whether I use them directly. The following piece of code will print 1.0 == 1.0 -> False But if you replace factors[units_from] with 10.0 and factors[units_to ] with 1.0 / 2.54 it will print 1.0 == 1.0 -> True #!/usr/bin/env python base = 'cm' factors = { 'cm' : 1.0, 'mm' : 10.0, 'm' : 0.01, 'km' : 1.0e-5, 'in' : 1.0 / 2.54, 'ft' : 1.0 / 2.54 / 12.0, 'yd' : 1.0 / 2.54 / 12.0 / 3.0, 'mile' : 1.0 / 2.54 / 12.0 / 5280, 'lightyear' : 1.0 / 2.54 / 12.0 / 5280 / 5.87849981e12, } # convert 25.4 mm to inches val = 25.4 units_from = 'mm' units_to = 'in' base_value = val / factors[units_from] ret = base_value * factors[units_to ] print ret, '==', 1.0, '->', ret == 1.0 Let me first say that I am pretty sure what is going on here. I have seen it before in C, just never in Python but since Python in implemented in C we're seeing it. I know that floating point numbers will change values going from a CPU register to cache and back. I know that comparing what should be two equal variables will return false if one of them was paged out while the other stayed resident in a register. Questions What is the best way to avoid problems like this?... In Python or in general. Am I doing something completely wrong? Side Note This is obviously part of a stripped down example but what I'm trying to do is come with with classes of length, volume, etc that can compare against other objects of the same class but with different units. Rhetorical Questions If this is a potentially dangerous problem since it makes programs behave in an undetermanistic matter, should compilers warn or error when they detect that you're checking equality of floats Should compilers support an option to replace all float equality checks with a 'close enough' function? Do compilers already do this and I just can't find the information.

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• WYSIWYG with Qt - font size woes

  - by Rob

  I am creating a custom Qt widget that mimics an A4 printed page and am having problems getting fonts to render at the correct size. My widget uses QPainter::setViewport and QPainter::setWindow to mimic the A4 page, using units of 10ths of a millimetre which enables me to draw easily. However, attempting to create a font at a specific point size doesn't seem to work and using QFont:setPixelSize isn't accurate. Here is some code: View::View(QWidget *parent) : QWidget(parent), printer(new QPrinter) { printer->setPaperSize(QPrinter::A4); printer->setFullPage(true); } void View::paintEvent(QPaintEvent*) { QPainter painter(this); painter.setWindow(0, 0, 2100, 2970); painter.setViewport(0, 0, printer->width(), printer->height()); // Draw a rect at x = 1cm, y = 1cm, 6cm wide and 1 inch high painter.drawRect(100, 100, 600, 254); // Create a 72pt (1 inch) high font QFont font("Arial"); font.setPixelSize(254); painter.setFont(font); // Draw in the same box // The font is too large painter.drawText(QRect(100, 100, 600, 254), tr("Wg\u0102")); // Ack - the actual font size reported by the metrics is 283 pixels! const QFontMetrics fontMetrics = painter.fontMetrics(); qDebug() << "Font height = " << fontMetrics.height(); } So I'm asking for a 254 high font (1 inch, 72 pts) and it's too big and sure enough when I query for the font height via QFontMetrics it is 283 high. Does anyone else know how to use font sizes in points when using custom mapping modes like this? It must be possible. Note that I cannot see how to convert between logical/device points either (i.e. the Win32 DPtoLP/LPtoDP equivalents.)

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• How to extend this design for a generic converter in java?

  - by Jay

  Here is a small currency converter piece of code: public enum CurrencyType { DOLLAR(1), POUND(1.2), RUPEE(.25); private CurrencyType(double factor) { this.factor = factor; } private double factor; public double getFactor() { return factor; } } public class Currency { public Currency(double value, CurrencyType type) { this.value = value; this.type = type; } private CurrencyType type; private double value; public CurrencyType getCurrencyType() { return type; } public double getCurrencyValue() { return value; } public void setCurrenctyValue(double value){ this.value = value; } } public class CurrencyConversion { public static Currency convert(Currency c1, Currency c2) throws Exception { if (c1 != null && c2 != null) { c2.setCurrenctyValue(c1.getCurrencyValue() * c1.getCurrencyType().getFactor() * c2.getCurrencyType().getFactor()); return c2; } else throw new Exception(); } } I would like to improve this code to make it work for different units of conversion, for example: kgs to pounds, miles to kms, etc etc. Something that looks like this: public class ConversionManager<T extends Convertible> { public T convert(T c1, T c2) { //return null; } } Appreciate your ideas and suggestions.

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• Componentizing complex functionality in an MVC web app

  - by NXT

  Hi Everyone, This is question about MVC web-app architecture, and how it can be extended to handle componentizing moderately complex units of functionality. I have an MVC style web-app with a customer facing credit card charge page. I've been asked to allow the admins to enter credit card payments as well, for times when credit cards are taken over the phone. The customer facing credit card charge section of the website is currently it's own controller, with approximately 3 pages and a login. That controller is responsible for: Customer login credential authentication Credit card data collection Calling a library to do the actual charge. reporting the results to the user. I would like to extract the card data collection pages into a component of some kind so that I can easily reuse the code on the admin side of the app. Right now my components are limited to single "view" pages with PHP style embedded Perl code. This is a simple, custom MVC framework written in Perl. Right now, controllers are called directly from the framework to service web requests. My idea is to allow controllers to be called from other controllers, so that I can componentize more complex functionality. For simplicity I think I prefer composition over inheritance, even though it will require writing a bunch of pass-through methods (actions). Being Perl, I could in theory do multiple inheritance. I'm wondering if anyone with experience in other MVC web frameworks can comment on how this sort of thing is usually done. Thank you.

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• Methods to Analyze Sell Orders (in a video game)

  - by Travis

  I'm building a market manager for EVE, but this problem should be solvable without any prior knowledge of the game. Basically, sell orders in EVE look like this: All I'm really concerned with is picking a good price. The numbers the program would pick are sent out to our production team so they can buy the items to build things. Just like in a real market, the numbers we send off need to reflect the cheapest price that still offers a good quantity. Also, available quantities change over time, so we can't just pick the lowest listed price. For example, in the screencap above, we would set the sell price between 2,800.00 ISK and 3,000.00 ISK, even if only 500 units were needed. Even though the cheapest order would fit the quantity, it would probably quickly disappear. It would be better to set the price a tad higher so we don't underpay the production people. The Question: It's easy enough to figure prices out just by looking at the data, but I can't figure out how to have a program [java] do it. Different items sell with much less or more quantities (i.e. 3 or 300 or 3000 items) so the program has to be able to modify itself based on the offerings. I don't really want code as much as I do a way to think this through. Thanks in advance.

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• SqlCE DB occasionally freezes on one handheld, not another

  - by Michael

  I have two types of custom handhelds which are similar, but slightly different, each running the same WinForm application and a WinCE database: Type 1: WinCE 4.2, 400 mhz, 93244 kb Type 2: WinCE 5.0, 520 mhz, 84208 kb Type 1 will happily proceed through a large batch db operation (initiated) by the app, by Type 2 will consistently begin c-r-a-w-l-i-n-g (for several to many cycles) at around the 200 cycle mark. As several points it will begin running normally and then crawl again. The app does several db op's (inserts, updates and selects, no deletes). To simplify my situation, I've built a small test app which essentially does this: command_s.CommandText = "select dvr from vr where vid = 2211250"; command_u.CommandText = "update pvr set LocationID=81 where Status='OK' and vri = 27861"; while(going) { command_s.ExecuteScalar(); command_u.ExecuteNonQuery(); } and set it off running on the two units side by side. Sure enough, the slower (400 mhz) unit is outpacing the faster (520 mhz) unit (it's about 5000 cycles ahead right now) and I can see noticable pauses on the 520 mhz unit. What is causing this?

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• Classes with the same name - is it restricted only within the same translation unit?

  - by LeopardSkinPillBoxHat

  Let's just I had the following code: foo.h class Foo { // ... }; foo.cpp #include "foo.h" // Functions for class Foo defined here... Let's say that Foo are built into a static library foo.lib. Now let's say I have the following: foo2.h class Foo { // ... }; foo2.cpp #include "foo2.h" // Functions for class Foo defined here... This is built into a separate static library foo2.lib. Now, if I re-link foo.lib and foo2.lib into an executable program foo.exe, should it be complaining that class Foo has been defined twice? In my experiences, neither the compiler or the linker are complaining. I wouldn't be expecting the compiler to complain, because they have been defined in separate translation units. But why doesn't the linker complain? How does the linker differentiate between the 2 versions of the Foo class? Does it work by decorating the symbols?

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• A GUID as the MySQL table's Primary Key or as a separate column

  - by Ben

  I have a multi-process program that performs, in a 2 hour period, 5-10 million inserts to a 34GB table within a single Master/Slave MySQL setup (plus an equal number of reads in that period). The table in question has only 5 fields and 3 (single field) indexes. The primary key is auto-incrementing. I am far from a DBA, but the database appears to be crippled during this two hour period. So, I have a couple of general questions. 1) How much bang will I get out of batching these writes into units of 10? Currently, I am writing each insert serially because, after writing, I immediately need to know, in my program, the resulting primary key of each insert. The PK is the only unique field presently and approximating the order of insertion with something like a Datetime field or a multi-column value is not acceptable. If I perform a bulk insert, I won't know these IDs, which is a problem. So, I've been thinking about turning the auto-increment primary key into a GUID and enforcing uniqueness. I've also been kicking around the idea of creating a new column just for the purposes of the GUID. I don't really see the what that achieves though, that the PK approach doesn't already offer. As far as I can tell, the big downside to making the PK a randomly generated number is that the index would take a long time to update on each insert (since insertion order would not be sequential). Is that an acceptable approach for a table that is taking this number of writes? Thanks, Ben

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• Ruby Alias and module_function

  - by Jesse J

  I'm trying to debug someone else's code and having trouble figuring out what's wrong. When I run rake, one of the errors I get is: 2) Error: test_math(TestRubyUnits): NoMethodError: undefined method `unit_sin' for CMath:Module /home/user/ruby-units/lib/ruby_units/math.rb:21:in `sin' This is the function that calls the method: assert_equal Math.sin(pi), Math.sin("180 deg".unit) And this is what the class looks like: module Math alias unit_sin sin def sin(n) Unit === n ? unit_sin(n.to('radian').scalar) : unit_sin(n) end alias unit_cos cos def cos(n) Unit === n ? unit_cos(n.to('radian').scalar) : unit_cos(n) end ... module_function :unit_sin module_function :sin module_function :unit_cos module_function :cos ... end (The ellipsis means "more of the same"). As far as I can see, this is valid Ruby code. Is there something I'm missing here that's causing the error, or could the error be coming from something else? Update: I'm wondering if the problem has to do with namespaces. This code is attempting to extend CMath, so perhaps the alias and/or module_function isn't actually getting into CMath, or something like that....

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• What are the arguments against the inclusion of server side scripting in JavaScript code blocks?

  - by James Wiseman

  I've been arguing for some time against embedding server-side tags in JavaScript code, but was put on the spot today by a developer who seemed unconvinced The code in question was a legacy ASP application, although this is largely unimportant as it could equally apply to ASP.NET or PHP (for example). The example in question revolved around the use of a constant that they had defined in ServerSide code. 'VB Const MY_CONST: MY_CONST = 1 If sMyVbVar = MY_CONST Then 'Do Something End If //JavaScript if (sMyJsVar === "<%= MY_CONST%>"){ //DoSomething } My standard arguments against this are: Script injection: The server-side tag could include code that can break the JavaScript code Unit testing. Harder to isolate units of code for testing Code Separation : We should keep web page technologies apart as much as possible. The reason for doing this was so that the developer did not have to define the constant in two places. They reasoned that as it was a value that they controlled, that it wasn't subject to script injection. This reduced my justification for (1) to "We're trying to keep the standards simple, and defining exception cases would confuse people" The unit testing and code separation arguments did not hold water either, as the page itself was a horrible amalgam of HTML, JavaScript, ASP.NET, CSS, XML....you name it, it was there. No code that was every going to be included in this page could possibly be unit tested. So I found myself feeling like a bit of a pedant insisting that the code was changed, given the circumstances. Are there any further arguments that might support my reasoning, or am I, in fact being a bit pedantic in this insistence?

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• Potential problem with C standard malloc'ing chars.

  - by paxdiablo

  When answering a comment to another answer of mine here, I found what I think may be a hole in the C standard (c1x, I haven't checked the earlier ones and yes, I know it's incredibly unlikely that I alone among all the planet's inhabitants have found a bug in the standard). Information follows: Section 6.5.3.4 ("The sizeof operator") para 2 states "The sizeof operator yields the size (in bytes) of its operand". Para 3 of that section states: "When applied to an operand that has type char, unsigned char, or signed char, (or a qualified version thereof) the result is 1". Section 7.20.3.3 describes void *malloc(size_t sz) but all it says is "The malloc function allocates space for an object whose size is specified by size and whose value is indeterminate". It makes no mention at all what units are used for the argument. Annex E startes the 8 is the minimum value for CHAR_BIT so chars can be more than one byte in length. My question is simply this: In an environment where a char is 16 bits wide, will malloc(10 * sizeof(char)) allocate 10 chars (20 bytes) or 10 bytes? Point 1 above seems to indicate the former, point 2 indicates the latter. Anyone with more C-standard-fu than me have an answer for this?

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• Wrapping text and div as a unit

  - by mathee

  I have the following that I would like wrapped as units. <div class='tag-box'> <a href=#>Axe Committee</a> <div class='circle'><a href=#>x</a></div> </div> The CSS for these classes are: .tag-box { display:inline; } .circle { display:inline; padding-left:4px; padding-right:4px; background:rgb(196,15,24); /*dark red*/ -moz-border-radius:10px; -webkit-border-radius:10px; } .circle a { font-size:10px; text-decoration:none; color:#fff; position:relative; top:-2px; } I can have upwards of 20 or 30 of these tag-boxes displayed inline. The problem is that the wrapping will break the words from each other or even break the red circle from the link. This makes it hard to differentiate which circle belongs to which link. (In the future, each circle corresponds to a different action with respect to the link.) See below. How do I prevent this kind of wrapping from occurring?

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• In SQL Server what is most efficient way to compare records to other records for duplicates with in

  - by Glenn

  We have an SQL Server that gets daily imports of data files from clients. This data is interrelated and we are always scrubbing it and having to look for suspect duplicate records between these files. Finding and tagging suspect records can get pretty complicated. We use logic that requires some field values to be the same, allows some field values to differ, and allows a range to be specified for how different certain field values can be. The only way we've found to do it is by using a cursor based process, and it places a heavy burden on the database. So I wanted to ask if there's a more efficient way to do this. I've heard it said that there's almost always a more efficient way to replace cursors with clever JOINS. But I have to admit I'm having a lot of trouble with this one. For a concrete example suppose we have 1 table, an "orders" table, with the following 6 fields. order_id, customer_id product_id, quantity, sale_date, price We want to look through the records to find suspect duplicates on the following example criteria. These get increasingly harder. 1. Records that have the same product_id, sale_date, and quantity but different customer_id's should be marked as suspect duplicates for review. 2. Records that have the same customer_id, product_id, quantity and have sale_dates within five days of each other should be marked as suspect duplicates for review 3. Records that have the same customer_id, product_id, but different quantities within 20 units, and sales dates within five days of each other should be considered suspect. Is it possible to satisfy each one of these criteria with a single SQL Query that uses JOINS? Is this the most efficient way to do this?

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• Call HashMap from jsp EL ?

  - by Parhs

  Here is my Entity Class public enum UnitType { HOSPITAL, HEALTHCENTER } public static LinkedHashMap<UnitType, String> unitType = new LinkedHashMap<UnitType, String>() { { put(UnitType.HEALTHCENTER, "???t?? ??e?a?"); put(UnitType.HOSPITAL, "??s???µe??"); } }; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String name; private String address; @Column(columnDefinition = "TEXT") private String info; @Enumerated(EnumType.STRING) private UnitType type; At my jsp <c:forEach var="unit" items="${requestScope.units}"> <tr> <td>${unit.id}</td> <td>${unit.name}</td> <td>${unit.address}</td> <td>??!?</td> <td><a href="#">?e??ss?te?a</a></td> </tr> </c:forEach> How can i place the text value of the enum at ??!? .. Any idea? Tried some ways but nothing worked..

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• SWIG_NewPointerObj and values always being nil

  - by Tom J Nowell

  I'm using SWIG to wrap C++ objects for use in lua, and Im trying to pass data to a method in my lua script, but it always comes out as 'nil' void CTestAI::UnitCreated(IUnit* unit){ lua_getglobal(L, "ai"); lua_getfield(L, -1, "UnitCreated"); swig_module_info *module = SWIG_GetModule( L ); swig_type_info *type = SWIG_TypeQueryModule( module, module, "IUnit *" ); SWIG_NewPointerObj(L,unit,type,0); lua_epcall(L, 1, 0); } Here is the lua code: function AI:UnitCreated(unit) if(unit == nil) then game:SendToConsole("I CAN HAS nil ?") else game:SendToConsole("I CAN HAS UNITS!!!?") end end unit is always nil. I have checked and in the C++ code, the unit pointer is never invalid/null I've also tried: void CTestAI::UnitCreated(IUnit* unit){ lua_getglobal(L, "ai"); lua_getfield(L, -1, "UnitCreated"); SWIG_NewPointerObj(L,unit,SWIGTYPE_p_IUnit,0); lua_epcall(L, 1, 0); } with identical results. Why is this failing? How do I fix it?

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