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• What happens to my PriorityQueue if my Comparator throws an exception while it's busy bubbling up or

  - by nieldw

  Hi, I'm trying order pairs of integers ascendantly where a pair is considered less than another pair if both its entries are strictly less than those of the other pair, and larger than the other pair if both its entries are strictly larger than those of the other pair. All other cases are considered incomparable. They way I want to solve this is by defining a Comparator that implements the above, but will throw an exception for incomparable cases, and provide that to a PriorityQueue. Of course, while inserting a pair the priority queue does several comparisons while bubbling the new entry up to its correct position in the heap, and many of these will be comparable. But it may happen during the bubbling process that a pair is encountered with which this new pair is incomparable, and an exception will be thrown. If this happens, what will be the state of the PriorityQueue? Will the pair I was trying to insert sit in the heap at the last position it was in before the exception was thrown? If I use the PriorityQueue's remove(Object o) method, will the PriorityQueue be restored to a consistent state? Thanks

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• Avoid the problem with BigDecimal when migrating to Java 1.4 to Java 1.5+

  - by romaintaz

  Hello, I've recently migrated a Java 1.4 application to a Java 6 environment. Unfortunately, I encountered a problem with the BigDecimal storage in a Oracle database. To summarize, when I try to store a "7.65E+7" BigDecimal value (76,500,000.00) in the database, Oracle stores in reality the value of 7,650,000.00. This defect is due to the rewritting of the BigDecimal class in Java 1.5 (see here). In my code, the BigDecimal was created from a double using this kind of code: BigDecimal myBD = new BigDecimal("" + someDoubleValue); someObject.setAmount(myBD); // Now let Hibernate persists my object in DB... In more than 99% of the cases, everything works fine. Except that in really few case, the bug mentioned above occurs. And that's quite annoying. If I change the previous code to avoid the use of the String constructor of BigDecimal, then I do not encounter the bug in my uses cases: BigDecimal myBD = new BigDecimal(someDoubleValue); someObject.setAmount(myBD); // Now let Hibernate persists my object in DB... However, how can I be sure that this solution is the correct way to handle the use of BigDecimal? So my question is to know how I have to manage my BigDecimal values to avoid this issue: Do not use the new BigDecimal(String) constructor and use directly the new BigDecimal(double)? Force Oracle to use toPlainString() instead of toString() method when dealing with BigDecimal (and in this case how to do that)? Any other solution? Environment information: Java 1.6.0_14 Hibernate 2.1.8 (yes, it is a quite old version) Oracle JDBC 9.0.2.0 and also tested with 10.2.0.3.0 Oracle database 10.2.0.3.0

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• Awk filtering values between two files when regions intersect (any solutions welcome)

  - by user964689

  This is building upon an earlier question Awk conditional filter one file based on another (or other solutions) I have an awk program that outputs a column from rows in a text file 'refGene.txt if values in that row match 2 out of 3 values in another text file. I need to include an additional criteria for finding a match between the two files. The criteria is inclusion if the range of the 2 numberical values specified in each row in file 1 overlap with the range of the two values in a row in refGene.txt. An example of a line in File 1: chr1 10 20 chr2 10 20 and an example line in file 2(refGene.txt) of the matching columns ($3, $5, $ 6): chr1 5 30 Currently the awk program does not treat this as a match because although the first column matches neither the 2nd or 3rd columns do no. But I would like a way to treat this as a match because the region 10-20 in file 1 is WITHIN the range of 5-30 in refGene.txt. However the second line in file 1 should NOT match because the first column does not match, which is necessary. If there is a way to include cases when any of the range in file 1 overlaps with any of the range in refGene.txt that would be really helpful. It should also replace the below conditional statements as it would also find all the cases currently described below. Please let me know if my question is unclear. Any help is really appreciated, thanks it advance! (solutions do not have to be in awk) Rubal FILES=/files/*txt for f in $FILES ; do awk ' BEGIN { FS = "\t"; } FILENAME == ARGV[1] { pair[ $1, $2, $3 ] = 1; next; } { if ( pair[ $3, $5, $6 ] == 1 ) { print $13; } } ' $(basename $f) /files/refGene.txt > /files/results/$(basename $f) ; done

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• JPanel.addComponentListener does not work when the listener is a class variable

  - by Coder

  I have a public class which has the following method and instance variable: public void setImagePanel(JPanel value) { imagePanel = value; if (imagePanel != null) { //method 1 : works imagePanel.addComponentListener(new ComponentAdapter() { public void componentResized(ComponentEvent evt) { System.out.println("Here 1"); } }); //method 2 : does not work panelResizeListener = new ResizeListener(); imagePanel.addComponentListener(panelResizeListener); //method 3 : works //ResizeListener listener = new ResizeListener(); //imagePanel.addComponentListener(listener); //method 4 : works //imagePanel.addComponentListener(new ResizeListener()); //method 5 : does not work -- THIS IS THE DESIRED CODE I WANT TO USE imagePanel.addComponentListener(panelResizeListener); } } public class ResizeListener extends ComponentAdapter { @Override public void componentResized(ComponentEvent evt) { System.out.println("RESIZE 3"); } } private ResizeListener panelResizeListener = new ResizeListener(); Each of the methods above correspond the to code immediately below until the next //method comment. What i don't understand is why i can't use the class instance variable and add that to the JPanel as a component listener. What happens in the cases above where i say that the method does not work is that i don't get the "RESIZE 3" log messages. In all cases where i list that it works, then i get the "RESIZE 3" messages. The outer class is public with no other modification except that it implements an interface that i created (which has no methods or variables in common with the methods and variables listed above). If anyone can help me i would greatly appreciate it. This problem makes no sense to me, the code should be identical.

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• Fast Lightweight Image Comparisson Metric Algorithm

  - by gav

  Hi All, I am developing an application for the Android platform which contains 1000+ image filters that have been 'evolved'. When a user selects a photo I want to present the most relevant filters first. This 'relevance' should be dependent on previous use cases. I have already developed tools that register when a filtered image is saved; this combination of filter and image can be seen as the training data for my system. The issue is that the comparison must occur between selecting an image and the next screen coming up. From a UI point of view I need the whole process to take less that 4 seconds; select an image- obtain a metric to use for similarity - check against use cases - return 6 closest matches. I figure with 4 seconds I can use animations and progress dialogs to keep the user happy. Due to platform contraints I am fairly limited in the computational expense of the algorithm. I have implemented a technique adapted from various online tutorials for running C code on the G1 and hence this language is available Specific Constraints; Qualcomm® MSM7201A™, 528 MHz Processor 320 x 480 Pixel bitmap in 32 bit ARGB ~ 2 seconds computational time for the native method to get the metric ~ 2 seconds to compare the metric of the current image with training data This is an academic project so all ideas are welcome, anything you can think of or have heard about would be of interest to me. My ideas; I want to keep the complexity down (O(n*m)?) by using pixel data only rather than a neighbourhood function I was looking at using the Colour historgram/Greyscale histogram/Texture/Entropy of the image, combining them to make the measure. There will be an obvious loss of information but I need the resultant metric to be substantially smaller than the memory footprint of the image (~0.512 MB) As I said, any ideas to direct my research would be fantastic. Kind regards, Gavin

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• MVC: model of type Nullable<T>

  - by Fyodor Soikin

  I have a partial view that inherits from ViewUserControl<Guid?> - i.e. it's model is of type Nullable<Guid>. Very simple view, nothing special, but that's not the point. Somewhere else, I do Html.RenderPartial( "MyView", someGuid ), where someGuid is of type Nullable<Guid>. Everything's perfectly legal, should work OK, right? But here's the gotcha: the second argument of Html.RenderPartial is of type object, and therefore, Nullable<Guid> being a value type, it must be boxed. But nullable types are somehow special in the CLR, so that when you box one of those, you actually get either a boxed value of type T (Nullable's argument), or a null if the nullable didn't have a value to begin with. And that last case is actually interesting. Turns out, sometimes, I do have a situation when someGuid.HasValue == false. And in those cases, I effectively get a call Html.RenderPartial( "MyView", null ). And what does the HtmlHelper do when the model is null? Believe it or not, it just goes ahead and takes the parent view's model. Regardless of it's type. So, naturally, in those cases, I get an exception saying: "The model item passed into the dictionary is of type 'Parent.View.Model.Type', but this dictionary requires a model item of type 'System.Guid?'" So the question is: how do I make MVC correctly pass new Nullable<Guid> { HasValue = false } instead of trying to grab the parent's model? Note: I did consider wrapping my Guid? in an object of another type, specifically created for this occasion, but this seems completely ridiculous. Don't want to do that as long as there's another way. Note 2: now that I've wrote all this, I've realized that the question may be reduced to how to pass a null for model without ending up with parent's model?

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• Finding a MIME type for a file on windows

  - by rmeador

  Is there a way to get a file's MIME type using some system call on Windows? I'm writing an IIS extension in C++, so it must be callable from C++, and I do have access to IIS if there is some functionality exposed. Obviously, IIS itself must be able to do this, but my googling has been unable to find out how. I did find this .net related question here on SO, but that doesn't give me much hope (as neither a good solution nor a C++ solution is mentioned there). I need it so I can serve up dynamic files using the appropriate content type from my app. My plan is to first consult a list of MIME types within my app, then fall back to the system's MIME type listing (however that works; obviously it exists since it's how you associate files with programs). I only have a file extension to work with in some cases, but in other cases I may have an actual on-disk file to examine. Since these will not be user-uploaded files, I believe I can trust the extension and I'd prefer an extension-only lookup solution since it seems simpler and faster. Thanks!

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• Legitimate uses of the Function constructor

  - by Marcel Korpel

  As repeatedly said, it is considered bad practice to use the Function constructor (also see the ECMAScript Language Specification, 5th edition, § 15.3.2.1): new Function ([arg1[, arg2[, … argN]],] functionBody) (where all arguments are strings containing argument names and the last (or only) string contains the function body). To recapitulate, it is said to be slow, as explained by the Opera team: Each time […] the Function constructor is called on a string representing source code, the script engine must start the machinery that converts the source code to executable code. This is usually expensive for performance – easily a hundred times more expensive than a simple function call, for example. (Mark ‘Tarquin’ Wilton-Jones) Though it's not that bad, according to this post on MDC (I didn't test this myself using the current version of Firefox, though). Crockford adds that [t]he quoting conventions of the language make it very difficult to correctly express a function body as a string. In the string form, early error checking cannot be done. […] And it is wasteful of memory because each function requires its own independent implementation. Another difference is that a function defined by a Function constructor does not inherit any scope other than the global scope (which all functions inherit). (MDC) Apart from this, you have to be attentive to avoid injection of malicious code, when you create a new Function using dynamic contents. Lots of disadvantages and it is intelligible that ECMAScript 5 discourages the use of the Function constructor by throwing an exception when using it in strict mode (§ 13.1). That said, T.J. Crowder says in an answer that [t]here's almost never any need for the similar […] new Function(...), either, again except for some advanced edge cases. So, now I am wondering: what are these “advanced edge cases”? Are there legitimate uses of the Function constructor?

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• Loader.php trying to load Doctrine classes, but we use Propel!

  - by kewpiedoll99

  We are finding cases where we get the following 500 error: File xyz.php does not exist or class "xyz" was not found in the file at () in SF_ROOT_DIR/lib/vendor/Zend/Loader.php line 107 ... where xyz == Memcache (when trying to use symfony cc on the command line) or sfDoctrineAdminGenerator (when using an old-ish AdminGenerator-generated CMS page). We use Propel, but Loader.php is trying to load classes used only for Doctrine. Currently I am using a filthy hack where I request Loader.php to check if the file is either of these two cases, and if so simply return rather than trying to load it. Obviously, this is unacceptable longer term. Has anybody encountered this, and how did you solve it? Edited to add: We have: class ProjectConfiguration extends sfProjectConfiguration { public function setup() { // for compatibility / remove and enable only the plugins you want $this->enableAllPluginsExcept(array('sfDoctrinePlugin')); } } And we have a propel.ini file in our top level config directory. This has only started in the past four weeks or so, and we've had a stable build for over a year now. I'm pretty sure Doctrine is totally disabled.

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• Handling missing/incomplete data in R--is there function to mask but not remove NAs?

  - by doug

  As you would expect from a DSL aimed at data analysis, R handles missing/incomplete data very well, for instance: Many R functions have an 'na.rm' flag that you can set to 'T' to remove the NAs: mean( c(5,6,12,87,9,NA,43,67), na.rm=T) But if you want to deal with NAs before the function call, you need to do something like this: to remove each 'NA' from a vector: vx = vx[!is.na(a)] to remove each 'NA' from a vector and replace it w/ a '0': ifelse(is.na(vx), 0, vx) to remove entire each row that contains 'NA' from a data frame: dfx = dfx[complete.cases(dfx),] All of these functions permanently remove 'NA' or rows with an 'NA' in them. Sometimes this isn't quite what you want though--making an 'NA'-excised copy of the data frame might be necessary for the next step in the workflow but in subsequent steps you often want those rows back (e.g., to calculate a column-wise statistic for a column that has missing rows caused by a prior call to 'complete cases' yet that column has no 'NA' values in it). to be as clear as possible about what i'm looking for: python/numpy has a class, 'masked array', with a 'mask' method, which lets you conceal--but not remove--NAs during a function call. Is there an analogous function in R?

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• cast operator to base class within a thin wrapper derived class

  - by miked

  I have a derived class that's a very thin wrapper around a base class. Basically, I have a class that has two ways that it can be compared depending on how you interpret it so I created a new class that derives from the base class and only has new constructors (that just delegate to the base class) and a new operator==. What I'd like to do is overload the operator Base&() in the Derived class so in cases where I need to interpret it as the Base. For example: class Base { Base(stuff); Base(const Base& that); bool operator==(Base& rhs); //typical equality test }; class Derived : public Base { Derived(stuff) : Base(stuff) {}; Derived(const Base& that) : Base(that) {}; Derived(const Derived& that) : Base(that) {}; bool operator==(Derived& rhs); //special case equality test operator Base&() { return (Base&)*this; //Is this OK? It seems wrong to me. } }; If you want a simple example of what I'm trying to do, pretend I had a String class and String==String is the typical character by character comparison. But I created a new class CaseInsensitiveString that did a case insensitive compare on CaseInsensitiveString==CaseInsensitiveString but in all other cases just behaved like a String. it doesn't even have any new data members, just an overloaded operator==. (Please, don't tell me to use std::string, this is just an example!) Am I going about this right? Something seems fishy, but I can't put my finger on it.

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• Bidirectional/Loopback UDP in .net

  - by Jason Williams

  I've got an app that needs to transmit and receive on the same port. This can happen in two cases: Where the PC is talking to a piece of remote hardware. It "replies to sender", so the datagrams come back in to my PC via the sending port. Where the PC is talking to itself (loopback mode) for testing and demoing (a test app feeds fake data into our main app via UDP). This only seems to fail when trying to achieve loopback. The only way I can get it working is to ensure that the receiver is set up first - something I cannot guarantee. Can anyone help narrow down my search by suggesting a "correct" way to implement the UdpClient(s) to handle the above situations reliably? (The only solution that I've found to work reliably with the remote hardware is to use a single UdpClient in a bidirectional manner, although I'm working with legacy code that may be influencing that finding. I've tried using two UdpClients, but they step on each others toes - In some cases, once one client is started up, the other client cannot connect. With ExclusiveAddressUse/ReuseAddress set up to allow port sharing, I can almost get it to work, apart from the receiver having to start first)

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• How to use symbols/punctuation characters in discriminated unions

  - by user343550

  I'm trying to create a discriminated union for part of speech tags and other labels returned by a natural language parser. It's common to use either strings or enums for these in C#/Java, but discriminated unions seem more appropriate in F# because these are distinct, read-only values. In the language reference, I found that this symbol ``...`` can be used to delimit keywords/reserved words. This works for type ArgumentType = | A0 // subject | A1 // indirect object | A2 // direct object | A3 // | A4 // | A5 // | AA // | ``AM-ADV`` However, the tags contain symbols like $, e.g. type PosTag = | CC // Coordinating conjunction | CD // Cardinal Number | DT // Determiner | EX // Existential there | FW // Foreign Word | IN // Preposision or subordinating conjunction | JJ // Adjective | JJR // Adjective, comparative | JJS // Adjective, superlative | LS // List Item Marker | MD // Modal | NN // Noun, singular or mass | NNP // Proper Noun, singular | NNPS // Proper Noun, plural | NNS // Noun, plural | PDT // Predeterminer | POS // Possessive Ending | PRP // Personal Pronoun | PRP$ //$ Possessive Pronoun | RB // Adverb | RBR // Adverb, comparative | RBS // Adverb, superlative | RP // Particle | SYM // Symbol | TO // to | UH // Interjection | VB // Verb, base form | VBD // Verb, past tense | VBG // Verb, gerund or persent participle | VBN // Verb, past participle | VBP // Verb, non-3rd person singular present | VBZ // Verb, 3rd person singular present | WDT // Wh-determiner | WP // Wh-pronoun | WP$ //$ Possessive wh-pronoun | WRB // Wh-adverb | ``#`` | ``$`` | ``''`` | ``(`` | ``)`` | ``,`` | ``.`` | ``:`` | `` //not sure how to escape/delimit this ``...`` isn't working for WP$ or symbols like ( Also, I have the interesting problem that the parser returns `` as a meaningful symbol, so I need to escape it as well. Is there some other way to do this, or is this just not possible with a discriminated union? Right now I'm getting errors like Invalid namespace, module, type or union case name Discriminated union cases and exception labels must be uppercase identifiers I suppose I could somehow override toString for these goofy cases and replace the symbols with some alphanumeric equivalent?

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• My android tests don't get internet access!

  - by Malachii

  The subject says it all. My application gets internet access thanks to the android.permission.INTERNET permission, but my test cases don't while using the instrumentation test runner. This means I can't test my server IO routines in my test cases. What's up? Here's my manifest in case it helps you. Thanks! Sorry about the lack of indents - could not get it working on short notice with this site. Thanks! <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.helloandroid" android:versionCode="1" android:versionName="1.0"> <uses-permission android:name="android.permission.INTERNET"></uses-permission> <application android:icon="@drawable/icon" android:label="@string/app_name"> <uses-library android:name="android.test.runner" /> <activity android:name=".HelloAndroid" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <uses-sdk android:minSdkVersion="2" /> <instrumentation android:name="android.test.InstrumentationTestRunner" android:targetPackage="qnext.mobile.redirect" android:label="Qnext Redirect Tests" /> </manifest>

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• Delphi Performance: Case Versus If

  - by Andreas Rejbrand

  I guess there might be some overlapping with previous SO questions, but I could not find a Delphi-specific question on this topic. Suppose that you want to check if an unsigned 32-bit integer variable "MyAction" is equal to any of the constants ACTION1, ACTION2, ... ACTIONn, where n is - say 1000. I guess that, besides being more elegant, case MyAction of ACTION1: {code}; ACTION2: {code}; ... ACTIONn: {code}; end; if much faster than if MyAction = ACTION1 then // code else if MyAction = ACTION2 then // code ... else if MyAction = ACTIONn then // code; I guess that the if variant takes time O(n) to complete (i.e. to find the right action) if the right action ACTIONi has a high value of i, whereas the case variant takes a lot less time (O(1)?). Am I correct that switch is much faster? Am I correct that the time required to find the right action in the switch case actually is independent of n? I.e. is it true that it does not really take any longer to check a million cases than to check 10 cases? How, exactly, does this work?

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• How can I tackle 'profoundly found elsewhere' syndrome (inverse of NIH)?

  - by Alistair Knock

  How can I encourage colleagues to embrace small-scale innovation within our team(s), in order to get things done quicker and to encourage skills development? (the term 'profoundly found elsewhere' comes from Wikipedia, although it is scarcely used anywhere else apart from a reference to Proctor & Gamble) I've worked in both environments where there is a strong opposition to software which hasn't been developed in-house (usually because there's a large community of developers), and more recently (with far fewer central developers) where off-the-shelf products are far more favoured for the usual reasons: maintenance, total cost over product lifecycle, risk management and so on. I think the off the shelf argument works in the majority of cases for the majority of users, even though as a developer the product never quite does what I'd like it to do. However, in some cases there are clear gaps where the market isn't able to provide specifically what we would need, or at least it isn't able to without charging astronomical consultancy rates for a bespoke solution. These can be small web applications which provide a short-term solution to a particular need in one specific department, or could be larger developments that have the potential to serve a wider audience, both across the organisation and into external markets. The problem is that while development of these applications would be incredibly cheap in terms of developer hours, and delivered very quickly without the need for glacial consultation, the proposal usually falls flat because of risk: 'Who'll maintain the project tracker that hasn't had any maintenance for the past 7 years while you're on holiday for 2 weeks?' 'What if one of our systems changes and the connector breaks?' 'How can you guarantee it's secure/better/faster/cheaper/holier than Company X's?' With one developer behind these little projects, the answers are invariably: 'Nobody, but...' 'It will break, just like any other application would...' 'I, uh...' How can I better answer these questions and encourage people to take a little risk in order to stimulate creativity and fast-paced, short-lifecycle development instead of using that 6 months to consult about what tender process we might use?

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• Copying a subset of data to an empty database with the same schema

  - by user193655

  I would like to export part of a database full of data to an empty database. Both databases has the same schema. I want to maintain referential integrity. To simplify my cases it is like this: MainTable has the following fields: 1) MainID integer PK 2) Description varchar(50) 3) ForeignKey integer FK to MainID of SecondaryTable SecondaryTable has the following fields: 4) MainID integer PK (referenced by (3)) 5) AnotherDescription varchar(50) The goal I'm trying to accomplish is "export all records from MainTable using a WHERE condition", for example all records where MainID < 100. To do it manually I shuold first export all data from SecondaryTable contained in this select: select * from SecondaryTable ST outer join PrimaryTable PT on ST.MainID=PT.MainID then export the needed records from MainTable: select * from MainTable where MainID < 100. This is manual, ok. Of course my case is much much much omre complex, I have 200+ tables, so donig it manually is painful/impossible, I have many cascading FKs. Is there a way to force the copy of main table only "enforcing referntial integrity". so that my query is something like: select * from MainTable where MainID < 100 WITH "COPYING ALL FK sources" In this cases also the field (5) will be copied. ====================================================== Is there a syntax or a tool to do this? Table per table I'd like to insert conditions (like MainID <100 is only for MainTable, but I have also other tables).

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• Does CSS have a "start over" feature?

  - by Rick Wayne

  I'm using calendar_date_select (henceforth CDS) in a Rails application, and have a stupid question. When I embed the CDS component in the middle of an already-CSS-styled page, all manner of things go ugly-wrong with it (spacing, fonts, etc.). Clearly the elements inside the CDS have inherited unwanted stuff from the styles already working in the containing page. Now, I could use a combination of, say, Safari's CSS debugging and analyze what's wrong element-by-element. But that's (A) tedious, and (B) might load up my component's styles with tons of container-defeating special cases. If nothing else, I'm certain to change the containing page's styles in the future and would have to maintain the special cases. My question: Is is possible to have a DIV in a page that essentially backs out all the existing styling? Is there a simple one-liner that will do this? Failing that, can it be done on an element-by-element basis? E.g. I know what tags the CDS generates, so I could list each of them: { p: "#--NOTHING--#"; a: "#--NOTHING--#"; } where #--NOTHING--# is the Magic Turn Off All Inherited Styles incantation. http://code.google.com/p/calendardateselect/ Thanks, peeps.

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• How to write this function as a pL/pgSQl function ?

  - by morpheous

  I am trying to implement some business logic in a PL/pgSQL function. I have hacked together some pseudo code that explains the type of business logic I want to include in the function. Note: This function returns a table, so I can use it in a query like: SELECT A.col1, B.col1 FROM (SELECT * from some_table_returning_func(1, 1, 2, 3)) as A, tbl2 as B; The pseudocode of the pl/PgSQL function is below: CREATE FUNCTION some_table_returning_func(uid int, type_id int, filter_type_id int, filter_id int) RETURNS TABLE AS $$ DECLARE where_clause text := 'tbl1.id = ' + uid; ret TABLE; BEGIN switch (filter_type_id) { case 1: switch (filter_id) { case 1: where_clause += ' AND tbl1.item_id = tbl2.id AND tbl2.type_id = filter_id'; break; //other cases follow ... } break; //other cases follow ... } // where clause has been built, now run query based on the type ret = SELECT [COL1, ... COLN] WHERE where_clause; IF (type_id <> 1) THEN return ret; ELSE return select * from another_table_returning_func(ret,123); ENDIF; END; $$ LANGUAGE plpgsql; I have the following questions: How can I write the function correctly to (i.e. EXECUTE the query with the generated WHERE clause, and to return a table How can I write a PL/pgSQL function that accepts a table and an integer and returns a table (another_table_returning_func) ?

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• Is it possible to replace values ina queryset before sending it to your template?

  - by Issy

  Hi Guys, Wondering if it's possible to change a value returned from a queryset before sending it off to the template. Say for example you have a bunch of records Date | Time | Description 10/05/2010 | 13:30 | Testing... etc... However, based on the day of the week the time may change. However this is static. For example on a monday the time is ALWAYS 15:00. Now you could add another table to configure special cases but to me it seems overkill, as this is a rule. How would you replace that value before sending it to the template? I thought about using the new if tags (if day=1), but this is more of business logic rather then presentation. Tested this in a custom template tag def render(self, context): result = self.model._default_manager.filter(from_date__lte=self.now).filter(to_date__gte=self.now) if self.day == 4: result = result.exclude(type__exact=2).order_by('time') else: result = result.order_by('type') result[0].time = '23:23:23' context[self.varname] = result return '' However it still displays the results from the DB, is this some how related to 'lazy' evaluation of templates? Thanks! Update Responding to comments below: It's not stored wrong in the DB, its stored Correctly However there is a small side case where the value needs to change. So for example I have a From Date & To date, my query checks if todays date is between those. Now with this they could setup a from date - to date for an entire year, and the special cases (like mondays as an example) is taken care off. However if you want to store in the DB you would have to capture several more records to cater for the side case. I.e you would be capturing the same information just to cater for that 1 day when the time changes. (And the time always changes on the same day, and is always the same)

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• C++ - passing references to boost::shared_ptr

  - by abigagli

  If I have a function that needs to work with a shared_ptr, wouldn't it be more efficient to pass it a reference to it (so to avoid copying the shared_ptr object)? What are the possible bad side effects? I envision two possible cases: 1) inside the function a copy is made of the argument, like in ClassA::take_copy_of_sp(boost::shared_ptr<foo> &sp) { ... m_sp_member=sp; //This will copy the object, incrementing refcount ... } 2) inside the function the argument is only used, like in Class::only_work_with_sp(boost::shared_ptr<foo> &sp) //Again, no copy here { ... sp->do_something(); ... } I can't see in both cases a good reason to pass the boost::shared_ptr by value instead of by reference. Passing by value would only "temporarily" increment the reference count due to the copying, and then decrement it when exiting the function scope. Am I overlooking something? Andrea. EDIT: Just to clarify, after reading several answers : I perfectly agree on the premature-optimization concerns, and I alwasy try to first-profile-then-work-on-the-hotspots. My question was more from a purely technical code-point-of-view, if you know what I mean.

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• How to change the date/time in Python for all modules?

  - by Felix Schwarz

  When I write with business logic, my code often depends on the current time. For example the algorithm which looks at each unfinished order and checks if an invoice should be sent (which depends on the no of days since the job was ended). In these cases creating an invoice is not triggered by an explicit user action but by a background job. Now this creates a problem for me when it comes to testing: I can test invoice creation itself easily However it is hard to create an order in a test and check that the background job identifies the correct orders at the correct time. So far I found two solutions: In the test setup, calculate the job dates relative to the current date. Downside: The code becomes quite complicated as there are no explicit dates written anymore. Sometimes the business logic is pretty complex for edge cases so it becomes hard to debug due to all these relative dates. I have my own date/time accessor functions which I use throughout my code. In the test I just set a current date and all modules get this date. So I can simulate an order creation in February and check that the invoice is created in April easily. Downside: 3rd party modules do not use this mechanism so it's really hard to integrate+test these. The second approach was way more successful to me after all. Therefore I'm looking for a way to set the time Python's datetime+time modules return. Setting the date is usually enough, I don't need to set the current hour or second (even though this would be nice). Is there such a utility? Is there an (internal) Python API that I can use?

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• Why do C# containers and GUI classes use int and not uint for size related members ?

  - by smerlin

  I usually program in C++, but for school i have to do a project in C#. So i went ahead and coded like i was used to in C++, but was surprised when the compiler complained about code like the following: const uint size = 10; ArrayList myarray = new ArrayList(size); //Arg 1: cannot convert from 'uint' to 'int Ok they expect int as argument type, but why ? I would feel much more comfortable with uint as argument type, because uint fits much better in this case. Why do they use int as argument type pretty much everywhere in the .NET library even if though for many cases negative numbers dont make any sense (since no container nor gui element can have a negative size). If the reason that they used int is, that they didnt expect that the average user cares about signedness, why didnt they add overloads for uint additonally ? Is this just MS not caring about sign correctness or are there cases where negative values make some sense/ carry some information (error code ????) for container/gui widget/... sizes ?

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• Is it possible to replace values in a queryset before sending it to your template?

  - by Issy

  Hi Guys, Wondering if it's possible to change a value returned from a queryset before sending it off to the template. Say for example you have a bunch of records Date | Time | Description 10/05/2010 | 13:30 | Testing... etc... However, based on the day of the week the time may change. However this is static. For example on a monday the time is ALWAYS 15:00. Now you could add another table to configure special cases but to me it seems overkill, as this is a rule. How would you replace that value before sending it to the template? I thought about using the new if tags (if day=1), but this is more of business logic rather then presentation. Tested this in a custom template tag def render(self, context): result = self.model._default_manager.filter(from_date__lte=self.now).filter(to_date__gte=self.now) if self.day == 4: result = result.exclude(type__exact=2).order_by('time') else: result = result.order_by('type') result[0].time = '23:23:23' context[self.varname] = result return '' However it still displays the results from the DB, is this some how related to 'lazy' evaluation of templates? Thanks! Update Responding to comments below: It's not stored wrong in the DB, its stored Correctly However there is a small side case where the value needs to change. So for example I have a From Date & To date, my query checks if todays date is between those. Now with this they could setup a from date - to date for an entire year, and the special cases (like mondays as an example) is taken care off. However if you want to store in the DB you would have to capture several more records to cater for the side case. I.e you would be capturing the same information just to cater for that 1 day when the time changes. (And the time always changes on the same day, and is always the same)

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• Box2D in Flash runs quicker when drawing debug data than not

  - by bowdengm

  I've created a small game with Box2d for AS3 - I have sprites attached to the stage that take their position from the underlying Box2d world. These sprites are mostly PNGs. When the game runs with DrawDebugData() bening called every update, it runs nice and smoothly. However when I comment this out, it runs choppily. In both cases all my sprites are being rendered. So it seems that it's running faster when it's drawing the debug data additionaly (i.e. my sprites are on the screen in both cases!) What's going on? Does drawing the debug data flick some sort of 'render quick' switch? If so, what's the switch!? I can't see it in the Box2D code. function Update(e){ m_world.Step(m_timeStep, m_velocityIterations, m_positionIterations); // draw debug? m_world.DrawDebugData(); // with the above line in, I get 27fps, without it, I get 19fps. // that's the only change that's causing such a huge difference. doStuff(); } Interestingly, If i set the debug draw scale to something different to my world scale, it slows down to 19fps. So there's something happening when it draws the boxes under my sprites causing it to run quicker.. Cheers, Guy

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