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Create a polynomial object from a number using change-class

- by charlieb

I have written a polynomial class along the lines described in SICP 2.5.3 (except using defclass). I would like to be able to seamlessly add and multiply polynomials and regular numbers but I can't make change-class accept a number. I tried to simplify the problem by changing class from an integer to a float: (change-class 4 'float) but that gave me the error: There is no applicable method for the generic function #<STANDARD-GENERIC-FUNCTION CHANGE-CLASS (7)> when called with arguments (4 #<BUILT-IN-CLASS FLOAT>). [Condition of type SIMPLE-ERROR] I get an error of the same form from (fyi): (change-class 4 'polynomial) I'm going to go ahead and implement a manual conversion but I would prefer to use the built-in clos facilities.

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T-SQL Dynamic SQL and Temp Tables

- by George

It looks like #temptables created using dynamic SQL via the EXECUTE string method have a different scope and can't be referenced by "fixed" SQLs in the same stored procedure. However, I can reference a temp table created by a dynamic SQL statement in a subsequence dynamic SQL but it seems that a stored procedure does not return a query result to a calling client unless the SQL is fixed. A simple 2 table scenario: I have 2 tables. Let's call them Orders and Items. Order has a Primary key of OrderId and Items has a Primary Key of ItemId. Items.OrderId is the foreign key to identify the parent Order. An Order can have 1 to n Items. I want to be able to provide a very flexible "query builder" type interface to the user to allow the user to select what Items he want to see. The filter criteria can be based on fields from the Items table and/or from the parent Order table. If an Item meets the filter condition including and condition on the parent Order if one exists, the Item should be return in the query as well as the parent Order. Usually, I suppose, most people would construct a join between the Item table and the parent Order tables. I would like to perform 2 separate queries instead. One to return all of the qualifying Items and the other to return all of the distinct parent Orders. The reason is two fold and you may or may not agree. The first reason is that I need to query all of the columns in the parent Order table and if I did a single query to join the Orders table to the Items table, I would be repoeating the Order information multiple times. Since there are typically a large number of items per Order, I'd like to avoid this because it would result in much more data being transfered to a fat client. Instead, as mentioned, I would like to return the two tables individually in a dataset and use the two tables within to populate a custom Order and child Items client objects. (I don't know enough about LINQ or Entity Framework yet. I build my objects by hand). The second reason I would like to return two tables instead of one is because I already have another procedure that returns all of the Items for a given OrderId along with the parent Order and I would like to use the same 2-table approach so that I could reuse the client code to populate my custom Order and Client objects from the 2 datatables returned. What I was hoping to do was this: Construct a dynamic SQL string on the Client which joins the orders table to the Items table and filters appropriate on each table as specified by the custom filter created on the Winform fat-client app. The SQL build on the client would have looked something like this: TempSQL = " INSERT INTO #ItemsToQuery OrderId, ItemsId FROM Orders, Items WHERE Orders.OrderID = Items.OrderId AND /* Some unpredictable Order filters go here */ AND /* Some unpredictable Items filters go here */ " Then, I would call a stored procedure, CREATE PROCEDURE GetItemsAndOrders(@tempSql as text) Execute (@tempSQL) --to create the #ItemsToQuery table SELECT * FROM Items WHERE Items.ItemId IN (SELECT ItemId FROM #ItemsToQuery) SELECT * FROM Orders WHERE Orders.OrderId IN (SELECT DISTINCT OrderId FROM #ItemsToQuery) The problem with this approach is that #ItemsToQuery table, since it was created by dynamic SQL, is inaccessible from the following 2 static SQLs and if I change the static SQLs to dynamic, no results are passed back to the fat client. 3 around come to mind but I'm look for a better one: 1) The first SQL could be performed by executing the dynamically constructed SQL from the client. The results could then be passed as a table to a modified version of the above stored procedure. I am familiar with passing table data as XML. If I did this, the stored proc could then insert the data into a temporary table using a static SQL that, because it was created by dynamic SQL, could then be queried without issue. (I could also investigate into passing the new Table type param instead of XML.) However, I would like to avoid passing up potentially large lists to a stored procedure. 2) I could perform all the queries from the client. The first would be something like this: SELECT Items.* FROM Orders, Items WHERE Order.OrderId = Items.OrderId AND (dynamic filter) SELECT Orders.* FROM Orders, Items WHERE Order.OrderId = Items.OrderId AND (dynamic filter) This still provides me with the ability to reuse my client sided object-population code because the Orders and Items continue to be returned in two different tables. I have a feeling to, that I might have some options using a Table data type within my stored proc, but that is also new to me and I would appreciate a little bit of spoon feeding on that one. If you even scanned this far in what I wrote, I am surprised, but if so, I woul dappreciate any of your thoughts on how to accomplish this best.

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dismissModalViewControllerAnimated: crashes in Simulator but not on phone

- by Jon

I'm doing the following: [self.parentViewController dismissModalViewControllerAnimated:YES] This code fails using the Simulator but works with no issues on the phone itself. The Simulator's console shows no erros. I used NSLog statements to pinpoint this line of code as the culprit. When running on the phone, however, the console(windoworganizer) shows that the above code is executed and the application proceeds forward with no problem. When running the code in debugger, the following statement appears at the bottom of the Xcode debug window: GDB: Data Formatters temporarily unavailable, will re-try after a 'continue'. (Not safe to call dlopen at this time.) Then a window dispalys stating: Loading 43672 stack frames. (that sounds bad) In the debug window the following line appears numerous times: [UIView(Hierarchy) _makeSubtreePerformSelector:withObject:withObject:copySublayers:] Without getting too deep into my code, does anyone know about or have experience with this type of condition? Thanks

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Proper way to copy a readonly NSMutableArray

- by Jon Hull

I have an object with a readonly property that I am trying to implement NSCopying for. It has a mutableArray called "subConditions" (which holds "SubCondition" objects). I have made it readonly because I want callers to be able to change the data in the array, but not the array itself. This worked really well until it was time to write the -copyWithZone: method. After fumbling around a bit, I managed to get something that seems to work. I am not sure if it is the best practice though. Here is a simplified version of my -copyWithZone: method: -(id)copyWithZone:(NSZone*)zone { Condition *copy = [[[self class]allocWithZone:zone]init]; NSArray *copiedArray = [[NSArray alloc]initWithArray:self.subConditions copyItems:YES]; [copy.subConditions setArray:copiedArray]; [copiedArray release]; return copy; } Is this the correct/best way to copy a readonly mutableArray?

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Most clever way to parse a Facebook OAuth 2 access token string

- by RyOnLife

It's a bit late, but I'm disappointed in myself for not coming up with something more elegant. Anyone have a better way to do this... When you pass an OAuth code to Facebook, it response with a query string containing access_token and expires values. access_token=121843224510409|2.V_ei_d_rbJt5iS9Jfjk8_A__.3600.1273741200-569255561|TxQrqFKhiXm40VXVE1OBUtZc3Ks.&expires=4554 Although if you request permission for offline access, there's no expires and the string looks like this: access_token=121843224510409|2.V_ei_d_rbJt5iS9Jfjk8_A__.3600.1273741200-569255561|TxQrqFKhiXm40VXVE1OBUtZc3Ks. I attempted to write a regex that would suffice for either condition. No dice. So I ended up with some really ugly Ruby: s = s.split("=") @oauth = {} if s.length == 3 @oauth[:access_token] = s[1][0, s[1].length - 8] @oauth[:expires] = s[2] else @oauth[:access_token] = s[1] end I know there must be a better way!

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Can't access web service when connected to the network :: HTTP 407

- by Ian

Hi All, I have a console application that communicates with a web service. Both of them are on the same machine. When I am accessing the web service with the LAN disabled, it connects without a problem. But if the LAN is enabled and connected to our office network, I receive this error: "HTTP 407 Proxy Authentication required - The ISA Server requires authorization to fulfill the request. Access to the Web Proxy service is denied." We've been hunting the source of the problem for three days now. We have tried everything that we can think of. Any ideas what's causing the problem? Additional notes: - The machine is in a Workgroup setup but with DNS suffix (computer.local). When accessing the web service, we type the address as "http://machine.computer.local/service.asmx" I talked to the IT guys and they said that we don't have an ISA server installed There is no "proxy" set in IE. The machine is in mint condition.

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POSIX threads and signals

- by Donal Fellows

I've been trying to understand the intricacies of how POSIX threads and POSIX signals interact. In particular, I'm interested in: What's the best way to control which thread a signal is delivered to (assuming it isn't fatal in the first place)? What is the best way to tell another thread (that might actually be busy) that the signal has arrived? (I already know that it's a bad idea to be using pthread condition variables from a signal handler.) For reference about why I want this, I'm researching how to convert the TclX package to support threads, or to split it up and at least make some useful parts support threads. Signals are one of those parts that is of particular interest.

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Linear complexity and quadratic complexity

- by jasonline

I'm just not sure... If you have a code that can be executed in either of the following complexities: A sequence of O(n), like for example: two O(n) in sequence O(n²) The preferred version would be the one that can be executed in linear time. Would there be a time such that the sequence of O(n) would be too much and that O(n²) would be preferred? In other words, is the statement C x O(n) < O(n²) always true for any constant C? Why or why not? What are the factors that would affect the condition such that it would be better to choose the O(n²) complexity?

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When should assertions stay in production code?

- by Carl Seleborg

Hi all, There's a discussion going on over at comp.lang.c++.moderated about whether or not assertions, which in C++ only exist in debug builds by default, should be kept in production code or not. Obviously, each project is unique, so my question here is not so much whether assertions should be kept, but in which cases this is recommendable/not a good idea. By assertion, I mean: A run-time check that tests a condition which, when false, reveals a bug in the software. A mechanism by which the program is halted (maybe after really minimal clean-up work). I'm not necessarily talking about C or C++. My own opinion is that if you're the programmer, but don't own the data (which is the case with most commercial desktop applications), you should keep them on, because a failing asssertion shows a bug, and you should not go on with a bug, with the risk of corrupting the user's data. This forces you to test strongly before you ship, and makes bugs more visible, thus easier to spot and fix. What's your opinion/experience? Cheers, Carl See related question here

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Return data from subroutine while the subroutine is still processing

- by Perl QuestionAsker

Is there any way to have a subroutine send data back while still processing? For instance (this example used simply to illustrate) - a subroutine reads a file. While it is reading through the file, if some condition is met, then "return" that line and keep processing. I know there are those that will answer - why would you want to do that? and why don't you just ...?, but I really would like to know if this is possible. Thank you so much in advance.

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Asynchronous Sockets - Handling false socket.AcceptAsync values

- by David

The Socket class has a method .AcceptAsync which either returns true or false. I'd thought the false return value was an error condition, but in the samples Microsoft provide for Async sockets they call the callback function synchronously after checking for failure, as shown here: public void StartAccept(SocketAsyncEventArgs acceptEventArg) { if (acceptEventArg == null) { acceptEventArg = new SocketAsyncEventArgs(); acceptEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(AcceptEventArg_Completed); } else { // socket must be cleared since the context object is being reused acceptEventArg.AcceptSocket = null; } m_maxNumberAcceptedClients.WaitOne(); bool willRaiseEvent = listenSocket.AcceptAsync(acceptEventArg); if (!willRaiseEvent) { ProcessAccept(acceptEventArg); } } /// <summary> /// This method is the callback method associated with Socket.AcceptAsync operations and is invoked /// when an accept operation is complete /// </summary> void AcceptEventArg_Completed(object sender, SocketAsyncEventArgs e) { ProcessAccept(e); } Why do they do this? It defeats the purpose of asynchronous sockets and stops the method from returning.

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Python TKinter connect variable to entry widget

- by Sano98

Hi everyone, I'm trying to associate a variable with a Tkinter entry widget, in a way that: Whenever I change the value (the "content") of the entry, mainly by typing something into it, the variable automatically gets assigned the value of what I've typed. Without me having to push a button "Update value " or something like that first. Whenever the variable gets changed (by some other part of the programm), I want the entry value displayed to be adjusted automatically. I believe that this could work via the textvariable. I read the example on http://effbot.org/tkinterbook/entry.htm, but it is not exactly helping me for what I have in mind. I have a feeling that there is a way of ensuring the first condition with using entry's "validate". Any ideas? Thank you for your input! Sano

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Help needed inorder to avoid recursion

- by Srivatsa

Hello All I have a method, which gives me the required number of Boxes based on number of devices it can hold.Currently i have implemented this logic using recursion private uint PerformRecursiveDivision(uint m_oTotalDevices,uint m_oDevicesPerBox, ref uint BoxesRequired) { if (m_oTotalDevices< m_oDevicesPerBox) { BoxesRequired = 1; } else if ((m_oTotalDevices- m_oDevicesPerBox>= 0) && (m_oTotalDevices- m_oDevicesPerBox) < m_oDevicesPerBox) { //Terminating condition BoxesRequired++; return BoxesRequired; } else { //Call recursive function BoxesRequired++; return PerformRecursiveDivision((m_oTotalDevices- m_oDevicesPerBox), m_oDevicesPerBox, ref BoxesRequired); } return BoxesRequired; } Is there any better method to implement the same logic without using recursion. Cos this method is making my application very slow for cases when number of devices exceeds 50000. Thanks in advance for your support Constant learner

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How to get rid of the following multiple alternatives warnings in my ANTLR3 grammar?

- by Jarrod Roberson

[11:45:19] warning(200): mygrammar.g:14:57: Decision can match input such as "','" using multiple alternatives: 1, 2 As a result, alternative(s) 2 were disabled for that input [11:45:19] warning(200): C:\Users\Jarrod Roberson\mygrammar.g:14:57: Decision can match input such as "','" using multiple alternatives: 1, 2 As a result, alternative(s) 2 were disabled for that input I want to be able to nest functions inside other functions. myfunction(x) -> sqr(a) -> a * a, y = sqr(x). here is the line it is complaining about function : ID '(' args ')' '->' statement (',' statement)* ; and here is what it is considering the alternative statement : ATOM | expression | assignment | function ; Here is what the synatx diagram looks like in ANTLRWorks I really like things to compile/work without any warnings. How do I resolve this warning condition?

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Replace values in a dataframe based on another factor which contains NA's in R

- by PaulHurleyuk

I have a dataframe which contains (among other things) a numeric column with a concentration, and a factor column with a status flag. This status flag contains NA's. Here's an example df<-structure(list(conc = c(101.769, 1.734, 62.944, 92.697, 25.091, 27.377, 24.343, 55.084, 0.335, 23.280), status = structure(c(NA, NA, NA, NA, NA, NA, 2L, NA, 1L, NA), .Label = c("<LLOQ", "NR"), class = "factor")), .Names = c("conc", "status"), row.names = c(NA, -10L), class = "data.frame") I want to replace the concentration column with a string for some values of the flag column, or with the concentration value formatted to a certain number of significant digits. When I try this ifelse(df$status=="NR","NR",df$conc) The NA's in the status flag don't trigger either the true or false condition (and return NA) - as the documentation suggests it will. I could loop over the rows and use IF then else on each one but this seems inefficient. Am I missing something ? I've tried as.character(df$status) as well which doesn't work. My mojo must be getting low....

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removing pairs of elements from numpy arrays that are NaN (or another value) in Python

- by user248237

I have an array with two columns in numpy. For example: a = array([[1, 5, nan, 6], [10, 6, 6, nan]]) a = transpose(a) I want to efficiently iterate through the two columns, a[:, 0] and a[:, 1] and remove any pairs that meet a certain condition, in this case if they are NaN. The obvious way I can think of is: new_a = [] for val1, val2 in a: if val2 == nan or val2 == nan: new_a.append([val1, val2]) But that seems clunky. What's the pythonic numpy way of doing this? thanks.

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TSQL -- Make it better

- by user319353

Hi: -- Very Narrow (all IDs are passed in) IF(@EmpID IS NOT NULL AND @DeptID IS NOT NULL AND @CityID IS NOT NULL) BEGIN SELECT e.EmpName ,d.DeptName ,c.CityName FROM Employee e WITH (NOLOCK) JOIN Department d WITH (NOLOCK) ON e.deptid = d.deptid JOIN City c WITH (NOLOCK) ON e.CityID = c.CityID WHERE e.EmpID = @EmpID END -- Just 2 IDs passed in ELSE IF(@DeptID IS NOT NULL AND @CityID IS NOT NULL) BEGIN SELECT e.EmpName ,d.DeptName ,NULL AS [CityName] FROM Employee e WITH (NOLOCK) JOIN Department d WITH (NOLOCK) ON e.deptid = d.deptid JOIN City c WITH (NOLOCK) ON e.CityID = c.CityID WHERE d.deptID = @DeptID END -- Very Broad (just 1 ID passed in) ELSE IF(@CityID IS NOT NULL) BEGIN SELECT e.EmpName ,NULL AS [DeptName] ,NULL AS [CityName] FROM Employee e WITH (NOLOCK) JOIN Department d WITH (NOLOCK) ON e.deptid = d.deptid JOIN City c WITH (NOLOCK) ON e.CityID = c.CityID WHERE c.CityID = @CityID END -- None (Nothing passed in) ELSE BEGIN SELECT NULL AS [EmpName] ,NULL AS [DeptName] ,NULL AS [CityName] END Question: Is there any better way (OR specifically can I do anything without IF...ELSE condition?

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assigning in system of differential equations

- by Alireza

hi every one! when i solve numerically a system of two differential equations: s1:=diff(nDi, t)=...; s2:=diff(nT, t)=...; ics:={...}; #initial condition. sys := {s1, s2, ics}: sol:=dsolve(sys,numeric); with respect to "t",then the solution (for example)for "t=4" is of the form, sol(4): [t=4, n1(t)=const1, n2(t)=const2]. now, how is possible to use values of n1(t) and n2(t) for all "t"'s in another equation, namely "p", which involved n1(t) or n2(t)(like: {p=a+n1(t)*n2(t)+f(t)},where "a" and "f(t)" are defined), and to plot "p" for an interval of "t"?

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AWK If/ElseConditional Problem

- by neversaint

I have a data that looks like this: foo foo scaffold_7 1 4845 6422 4845 bar bar scaffold_7 -1 14689 16310 16310 What I want to do is to process the above lines where I just want to print column 1,2,3, 7 and one more column after 7th. But with condition when printing column 7 onwards. Below is my awk script: awk '{ if ($4=="+") { {end=$6-$5}{print $1 "\t" $2 "\t" $3 "\t" $4 "\t" $7 "\t" end+$7} } else {end=$6-$5}{print $1 "\t" $2 "\t" $3 "\t" $4 "\t" $7-end "\t" $7} }' But why it doesn't achieve the desired result like this? foo foo scaffold_7 1 4845 6422 bar bar scaffold_7 -1 14689 16310 Note that the arithmetic (e.g. $7-end or end+$7) is a must. So we can't just swap column from input file. Furthermore this AWK will be inside a bash script.

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Create signed urls for CloudFront with Ruby

- by wiseleyb

History: I created a key and pem file on Amazon. I created a private bucket I created a public distribution and used origin id to connect to the private bucket: works I created a private distribution and connected it the same as #3 - now I get access denied: expected I'm having a really hard time generating a url that will work. I've been trying to follow the directions described here: http://docs.amazonwebservices.com/AmazonCloudFront/latest/DeveloperGuide/index.html?PrivateContent.html This is what I've got so far... doesn't work though - still getting access denied: def url_safe(s) s.gsub('+','-').gsub('=','_').gsub('/','~').gsub(/\n/,'').gsub(' ','') end def policy_for_resource(resource, expires = Time.now + 1.hour) %({"Statement":[{"Resource":"#{resource}","Condition":{"DateLessThan":{"AWS:EpochTime":#{expires.to_i}}}}]}) end def signature_for_resource(resource, key_id, private_key_file_name, expires = Time.now + 1.hour) policy = url_safe(policy_for_resource(resource, expires)) key = OpenSSL::PKey::RSA.new(File.readlines(private_key_file_name).join("")) url_safe(Base64.encode64(key.sign(OpenSSL::Digest::SHA1.new, (policy)))) end def expiring_url_for_private_resource(resource, key_id, private_key_file_name, expires = Time.now + 1.hour) sig = signature_for_resource(resource, key_id, private_key_file_name, expires) "#{resource}?Expires=#{expires.to_i}&Signature=#{sig}&Key-Pair-Id=#{key_id}" end resource = "http://d27ss180g8tp83.cloudfront.net/iwantu.jpeg" key_id = "APKAIS6OBYQ253QOURZA" pk_file = "doc/pk-APKAIS6OBYQ253QOURZA.pem" puts expiring_url_for_private_resource(resource, key_id, pk_file) Can anyone tell me what I'm doing wrong here?

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Create Custom Builds of an Xcode Project

- by macinjosh

I am going to build a Mac application written in Obj-C with Xcode. For argument's sake let's say it will have 10 optional features. I need a way to enable or disable those features to create custom builds of the application. These builds would be automated (most likely through the Mac OS X Terminal) so I would need a way to state which of these features are enabled/disabled at build time (a configuration file or CLI arguments would be ideal.) So what is the best way to accomplish this? I'm trying to plan this out before I start coding so that there is proper separation in my code base to allow for these features to come and go. Ideally the custom build would only contain compiled code for the features it should have. In other words I don't want to always compile all the features and condition them out at runtime.

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Issue with footer in IE8

- by Blaze

i have an issue with my footer in IE8 only. The footer itself detaches from the rest of the page almost as if there was a line break. I used this condition statement to fix it but i got nothing  How do i target IE8 only? any suggestions?

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Why is my AJAX request hanging after running for a while?

- by JustJon

My AJAX calls from a page I wrote is hanging after an indeterminate number of calls. The page makes a request after a preset amount of time (currently 5 seconds) gets data from my server then waits the amount of time again. When I put the following as my AJAX Request: myAjax = new Ajax.Request( url, { method: 'get', asynchronous: true, url: url, parameters: querystring, onInteractive: document.getElementById('meh').innerHTML='Interactive', onSuccess: processXML }); The div with the id "meh" will get the word Interactive written to it, but the Success condition never gets executed (same if onSuccess is replaced with onComplete). So why is my code doing this? Thanks.

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Most efficient way to check if a date falls between two dates?

- by Dave Jarvis

Given: Start Month & Start Day End Month & End Day Any Year What SQL statement results in TRUE if a date lands between the Start and End days? 1st example: Start Date = 11-22 End Date = 01-17 Year = 2009 Specific Date = 2010-01-14 TRUE 2nd example: Start Date = 11-22 End Date = 11-16 Year = 2009 Specific Date = 2010-11-20 FALSE 3rd example: Start Date = 02-25 End Date = 03-19 Year = 2004 Specific Date = 2004-02-29 TRUE I was thinking of using the MySQL functions datediff and sign plus a CASE condition to determine whether the year wraps, but it seems rather expensive. Am looking for a simple, efficient calculation. Update The problem is the end date cannot simply use the year. The year must be increased if the end month/day combination happens before the start date. The start date is easy: Start Date = date( concat_ws( '-', year, Start Month, Start Day ) The end date is not so simple. Thank you!

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C# Finisar SQLite DateTime Comparison Problem

- by Emanuel

My "task" database table look like this: [title] [content] [start_date] [end_date] [...] [...] [01.06.2010 20:10:36] [06.06.2010 20:10:36] [...] [...] [05.06.2010 20:10:36] [06.06.2010 20:10:36] And I want to find only those records that meet the condition that a given day is between start_date and end_date. I've tried the following SQL expression: SELECT * FROM task WHERE strftime ('%d', start_date) <= @day AND @day <= strftime ('%d', end_date) Where @day is an SQLiteParameter (eq 5). But no result is returned. How can I solve this problem? Thanks.

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