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  • Is there any valid reason radians are used as the inputs to trig function in many modern languages?

    - by johnmortal
    Is there any pressing reason trig functions should use radian inputs in modern programming languages? As far as I know radians are typically ugly to deal with except in three cases: (1) You want to compute an arc length and you know the angle of the arc and (2) You need to do symbolic calculus with trig functions (3) certain infinite series expansion look prettier if the input is in radians. None of these scenarios seem like a worthy justification for every programming language I am familiar with using radian inputs for Sin, Cos, Tangent, etc... The third one sounds good because it might mean one gets faster computations using radians (very slightly faster- the cost of one additional floating point multiplication ) , but I am dubious even of that because most commonly the developer had to take an extra step to put the angle in radians in the first place. The other two are ridiculous justifications for all the added obscurity.

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  • Any AOP support library for Python ?

    - by edomaur
    I am trying to use some AOP in my Python programming, but I do not have any experience of the various libs that exists. So my question is : What AOP support exists for Python, and what are the advantages of the differents libraries between them ? Edit : I've found some, but I don't know how they compare : Aspyct Lightweight AOP for Python Edit2 : In which context will I use this ? I have two applications, written in Python, which have typically methods which compute taxes and other money things. I'd like to be able to write a "skeleton" of a functionnality, and customize it at runtime, for example changing the way local taxes are applied (by country, or state, or city, etc.) without having to overload the full stack.

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  • Hashing a python method to regenerate output when method is modified

    - by Seth Johnson
    I have a python method that has a deterministic result. It takes a long time to run and generates a large output: def time_consuming_method(): # lots_of_computing_time to come up with the_result return the_result I modify time_consuming_method from time to time, but I would like to avoid having it run again while it's unchanged. [Time_consuming_method only depends on functions that are immutable for the purposes considered here; i.e. it might have functions from Python libraries but not from other pieces of my code that I'd change.] The solution that suggests itself to me is to cache the output and also cache some "hash" of the function. If the hash changes, the function will have been modified, and we have to re-generate the output. Is this possible or a ridiculous idea? If this isn't a terrible idea, is the best implementation to write f = """ def ridiculous_method(): a = # # lots_of_computing_time return a """ , use the hashlib module to compute a hash for f, and use compile or eval to run it as code?

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  • Single Query returning me 4 tables, How to get all of them back into dataset ?

    - by Shantanu Gupta
    How to fill multiple tables in a dataset. I m using a query that returns me four tables. At the frontend I am trying to fill all the four resultant table into dataset. Here is my Query. Query is not complete. But it is just a refrence for my Ques Select * from tblxyz compute sum(col1) suppose this query returns more than one table, I want to fill all the tables into my dataset I am filling result like this con.open(); adp.fill(dset); con.close(); Now when i checks this dataset. It shows me that it has four tables but only first table data is being displayed into it. rest 3 dont even have schema also. What i need to do to get desired output

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  • C++ Sentinel/Count Controlled Loop beginning programming

    - by Bryan Hendricks
    Hello all this is my first post. I'm working on a homework assignment with the following parameters. Piecework Workers are paid by the piece. Often worker who produce a greater quantity of output are paid at a higher rate. 1 - 199 pieces completed $0.50 each 200 - 399 $0.55 each (for all pieces) 400 - 599 $0.60 each 600 or more $0.65 each Input: For each worker, input the name and number of pieces completed. Name Pieces Johnny Begood 265 Sally Great 650 Sam Klutz 177 Pete Precise 400 Fannie Fantastic 399 Morrie Mellow 200 Output: Print an appropriate title and column headings. There should be one detail line for each worker, which shows the name, number of pieces, and the amount earned. Compute and print totals of the number of pieces and the dollar amount earned. Processing: For each person, compute the pay earned by multiplying the number of pieces by the appropriate price. Accumulate the total number of pieces and the total dollar amount paid. Sample Program Output: Piecework Weekly Report Name Pieces Pay Johnny Begood 265 145.75 Sally Great 650 422.50 Sam Klutz 177 88.5 Pete Precise 400 240.00 Fannie Fantastic 399 219.45 Morrie Mellow 200 110.00 Totals 2091 1226.20 You are required to code, compile, link, and run a sentinel-controlled loop program that transforms the input to the output specifications as shown in the above attachment. The input items should be entered into a text file named piecework1.dat and the ouput file stored in piecework1.out . The program filename is piecework1.cpp. Copies of these three files should be e-mailed to me in their original form. Read the name using a single variable as opposed to two different variables. To accomplish this, you must use the getline(stream, variable) function as discussed in class, except that you will replace the cin with your textfile stream variable name. Do not forget to code the compiler directive #include < string at the top of your program to acknowledge the utilization of the string variable, name . Your nested if-else statement, accumulators, count-controlled loop, should be properly designed to process the data correctly. The code below will run, but does not produce any output. I think it needs something around line 57 like a count control to stop the loop. something like (and this is just an example....which is why it is not in the code.) count = 1; while (count <=4) Can someone review the code and tell me what kind of count I need to introduce, and if there are any other changes that need to be made. Thanks. [code] //COS 502-90 //November 2, 2012 //This program uses a sentinel-controlled loop that transforms input to output. #include <iostream> #include <fstream> #include <iomanip> //output formatting #include <string> //string variables using namespace std; int main() { double pieces; //number of pieces made double rate; //amout paid per amount produced double pay; //amount earned string name; //name of worker ifstream inFile; ofstream outFile; //***********input statements**************************** inFile.open("Piecework1.txt"); //opens the input text file outFile.open("piecework1.out"); //opens the output text file outFile << setprecision(2) << showpoint; outFile << name << setw(6) << "Pieces" << setw(12) << "Pay" << endl; outFile << "_____" << setw(6) << "_____" << setw(12) << "_____" << endl; getline(inFile, name, '*'); //priming read inFile >> pieces >> pay >> rate; // ,, while (name != "End of File") //while condition test { //begining of loop pay = pieces * rate; getline(inFile, name, '*'); //get next name inFile >> pieces; //get next pieces } //end of loop inFile.close(); outFile.close(); return 0; }[/code]

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  • How to find largest common sub-tree in the given two binary search trees?

    - by Bhushan
    Two BSTs (Binary Search Trees) are given. How to find largest common sub-tree in the given two binary trees? EDIT 1: Here is what I have thought: Let, r1 = current node of 1st tree r2 = current node of 2nd tree There are some of the cases I think we need to consider: Case 1 : r1.data < r2.data 2 subproblems to solve: first, check r1 and r2.left second, check r1.right and r2 Case 2 : r1.data > r2.data 2 subproblems to solve: - first, check r1.left and r2 - second, check r1 and r2.right Case 3 : r1.data == r2.data Again, 2 cases to consider here: (a) current node is part of largest common BST compute common subtree size rooted at r1 and r2 (b)current node is NOT part of largest common BST 2 subproblems to solve: first, solve r1.left and r2.left second, solve r1.right and r2.right I can think of the cases we need to check, but I am not able to code it, as of now. And it is NOT a homework problem. Does it look like?

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  • Doing arithmetic with up to two decimal places in Python?

    - by user248237
    I have two floats in Python that I'd like to subtract, i.e. v1 = float(value1) v2 = float(value2) diff = v1 - v2 I want "diff" to be computed up to two decimal places, that is compute it using %.2f of v1 and %.2f of v2. How can I do this? I know how to print v1 and v2 up to two decimals, but not how to do arithmetic like that. The particular issue I am trying to avoid is this. Suppose that: v1 = 0.982769777778 v2 = 0.985980444444 diff = v1 - v2 and then I print to file the following: myfile.write("%.2f\t%.2f\t%.2f\n" %(v1, v2, diff)) then I will get the output: 0.98 0.99 0.00, suggesting that there's no difference between v1 and v2, even though the printed result suggests there's a 0.01 difference. How can I get around this? thanks.

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  • Tool to diagonalize large matrices

    - by Xodarap
    I want to compute a diffusion kernel, which involves taking exp(b*A) where A is a large matrix. In order to play with values of b, I'd like to diagonalize A (so that exp(A) runs quickly). My matrix is about 25k x 25k, but is very sparse - only about 60k values are non-zero. Matlab's "eigs" function runs of out memory, as does octave's "eig" and R's "eigen." Is there a tool to find the decomposition of large, sparse matrices? Dunno if this is relevant, but A is an adjacency matrix, so it's symmetric, and it is full rank.

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  • How does Hibernate detect dirty state of an entity object?

    - by ???'Lenik
    Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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  • Get the last N rows in the database in order?

    - by Kristopher
    Let's say I have the following database table: record_id | record_date | record_value -----------+-------------+-------------- 1 | 2010-05-01 | 195.00 2 | 2010-07-01 | 185.00 3 | 2010-09-01 | 175.00 4 | 2010-05-01 | 189.00 5 | 2010-06-01 | 185.00 6 | 2010-07-01 | 180.00 7 | 2010-08-01 | 175.00 8 | 2010-09-01 | 170.00 9 | 2010-10-01 | 165.00 I want to grab the last 5 rows with the data ordered by record_date ASC. This is easy to do with: SELECT * FROM mytable ORDER BY record_date ASC LIMIT 5 OFFSET 4 Which would give me: record_id | record_date | record_value -----------+-------------+-------------- 6 | 2010-07-01 | 180.00 7 | 2010-08-01 | 175.00 3 | 2010-09-01 | 175.00 8 | 2010-09-01 | 170.00 9 | 2010-10-01 | 165.00 But how do I do this when I don't know how many records there are and can't compute the magic number of 4? I've tried this query, but if there are less than 5 records, it results in a negative OFFSET, which is invalid: SELECT * FROM mytable ORDER BY record_date ASC LIMIT 5 OFFSET (SELECT COUNT(*) FROM mytable) - 5; So how do I accomplish this?

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  • MATLAB: draw centroids

    - by Myx
    Hello - my main question is given a feature centroid, how can I draw it in MATLAB? In more detail, I have an NxNx3 image (an rgb image) of which I take 4x4 blocks and compute a 6-dimensional feature vector for each block. I store these feature vectors in an Mx6 matrix on which I run kmeans function and obtain the centroids in a kx6 matrix, where k is the number of clusters and 6 is the number of features for each block. How can I draw these center clusters in my image in order to visualize if the algorithm is performing the way I wish it to perform? Or if anyone has any other way/suggestions on how I can visualize the centroids on my image, I'd greatly appreciate it. Thank you.

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  • Determine the lat lngs of markers within a polygon

    - by subh
    I have a google maps app which plots markers as it loads. One of the new requirment is to to add a Polygon overlay encompassing a selection of markers by the user. I was able to achieve that using the Geometry Controls of the GMaps Utility Library Now, the next step is to form a group of the selected markers for which I would need to determine if the lat lngs of the markers falls within the lat lngs of the polygon? Is there a way to determine the lat lngs of a polygon and compute if the marker's lat lng is within its boundaries?

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  • Does Microsoft hate firefox? ASP.Net gridview performance in firefox bug?

    - by Maxim Gershkovich
    Could someone please explain the significant difference in speed between a firefox updatepanel async postback and one performed in IE? Average Firefox Postback Time For 500 objects: 1.183 Second Average IE Postback Time For 500 objects: 0.295 Seconds Using firebug I can see that the majority of this time in FireFox is spent on the server side. A total of 1.04 seconds. Given this fact the only thing I can assume is causing this problem is the way that ASP.Net renders its controls between the two browsers. Has anyone run into this problem before? VB.Net Code Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click GridView1.DataBind() End Sub Public Function GetStockList() As StockList Dim res As New StockList For l = 0 To 500 Dim x As New Stock With {.Description = "test", .ID = Guid.NewGuid} res.Add(x) Next Return res End Function Public Class Stock Private m_ID As Guid Private m_Description As String Public Sub New() End Sub Public Property ID() As Guid Get Return Me.m_ID End Get Set(ByVal value As Guid) Me.m_ID = value End Set End Property Public Property Description() As String Get Return Me.m_Description End Get Set(ByVal value As String) Me.m_Description = value End Set End Property End Class Public Class StockList Inherits List(Of Stock) End Class Markup <form id="form1" runat="server"> <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> <script type="text/javascript" language="Javascript"> function timestamp_class(this_current_time, this_start_time, this_end_time, this_time_difference) { this.this_current_time = this_current_time; this.this_start_time = this_start_time; this.this_end_time = this_end_time; this.this_time_difference = this_time_difference; this.GetCurrentTime = GetCurrentTime; this.StartTiming = StartTiming; this.EndTiming = EndTiming; } //Get current time from date timestamp function GetCurrentTime() { var my_current_timestamp; my_current_timestamp = new Date(); //stamp current date & time return my_current_timestamp.getTime(); } //Stamp current time as start time and reset display textbox function StartTiming() { this.this_start_time = GetCurrentTime(); //stamp current time } //Stamp current time as stop time, compute elapsed time difference and display in textbox function EndTiming() { this.this_end_time = GetCurrentTime(); //stamp current time this.this_time_difference = (this.this_end_time - this.this_start_time) / 1000; //compute elapsed time return this.this_time_difference; } //--> </script> <script type="text/javascript" language="javascript"> var time_object = new timestamp_class(0, 0, 0, 0); //create new time object and initialize it Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler); Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler); function BeginRequestHandler(sender, args) { var elem = args.get_postBackElement(); ActivateAlertDiv('visible', 'divAsyncRequestTimer', elem.value + ''); time_object.StartTiming(); } function EndRequestHandler(sender, args) { ActivateAlertDiv('visible', 'divAsyncRequestTimer', '(' + time_object.EndTiming() + ' Seconds)'); } function ActivateAlertDiv(visstring, elem, msg) { var adiv = $get(elem); adiv.style.visibility = visstring; adiv.innerHTML = msg; } </script> <asp:UpdatePanel ID="UpdatePanel1" runat="server"> <Triggers> <asp:AsyncPostBackTrigger ControlID="Button1" EventName="click" /> </Triggers> <ContentTemplate> <asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1"> </asp:UpdateProgress> <asp:Button ID="Button1" runat="server" Text="Button" /> <div id="divAsyncRequestTimer" style="font-size:small;"> </div> <asp:GridView ID="GridView1" runat="server" DataSourceID="ObjectDataSource1" AutoGenerateColumns="False"> <Columns> <asp:BoundField DataField="ID" HeaderText="ID" SortExpression="ID" /> <asp:BoundField DataField="Description" HeaderText="Description" SortExpression="Description" /> </Columns> </asp:GridView> <asp:ObjectDataSource ID="ObjectDataSource1" runat="server" SelectMethod="GetStockList" TypeName="WebApplication1._Default"> </asp:ObjectDataSource> </ContentTemplate> </asp:UpdatePanel> </form>

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  • Preallocate memory for a program in Linux before it gets started

    - by Fyg
    Hi, folks, I have a program that repeatedly solves large systems of linear equations using cholesky decomposition. Characterising is that I sometimes need to store the complete factorisation which can exceed about 20 GB of memory. The factorisation happens inside a library that I call. Furthermore, this matrix and the resulting factorisation changes quite frequently and as such the memory requirements as well. I am not the only person to use this compute-node. Therefore, is there a way to start the program under Linux and preallocate free memory for the process? Something like: $: prealloc -m 25G ./program

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  • for loop will not loop

    - by Bjørn Jostein Aurheim
    I have a for loop that I will use to compute time intervals to add to an ArrayList. The problem is that I can not prove that the for loop is being executed. Nothing is printed when using the system.out.println() statement, and nothing is added to the array from inside the loop ... any sugestions? // lager tidspunkter og legger disse inn i en Array kalt tider tid.setTimer(16); tid.setMinutter(0); tid.setSekunder(0); tider.add(tid.asString());// String "16:00" is added as it should System.out.println("tiden er: "+tid.asString());// gives 16:00 printed for(int i=0;i>12;i++){ System.out.println("er i løkken");// gives nothing printed tid.increaseMinutter(30); System.out.println(tid.asString());// gives nothing printed tider.add(tid.asString()); }

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  • Adjusting for compass wrap around in a navigation application

    - by chris12892
    I have a application where I am guiding a vehicle on compass headings and I am having an issue when the vehicle is crossing from 360 degrees to 0 degrees. In this case, there are no smarts in the control loop to compute that the nearest way to turn to follow a heading. For example, if the vehicle is instructed to follow a heading of 360 degrees, it will inevitably drifts a few degrees to ether side. If it drifts over to 0+ degrees, the control loop will go nuts and try to steer the vehicle all the way around to get it to 360 degrees again. Is there a graceful way to deal with this? The way the navigate function is written, I use an external PID controller class and I calculate the heading like this: lock (steering) { if (!Engaged) { return; } double mv = 90 + Trim + pidController.CalculateCorrection(flyHeading, currentHeading); steering.Degree = mv; } Thanks!

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  • Measuring time taken to display an object in Flex

    - by dta
    For e.g. function showIt():void { something.visible = true; } function init():void { time1 = flash.utils.getTimer(); showIt(); time2 = flash.utils.getTimer(); } <mx:st id="something" visible="false"/> <mx:Button click="init()"/> In the above code, I want to measure the time taken to display st on screen. Is it enough to compute time2 - time1? Or should I put an event handler on render? Or some other way?

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  • java memory usage

    - by xdevel2000
    I know I always post a similar question about array memory usage but now I want post the question more specific. After I read this article: http://www.javamex.com/tutorials/memory/object_memory_usage.shtml I didn't understand some things: the size of a data type is always the same also on different platform (Linux / Windows 32 / 64 bit)??? so an int will be always 32 bit?; when I compute the memory usage I must put also the reference value itself? If I have an object to a class that has an int field its memory will be 12 (object header) + 4 reference + 4 (the int field) + 3 (padding) = 24 bytes??

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  • Efficient bitshifting an array of int?

    - by nn
    Hi, To be on the same page, let's assume sizeof(int)=4 and sizeof(long)=8. Given an array of integers, what would be an efficient method to bitshift the array to either the left or right? I am contemplating an auxiliary variable such as a long, that will compute the bitshift for the first pair of elements (index 0 and 1) and set the first element (0). Continuing in this fashion the bitshift for elements (index 1 and 2) will be computer, and then index 1 will be set. I think this is actually a fairly efficient method, but there are drawbacks. I cannot bitshift greater than 32 bits. I think using multiple auxiliary variables would work, but I'm envisioning recursion somewhere along the line.

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  • How can I intercept a Tomcat request at socket level?

    - by Miguel Pardal
    Hi, I'm doing a performance study for a web application framework running on Apache Tomcat 6. I'm trying to measure the time overhead of handling HTTP requests. What I would like to do is: / // just before first request byte is read long t1 = System.nanoTime(); // request is processed... // just after final byte is written to response long t2 = System.nanoTime(); / Then I would compute the total time (t2 - t1). Is there a way to do this? Thanks for your help!

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  • Drawing rectangles on a grid in a web browser

    - by Dhruv
    I would like to create an online, simple WYSIWYG drawing editor allowing people to draw rectangular shapes. I'm thinking of a grid which the lines and points can snap on to, ensuring that the lines are strictly vertical or horizontal. I will be parsing the rectangular shapes to obtain some area calculations and compute certain things. How can I achieve the drawing ability? The new canvas tag is good but people have been telling me that IE does not support it. I found some Java applets but I have never programmed in Java before. Is there a way to do this using pure javascript or jquery? Does ASP.NET help at all? Thanks.

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  • Windows azure deployment

    - by smoothe
    I just built a simple hello world windows azure service containing just one web role, I used visual studio 2008 and Windows azure tools for VS 1.2 I am pretty new to this and I have been trying to deploy an application all afternoon now. I'm in australia and deploying in the region Asia anywhere. I have pretty much followed the info provided on MSDN and it says uploaded 95% then after about ten minutes the deployment disappears. I have tried using the old windows azure developer portal and 30minutes later I can not access the service and it's status is either busy or stopped. I have the introductory offer for an extra small compute instance on the subscription I am deploying to. Can anyone with experience with windows azure elaborate on the subject of deploying apps and the status on my application, I am very keen to get into the platform and this issue has just about spoiled my weekend.

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  • Distance between hyperplanes

    - by michael dillard
    I'm trying to teach myself some machine learning, and have been using the MNIST database (http://yann.lecun.com/exdb/mnist/) do so. The author of that site wrote a paper in '98 on all different kinds of handwriting recognition techniques, available at http://yann.lecun.com/exdb/publis/pdf/lecun-98.pdf. The 10th method mentioned is a "Tangent Distance Classifier". The idea being that if you place each image in a (NxM)-dimensional vector space, you can compute the distance between two images as the distance between the hyperplanes formed by each where the hyperplane is given by taking the point, and rotating the image, rescaling the image, translating the image, etc. I can't figure out enough to fill in the missing details. I understand that most of these are indeed linear operators, so how does one use that fact to then create the hyperplane? And once we have a hyperplane, how do we take its distance with other hyperplanes?

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  • How to order by results from 2 seperate tables in PHP and MySQL.

    - by Vafello
    I am trying to output results of 2 sql queries to one JSON file. The problem is that I would like to order them ascending by distance which is the result of equation that takes homelat and homelon from the users table and lat, lng from locations table.(basically it takes lattitude and longitude of one point and another and computes the distance between these points). Is it possible to take some parameters from both select queries, compute it and output the result in ascending order? $wynik = mysql_query("SELECT homelat, homelon FROM users WHERE guid='2'") or die(mysql_error()); ; $query = "SELECT * FROM locations WHERE timestamp"; $result = map_query($query); $points = array(); while ($aaa = mysql_fetch_assoc($wynik)) { while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) { array_push($points, array('name'=>$row['name'], 'lat'=>$row['lat'], 'lng'=>$row['lng'], 'description'=>$row['description'], 'eventType'=>$row['eventType'], 'date'=>$row['date'], 'isotime'=>date('c', ($row['timestamp'])), 'homelat'=>$aaa['homelat'], 'homelon'=>$aaa['homelon'])); } echo json_encode(array("Locations"=>$points));

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  • Create a date from Credit Card expire in MMYY format

    - by Sophtware
    I need to convert a credit card expire field from MMYY to a date field I can use in a MS SQL query so I can compute when credit cards are expiring in the future. Basically, I need to go from MMYY to MM/DD/YYYY, where the day part could just be '01' (the first of the month). I'm looking for credit cards that are expiring next month from a database. The problem I'm running into is when next month is the first month of the next year. Here's the code I have for determining expired card: (CAST(SUBSTRING(CCExpire,3,2) as int) + 2000 < YEAR(GETDATE())) or ( (CAST(SUBSTRING(CCExpire,3,2) as int) + 2000 = YEAR(GETDATE())) AND (CAST(SUBSTRING(CCExpire,1,2) as int) < MONTH(GETDATE())) ) And here's the code for cards expiring this month: (CAST(SUBSTRING(CCExpire,3,2) as int) + 2000 = YEAR(GETDATE())) AND (CAST(SUBSTRING(CCExpire,1,2) as int) = MONTH(GETDATE())) Now I need code for cards expiring next month...

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