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• Add time to a Date object in javascript

  - by baiano

  I am trying to add time to a Date object in javascript but am not getting the results that I am expecting. I am trying to pull a timer off of the page and add it to the current time to get the unix timestamp value of when the timer will hit zero. The time on the page is displayed as " HH:MM:SS ". This is what I have: time=getTimerText.split(":"); seconds=(time[0]*3600+time[1]*60+time[2])*1000; to convert the time into milliseconds. fDate=new Date(); fDate.setTime(fDate.getTime()+seconds); add the milliseconds to the javascript timestamp alert(Math.round(fDate.getTime() / 1000)); convert the javascript timestamp to a unix timestamp Since the timer is counting down I should get the same result every time i run the script, but I don't. Can anyone see what I might be doing wrong here?

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• Python frequency detection

  - by Tsuki

  Ok what im trying to do is a kind of audio processing software that can detect a prevalent frequency an if the frequency is played for long enough (few ms) i know i got a positive match. i know i would need to use FFT or something simiral but in this field of math i suck, i did search the internet but didn not find a code that could do only this. the goal im trying to accieve is to make myself a custom protocol to send data trough sound, need very low bitrate per sec but im also very limited on the transmiting end so the recieving software will need to be able custom (cant use an actual hardware/software modem) also i want this to be software only (no additional hardware except soundcard) thanks alot for the help.

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• converting tag number to int

  - by Ehtesham Sajed

  i m using Visual C++2008. i've assigned tag value=2 of all buttons from button property(using drag n drop). now i want to make some math calculation with tag value. need to change it in int. what is the default data type tag? i used this code, //code sample if(((int)this-button1-Tag)((int)this-button2-Tag)((int)this-button3-Tag)==50) { ........ //i.e, if tag value of button1*tag value of button2*tag value of button 3==50 then... ........ } generated following run time error on a messegebox An unhandled exception of type 'System.InvalidCastException' occurred in learncpp1.exe Additional information: Specified cast is not valid.

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• Programming Exercises for Learning Purposes?

  - by cam

  Are there any programming exercises that apply to any language? Before I got my first job, I thought I knew C# pretty well, then I was thrown right into the deep end, and now I know I have a good command over the language. I would like to apply the same method to other languages, but unfortunately, I'm sort of stuck with C# at work. Ideally, something similar (but broader in scope) to Project Euler is ideal. Project Euler helped me learn a ton of C++/F#, some math, algorithms, handling bignums, etc. I'm looking for something like this.

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• Background subtracting in MATLAB

  - by eiphyomin

  I'm looking to do background subtracting on an image. I'm new to MATLAB and new to image processing/analysis, so sorry if any of this sounds stupid. 1) Other than imsubtract() are there other ways to do background subtracting (besides comparing one image to another)? 2) In the Math Works explanation for imsubtract() why do they make their structuring element a disk? This seems rather difficult so far because every time I try something, I end up not only subtracting the noisy background but also losing the parts of the image I want to look at!

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• how to calculate the beginning of a day given milliseconds?

  - by conman

  i want to figure out the time from the beginning of the day given a days milliseconds. so say i'm given this: 1340323100024 which is like mid day of 6/21/2012. now i want the milliseconds from the beginning of the day, which would be 1340262000000 (at least i think that's what it's supposed to be.) how do i get 1340262000000 from 1340323100024? i tried doing Math.floor(1340323100024/86400000) * 86400000 but that gives me 1340236800000, which if i create a date object out of it, says its the 20th. i know i can create a date object from 1340323100024, then get the month, year, and date, to create a new object which would give me 1340262000000, but i find it ridiculous i can't figure out something so simple. any help would be appreciated. btw, i'm doing this in javascript if it makes any difference.

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• What is your favorite Project Euler question?

  - by A. Rex

  I was searching around for questions related to Project Euler on Stack Overflow, and it seems that there were plenty of people asking about it, and even more people recommending it, whether for fun, to learn a new language, or to practice for interview questions. All this seems to imply to me that there are lots of people on SO that solve Project Euler problems now and then. I just started, so I was wondering: What was your favorite Project Euler question? Why? Did you think of a clever trick, or did you learn some new math, or did you discover a feature of a new programming language? (If possible, please include the actual question in your answer.)

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• How do I display and calculate numbers from a database on iPhone?

  - by JoshD

  I am new to designing apps and have a basic understand of Ob-C and how everything works. What I would like to do is have two tabs, one is a home screen that displays numbers and percentages that are entered on the second tab. The user will be able to store that information and refer back to it and update it. What is the best way to complete that math from the database to the "home screen"? Any tutorials, advice is great! Thanks.

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• One Database Field to Hold Survey Answer

  - by yar

  Skipping the question of whether this is bad design (and the question of why I would want/need to do this), I'm just wondering if my 'math' is right... I have n things that need to be put in order (n is always less than 5): thing1 thing2 thing3 ... and I'd like to store these results in a single integer for thing. My initial thought is that (obviously the code will not look like this): thing = thing1 * 1 + thing2 * 2 + thing3 * 4 + thing5 * 8 will always give me a unique value, and that any value for thing will always translate back to its values for thing1...thingn. Is this correct?

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• Hashing and salting values

  - by Avanst

  I am developing a small web app that internally authenticates users. Once the user is authenticated my web app then passes some information such as userID and Person's name to a third party web application. The third party developer is suggesting that we hash and salt the values. Forgive my ignorance, but what exactly does that mean? I am writing the app in Java. So what I am planning on doing is hashing the userID, Person's name, and some Math.random() value as the salt with Apache Commons Digest Utils SHA512 and passing that hashed string along with the userID and person's name. Is that the standard practice? I should be passing the third party the salt as well correct?

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• Cross vertion line matching.

  - by BCS

  I'm considering how to do automatic bug tracking and as part of that I'm wondering what is available to match source code line numbers (or more accurate numbers mapped from instruction pointers via something like addr2line) in one version of a program to the same line in another. (Assume everything is in some kind of source control and is available to my code) The simplest approach would be to use a diff tool/lib on the files and do some math on the line number spans, however this has some limitations: It doesn't handle cross file motion. It might not play well with lines that get changed It doesn't look at the information available in the intermediate versions. It provides no way to manually patch up lines when the diff tool gets things wrong. It's kinda clunky Before I start diving into developing something better: What already exists to do this? What features do similar system have that I've not thought of?

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• How to calculate end-point at a given center plus an radius and angle?

  - by mystify

  I'm trying to do some basic quartz core drawing with arcs, but have an F in math ;-) I have a point: CGPoint center = CGPointMake(100.0f, 100.0f); CGFloat radius = 50.0f; CGFloat startAngle = 20.0f / 180.0f * M_PI; CGFloat endAngle = 150.0f / 180.0f * M_PI; CGContextAddArc(c, center.x, center.y, radius, startAngle, endAngle, 0); Now I want to draw a little dot on the middle of the arc. I mean, not the center point, but the little curve (arc) which is made up between the angles 20-150 degrees. I looked into quartz but unfortunately, there seems no helper function to calculate this. Probably some hardcore trigonometric logic with atan and stuff of this kind needed?

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• Trying to zoom in on an arbitrary rect within a screen-aligned quad.

  - by mos

  I've got a screen-aligned quad, and I'd like to zoom into an arbitrary rectangle within that quad, but I'm not getting my math right. I think I've got the translate worked out, just not the scaling. Basically, my code is the following: // // render once zoomed in glPushMatrix(); glTranslatef(offX, offY, 0); glScalef(?wtf?, ?wtf?, 1.0f); RenderQuad(); glPopMatrix(); // // render PIP display glPushMatrix(); glTranslatef(0.7f, 0.7f, 0); glScalef(0.175f, 0.175f, 1.0f); RenderQuad(); glPopMatrix(); Anyone have any tips? The user selects a rect area, and then those values are passed to my rendering object as [x, y, w, h], where those values are percentages of the viewport's width and height.

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• Flex Application for PlayBook Text Input Variable

  - by user568128

  I know this is probably a very simple question, but can someone please walk me through how to take what a user inputs into a s:TextInput and use that as a variable in a JSON data request? Basically, I want to have a user enter a search term, like "math" and then have that placed into a variable so I can use it in a JSON request. Something like public var q:String, except that my search box (and hence user input) is on another "view" of the application. I've just started with Flex Mobile applications and I might be way out of my league. Does anyone know how to do this?

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• AS3 Random repeat x seconds function

  - by Lilk

  Hi, I have the following function: function update(e:Event):void { var val:Number = Math.random() * 120; rgb.r.x = rgb.r.y = val; rgb.b.x = rgb.b.y = -val; } And im looping it with: stage.addEventListener(Event.ENTER_FRAME, update); But what I need to do would be something like: Random number between 1 and 20 If the number is > 10 Call function Update and keep caling it for 20 seconds else do nothing for 10 seconds Repeat this block of code forever Can someone help me write this please?

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• unit testing methods with arrays as argument

  - by Ryan

  I am porting over some C++ assembly to VB that performs demodulation of various waveforms. I decided to go the unit test route instead of building a test app to get a feel for how testing is performed. The original demodulation code accepts an array that is the waveform along with some other arguments. How should one go about performing a test on something that has an array as an argument? Is it acceptable to generate fake data in a file and read it in at the beginning of the test? On a side note - The original C++ code was written because we were performing math that we couldn't do in VB6 so we had to cross boundaries between C++ and VB6 and arrays were used. Is there a "better" way of handling large amounts of data in the .NET world that us VB6 programmers may not yet be privy to? Or if we aren't crossing that managed/un-managed boundary, should we be representing our data as objects instead? Thanks all!

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• Strange python error

  - by Werner

  Hi, I am trying to write a python program that calculates a histogram, given a list of numbers like: 1 3 2 3 4 5 3.2 4 2 2 so the input parameters are the filename and the number of intervals. The program code is: #!/usr/bin/env python import os, sys, re, string, array, math import numpy Lista = [] db = sys.argv[1] db_file = open(db,"r") ic=0 nintervals= int(sys.argv[2]) while 1: line = db_file.readline() if not line: break ll=string.split(line) #print ll[6] Lista.insert(ic,float(ll[0])) ic=ic+1 lmin=min(Lista) print "min= ",lmin lmax=max(Lista) print "max= ",lmax width=666.666 width=(lmax-lmin)/nintervals print "width= ",width nelements=len(Lista) print "nelements= ",nelements print " " Histogram = numpy.zeros(shape=(nintervals)) for item in Lista: #print item int_number = 1 + int((item-lmin)/width) print " " print "item,lmin= ",item,lmin print "(item-lmin)/width= ",(item-lmin)," / ",width," ====== ",(float(item)-float(lmin))/float(width) print "int((item-lmin)/width)= ",int((item-lmin)/width) print item , " belongs to interval ", int_number, " which is from ", lmin+width*(int_number-1), " to ",lmin+width*int_number Histogram[int_number] = Histogram[int_number] + 1 4 but somehow I am completely lost, I get strange errors, can anybody help¿ Thanks

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• How to find the largest power of 2 less than the given number

  - by nazar_art

  I need to find the largest power of 2 less than the given number. And I stuck and can't find any solution. Code: public class MathPow { public int largestPowerOf2 (int n) { int res = 2; while (res < n) { res =(int)Math.pow(res, 2); } return res; } } This doesn't work correctly. Testing output: Arguments Actual Expected ------------------------- 9 16 8 100 256 64 1000 65536 512 64 256 32 How to solve this issue?

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• Cross version line matching.

  - by BCS

  I'm considering how to do automatic bug tracking and as part of that I'm wondering what is available to match source code line numbers (or more accurate numbers mapped from instruction pointers via something like addr2line) in one version of a program to the same line in another. (Assume everything is in some kind of source control and is available to my code) The simplest approach would be to use a diff tool/lib on the files and do some math on the line number spans, however this has some limitations: It doesn't handle cross file motion. It might not play well with lines that get changed It doesn't look at the information available in the intermediate versions. It provides no way to manually patch up lines when the diff tool gets things wrong. It's kinda clunky Before I start diving into developing something better: What already exists to do this? What features do similar system have that I've not thought of?

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• return type while using GMP.h header file

  - by Raveesh_Kumar

  While i m using gmp.h header file. i need a fuction which takes inputs of type mpz_t and return mpz_t type too. I m very beginner of using gmp.h So, Here is snaps follows of my approached code.... mpz_t sum_upto(mpz_t max) { mpz_t sum; mpz_init(sum); mpz_init(result); for(int i=0;i<=max-1;i++) mpz_add_ui(sum,sum,pow(2,i)); return sum; } but it will show error 1 ." pow has been not used in this scope.",although i have added math.h in very beginnig of the file. 2 . sum_upto declared as function returning an array... do tell as soon as possible. i have to complete my very big project....

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• Rails nil can't be coerced into Float

  - by alex

  After adding items, attempting to view my cart leads me to this error: nil can't be coerced into Float with the math line in this method in my line_item model highlighted: def total_price product.price * quantity end line items create action def create product = Product.find(params[:product_id]) @line_item = @cart.add_product(product.id) @line_item.quantity = params[:quantity] view <div id= "text_field"><%= text_field_tag 'quantity' %> </div> <%= button_to 'Add to Cart', line_items_path(:product_id => product) %> This has held me back for a couple days. (I'm new). Thanks.

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• Converting between square and rectangular pixel co-ordinates

  - by FlyboyUtah

  I'm new at using transforms and this type of math, and would appreciate some direction solving my coding problem. I'm writing in XCode for the iphone, and am working with CGraphics. Problem: In Xcode, I want to draw curves, lines and so on it's screen of of square pixels. Then convert those points, as close as possible, into non-square pixel sysem. For example if the original coordinate system is 500 x 500 pixels that are displayed on square screen of 10 by 10 inchs I draw a round circle with the circle formula. It looks round, and all is well. Now, I draw the same circle on a second 10 x 10 inch screen that is 850 pixels by 500 pixels. Without changing the coordinates, the same circle formual displays something that looks like an egg. How can I draw the circle on the second screen in a different coordinate system? And in addition, I need to access the set of points x,y system individually. s

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• How to convert string to integer?

  - by user1260584

  So I'm having a hard time with my situation and need some advice. I'm trying to convert my two Strings that I have into integers, so that I can use them in math equations. Here is what I tried, however it brings me an error in the app. ' equals.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) { // TODO Auto-generated method stub num1 = edit.getText().toString(); num2 = edit.getText().toString(); int first = Integer.parseInt(num1); int second = Integer.parseInt(num2); edit.setText(first + second); } }); Is there something that I am doing wrong? Thank you for any help. EDIT: Yes this is Java. num1 and num2 are strings that I have previously named. What do you mean by trim?

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• Exception for java Swing application?

  - by Rich Fluckiger

  For some reason this is locking up the java application. Did I handle the exception correctly? private void submitButtonActionPerformed(java.awt.event.ActionEvent evt) { double amount, interest,rateCalc, a, b, c, payment; int years, months; while (true){ try{ amount = Double.valueOf(loanAmount.getText()); interest = Double.valueOf(interestRate.getText()); years = Integer.valueOf(loanYears.getText()); rateCalc = (interest/12); months = (years*12); a = Math.pow((1+rateCalc),months); b = (a*rateCalc); c = (a-1); payment = (amount *(b/c)); monthlyPayment.setText("Mortgage Payment $ = " + payment); } catch (NumberFormatException nfe){ javax.swing.JOptionPane.showMessageDialog(null, "Please enter numbers and not letters"); return; } } } monthlyPayment returns to the java app.

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• between syntax, are there any equal function

  - by gcc

  /* char **mainp=malloc(sizeof(char *)*2); mainp[0]=malloc(sizeof(char)*300); mainp[1]=malloc(sizeof(char )*300); */ *I have some input about propositional calculus *After calculating some math funtion-removing paranthesis-changing"&" with ","-replacing "|" with"," I have >> (1) P,-Q,Q,-R is stored in mainp[0] R,A,P,B,F is stored in mainp[1] *My question is: Between comma , I have want to compare two pointer array. If there is any equal two or more functions(Q,-R is function representation) ,function which you will show me how to write must return int. According to example (1),function will return 1 (I expect like that) /*I have som thought://which function should I have use:*/ in for loop if( strspn(mainp[0][i])==1 ) increment d; continue; or in for loop srtcmp(mainp[0][i],mainp[1]);

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