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• In what order should the Python concepts be explained to absolute beginners?

  - by Tomaž Pisanski

  I am teaching Python to undergraduate math majors. I am interested in the optimal order in which students should be introduced to various Python concepts. In my view, at each stage the students should be able to solve a non-trivial programming problem using only the tools available at that time. Each new tool should enable a simpler solution to a familiar problem. A selection of numerous concepts available in Python is essential in order to keep students focused. They should also motivated and should appreciate each newly mastered tool without too much memorization. Here are some specific questions: For instance, my predecessor introduced lists before strings. I think the opposite is a better solution. Should function definitions be introduced at the very beginning or after mastering basic structured programming ideas, such as decisions (if) and loops (while)? Should sets be introduced before dictionaries? Is it better to introduce reading and writing files early in the course or should one use input and print for most of the course? Any suggestions with explanations are most welcome.

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• Animate screen while loading textures

  - by Omega

  My RPG-like game has random battles. When the player enters a random battle, it is necessary for my game to load the textures used within that battle (animated monsters, animations, etc). The textures are quite a lot, and rather big (the battles are very graphical intensive). Such process consumes significant time. And while it is loading, the whole screen freezes. The game's map freezes, and the wait time is significant - I personally find it annoying. I can't afford to preload the textures because, after doing some math, I realized: If I preload all the textures at the beginning of the game, the application will definitely crash. If I preload the textures that are used in a specific map when the player enters the map, the application is very likely to crash as well. I can only afford to load the textures when I need them, and dispose of them as soon as the battle ends. I'd prefer to not use a "loading screen" image because it affects my game's design and concept. I want to avoid this approach. If I could do some kind of animation while loading the textures, it would be great, which leads to my question: is that possible? What kind of animation, you ask? Well, how about... you remember when Final Fantasy used to distort the screen while apparently loading the textures? Something like that. But well, distorting is quite a time-consuming process as well, so maybe just a cool frame-by-frame animation or something. While writing this, I realized that I could make small pauses between textures (there are multiple textures), and during such pauses, I update the screen to represent the animation's state. However, this is very unlikely to happen, because each texture is 2048x2048, so the animation would be refreshed at a rather laggy (and annoying) rate. I'd prefer to avoid this as well.

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• Recoverable error while running XSL

  - by Kate

  XSL: <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:ve="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" xmlns:m="http://schemas.openxmlformats.org/officeDocument/2006/math" xmlns:v="urn:schemas-microsoft-com:vml" xmlns:wp="http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing" xmlns:w10="urn:schemas-microsoft-com:office:word" xmlns:w="http://schemas.openxmlformats.org/wordprocessingml/2006/main" xmlns:wne="http://schemas.microsoft.com/office/word/2006/wordml" exclude-result-prefixes="wp wne w10 w ve o r m v" version="2.0"> <xsl:output method="text"/> <xsl:param name="styleName"/> <xsl:template match="w:p"> <xsl:apply-templates/><xsl:text>&#10;</xsl:text> </xsl:template> <xsl:template match="w:r[not ((parent::w:hyperlink[@w:anchor[matches(.,concat('^(',$styleName,')')),'i']]))]"> <xsl:value-of select="replace(., '.', '&#xFF00;')"/> </xsl:template> </xsl:stylesheet> While processing the above XSL, I am getting the below error, Recoverable Error: Recoverable error on line 11 FORG0006: An error occurred matching pattern {w:r[not ((parent::w:hyperlink[@w:anchor[matches(.,concat('^(',$styleName,')')),'i']]))]}: Effective boolean value is not defined for a sequence of two or more items starting with a boolean Please Help. I am not able to figure out this.

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• Why are changes to classes ignored after dom changes?

  - by Lg102

  I have a price grid that uses relative positioning to move a field around, beneath a box with: overflow: hidden;. In this is field, there are absolute-positioned boxes containing prices. When this box is hovered, the matching values above and left of the will change color. In order to achieve this, a class is toggled using jQuery. This initially works. However, after the grid is moved, the class change doesn't affect the block above the grid anymore. In the Chrome console, i can see the class being added, but it's css-styling isn't applied. No other styles for the element have changed. I am 100% sure there is no other style-rule influencing the element, it just stops responding to the change in class after the DOM has been altered. Can i 'refresh' the DOM somehow? Edit: I've tried to get the relevant code only: Adding the cell in the first place: $("#price_dates_cells").append("<div id='"+weekday[theBeginDate.getDay()]+"-"+theBeginDate.getDate()+"-"+(theBeginDate.getMonth()-1)+"' class='datecell' style='left: "+( Math.floor( difference / ( 3600 * 24 * 1000) ) * ( cellwidth ) )+"px'>"+weekday[theBeginDate.getDay()]+"<br>"+theBeginDate.getDate()+" "+yearmonth[theBeginDate.getMonth()]+"</div>"); Toggle the class: var str_element = "#"+weekday[Bdate.getDay()]+"-"+Bdate.getDate()+"-"+(Bdate.getMonth()-1); $(str_element).toggleClass("red"); and the movement that seems to cause the problem: $('#price_grid').animate({"top": (( ( horizontalMovement ) * cellheight)) }, 'fast', 'linear');

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• How to proceed jpeg Image file size after read--rotate-write operations in Java?

  - by zamska

  Im trying to read a JPEG image as BufferedImage, rotate and save it as another jpeg image from file system. But there is a problem : after these operations I cannot proceed same file size. Here the code //read Image BufferedImage img = ImageIO.read(new File(path)); //rotate Image BufferedImage rotatedImage = new BufferedImage(image.getHeight(), image.getWidth(), BufferedImage.TYPE_3BYTE_BGR); Graphics2D g2d = (Graphics2D) rotatedImage.getGraphics(); g2d.rotate(Math.toRadians(PhotoConstants.ROTATE_LEFT)); int height=-rotatedImage.getHeight(null); g2d.drawImage(image, height, 0, null); g2d.dispose(); //Write Image Iterator iter = ImageIO.getImageWritersByFormatName("jpeg"); ImageWriter writer = (ImageWriter)iter.next(); // instantiate an ImageWriteParam object with default compression options ImageWriteParam iwp = writer.getDefaultWriteParam(); try { FileImageOutputStream output = null; iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT); iwp.setCompressionQuality(0.98f); // an integer between 0 and 1 // 1 specifies minimum compression and maximum quality File file = new File(path); output = new FileImageOutputStream(file); writer.setOutput(output); IIOImage iioImage = new IIOImage(image, null, null); writer.write(null, iioImage, iwp); output.flush(); output.close(); writer.dispose(); Is it possible to access compressionQuality parameter of original jpeg image in the beginning. when I set 1 to compression quality, the image gets bigger size. Otherwise I set 0.9 or less the image gets smaller size. How can i proceed the image size after these operations? Thank you,

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• Testing When Correctness is Poorly Defined?

  - by dsimcha

  I generally try to use unit tests for any code that has easily defined correct behavior given some reasonably small, well-defined set of inputs. This works quite well for catching bugs, and I do it all the time in my personal library of generic functions. However, a lot of the code I write is data mining code that basically looks for significant patterns in large datasets. Correct behavior in this case is often not well defined and depends on a lot of different inputs in ways that are not easy for a human to predict (i.e. the math can't reasonably be done by hand, which is why I'm using a computer to solve the problem in the first place). These inputs can be very complex, to the point where coming up with a reasonable test case is near impossible. Identifying the edge cases that are worth testing is extremely difficult. Sometimes the algorithm isn't even deterministic. Usually, I do the best I can by using asserts for sanity checks and creating a small toy test case with a known pattern and informally seeing if the answer at least "looks reasonable", without it necessarily being objectively correct. Is there any better way to test these kinds of cases?

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• Using "from __future__ import division" in my program, but it isn't loaded with my program

  - by Sara Fauzia

  I wrote the following program in Python 2 to do Newton's method computations for my math problem set, and while it works perfectly, for reasons unbeknownst to me, when I initially load it in ipython with %run -i NewtonsMethodMultivariate.py, the Python 3 division is not imported. I know this because after I load my Python program, entering x**(3/4) gives "1". After manually importing the new division, then x**(3/4) remains x**(3/4), as expected. Why is this? # coding: utf-8 from __future__ import division from sympy import symbols, Matrix, zeros x, y = symbols('x y') X = Matrix([[x],[y]]) tol = 1e-3 def roots(h,a): def F(s): return h.subs({x: s[0,0], y: s[1,0]}) def D(s): return h.jacobian(X).subs({x: s[0,0], y: s[1,0]}) if F(a) == zeros(2)[:,0]: return a else: while (F(a)).norm() > tol: a = a - ((D(a))**(-1))*F(a) print a.evalf(10) I would use Python 3 to avoid this issue, but my Linux distribution only ships SymPy for Python 2. Thanks to the help anyone can provide. Also, in case anyone was wondering, I haven't yet generalized this script for nxn Jacobians, and only had to deal with 2x2 in my problem set. Additionally, I'm slicing the 2x2 zero matrix instead of using the command zeros(2,1) because SymPy 0.7.1, installed on my machine, complains that "zeros() takes exactly one argument", though the wiki suggests otherwise. Maybe this command is only for the git version.

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• How to display buttons after enterframe event is over in Corona?

  - by user1463542

  I am trying to display two buttons called countd_again and main_menu after my enterframe event is over. I can't see those buttons after enterframe event is over,though. Can you check my code,please? And also i want to add new addListener for the buttons using director and scene. module(..., package.seeall) function new() local localGroup = display.newGroup(); display.setStatusBar(display.HiddenStatusBar) local background = display.newImage("background.png") start=os.time() cnt=1 local countd_again = display.newImage("yeniden.png") countd_again.x=100 countd_again.y=100 countd_again.isVisible= false; countd_again.alpha=0; countd_again.scene="helloWorld"; local main_menu= display.newImage("anamenu.png") main_menu.x=100 main_menu.y=300 main_menu.isVisible=false; main_menu.alpha=0; main_menu.scene="helloWorld" -- listener function local function onEveryFrame( event ) if (cnt~=0) then cnt= 3-(os.time()-start) minute = math.floor(cnt/60) second=cnt%60 --print(minute,second) minTxt=display.newText(minute,50,50,nil,100) secTxt=display.newText(second,250,50,nil,100) transition.to(minTxt, {time=100, alpha=0}) transition.to(secTxt,{time=100, alpha=0}) else Runtime: removeEventListener("enterFrame",onEveryFrame) countd_again.isVisible=true; main_menu.isVisible=true; transition.to(countd_again,{time=500,alpha=1}); transition.to(main_menu,{time=500,alpha=1}); countd_again: addEventListener("touch", changeScene) main_menu: addEventListener("touch", changeScene) end end -- assign the above function as an "enterFrame" listener Runtime:addEventListener( "enterFrame", onEveryFrame ) function changeScene(e) if(e.phase=="ended") then director:changeScene(e.target.scene); end end countd_again: addEventListener("touch", changeScene) main_menu: addEventListener("touch", changeScene) localGroup: insert(countd_again) localGroup:insert(main_menu) localGroup:insert(background) return localGroup; end

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• Project Euler, Problem 10 java solution now working

  - by Dennis S

  Hi, I'm trying to find the sum of the prime numbers < 2'000'000. This is my solution in java but I can't seem get the correct answer. Please give some input on what could be wrong and general advice on the code is appreciated. Printing 'sum' gives: 1308111344, which is incorrect. /* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. */ class Helper{ public void run(){ Integer sum = 0; for(int i = 2; i < 2000000; i++){ if(isPrime(i)) sum += i; } System.out.println(sum); } private boolean isPrime(int nr){ if(nr == 2) return true; else if(nr == 1) return false; if(nr % 2 == 0) return false; for(int i = 3; i < Math.sqrt(nr); i += 2){ if(nr % i == 0) return false; } return true; } } class Problem{ public static void main(String[] args){ Helper p = new Helper(); p.run(); } }

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• What OpenGL functions are not GPU accelerated?

  - by Xavier Ho

  I was shocked when I read this (from the OpenGL wiki): glTranslate, glRotate, glScale Are these hardware accelerated? No, there are no known GPUs that execute this. The driver computes the matrix on the CPU and uploads it to the GPU. All the other matrix operations are done on the CPU as well : glPushMatrix, glPopMatrix, glLoadIdentity, glFrustum, glOrtho. This is the reason why these functions are considered deprecated in GL 3.0. You should have your own math library, build your own matrix, upload your matrix to the shader. For a very, very long time I thought most of the OpenGL functions use the GPU to do computation. I'm not sure if this is a common misconception, but after a while of thinking, this makes sense. Old OpenGL functions (2.x and older) are really not suitable for real-world applications, due to too many state switches. This makes me realise that, possibly, many OpenGL functions do not use the GPU at all. So, the question is: Which OpenGL function calls don't use the GPU? I believe knowing the answer to the above question would help me become a better programmer with OpenGL. Please do share some of your insights.

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• Compilation problem in the standard x86_64 libraries

  - by user350282

  Hi everyone, I am having trouble compiling a program I have written. I have two different files with the same includes but only one generates the following error when compiled with g++ /usr/lib/gcc/x86_64-linux-gnu/4.4.1/../../../../lib/crt1.o: In function `_start': /build/buildd/eglibc-2.10.1/csu/../sysdeps/x86_64/elf/start.S:109: undefined reference to `main' collect2: ld returned 1 exit status The files I am including in my header are as follows: #include <google/sparse_hash_map> using google::sparse_hash_map; #include <ext/hash_map> #include <math.h> #include <iostream> #include <queue> #include <vector> #include <stack> using std::priority_queue; using std::stack; using std::vector; using __gnu_cxx::hash_map; using __gnu_cxx::hash; using namespace std; Searching the internet for those two lines hasn't resulted in anything to help me. I would be very grateful for any advice. Thank you

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• Flash AS3: How to Make scroll bar react to dynamic textfield movement?

  - by HeroicNate

  I've been looking for a tutorial and answer to this for a while but can't find what I'm looking for. I am loading html text into a dynamic textfield, and I have a scrollbar controlling the scroll using the code below. What I want to do is also add scroll up/down buttons and have the scroll bar move in relation to the text scroll. I was just going to use "tracklistingtext.scrollV -- " for the scroll buttons, but right now the scroll bar doesn't recognize the text movement. What do I need to do to get the scroll bar to listen to the text scroll position? var listTextreq:URLRequest=new URLRequest("tracklist.txt"); var listTextLoader:URLLoader = new URLLoader(); var bounds:Rectangle=new Rectangle(scrollMC.x,scrollMC.y,0,300); var scrolling:Boolean=false; function fileLoaded(event:Event):void { tracklistingtext.htmlText=listTextLoader.data; tracklistingtext.multiline=true; tracklistingtext.wordWrap=true; scrollMC.addEventListener(MouseEvent.MOUSE_DOWN, startScroll); stage.addEventListener(MouseEvent.MOUSE_UP, stopScroll); addEventListener (Event.ENTER_FRAME, enterHandler); } listTextLoader.addEventListener(Event.COMPLETE, fileLoaded); listTextLoader.load(listTextreq); function startScroll(e:Event):void { scrolling=true; scrollMC.startDrag(false,bounds); } function stopScroll(e:Event):void { scrolling=false; scrollMC.stopDrag(); } function enterHandler (e:Event):void { if (scrolling == true) { tracklistingtext.scrollV = Math.round(((scrollMC.y - bounds.y)/300)*tracklistingtext.maxScrollV); } } Any help is greatly appreciated.

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• Instrumenting a string

  - by George Polevoy

  Somewhere in C++ era i have crafted a library, which enabled string representation of the computation history. Having a math expression like: TScalar Compute(TScalar a, TScalar b, TScalar c) { return ( a + b ) * c; } I could render it's string representation: r = Compute(VerbalScalar("a", 1), VerbalScalar("b", 2), VerbalScalar("c", 3)); Assert.AreEqual(9, r.Value); Assert.AreEqual("(a+b)*c==(1+2)*3", r.History ); C++ operator overloading allowed for substitution of a simple type with a complex self-tracking entity with an internal tree representation of everything happening with the objects. Now i would like to have the same possibility for NET strings, only instead of variable names i would like to see a stack traces of all the places in code which affected a string. And i want it to work with existing code, and existing compiled assemblies. Also i want all this to hook into visual studio debugger, so i could set a breakpoint, and see everything that happened with a string. Which technology would allow this kind of things? I know it sound like an utopia, but I think visual studio code coverage tools actually do the same kind of job while instrumenting the assemblies.

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• F# How to tokenise user input: separating numbers, units, words?

  - by David White

  I am fairly new to F#, but have spent the last few weeks reading reference materials. I wish to process a user-supplied input string, identifying and separating the constituent elements. For example, for this input: XYZ Hotel: 6 nights at 220EUR / night plus 17.5% tax the output should resemble something like a list of tuples: [ ("XYZ", Word); ("Hotel:", Word); ("6", Number); ("nights", Word); ("at", Operator); ("220", Number); ("EUR", CurrencyCode); ("/", Operator); ("night", Word); ("plus", Operator); ("17.5", Number); ("%", PerCent); ("tax", Word) ] Since I'm dealing with user input, it could be anything. Thus, expecting users to comply with a grammar is out of the question. I want to identify the numbers (could be integers, floats, negative...), the units of measure (optional, but could include SI or Imperial physical units, currency codes, counts such as "night/s" in my example), mathematical operators (as math symbols or as words including "at" "per", "of", "discount", etc), and all other words. I have the impression that I should use active pattern matching -- is that correct? -- but I'm not exactly sure how to start. Any pointers to appropriate reference material or similar examples would be great.

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• Cannot make a static reference to the non-static type MyRunnable

  - by kaiwii ho

  Here is the whole code : import java.util.ArrayList; public class Test{ ThreadLocal<ArrayList<E>>arraylist=new ThreadLocal<ArrayList<E>>(){ @Override protected ArrayList<E> initialValue() { // TODO Auto-generated method stub //return super.initialValue(); ArrayList<E>arraylist=new ArrayList<E>(); for(int i=0;i<=20;i++) arraylist.add((E) new Integer(i)); return arraylist; } }; class MyRunnable implements Runnable{ private Test mytest; public MyRunnable(Test test){ mytest=test; // TODO Auto-generated constructor stub } @Override public void run() { System.out.println("before"+mytest.arraylist.toString()); ArrayList<E>myarraylist=(ArrayList<E>) mytest.arraylist.get(); myarraylist.add((E) new Double(Math.random())); mytest.arraylist.set(myarraylist); System.out.println("after"+mytest.arraylist.toString()); } // TODO Auto-generated method stub } public static void main(String[] args){ Test test=new Test<Double>(); System.out.println(test.arraylist.toString()); new Thread(new MyRunnable(test)).start(); new Thread(new MyRunnable(test)).start(); System.out.println(arraylist.toString()); } } my questions are: 1\ why the new Thread(new MyRunnable(test)).start(); cause the error: Cannot make a static reference to the non-static type MyRunnable ? 2\ what is the static reference refer to right here? thx in advanced

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• Int - number too large. How to get program to fail?

  - by Dave

  Hi Problem: How do you get a program to fail if a number goes beyond the bounds of its type? This code below gives the wrong answer for sum of primes under 2 million as I'd used an int instead of a long. [TestMethod] public void CalculateTheSumOfPrimesBelow2million() { int result = PrimeTester.calculateTheSumOfPrimesBelow(2000000); // 2million Assert.AreEqual(1, result); // 1,179,908,154 .. this was what I got with an int... // correct answer was 142,913,828,922 with a long } public static class PrimeTester { public static int calculateTheSumOfPrimesBelow(int maxPrimeBelow) { // we know 2 is a prime number int sumOfPrimes = 2; int currentNumberBeingTested = 3; while (currentNumberBeingTested < maxPrimeBelow) { double squareRootOfNumberBeingTested = (double)Math.Sqrt(currentNumberBeingTested); bool isPrime = true; for (int i = 2; i <= squareRootOfNumberBeingTested; i++) { if (currentNumberBeingTested % i == 0) { isPrime = false; break; } } if (isPrime) sumOfPrimes += currentNumberBeingTested; currentNumberBeingTested += 2; // as we don't want to test even numbers } return sumOfPrimes; } }

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• Computation overhead in C# - Using getters/setters vs. modifying arrays directly and casting speeds

  - by Jeffrey Kern

  I was going to write a long-winded post, but I'll boil it down here: I'm trying to emulate the graphical old-school style of the NES via XNA. However, my FPS is SLOW, trying to modify 65K pixels per frame. If I just loop through all 65K pixels and set them to some arbitrary color, I get 64FPS. The code I made to look-up what colors should be placed where, I get 1FPS. I think it is because of my object-orented code. Right now, I have things divided into about six classes, with getters/setters. I'm guessing that I'm at least calling 360K getters per frame, which I think is a lot of overhead. Each class contains either/and-or 1D or 2D arrays containing custom enumerations, int, Color, or Vector2D, bytes. What if I combined all of the classes into just one, and accessed the contents of each array directly? The code would look a mess, and ditch the concepts of object-oriented coding, but the speed might be much faster. I'm also not concerned about access violations, as any attempts to get/set the data in the arrays will done in blocks. E.g., all writing to arrays will take place before any data is accessed from them. As for casting, I stated that I'm using custom enumerations, int, Color, and Vector2D, bytes. Which data types are fastest to use and access in the .net Framework, XNA, XBox, C#? I think that constant casting might be a cause of slowdown here. Also, instead of using math to figure out which indexes data should be placed in, I've used precomputed lookup tables so I don't have to use constant multiplication, addition, subtraction, division per frame. :)

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• Three most critical programming concepts

  - by Todd

  I know this has probably been asked in one form or fashion but I wanted to pose it once again within the context of my situation (and probably others here @ SO). I made a career change to Software Engineering some time ago without having an undergrad or grad degree in CS. I've supplemented my undergrad and grad studies in business with programming courses (VB, Java,C, C#) but never performed academic coursework in the other related disciplines (algorithms, design patterns, discrete math, etc.)...just mostly self-study. I know there are several of you who have either performed interviews and/or made hiring decisions. Given recent trends in demand, what would you say are the three most essential Comp Sci concepts that a developer should have a solid grasp of outside of language syntax? For example, I've seen blog posts of the "Absolute minimum X that every programmer must know" variety...that's what I'm looking for. Again if it's truly a redundancy please feel free to close; my feelings won't be hurt. (Closest ones I could find were http://stackoverflow.com/questions/164048/basic-programming-algorithmic-concepts- which was geared towards a true beginner, and http://stackoverflow.com/questions/648595/essential-areas-of-knowledge-which I didn't feel was concrete enough). Thanks in advance all! T.

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• Problem finding the difference in days between two dates

  - by James

  I have been using a tidy little routine that I found here to calculate the difference in days between two dates in AS3. I am getting some strange results and I am wondering if any of you inter-codal-mega-lords can shed some light? Why is Q1 of 2010 coming up one day short, when in all other cases the routine is performing fine? Many thanks in advance to anyone who can help! function countDays( startDate:Date, endDate:Date ):int { var oneDay:int = 24*60*60*1000; // hours*minutes*seconds*milliseconds var diffDays:int = Math.abs((startDate.getTime() - endDate.getTime())/(oneDay)); return diffDays; } countDays( new Date( 2010, 00, 01 ), new Date( 2011, 00, 01 ) ); // returns 365, which is correct countDays( new Date( 2010, 00, 01 ), new Date( 2010, 03, 01 ) ); // returns 89, which is 1 day short countDays( new Date( 2010, 03, 01 ), new Date( 2010, 06, 01 ) ); // returns 91, which is correct countDays( new Date( 2010, 06, 01 ), new Date( 2010, 09, 01 ) ); // returns 92, which is correct countDays( new Date( 2010, 09, 01 ), new Date( 2011, 00, 01 ) ); // returns 92, which is correct

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• Python parsing error message functions

  - by user1716168

  The code below was created by me with the help of many SO veterans: The code takes an entered math expression and splits it into operators and operands for later use. I have created two functions, the parsing function that splits, and the error function. I am having problems with the error function because it won't display my error messages and I feel the function is being ignored when the code runs. An error should print if an expression such as this is entered: 3//3+4,etc. where there are two operators together, or there are more than two operators in the expression overall, but the error messages dont print. My code is below: def errors(): numExtrapolation,opExtrapolation=parse(expression) if (len(numExtrapolation) == 3) and (len(opExtrapolation) !=2): print("Bad1") if (len(numExtrapolation) ==2) and (len(opExtrapolation) !=1): print("Bad2") def parse(expression): operators= set("*/+-") opExtrapolate= [] numExtrapolate= [] buff=[] for i in expression: if i in operators: numExtrapolate.append(''.join(buff)) buff= [] opExtrapolate.append(i) opExtrapolation=opExtrapolate else: buff.append(i) numExtrapolate.append(''.join(buff)) numExtrapolation=numExtrapolate #just some debugging print statements print(numExtrapolation) print("z:", len(opExtrapolation)) return numExtrapolation, opExtrapolation errors() Any help would be appreciated. Please don't introduce new code that is any more advanced than the code already here. I am looking for a solution to my problem... not large new code segments. Thanks.

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• What to call factory-like (java) methods used with immutable objects

  - by StaxMan

  When creating classes for "immutable objects" immutable meaning that state of instances can not be changed; all fields assigned in constructor) in Java (and similar languages), it is sometimes useful to still allow creation of modified instances. That is, using an instance as base, and creating a new instance that differs by just one property value; other values coming from the base instance. To give a simple example, one could have class like: public class Circle { final double x, y; // location final double radius; public Circle(double x, double y, double r) { this.x = x; this.y = y; this.r = r; } // method for creating a new instance, moved in x-axis by specified amount public Circle withOffset(double deltaX) { return new Circle(x+deltaX, y, radius); } } So: what should method "withOffset" be called? (note: NOT what its name ought to be -- but what is this class of methods called). Technically it is kind of a factory method, but somehow that does not seem quite right to me, since often factories are just given basic properties (and are either static methods, or are not members of the result type but factory type). So I am guessing there should be a better term for such methods. Since these methods can be used to implement "fluent interface", maybe they could be "fluent factory methods"? Better suggestions? EDIT: as suggested by one of answers, java.math.BigDecimal is a good example with its 'add', 'subtract' (etc) methods. Also: I noticed that there's this question (by Jon Skeet no less) that is sort of related (although it asks about specific name for method)

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• C++ program crashes at runtime

  - by qwerty

  Hello, I have this simple c++ program #include <cstdlib> #include <iostream> #include <math.h> #include <stdlib.h> #include <time.h> #include <vector> using namespace std; int aleator(int n) { return (rand()%n)+1; } int main() { int r; int indexes[100]={0}; // const int size=100; //int a[size]; std::vector<int>v; srand(time(0)); for (int i=0;i<25;i++) { int index = aleator(100); if (indexes[index] != 0) { // try again i--; continue; } indexes[index] = 1; cout << v[index] ; } cout<<" "<<endl; system("pause"); return 0; } But at runtime it crashes, so i got that error with 'Send error report' and 'Don't send'. What i'm doing wrong? Thanks!

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• [Ruby] Modifying object inside a loop doesn't change object outside of the loop?

  - by Jergason

  I am having problems with modifying objects inside blocks and not getting the expected values outside the blocks. This chunk of code is supposed to transform a bunch of points in 3d space, calculate a score (the rmsd or root mean squared deviation), and store both the score and the set of points that produced that score if it is lower than the current lowest score. At the end, I want to print out the best bunch of points. first = get_transformed_points(ARGV[0]) second = get_transformed_points(ARGV[1]) best_rmsd = first.rmsd(second) best_points = second #transform the points around x, y, and z and get the rmsd. If the new points # have a smaller rmsd, store them. ROTATION = 30 #rotate by ROTATION degrees num_rotations = 360/ROTATION radians = ROTATION * (Math::PI/180) num_rotations.times do |i| second = second * x_rotate num_rotations.times do |j| second = second * y_rotate num_rotations.times do |k| second = second * z_rotate rmsd = first.rmsd(second) if rmsd < best_rmsd then best_points = second best_rmsd = rmsd end end end end File.open("#{ARGV[1]}.out", "w") {|f| f.write(best_points.to_s)} I can print out the points that are getting stored inside the block, and they are getting transformed and stored correctly. However, when I write out the points to a file at the end, they are the same as the initial set of points. Somehow the best_points = second chunk doesn't seem to be doing anything outside of the block. It seems like there are some scoping rules that I don't understand here. I had thought that since I declared and defined best_points above, outside of the blocks, that it would be updated inside the blocks. However, it seems that when the blocks end, it somehow reverts back to the original value. Any ideas how to fix this? Is this a problem with blocks specifically?

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• jquery ajax result with a wrong format

  - by ???

  I am facing a problem which is the result processed by AJAX, this situation is I would like to pass the result (from AJAX) 'f f f f \'' into get_option(''), I don't know why it become like this:- <li \'');="" f="" onclick="get_option('f" class="option normal_size"> <a href="javascript:void(0);">f f f f \'</a> </li> What I want is :- <li onclick="get_option('f f f f\'')" class="option normal_size"> <a href="javascript:void(0);">f f f f \'</a> </li> I guess the problem might be the space, but I don't know how to solve it, can anyone do me a favour? my AJAX coding is:- .ajax({ url:'inc_board_saving.php?board_title_input='+board_title_input_encode+'&cate_selected='+cate_selected_input_encode+'&cate_setting_selected='+cate_setting_selected, type:'GET', data:"nums="+Math.random()*1235, success: function(data){ try{ var content=""; var obj = eval('('+data+')'); for (var i=0;i<obj.length;i++){ content += "<li class='option normal_size' onclick=get_option('"+obj[i].board_name_encode+"');><a href='javascript:void(0);'>"+obj[i].board_name+"</a></li>"; } }catch(e){ return; } } }); Result:- [{"board_id":"66","board_name":"f f f f '","board_name_encode":"f f f f \'"},{"board_id":"65","board_name":"t t t t t","board_name_encode":"t t t t t"},{"board_id":"64","board_name":"yy yyy yy","board_name_encode":"yy yyy yy"}] Thanks all

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• Average over a timeframe with missing data

  - by BHare

  Assuming a table such as: UID Name Datetime Users 4 Room 4 2012-08-03 14:00:00 3 2 Room 2 2012-08-03 14:00:00 3 3 Room 3 2012-08-03 14:00:00 1 1 Room 1 2012-08-03 14:00:00 2 3 Room 3 2012-08-03 14:15:00 1 2 Room 2 2012-08-03 14:15:00 4 1 Room 1 2012-08-03 14:15:00 3 1 Room 1 2012-08-03 14:30:00 6 1 Room 1 2012-08-03 14:45:00 3 2 Room 2 2012-08-03 14:45:00 7 3 Room 3 2012-08-03 14:45:00 8 4 Room 4 2012-08-03 14:45:00 4 I wanted to get the average user count of each room (1,2,3,4) from the time 2PM to 3PM. The problem is that sometimes the room may not "check in" at the 15 minute interval time, so the assumption has to be made that the previous last known user count is still valid. For example the check-in's for 2012-08-03 14:15:00 room 4 never checked in, so it must be assumed that room 4 had 3 users at 2012-08-03 14:15:00 because that is what it had at 2012-08-03 14:00:00 This follows on through so that the average user count I am looking for is as follows: Room 1: (2 + 3 + 6 + 3) / 4 = 3.5 Room 2: (3 + 4 + 4 + 7) / 4 = 4.5 Room 3: (1 + 1 + 1 + 8) / 4 = 2.75 Room 4: (3 + 3 + 3 + 4) / 4 = 3.25 where # is the assumed number based on the previous known check-in. I am wondering if it's possible to so this with SQL alone? if not I am curious of a ingenious PHP solution that isn't just bruteforce math, as such as my quick inaccurate pseudo code: foreach ($rooms_id_array as $room_id) { $SQL = "SELECT * FROM `table` WHERE (`UID` == $room_id && `Datetime` >= 2012-08-03 14:00:00 && `Datetime` <= 2012-08-03 15:00:00)"; $result = query($SQL); if ( count($result) < 4 ) { // go through each date and find what is missing, and then go to previous date and use that instead } else { foreach ($result) $sum += $result; $avg = $sum / 4; } }

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