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• Portable Programming IDE

  - by Click Ok

  Frequently I'm brainstormed with programming ideas that I would like to directly code. More or less like "Wow, that algorithm will rock! I need to write it now!". For this kind of "impulse" to write, I use http://www.jarte.com/ that is a cool portable text editor. If I'm near a cybecafe or a friend computer, I just plug the usb pen drive and start to write... So, I would like: 1) a portable minimalist IDE 2) with minimal OS requirement (ie.: I want run from XP, Vista, etc...) 3) any modern language (I can learn a new language if needed. I just want write/test the algoritm) 4) Syntax Highlight/intellisense is good, but not required 5) Free Is there something like this?

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• Casting array of pointers to objects

  - by ritmbo

  If B is subclass of A. And I have in main(): B** b = new B*[10]; ... some algorithm that do b[i] = new B(..); ... So I have an array of pointers to objets B. Then I have a function: void f(A** foo); If in main, I do: f(b); I get a warning, but obviously if I do: f((A**)b);, i dont. The (A**) its a bit nasty. I was wondering if there's a more elegant way in C++ that at least do type checking as dynamic_cast.

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• set / line intersection solution

  - by Xavier

  I have two lists in python and I want to know if they intersect at the same index. Is there a mathematical way of solving this? For example if I have [9,8,7,6,5] and [3,4,5,6,7] I'd like a simple and efficient formula/algorithm that finds that at index 3 they intersect. I know I could do a search just wondering if there is a better way. I know there is a formula to solve two lines in y = mx + b form by subtracting them from each other but my "line" isn't truly a line because its limited to the items in the list and it may have curves. Any help is appreciated.

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• is it possible to dynamically set the level of for loop nesting

  - by galaxy

  I'm working out an algorithm to get permutations like 123 132 213 231 312 321 I'm doing it using nested foreach loops. for (..) { for(..) { for(..) { echo $i . $j . $k . "<br />"; } } } Problem is those # of nested loops are optimized for 3-spot permutations. How can I could I dynamically set the number of nested for loops to generate 4-letter or 5-letter permutations?

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• Drawing bezier curve with limited subdivisions in OpenGL

  - by xEnOn

  Is it possible to tell OpenGL to draw a 4 degree (5 control points) bezier curve with 10 subdivisions? I was trying with this: point ctrlpts[] = {..., ..., ..., ...}; glMap1f(GL_MAP1_VERTEX_3, 0, 1, 3, 5, ctrlpts); glBegin(GL_LINE_STRIP); for (i = 0; i <= 30; i++) glEvalCoord1f((GLfloat) i/30.0); glEnd(); But this just draws the curve nicely. I am thinking that I want the algorithm inside the bezier curve to draw only until 10 subdivisions and then stop. The line should look a little facet.

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• C#: Efficiently search a large string for occurences of other strings

  - by Jon

  Hi, I'm using C# to continuously search for multiple string "keywords" within large strings, which are = 4kb. This code is constantly looping, and sleeps aren't cutting down CPU usage enough while maintaining a reasonable speed. The bog-down is the keyword matching method. I've found a few possibilities, and all of them give similar efficiency. 1) http://tomasp.net/articles/ahocorasick.aspx -I do not have enough keywords for this to be the most efficient algorithm. 2) Regex. Using an instance level, compiled regex. -Provides more functionality than I require, and not quite enough efficiency. 3) String.IndexOf. -I would need to do a "smart" version of this for it provide enough efficiency. Looping through each keyword and calling IndexOf doesn't cut it. Does anyone know of any algorithms or methods that I can use to attain my goal?

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• Need help using the Windows IP Helper API & ParseNetworString in C#.

  - by JohnnyNoir

  I'm attempting to rewrite some C# web service code that uses the Windows IP Helper API call "SendARP" to retreive a remote system's MAC address. SendARP works great - until you cross a network segment as Arp requests aren't routed. I've been looking at the "ParseNetworkString" documentation after happening across its existance on StackOverflow. The quick & dirty algorithm I have in mind is: public static string GetMacAddress(string strHostOrIP) { if (strHostOrIP is IPAddress) { parse results of nbstat -A strHostOrIP return macAddress } if (strHostOrIP is Hostname) { IPHostEntry hostEntry = null; try { hostEntry = Dns.GetHostEntry(strHostOrIP); } catch { return null; } if (hostEntry.AddressList.Length == 0) { return null; } foreach (IPAddress ip in hostEntry.AddressList) { if (ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork) { ipAddress = ip; break; } } } return GetMACAddress(ipAddress); } "ParseNetworkString" is new with Vista/Win2008 so I haven't been able to find example C# code demonstrating its use and I'm no C++ coder so if anyone can point me in the right direction...

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• How do I visualize a complex graph in .Net?

  - by Ivan

  I need to visualize a graph (technically being a set of Entity Framework objects, but I can translate it to another representation if needed) of this kind. I don't know how to name it (by the way, if you know - I'll appreciate if you tell me). It would be ideal for graph elements to be clickable (so that when user clicks on a block, I can handle an event with the element id specified) but I can survive even without any interactivity. Are there any components available good for this task? If no, what should I look for to help me to develop an algorithm for drawing such a graph with visually-comfortable layout?

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• Python or matplotlib limitation error

  - by Werner

  Hi, I wrote an algorithm using python and matplotlib that generates histograms from some text input data. When the number of data input is approx. greater than 15000, I get in the (append) line of my code: mydata = [] for i in range(len(data)): mydata.append(string.atof(data[i])) the error: Traceback (most recent call last): File "get_histogram_picture.py", line 25, in <module> mydata.append(string.atof(data[i])) File "/usr/lib/python2.6/string.py", line 388, in atof return _float(s) ValueError: invalid literal for float(): -a can it be an error in python ? What is the solution ? Thanks

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• Why might different computers calculate different arithmetic results in VB.NET?

  - by Eyal

  I have some software written in VB.NET that performs a lot of calculations, mostly extracting jpegs to bitmaps and computing calculations on the pixels like convolutions and matrix multiplication. Different computers are giving me different results despite having identical inputs. What might be the reason? Edit: I can't provide the algorithm because it's proprietary but I can provide all the relevant operations: ULong \ ULong (Turuncating division) Bitmap.Load("filename.bmp') (Load a bitmap into memory) Bitmap.GetPixel(Integer, Integer) (Get a pixel's brightness) Double + Double Double * Double Math.Sqrt(Double) Math.PI Math.Cos(Double) ULong - ULong ULong * ULong ULong << ULong List.OrderBy(Of Double)(Func) Hmm... Is it possible that OrderBy is using a non-stable QuickSort and that QuickSort is using a random pivot? Edit: Just tested, nope. The sort is stable.

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• Color space - RGB and YCbCr question

  - by HardCoder1986

  Hello! I am now trying to understand how JPEG encoding works and everything seems fine except the color transformation part. Before attempting to do a DCT in JPEG algorithm, the image is transformed into YCbCr color space. To me this essentially means that we just (comparing to initial RGB image) take a chunk of color information and dispose it while applying the RGB -> YCbCr transformation. So, our encoding steps look generally like RGB -> YCbCr -> DCT -> Huffman. The decoding means inversing this process. And my question is - why does the image (for example, created and exported to JPEG) remain the same in terms of color, although we have to make inverse YCbCr -> RGB transform. Where does the disposed part of color information comes from or how is it handled?

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• Calculating Divergent Paths on Subtending Rings

  - by Russ

  I need to calculate two paths from A to B in the following graph, with the constraint that the paths can't share any edges: hmm, okay, can't post images, here's a link. All edges have positive weights; for this example I think we can assume that they're equal. My naive approach is to use Djikstra's algorithm to calculate the first path, shown in the second graph in the above image. Then I remove the edges from the graph and try to calculate the second path, which fails. Is there a variation of Djikstra, Bellman-Ford (or anything else) that will calculate the paths shown in the third diagram above? (Without special knowledge and removal of the subtending link, is what I mean)

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• Security & Authentication: SSL vs SASL

  - by 4herpsand7derpsago

  My understanding is that SSL combines an encryption algorithm (like AES, DES, etc.) with akey exchange method (like Diffier-Hellman) to provide secure encryption and identification services between two endpoints on an un-secure network (like the Internet). My understanding is that SASL is an MD5/Kerberos protocol that pretty much does the same thing. So my question: what are the pros/cons to choosing both and what scenarios make both more preferable? Basically, I'm looking for a guidelines to follow when choosing SSL or to go with SASL instead. Thanks in advance!

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• C++: call original definition of operator equals

  - by Luis Daniel

  I am overloading the operator equals (==) as show bellow: #include <string> #include <algorithm> bool operator == (std::string str1, std::string str2) { std::transform(str1.begin(), str1.end(), str1.begin(), ::tolower); std::transform(str2.begin(), str2.end(), str2.begin(), ::tolower); return (str1 == str2); } but, the problem appear on line return (str1 == str2), because operator == is called recursively. So, how can I call the original definition for operator equals (not the overloaded) ? Best regards

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• "painting" one array onto another using python / numpy

  - by Nate

  I'm writing a library to process gaze tracking in Python, and I'm rather new to the whole numpy / scipy world. Essentially, I'm looking to take an array of (x,y) values in time and "paint" some shape onto a canvas at those coordinates. For example, the shape might be a blurred circle. The operation I have in mind is more or less identical to using the paintbrush tool in Photoshop. I've got an interative algorithm that trims my "paintbrush" to be within the bounds of my image and adds each point to an accumulator image, but it's slow(!), and it seems like there's probably a fundamentally easier way to do this. Any pointers as to where to start looking?

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• c program for this quesion

  - by sashi

  suppose that a disk drive has 5000 cylinders, numbered 0 to 4999. the drive is currently serving a request at cylinder 143 and the previous request was at cylinder 125. the ueue of pending requests in the given order is 86,1470,913,17774,948,1509,1022,1750,130. write a 'c' program for finding the total distance in cylinders that the disk arm moves to satisfy all the pending reuests from the current heads position, using SSTF scheduling algorith. seek time is the time for the disk arm to move the head to the cylider containing the desired sector. sstf algorithm selects the minimum seek time from the current head position.

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• How do I draw an ellipse with arbitrary orientation pixel by pixel?

  - by amc

  Hi, I have to draw an ellipse of arbitrary size and orientation pixel by pixel. It seems pretty easy to draw an ellipse whose major and minor axes align with the x and y axes, but rotating the ellipse by an arbitrary angle seems trickier. Initially I though it might work to draw the unrotated ellipse and apply a rotation matrix to each point, but it seems as though that could cause errors do to rounding, and I need rather high precision. Is my suspicion about this method correct? How could I accomplish this task more precisely? I'm programming in C++ (although that shouldn't really matter since this is a more algorithm-oriented question).

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• deleting and reusing a temp table in a stored precedure

  - by Sheagorath

  Hi I need to SELECT INTO a temp table multiple times with a loop but I just can't do it, because after the table created by SELECT INTO you can't simply drop the table at the end of the loop, because you can't delete a table and create it again in the same batch. so how can I delete a table in a stored procedure and create it again? is it possible to this without using a temp table? here is a snippet of where I am actualy using the temp table which is supposed to be a pivoting algorithm: WHILE @offset<@NumDays BEGIN SELECT bg.*, j.ID, j.time, j.Status INTO #TEMP1 FROM #TEMP2 AS bg left outer join PersonSchedule j on bg.PersonID = j.PersonID and bg.TimeSlotDateTime = j.TimeSlotDateTime and j.TimeSlotDateTime = @StartDate + @offset DROP TABLE #TEMP2; SELECT * INTO #TEMP2 FROM #TEMP1 DROP TABLE #TEMP1 SET @offset = @offset + 1 END

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• What is better for a student programming in C++ to learn for writing GUI: C# vs QT?

  - by flashnik

  I'm a teacher(instructor) of CS in the university. The course is based on Cormen and Knuth and students program algorithms in C++. But sometimes it is good to show how an algorithm works or just a result of task through GUI. Also in my opinion it's very imporant to be able to write full programs. They will have courses concerning GUI but a three years, later, in fact, before graduatuion. I think that they should be able to write simple GUI applications earlier. So I want to teach them it. How do you think, what is more useful for them to learn: programming GUI with QT or writing GUI in C# and calling unmanaged C++ library?

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• Gradients and memory

  - by user146780

  I'm creating a drawing application with OpenGL. I'v created an algorithm that generates gradient textures. I then map these to my polygons and this works quite well. What I realized is how much memory this requires. Creating 1000 gradients takes about 800MB and that's way too much. Is there an alternative to textures, or a way to compress them, or another way to map gradients to polygons that doesn't use up as much memory? Thanks My polygons are concave, I use GLUTesselator, and they are multicolored and point to point

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• Reverse Bredth First Search in C#

  - by Ngu Soon Hui

  Anyone has a ready implementation of the Reverse Bredth First Search algorithm in C#? By Reverse Bredth First Search, I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node. Let's see the below figure, this is the output of a Bredth First Search: In my reverse bredth first search, 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found. Any ideas or pointers?

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• Loading dictionary for input method suggestion list

  - by jpspringall

  Hi, For various reasons, i'm trying to write my own input keyboard. So far all is going well except that of creating the suggestions. I've found the latinIME algorithm, which is all good. However i'm having major difficulty working out how to load the dictionary in the first place. I've had a good look round the net, and found various suggestions, but no definitive answers, and i cant seem to get any of them to work. If anyone has any suggestions on how best to do it, or even better some sample code, that would be brilliant. Many Thanks James

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• How do I measure distances in an image?

  - by Ram Bhat

  Let's say we have an image like so Let's say we've already used filters and an edge detection algorithm in this pic. Now my goal is to measure distances (NOT actual distances, distance can be in any arbitrary unit) . eg: How do I find the length of the hall? (until the window) Or the height of the bookshelves? How exactly do you place the "scale" and measure. I'm looking for ideas. However it would help if the answers were in terms of OpenCV.

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• Straight Line Equation between two points

  - by dafero

  Hi, I need to paint the line witch links two points. I developed my own solution using the straight line equation, but my results are different than using the "professional" programs (such as GIMP or even MS Paint). Here is a example of what I want: But my algorithm does this: *The green point is out of the figure and this is not possible. Any ideas? Anyone know which code is been using for this, in "professional" apps? Thanks! Daniel.

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• How to automatically email customers registration keys?

  - by Danny

  I've written a bit of software that I'd like to share with others (a Mac Dashboard widget, specifically), but I'd also like to be compensated a bit for the time I spent on it. I've devised my own simple registration key algorithm, which takes a customer's email address and creates a 12-character alphanumeric key. The software itself is finished, demo limitations, key validation & all. I just need to get the keys to customers. How do I simply alert a key generation script to automatically email a customer a key, upon notification that they paid my account? Can I use PayPal IPN & JavaScript? The simplest solution will do - this is a five dollar widget. :)

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