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• Which book should I choose?

  - by sebastianlarsson

  Hi guys, I'm looking for a good read on object oriented design. The two books I'm currently looking Head First Design Patterns and Head First Object object-oriented analysis & design. They seem very similar when looking at the contents and browsing through available sample text. Which one would be the best choice? About myself: I have a bachelor in computer science and I am currently studying Msc. Software Quality Engineering (read Software Engineering with focus on Quality). I am already confident in object-oriented design and have a lot of programming courses in my backpack. I have done games in c++, courses in advanced java programming (I am SCJP certified), but my preferred language is C#. I have also worked with Java for the last 7 months while studying. I am currently also studying for certificates in C# (apart from my usual studies). So I believe I have the prerequisites of actually understanding the contents of both books. Reason: I just want to be better and keep evolving as a programmer. I think it is fun. I believe Bert Bates and Kathy Sierra are involved in both these books and I have previously read their SCJP preparation book in java. I really do enjoy their style of writing. Other books which I am considering are: Clean Code: A Handbook Of Agile Software Craftsmanship Thx in advance Sebastian

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• Writing catch block with cleanup operations in Java ...

  - by kedarmhaswade

  I was not able to find any advise on catch blocks in Java that involve some cleanup operations which themselves could throw exceptions. The classic example is that of stream.close() which we usually call in the finally clause and if that throws an exception, we either ignore it by calling it in a try-catch block or declare it to be rethrown. But in general, how do I handle cases like: public void doIt() throws ApiException { //ApiException is my "higher level" exception try { doLower(); } catch(Exception le) { doCleanup(); //this throws exception too which I can't communicate to caller throw new ApiException(le); } } I could do: catch(Exception le) { try { doCleanup(); } catch(Exception e) { //ignore? //log? } throw new ApiException(le); //I must throw le } But that means I will have to do some log analysis to understand why cleanup failed. If I did: catch(Exception le) { try { doCleanup(); } catch(Exception e) { throw new ApiException(e); } It results in losing the le that got me here in the catch block in the fist place. What are some of the idioms people use here? Declare the lower level exceptions in throws clause? Ignore the exceptions during cleanup operation?

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• ECM (Niche Vs Mass Market)

  - by Luj Reyes

  Hi Everyone, I recently started a little company with a couple of guys. Ours is the typical startup, a lot of ideas, dreams, talent and work hours :P. Our initial business plan was to develop a DM (Document Manager) with several features found on DropBox and other tools but with a big differentiator. Then we got in the team this Business Guy (I must say that several of us could be called 'Business Guys' but we are mainly hackers, he is just Another 'Networking Guy'), and along with him came this market analysis for a DM aimed at a very specific and narrow niche. We have many elements to believe in his market study and the idea is the classic "The market is X million, so if we grab a 10%...", and the market is really there to grab because all big providers deemed it too little and fled, let's say that the market is 5 million USD and demand very specific features. If we decide to go for this niche product we face a sales cycle of about 7 months, and the main goal of these revenue is to develop more ambitious projects. (Institutional VC is out of the question if you want to keep a marginal ownership of your company in my country). The only overlap between the niche and the mass market product features is the ability to store documents; everything else requires that we focus all of our efforts towards one or the other. I've studied a lot about the differences between Mass and Niche Markets, but I want to hear from people with actual experience. So everything comes down to this: If you have a really “saleable” idea what is the right thing to do: to go for the niche or go for the big prize and target primarily the mass market? Thanks for your input

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• I have two choices of Master's classes this fall. Which is the most useful?

  - by ahplummer

  (For background purposes and context): I am a Software Engineer, and manage other Software Engineers currently. I kind of wear two hats right now: one of a programmer, and one as a 'team lead'. In this regard, I've started going back to school to get my Master's degree with an emphasis in Computer Science. I already have a Bachelor's in Computer Science, and have been working in the field for about 13 years. Our primary development environment is a Windows environment, writing in .NET, Delphi, and SQL Server. Choice #1: CST 798 DATA VISUALIZATION Course Description: Basically, this is a course on the "Processing" language: http://processing.org/ Choice #2: CST 711 INFORMATICS Course Description: (From catalog): Informatics is the science of the use and processing of data, information, and knowledge. This course covers a variety of applied issues from information technology, information management at a variety of levels, ranging from simple data entry, to the creation, design and implementation of new information systems, to the development of models. Topics include basic information representation, processing, searching, and organization, evaluation and analysis of information, Internet-based information access tools, ethics and economics of information sharing.

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• How to perform Linq select new with datetime in SQL 2008

  - by kd7iwp

  In our C# code I recently changed a line from inside a linq-to-sql select new query as follows: OrderDate = (p.OrderDate.HasValue ? p.OrderDate.Value.Year.ToString() + "-" + p.OrderDate.Value.Month.ToString() + "-" + p.OrderDate.Value.Day.ToString() : "") To: OrderDate = (p.OrderDate.HasValue ? p.OrderDate.Value.ToString("yyyy-mm-dd") : "") The change makes the line smaller and cleaner. It also works fine with our SQL 2008 database in our development environment. However, when the code deployed to our production environment which uses SQL 2005 I received an exception stating: Nullable Type must have a value. For further analysis I copied (p.OrderDate.HasValue ? p.OrderDate.Value.ToString("yyyy-mm-dd") : "") into a string (outside of a Linq statement) and had no problems at all, so it only causes an in issue inside my Linq. Is this problem just something to do with SQL 2005 using different date formats than from SQL 2008? Here's more of the Linq: dt = FilteredOrders.Where(x => x != null).Select(p => new { Order = p.OrderId, link = "/order/" + p.OrderId.ToString(), StudentId = (p.PersonId.HasValue ? p.PersonId.Value : 0), FirstName = p.IdentifierAccount.Person.FirstName, LastName = p.IdentifierAccount.Person.LastName, DeliverBy = p.DeliverBy, OrderDate = p.OrderDate.HasValue ? p.OrderDate.Value.Date.ToString("yyyy-mm-dd") : ""}).ToDataTable(); This is selecting from a List of Order objects. The FilteredOrders list is from another linq-to-sql query and I call .AsEnumerable on it before giving it to this particular select new query. Doing this in regular code works fine: if (o.OrderDate.HasValue) tempString += " " + o.OrderDate.Value.Date.ToString("yyyy-mm-dd");

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• Memory usage in Flash / Flex / AS3

  - by ggambett

  I'm having some trouble with memory management in a flash app. Memory usage grows quite a bit, and I've tracked it down to the way I load assets. I embed several raster images in a class Embedded, like this [Embed(source="/home/gabriel/text_hard.jpg")] public static var ASSET_text_hard_DOT_jpg : Class; I then instance the assets this way var pClass : Class = Embedded[sResource] as Class; return new pClass() as Bitmap; At this point, memory usage goes up, which is perfectly normal. However, nulling all the references to the object doesn't free the memory. Based on this behavior, looks like the flash player is creating an instance of the class the first time I request it, but never ever releases it - not without references, calling System.gc(), doing the double LocalConnection trick, or calling dispose() on the BitmapData objects. Of course, this is very undesirable - memory usage would grow until everything in the SWFs is instanced, regardless of whether I stopped using some asset long ago. Is my analysis correct? Can anything be done to fix this?

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• Oracle why does creating trigger fail when there is a field called timestamp?

  - by Omar Kooheji

  I've just wasted the past two hours of my life trying to create a table with an auto incrementing primary key bases on this tutorial, The tutorial is great the issue I've been encountering is that the Create Target fails if I have a column which is a timestamp and a table that is called timestamp in the same table... Why doesn't oracle flag this as being an issue when I create the table? Here is the Sequence of commands I enter: Creating the Table: CREATE TABLE myTable (id NUMBER PRIMARY KEY, field1 TIMESTAMP(6), timeStamp NUMBER, ); Creating the Sequence: CREATE SEQUENCE test_sequence START WITH 1 INCREMENT BY 1; Creating the trigger: CREATE OR REPLACE TRIGGER test_trigger BEFORE INSERT ON myTable REFERENCING NEW AS NEW FOR EACH ROW BEGIN SELECT test_sequence.nextval INTO :NEW.ID FROM dual; END; / Here is the error message I get: ORA-06552: PL/SQL: Compilation unit analysis terminated ORA-06553: PLS-320: the declaration of the type of this expression is incomplete or malformed Any combination that does not have the two lines with a the word "timestamp" in them works fine. I would have thought the syntax would be enough to differentiate between the keyword and a column name. As I've said I don't understand why the table is created fine but oracle falls over when I try to create the trigger... CLARIFICATION I know that the issue is that there is a column called timestamp which may or may not be a keyword. MY issue is why it barfed when I tried to create a trigger and not when I created the table, I would have at least expected a warning. That said having used Oracle for a few hours, it seems a lot less verbose in it's error reporting, Maybe just because I'm using the express version though. If this is a bug in Oracle how would one who doesn't have a support contract go about reporting it? I'm just playing around with the express version because I have to migrate some code from MySQL to Oracle.

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• mysql subselect alternative

  - by Arnold

  Hi, Lets say I am analyzing how high school sports records affect school attendance. So I have a table in which each row corresponds to a high school basketball game. Each game has an away team id and a home team id (FK to another "team table") and a home score and an away score and a date. I am writing a query that matches attendance with this seasons basketball games. My sample output will be (#_students_missed_class, day_of_game, home_team, away_team, home_team_wins_this_season, away_team_wins_this_season) I now want to add how each team did the previous season to my analysis. Well, I have their previous season stored in the game table but i should be able to accomplish that with a subselect. So in my main select statement I add the subselect: SELECT COUNT(*) FROM game_table WHERE game_table.date BETWEEN 'start of previous season' AND 'end of previous season' AND ( (game_table.home_team = team_table.id AND game_table.home_score > game_table.away_score) OR (game_table.away_team = team_table.id AND game_table.away_score > game_table.home_score)) In this case team-table.id refers to the id of the home_team so I now have all their wins calculated from the previous year. This method of calculation is neither time nor resource intensive. The Explain SQL shows that I have ALL in the Type field and I am not using a Key and the query times out. I'm not sure how I can accomplish a more efficient query with a subselect. It seems proposterously inefficient to have to write 4 of these queries (for home wins, home losses, away wins, away losses). I am sure this could be more lucid. I'll absolutely add color tomorrow if anyone has questions

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• ploting 3d graph in matlab?

  - by lytheone

  Hello, I am currently a begineer, and i am using matlab to do a data analysis. I have a a text file with data at the first row is formatted as follow: time;wave height 1;wave height 2;....... I have column until wave height 19 and rows total 4000 rows. Data in the first column is time in second. From 2nd column onwards, it is wave height elevation which is in meter. At the moment I like to ask matlab to plot a 3d graph with time on the x axis, wave elevation on the y axis, and wave elevation that correspond to wave height number from 1 to 19, i.e. data in column 2 row 10 has a let say 8m which is correspond to wave height 1 and time at the column 1 row 10. I have try the following: clear; filename='abc.daf'; path='C:\D'; a=dlmread([path '\' filename],' ', 2, 1); [nrows,ncols]=size(a); t=a(1:nrows,1);%define t from text file for i=(1:20), j=(2:21); end wi=a(:,j); for k=(2:4000), l=k; end r=a(l,:); But everytime i use try to plot them, the for loop wi works fine, but for r=a(l,:);, the plot only either give me the last time data only but i want all data in the file to be plot. Is there a way i can do that. I am sorry as it is a bit confusing but i will be very thankful if anyone can help me out. Thank you!!!!!!!!!!

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• Handling missing/incomplete data in R--is there function to mask but not remove NAs?

  - by doug

  As you would expect from a DSL aimed at data analysis, R handles missing/incomplete data very well, for instance: Many R functions have an 'na.rm' flag that you can set to 'T' to remove the NAs: mean( c(5,6,12,87,9,NA,43,67), na.rm=T) But if you want to deal with NAs before the function call, you need to do something like this: to remove each 'NA' from a vector: vx = vx[!is.na(a)] to remove each 'NA' from a vector and replace it w/ a '0': ifelse(is.na(vx), 0, vx) to remove entire each row that contains 'NA' from a data frame: dfx = dfx[complete.cases(dfx),] All of these functions permanently remove 'NA' or rows with an 'NA' in them. Sometimes this isn't quite what you want though--making an 'NA'-excised copy of the data frame might be necessary for the next step in the workflow but in subsequent steps you often want those rows back (e.g., to calculate a column-wise statistic for a column that has missing rows caused by a prior call to 'complete cases' yet that column has no 'NA' values in it). to be as clear as possible about what i'm looking for: python/numpy has a class, 'masked array', with a 'mask' method, which lets you conceal--but not remove--NAs during a function call. Is there an analogous function in R?

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• How to identify ideas and concepts in a given text

  - by Nick

  I'm working on a project at the moment where it would be really useful to be able to detect when a certain topic/idea is mentioned in a body of text. For instance, if the text contained: Maybe if you tell me a little more about who Mr Balzac is, that would help. It would also be useful if I could have a description of his appearance, or even better a photograph? It'd be great to be able to detect that the person has asked for a photograph of Mr Balzac. I could take a really naïve approach and just look for the word "photo" or "photograph", but this would obviously be no good if they wrote something like: Please, never send me a photo of Mr Balzac. Does anyone know where to start with this? Is it even possible? I've looked into things like nltk, but I've yet to find an example of someone doing something similar and am still not entirely sure what this kind of analysis is called. Any help that can get me off the ground would be great. Thanks!

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• What is a good programming language/environment for Linux database applications?

  - by Dkellygb

  I could use some advice on my move from the Windows world to Linux. For my business, I have used VB6 and Microsoft Access with both Access databases and SQL server in the past. The easy to use forms, report writers and programming language were perfect for CRUD apps and analysis for our small hotel/restaurant business. After using Linux at home for some time I would like to convert our small business. Our server is already a Linux box using Samba. I am happy with the OpenOffice.org applications instead of Microsoft Office. The only thing which is holding me back is a desktop database application where I can develop the forms and reports we require. Base does not seem to be up to the job yet from my experience. I would like something like VB.Net with visual studio (express) but I would like to avoid Mono – I just don’t see the point of it. (You can correct me if I’m wrong.) But a good collection of forms, controls and a good report writer would be ideal. I have looked at web based stuff like Ruby on Rails, but I think a webserver for our 5 pc network is overkill. I don’t mind running a proper database on our Ubuntu 9.10 server. I may have exposed a few prejudices above but my mind is open. Any thoughts?

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• Reconstructing trees from a "fingerprint"

  - by awshepard

  I've done my SO and Google research, and haven't found anyone who has tackled this before, or at least, anyone who has written about it. My question is, given a "universal" tree of arbitrary height, with each node able to have an arbitrary number of branches, is there a way to uniquely (and efficiently) "fingerprint" arbitrary sub-trees starting from the "universal" tree's root, such that given the universal tree and a tree's fingerprint, I can reconstruct the original tree? For instance, I have a "universal" tree (forgive my poor illustrations), representing my universe of possibilities: Root / / / | \ \ ... \ O O O O O O O (Level 1) /|\/|\...................\ (Level 2) etc. I also have tree A, a rooted subtree of my universe Root / /|\ \ O O O O O / Etc. Is there a way to "fingerprint" the tree, so that given that fingerprint, and the universal tree, I could reconstruct A? I'm thinking something along the lines of a hash, a compression, or perhaps a functional/declarative construction? Big-O analysis (in time or space) is a plus. As a for-instance, a nested expression like: {{(Root)},{(1),(2),(3)},{(2,3),(1),(4,5)}...} representing the actual nodes present at each level in the tree is probably valid, but can it be done more efficiently?

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• MySQL table data transformation -- how can I dis-aggreate MySQL time data?

  - by lighthouse65

  We are coding for a MySQL data warehousing application that stores descriptive data (User ID, Work ID, Machine ID, Start and End Time columns in the first table below) associated with time and production quantity data (Output and Time columns in the first table below) upon which aggregate (SUM, COUNT, AVG) functions are applied. We now wish to dis-aggregate time data for another type of analysis. Our current data table design: +---------+---------+------------+---------------------+---------------------+--------+------+ | User ID | Work ID | Machine ID | Event Start Time | Event End Time | Output | Time | +---------+---------+------------+---------------------+---------------------+--------+------+ | 080025 | ABC123 | M01 | 2008-01-24 16:19:15 | 2008-01-24 16:34:45 | 2120 | 930 | +---------+---------+------------+---------------------+---------------------+--------+------+ Reprocessing dis-aggregation that we would like to do would be to transform table content based on a granularity of minutes, rather than the current production event ("Event Start Time" and "Event End Time") granularity. The resulting reprocessing of existing table rows would look like: +---------+---------+------------+---------------------+--------+ | User ID | Work ID | Machine ID | Production Minute | Output | +---------+---------+------------+---------------------+--------+ | 080025 | ABC123 | M01 | 2010-01-24 16:19 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:20 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:21 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:23 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:24 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:25 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:26 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:27 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:28 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:29 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:30 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:31 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:22 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:33 | 133 | | 080025 | ABC123 | M01 | 2010-01-24 16:34 | 133 | +---------+---------+------------+---------------------+--------+ So the reprocessing would take an existing row of data created at the granularity of production event and modify the granularity to minutes, eliminating redundant (Event End Time, Time) columns while doing so. It assumes a constant rate of production and divides output by the difference in minutes plus one to populate the new table's Output column. I know this can be done in code...but can it be done entirely in a MySQL insert statement (or otherwise entirely in MySQL)? I am thinking of a INSERT ... INTO construction but keep getting stuck. An additional complexity is that there are hundreds of machines to include in the operation so there will be multiple rows (one for each machine) for each minute of the day. Any ideas would be much appreciated. Thanks.

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• Asymptotic runtime of list-to-tree function

  - by Deestan

  I have a merge function which takes time O(log n) to combine two trees into one, and a listToTree function which converts an initial list of elements to singleton trees and repeatedly calls merge on each successive pair of trees until only one tree remains. Function signatures and relevant implementations are as follows: merge :: Tree a -> Tree a -> Tree a --// O(log n) where n is size of input trees singleton :: a -> Tree a --// O(1) empty :: Tree a --// O(1) listToTree :: [a] -> Tree a --// Supposedly O(n) listToTree = listToTreeR . (map singleton) listToTreeR :: [Tree a] -> Tree a listToTreeR [] = empty listToTreeR (x:[]) = x listToTreeR xs = listToTreeR (mergePairs xs) mergePairs :: [Tree a] -> [Tree a] mergePairs [] = [] mergePairs (x:[]) = [x] mergePairs (x:y:xs) = merge x y : mergePairs xs This is a slightly simplified version of exercise 3.3 in Purely Functional Data Structures by Chris Okasaki. According to the exercise, I shall now show that listToTree takes O(n) time. Which I can't. :-( There are trivially ceil(log n) recursive calls to listToTreeR, meaning ceil(log n) calls to mergePairs. The running time of mergePairs is dependent on the length of the list, and the sizes of the trees. The length of the list is 2^h-1, and the sizes of the trees are log(n/(2^h)), where h=log n is the first recursive step, and h=1 is the last recursive step. Each call to mergePairs thus takes time (2^h-1) * log(n/(2^h)) I'm having trouble taking this analysis any further. Can anyone give me a hint in the right direction?

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• Raw types and subtyping

  - by Dmitrii

  We have generic class SomeClass<T>{ } We can write the line: SomeClass s= new SomeClass<String>(); It's ok, because raw type is supertype for generic type. But SomeClass<String> s= new SomeClass(); is correct to. Why is it correct? I thought that type erasure was before type checking, but it's wrong. From Hacker's Guide to Javac When the Java compiler is invoked with default compile policy it performs the following passes: parse: Reads a set of *.java source files and maps the resulting token sequence into AST-Nodes. enter: Enters symbols for the definitions into the symbol table. process annotations: If Requested, processes annotations found in the specified compilation units. attribute: Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. flow: Performs data ow analysis on the trees from the previous step. This includes checks for assignments and reachability. desugar: Rewrites the AST and translates away some syntactic sugar. generate: Generates Source Files or Class Files. Generic is syntax sugar, hence type erasure invoked at 6 pass, after type checking, which invoked at 4 pass. I'm confused.

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• writing into csv file

  - by arin

  I recived alarms in a form of text as the following NE=JKHGDUWJ3 Alarm=Data Center STALZ AC Failure Occurrence=2012/4/3 22:18:19 GMT+02:00 Clearance=Details=Cabinet No.=0, Subrack No.=40, Slot No.=0, Port No.=5, Board Type=EDS, Site No.=49, Site Type=HSJYG500 GSM, Site Name=Google1 . I need to fill it in csv file so later I can perform some analysis I came up with this namespace AlarmSaver { public partial class Form1 : Form { string filesName = "c:\\alarms.csv"; public Form1() { InitializeComponent(); } private void buttonSave_Click(object sender, EventArgs e) { if (!File.Exists(filesName)) { string header = "NE,Alarm,Occurrence,Clearance,Details"; File.AppendAllText(filesName,header+Environment.NewLine); } StringBuilder sb = new StringBuilder(); string line = textBoxAlarm.Text; int index = line.IndexOf(" "); while (index > 0) { string token = line.Substring(0, index).Trim(); line = line.Remove(0, index + 2); string[] values = token.Split('='); if (values.Length ==2) { sb.Append(values[1] + ","); } else { if (values.Length % 2 == 0) { string v = token.Remove(0, values[0].Length + 1).Replace(',', ';'); sb.Append(v + ","); } else { sb.Append("********" + ","); string v = token.Remove(0, values[0].Length + 1 + values[1].Length + 1).Replace(',', ';'); sb.Append(v + ","); } } index = line.IndexOf(" "); } File.AppendAllText(filesName, sb.ToString() + Environment.NewLine); } } } the results are as I want except when I reach the part of Details=Cabinet No.=0, Subrack No.=40, Slot No.=0, Port No.=5, Board Type=KDL, Site No.=49, Site Type=JDKJH99 GSM, Site Name=Google1 . I couldnt split them into seperate fields. as the results showing is as I want to split the details I want each element in details to be in a column to be somthin like its realy annoying :-) please help , thank you in advance

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• Generating easy-to-remember random identifiers

  - by Carl Seleborg

  Hi all, As all developers do, we constantly deal with some kind of identifiers as part of our daily work. Most of the time, it's about bugs or support tickets. Our software, upon detecting a bug, creates a package that has a name formatted from a timestamp and a version number, which is a cheap way of creating reasonably unique identifiers to avoid mixing packages up. Example: "Bug Report 20101214 174856 6.4b2". My brain just isn't that good at remembering numbers. What I would love to have is a simple way of generating alpha-numeric identifiers that are easy to remember. Examples would be "azil3", "ulmops", "fel2way", etc. I just made these up, but they are much easier to recognize when you see many of them at once. I know of algorithms that perform trigram analysis on text (say you feed them a whole book in German) and that can generate strings that look and feel like German words. This requires lots of data, though, and makes it slightly less suitable for embedding in an application just for this purpose. Do you know of anything else? Thanks! Carl

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• What is the the relation between programming and mathematics?

  - by Math Grad

  Programmers seem to think that their work is quite mathematical. I understand this when you try to optimize something in performance, find the most efficient alogithm, etc.. But it patently seems false when you look at a billing application for a shop, or a systems software riddled with I/O calls. So what is it exactly? Is computation and associated programming really mathematical? Here I have in mind particularly the words of the philosopher Schopenhauer in mind: That arithmetic is the basest of all mental activities is proved by the fact that it is the only one that can be accomplished by means of a machine. Take, for instance, the reckoning machines that are so commonly used in England at the present time, and solely for the sake of convenience. But all analysis finitorum et infinitorum is fundamentally based on calculation. Therefore we may gauge the “profound sense of the mathematician,” of whom Lichtenberg has made fun, in that he says: “These so-called professors of mathematics have taken advantage of the ingenuousness of other people, have attained the credit of possessing profound sense, which strongly resembles the theologians’ profound sense of their own holiness.” I lifted the above quote from here. It seems that programmers are doing precisely the sort of mechanized base mental activity the grand old man is contemptuous about. So what exactly is the deal? Is programming really the "good" kind of mathematics, or just the baser type, or altogether something else just meant for business not to be confused with a pure discipline?

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• How do I get started designing and implementing a script interface for my .NET application?

  - by Peter Mortensen

  How do I get started designing and implementing a script interface for my .NET application? There is VSTA (the .NET equivalent of VBA for COM), but as far as I understand I would have to pay a license fee for every installation of my application. It is an open source application so this will not work. There is also e.g. the embedding of interpreters (IronPython?), but I don't understand how this would allow exposing an "object model" (see below) to external (or internal) scripts. What is the scripting interface story in .NET? Is it somehow trivial in .NET to do this? Background: I have once designed and implemented a fairly involved script interface for a Macintosh application for acquisition and analysis of data from a mass spectrometer (Mac OS, System 7) and later a COM interface for a Windows application. Both were designed with an "object model" and classes (that can have properties). These are overloaded words, but in a scripting interface context object model is essentially a containment hiarchy of objects of specific classes. Classes have properties and lists of contained objects. E.g. like in the COM interfaces exposed in Microsoft Office applications, where the application object can be used to add to its list of documents (with the side effect of creating the GUI representation of a document). External scripts can create new objects in a container and navigate through the content of the hiarchy at any given time. In the Macintosh case scripts could be written in e.g. AppleScript or Frontier. On the Macintosh the implementation of a scripting interface was very complicated. Support for it in Metroworks' C++ class library (the name escapes me right now) made it much simpler.

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• How to reuse results with a schema for end of day stock-data

  - by Vishalrix

  I am creating a database schema to be used for technical analysis like top-volume gainers, top-price gainers etc.I have checked answers to questions here, like the design question. Having taken the hint from boe100 's answer there I have a schema modeled pretty much on it, thusly: Symbol - char 6 //primary Date - date //primary Open - decimal 18, 4 High - decimal 18, 4 Low - decimal 18, 4 Close - decimal 18, 4 Volume - int Right now this table containing End Of Day( EOD) data will be about 3 million rows for 3 years. Later when I get/need more data it could be 20 million rows. The front end will be asking requests like "give me the top price gainers on date X over Y days". That request is one of the simpler ones, and as such is not too costly, time wise, I assume. But a request like " give me top volume gainers for the last 10 days, with the previous 100 days acting as baseline", could prove 10-100 times costlier. The result of such a request would be a float which signifies how many times the volume as grown etc. One option I have is adding a column for each such result. And if the user asks for volume gain in 10 days over 20 days, that would require another table. The total such tables could easily cross 100, specially if I start using other results as tables, like MACD-10, MACD-100. each of which will require its own column. Is this a feasible solution? Another option being that I keep the result in cached html files and present them to the user. I dont have much experience in web-development, so to me it looks messy; but I could be wrong ( ofc!) . Is that a option too? Let me add that I am/will be using mod_perl to present the response to the user. With much of the work on mysql database being done using perl. I would like to have a response time of 1-2 seconds.

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• Access Violation in std::pair

  - by sameer karjatkar

  I have an application which is trying to populate a pair. Out of nowhere the application crashes. The Windbg analysis on the crash dump suggests: PRIMARY_PROBLEM_CLASS: INVALID_POINTER_READ DEFAULT_BUCKET_ID: INVALID_POINTER_READ STACK_TEXT: 0389f1dc EPFilter32!std::vector<std::pair<unsigned int,unsigned int>,std::allocator<std::pair<unsigned int,unsigned int> > >::size+0xc INVALID_POINTER_READ_c0000005_Test.DLL!std::vector_std::pair_unsigned_int, unsigned_int_,std::allocator_std::pair_unsigned_int,unsigned_int_____::size Following is the code snap in the code where it fails: for (unsigned i1 = 0; i1 < size1; ++i1) { for (unsigned i2 = 0; i2 < size2; ++i2) { const branch_info& b1 = en1.m_branches[i1]; //Exception here :crash const branch_info& b2 = en2.m_branches[i2]; } } where branch_info is std::pair<unsigned int,unsigned int> and the en1.m_branches[i1] fetches me a pair value.

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• How can I superimpose modified loess lines on a ggplot2 qplot?

  - by briandk

  Background Right now, I'm creating a multiple-predictor linear model and generating diagnostic plots to assess regression assumptions. (It's for a multiple regression analysis stats class that I'm loving at the moment :-) My textbook (Cohen, Cohen, West, and Aiken 2003) recommends plotting each predictor against the residuals to make sure that: The residuals don't systematically covary with the predictor The residuals are homoscedastic with respect to each predictor in the model On point (2), my textbook has this to say: Some statistical packages allow the analyst to plot lowess fit lines at the mean of the residuals (0-line), 1 standard deviation above the mean, and 1 standard deviation below the mean of the residuals....In the present case {their example}, the two lines {mean + 1sd and mean - 1sd} remain roughly parallel to the lowess {0} line, consistent with the interpretation that the variance of the residuals does not change as a function of X. (p. 131) How can I modify loess lines? I know how to generate a scatterplot with a "0-line,": # First, I'll make a simple linear model and get its diagnostic stats library(ggplot2) data(cars) mod <- fortify(lm(speed ~ dist, data = cars)) attach(mod) str(mod) # Now I want to make sure the residuals are homoscedastic qplot (x = dist, y = .resid, data = mod) + geom_smooth(se = FALSE) # "se = FALSE" Removes the standard error bands But does anyone know how I can use ggplot2 and qplot to generate plots where the 0-line, "mean + 1sd" AND "mean - 1sd" lines would be superimposed? Is that a weird/complex question to be asking?

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• Which to use, XMP or RDF?

  - by zotty

  What's the difference between RDF and XMP? From what I can tell, XMP is derived from RDF... so what does it offer that RDF doesn't? My particular situation is this: I've got some images which need tagging with details of how an experiment was performed, and what sort of data analysis has been performed on the images. A colleague of mine is pushing for XMP, but he's thinking of the images as photos - they're not really, they're just bits of data. From what I've seen (mainly by opening images in notepad++) the XMP data looks very similar to RDF - even so far as using RDF in the tag names (e.g. <rdf:Seq>). I'd like this data to be usable by other people who use similar instruments for similar experiments, so creating a mini standard (schema?) seems like the way to go. Apologies for the lack of fundemental understanding - I'm a Doctor, not a programmer! If it makes any difference, the language of choice will be C#. Edit for more information: First off, thanks for the excellent replies - thinking of XMP as a vocabulary for RDF makes things a lot clearer. The sort of data I'll be storing wont be avaliable in any of the pre-defined sets. It'll detail experimental set ups, locations and results. I think using RDF is the way to go.

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• Deterministic and non uniform long string generation from seed

  - by Limonup

  I had this weird idea for an encryption that I wanted to try out, it may be bad, and it may have done before, but I'm just doing it for fun. The short version of the question is: Is it possible to generate a long, deterministic and non-uniformly distributed string/sequence of numbers from a small seed? Long(er) version: I was thinking to encrypt a text by changing encoding. The new encoding would be generated via Huffman algorithm. To work well, the Huffman algorithm would need a fairly long text with non uniform distribution. Then characters can have different bit-lengths which would be the primary strength of this encryption. The problem is that its impractical to enter in/remember a long text each time you want to decrypt the text. So I was wondering if it was possible to generate a text from password seed? It doesn't matter what the text is, as long as it has non uniform distribution of characters and that the exact same sequence can be recreated each time you give it the same seed. Preferably, are there any functions/extensions in Python that can do this? EDIT: To expand on the "strength" of varying bit length: if I have a string "test", ASCII values 116, 101, 115, 116, which gives bit values of 1110100 1100101 1110011 1110100 Then, say my Huffman algorithm generates encoding like t = 101 e = 1100111 s = 10001 The final string is 101 1100111 10001 101, if we encode this back to ASCII, we get 1011100 1111000 1101000, which is 3 entirely different characters. Obviously its impossible to perform any kind of frequency analysis or something like that on this.

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