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  • Best ORM, Simple data Structures, Strong Query analysis.

    - by sayth
    What is the best ORM db combination for simple data structures. That is data that contains names as identifiers and locations, but whose main interaction will be numerical data for times(sports durations), and currency related data. I initially want to create a sports data base that will take names and statistics. Secondarily I plan to start into an investment and stock analysis db. Which ORM suits storing many numerical types and have strong query functions? I really am not biased to db engine (most likely use sqlite or mongo) so any suggestions to best network less db server to suit said ORM appreciated.

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  • SQL Server won't perform regular expression validation on XML column

    - by Kirk Broadhurst
    Hi I have an XML column in my table which contains this xsd snippet: <xsd:element name="Postcode" minOccurs="0"> <xsd:simpleType> <xsd:restriction base="xsd:string"> <xsd:pattern value="^[0-9]{4}$" /> </xsd:restriction> </xsd:simpleType> </xsd:element> The regular expression should require a string containing 4 numerical digits. It validates perfectly in Visual Studio and is a correct regular expression. SQL Server, on the other hand, won't accept it. The error message I receive is: XML Validation: Invalid simple type value: '1234'. Location: / * : Donor[1]/*:Postcode[1]. I have an email address regex working fine, but can't get this simple numerical regex to work.

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  • How are integers converted to strings under the hood?

    - by CrazyJugglerDrummer
    I suppose the real question is how to convert base2/binary to base10. The most common application of this would probably be in creating strings for output: turning a chunk of binary numerical data into an array of characters. How exactly is this done? my guess: Seeing as there probably isn't a string predefined for each numerical value, I'm guessing that the computer goes through each bit of the integer from right to left, each time incrementing the appropriate values in the char array/base10 notation places. If we take the number 160 in binary (10100000), it would know that a 1 in the 8th place means 128, so it places 1 into the third column, 2 in the second, and 8 in the third. The 1 in the 6th column means 32, and it would add those values to the second and first place, carrying over if needed. After this it's an easy conversion to actual char codes.

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  • A database of questions with unambiguous numeric answers.

    - by dreeves
    I (and co-hackers) are building a sort of trivia game inspired by this blog post: http://messymatters.com/calibration. The idea is to give confidence intervals and learn how to be calibrated (when you're "90% sure" you should be right 90% of the time). We're thus looking for, ideally, thousands of questions with unambiguous numerical answers. Also, they shouldn't be too boring. There are a lot of random statistics out there -- eg, enclosed water area in different countries -- that would make the game mind-numbing. Things like release dates of classic movies are more interesting (to most people). Other interesting ones we've found include Olympic records, median incomes for different professions, dates of famous inventions, and celebrity ages. Scraping things like above, by the way, was my reason for asking this question: http://stackoverflow.com/questions/2611418/scrape-html-tables So, if you know of other sources of interesting numerical facts (in a parsable form) I'm eager for pointers to them. Thanks!

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  • Changing a datatype solely for the purpose of Excel Export in Crystal Reports

    - by yeahumok
    I have a report that has several numerical fields. To fill a project requirement, i had to use the following formula: if {DataTable1.No of Investments}>9999 then '*****' else toText({DataTable1.No of Investments},0) Basically, if the number fed in is bigger than 9999 it turns into * on the report. Now, when i try to export into excel, not only is the data type for all fields, strings...but the * show up versus numbers. I was wondering if there was a way to re-cast this back into a numerical value SOLELY for the purpose of excel exportation so that i'd be able to use excel formulas as well as see numbers instead of asterisks. I'd only be doing data-only excel exports. Any ideas?

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  • Encoding a string as an integer .NET

    - by Paul Knopf
    I have a string that I would like represented uniquely as an integer. For example: A3FJEI = 34950140 How would I go about writing a EncodeAsInteger(string) method. I understand that the amount of characters in the string will make the integer increase greatly, forcing the value to become a long, not an int. Since I need the value to be an integer, I don't need the numerical representation to be entirely unique to the string. Maybe I can foreach through all the characters of the string and sum the numerical keycode of the character.

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  • How do i plot a vertical axis with variable intervals (Flex Charts or any other)

    - by satish
    How do i plot a vertical axis with variable intervals? on a Flex Chart. I want to plot a data set that has values from 0.1 to 800. When I use a standard Numerical Axis, I have to define a interval. I tried using Log-Axis, but I am not sure how to plot the point values. Looks like something in lines of semi-log axis would be better. A axis with initial values in Numerical, but later shifting gears to a Log-Axis. Any ideas or pointers to implement this in Flex?

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  • Allow only numeric values in textbox not working in Firefox

    - by AsM
    I have one Textbox accepting Bank A/c Number value which should be numerical only. I have written one javascript function for this as follows. function fncInputNumericValuesOnly() { if(!(event.keyCode=48||event.keyCode<=57)) { event.returnValue=false; } } This code is not allowing non-numerical values in IE. but same is not working in Firefox. I also tried to use onkeyup event. & also tried on pageload txtAccountNumber.Attributes.Add("onkeyup","fncInputNumericValuesOnly()") Why this is not working with firefox 3.

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  • ID number for sites [closed]

    - by Jonathan
    Possible Duplicate: please add a key fields to stackauth results It would be easier if sites each had an ID, it help with keeping track of them, not only in a numerical way (which is generally easier and smaller than using name strings). Also changes of site names (such as when a site progresses from beta, or decides it's name is not quite right during beta). Everything else has IDs so why not sites?

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  • Dynamic Number Table

    - by Derek D.
    Using a numbers table is helpful for many things. Like finding gaps in a supposed sequence of primary keys, or generating date ranges or any numerical range. In some cases, you will be in a production system that does not already contain a numbers table and you will also be unable to add [...]

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  • June 23, 1983: First Successful Test of the Domain Name System [Geek History]

    - by Jason Fitzpatrick
    Nearly 30 years ago the first Domain Name System (DNS) was tested and it changed the way we interacted with the internet. Nearly impossible to remember number addresses became easy to remember names. Without DNS you’d be browsing a web where numbered addresses pointed to numbered addresses. Google, for example, would look like http://209.85.148.105/ in your browser window. That’s assuming, of course, that a numbers-based web every gained enough traction to be popular enough to spawn a search giant like Google. How did this shift occur and what did we have before DNS? From Wikipedia: The practice of using a name as a simpler, more memorable abstraction of a host’s numerical address on a network dates back to the ARPANET era. Before the DNS was invented in 1983, each computer on the network retrieved a file called HOSTS.TXT from a computer at SRI. The HOSTS.TXT file mapped names to numerical addresses. A hosts file still exists on most modern operating systems by default and generally contains a mapping of the IP address 127.0.0.1 to “localhost”. Many operating systems use name resolution logic that allows the administrator to configure selection priorities for available name resolution methods. The rapid growth of the network made a centrally maintained, hand-crafted HOSTS.TXT file unsustainable; it became necessary to implement a more scalable system capable of automatically disseminating the requisite information. At the request of Jon Postel, Paul Mockapetris invented the Domain Name System in 1983 and wrote the first implementation. The original specifications were published by the Internet Engineering Task Force in RFC 882 and RFC 883, which were superseded in November 1987 by RFC 1034 and RFC 1035.Several additional Request for Comments have proposed various extensions to the core DNS protocols. Over the years it has been refined but the core of the system is essentially the same. When you type “google.com” into your web browser a DNS server is used to resolve that host name to the IP address of 209.85.148.105–making the web human-friendly in the process. Domain Name System History [Wikipedia via Wired] What is a Histogram, and How Can I Use it to Improve My Photos?How To Easily Access Your Home Network From Anywhere With DDNSHow To Recover After Your Email Password Is Compromised

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  • JavaOne 2012: Lessons from Mathematics

    - by darcy
    I was pleased to get notification recently that my bof proposal for Lessons from Mathematics was accepted for JavaOne 2012. This is a bit of a departure from the project-centric JavaOne talks I usually give, but whisps of this kind of material have appeared before. I'm looking forward to presenting material from linear algebra, stochastics, and numerical optimization that have influence my thinking about technical problems in the JDK and elsewhere.

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  • Infragistics and CenterSpace Software Team Up to Deliver Mathematical Charting Solution

    Princeton, N.J. & Elstree, England & Corvallis, OR – May 5, 2010 — Infragistics, a world leader in user interface (UI) development tools and experts in the User Experience (UX) market, and CenterSpace Software, a leading provider of enterprise class numerical component libraries for the .NET platform, today announced that they have teamed up to bring a complete mathematical charting solution to .NET developers.

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  • Well-tested libraries for player ratings?

    - by Lucky
    It's common in games to implement some sort of numerical ranking system -- the ELO system is usually used in chess. I could implement this system naively using Wikipedia's descriptions, but I suspect that this would open up a whole box of problems that have already been solved: rating inflation, etc -- for instance, the ELO system has a K constant that's 'fudged' according to rating, duration, pairings, statistics, ... What are some libraries (I'm looking at Python, but anything is okay) that implements rating systems? It also doesn't have to be ELO.

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  • What is Google Page Rank and Why is it So Important?

    What exactly is PageRank? It is basically a link analysis algorithm, which was influenced by citation analysis, which dates way back to the fifties, when it was conceived by Eugene Garfield and later on by Massimo Marchiori. This link analysis algorithm essentially gives set of hyperlinked documents, where they are weighed in numerical form, and are given a number assignment between zero to ten.

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  • Can a whitespace regex character be used to perform a javascript injection? [migrated]

    - by webose
    if I want to validate the input of a <textarea>, and want it to contain, for example, only numerical values, but even want to give users the possibility to insert new lines, I can selected wanted characters with a javascript regex that includes even the whitespace characters. /[0-9\s]/ The question is: do a whitecharacter can be used to perform injections, XSS,even if I think this last option is impossible, or any other type of attack ? thanks

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  • Nice level not working on linux

    - by xioxox
    I have some highly floating point intensive processes doing very little I/O. One is called "xspec", which calculates a numerical model and returns a floating point result back to a master process every second (via stdout). It is niced at the 19 level. I have another simple process "cpufloattest" which just does numerical computations in a tight loop. It is not niced. I have a 4-core i7 system with hyperthreading disabled. I have started 4 of each type of process. Why is the Linux scheduler (Linux 3.4.2) not properly limiting the CPU time taken up by the niced processes? Cpu(s): 56.2%us, 1.0%sy, 41.8%ni, 0.0%id, 0.0%wa, 0.9%hi, 0.1%si, 0.0%st Mem: 12297620k total, 12147472k used, 150148k free, 831564k buffers Swap: 2104508k total, 71172k used, 2033336k free, 4753956k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 32399 jss 20 0 44728 32m 772 R 62.7 0.3 4:17.93 cpufloattest 32400 jss 20 0 44728 32m 744 R 53.1 0.3 4:14.17 cpufloattest 32402 jss 20 0 44728 32m 744 R 51.1 0.3 4:14.09 cpufloattest 32398 jss 20 0 44728 32m 744 R 48.8 0.3 4:15.44 cpufloattest 3989 jss 39 19 1725m 690m 7744 R 44.1 5.8 1459:59 xspec 3981 jss 39 19 1725m 689m 7744 R 42.1 5.7 1459:34 xspec 3985 jss 39 19 1725m 689m 7744 R 42.1 5.7 1460:51 xspec 3993 jss 39 19 1725m 691m 7744 R 38.8 5.8 1458:24 xspec The scheduler does what I expect if I start 8 of the cpufloattest processes, with 4 of them niced (i.e. 4 with most of the CPU, and 4 with very little)

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  • Event Log "Wake Source" when system wakes from sleep

    - by Doltknuckle
    So I've been troubleshooting sleep timers for our systems and have run across an interesting issue. I need a way to report how long a system was awake after a number of different inputs. Now, I've discovered that the System Log tracks wake and sleep events and even tells you the times that everything happens at. The thing is doesn't tell you is what triggered the wake event. It does give you a numerical code however. Here are some examples of what I am finding. Index : 2901 EntryType : Information InstanceId : 1 Message : The system has resumed from sleep. Sleep Time: 2010-10-01T23:20:06.097488100Z Wake Time: 2010-10-03T17:41:12.796400500Z Wake Source: 0 Category : (0) CategoryNumber : 0 Source : Microsoft-Windows-Power-Troubleshooter -- Index : 2841 EntryType : Information InstanceId : 1 Message : The system has resumed from sleep. Sleep Time: 2010-10-01T19:19:37.239789600Z Wake Time: 2010-10-01T21:28:48.921200800Z Wake Source: 4HID Keyboard Device Category : (0) CategoryNumber : 0 Source : Microsoft-Windows-Power-Troubleshooter So here's my question: Does anyone know what the different numerical codes for the "Wake Source" mean? I think "0" is a magic packet and "4" is a USB device. Does anyone have any idea if there is any documentation out there on this for Windows 7? Thanks in advance

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  • Interactive Data Language, IDL: Does anybody care?

    - by Alex
    Anyone use a language called Interactive Data Language, IDL? It is popular with scientists. I think it is a poor language because it is proprietary (every terminal running it has to have an expensive license purchased) and it has minimal support (try searching for IDL, the language, right now on stack) . I am trying to convince my colleagues to stop using it and learn C/C++/Python/Fortran/Java/Ruby. Does anybody know about or even care about IDL enough to have opinions on it? What do you think of it? Should I tell my colleagues to stop wasting their time on it now? How can I convince them? Edit: People are getting the impression that I don't know or use IDL. Also, I said IDL has minimal support which is true in one sense, so I must clarify that the scientific libraries are indeed large. I use IDL all the time, but this is exactly the problem: I am only using IDL because colleagues use it. There is a file format IDL uses, the .sav, which can only be opened in IDL. So I must use IDL to work with this data and transfer the data back to colleagues, but I know I would be more efficient in another language. This is like someone sending you a microsoft word file in an email attachment and if you don't understand how wrong that is then you probably write too many words not enough code and you bought microsoft word. Edit: As an alternative to IDL Python is popular. Here is a list of The Pros of IDL (and the cons) from AstroBetter: Pros of IDL Mature many numerical and astronomical libraries available Wide astronomical user base Numerical aspect well integrated with language itself Many local users with deep experience Faster for small arrays Easier installation Good, unified documentation Standard GUI run/debug tool (IDLDE) Single widget system (no angst about which to choose or learn) SAVE/RESTORE capability Use of keyword arguments as flags more convenient Cons of IDL Narrow applicability, not well suited to general programming Slower for large arrays Array functionality less powerful Table support poor Limited ability to extend using C or Fortran, such extensions hard to distribute and support Expensive, sometimes problem collaborating with others that don’t have or can’t afford licenses. Closed source (only RSI can fix bugs) Very awkward to integrate with IRAF tasks Memory management more awkward Single widget system (useless if working within another framework) Plotting: Awkward support for symbols and math text Many font systems, portability issues (v5.1 alleviates somewhat) not as flexible or as extensible plot windows not intrinsically interactive (e.g., pan & zoom) Pros of Python Very general and powerful programming language, yet easy to learn. Strong, but optional, Object Oriented programming support Very large user and developer community, very extensive and broad library base Very extensible with C, C++, or Fortran, portable distribution mechanisms available Free; non-restrictive license; Open Source Becoming the standard scripting language for astronomy Easy to use with IRAF tasks Basis of STScI application efforts More general array capabilities Faster for large arrays, better support for memory mapping Many books and on-line documentation resources available (for the language and its libraries) Better support for table structures Plotting framework (matplotlib) more extensible and general Better font support and portability (only one way to do it too) Usable within many windowing frameworks (GTK, Tk, WX, Qt…) Standard plotting functionality independent of framework used plots are embeddable within other GUIs more powerful image handling (multiple simultaneous LUTS, optional resampling/rescaling, alpha blending, etc) Support for many widget systems Strong local influence over capabilities being developed for Python Cons of Python More items to install separately Not as well accepted in astronomical community (but support clearly growing) Scientific libraries not as mature: Documentation not as complete, not as unified Not as deep in astronomical libraries and utilities Not all IDL numerical library functions have corresponding functionality in Python Some numeric constructs not quite as consistent with language (or slightly less convenient than IDL) Array indexing convention “backwards” Small array performance slower No standard GUI run/debug tool Support for many widget systems (angst regarding which to choose) Current lack of function equivalent to SAVE/RESTORE in IDL matplotlib does not yet have equivalents for all IDL 2-D plotting capability (e.g., surface plots) Use of keyword arguments used as flags less convenient Plotting: comparatively immature, still much development going on missing some plot type (e.g., surface) 3-d capability requires VTK (though matplotlib has some basic 3-d capability)

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  • F# in ASP.NET, mathematics and testing

    - by DigiMortal
    Starting from Visual Studio 2010 F# is full member of .NET Framework languages family. It is functional language with syntax specific to functional languages but I think it is time for us also notice and study functional languages. In this posting I will show you some examples about cool things other people have done using F#. F# and ASP.NET As I am ASP/ASP.NET MVP I am – of course – interested in how people use different languages and technologies with ASP.NET. C# MVP Tomáš Petrícek writes about developing ASP.NET MVC applications using F#. He also shows how to use LINQ To SQL in F# (using F# PowerPack) and provides sample solution and Visual Studio 2010 template for F# MVC web applications. You may also find interesting how you can create controllers in F#. Excellent work, Tomáš! Vladimir Matveev has interesting example about how to use F# and ApplicationHost class to process ASP.NET requests ouside of IIS. This is simple and very straight-forward example and I strongly suggest you to take a look at it. Very cool example is project Strom in Codeplex. Storm is web services testing tool that is fully written on F#. Take a look at this site because Codeplex offers also source code besides binaries. Math Functional languages are strong in fields like mathematics and physics. When I wrote my C# example about BigInteger class I found out that recursive version of Fibonacci algorithm in C# is not performing well. In same time I made same experiment on F# and in F# there were no performance problems with recursive version. You can find F# version of Fibonacci algorithm from Bob Palmer’s blog posting Fibonacci numbers in F#. Although golden spiral is useful for solving many problems I looked for some practical code example and found one. Kean Walmsley published in his Through the Interface blog very interesting posting Creating Fibonacci spirals in AutoCAD using F#. There are also other cool examples you may be interested in. Using numerical components by Extreme Optimization  it is possible to make some numerical integration (quadrature method) using F# (also C# example is available). fsharp.it introduces factorials calculation on F#. Robert Pickering has made very good work on programming The Game of Life in Silverlight and F# – I definitely suggest you to try out this example as it is very illustrative too. Who wants something more complex may take a look at Newton basin fractal example in F# by Jonathan Birge. Testing After some searching and surfing I found out that there is almost everything available for F# to write tests and test your F# code. FsCheck - FsCheck is a port of Haskell's QuickCheck. Important parts of the manual for using FsCheck is almost literally "adapted" from the QuickCheck manual and paper. Any errors and omissions are entirely my responsibility. FsTest - This project is designed to Language Oriented Programming constructs around unit testing and behavior testing in F#. The goal of this project is to create a Domain Specific Language for testing F# code in a way that makes sense for functional programming. FsUnit - FsUnit makes unit-testing with F# more enjoyable. It adds a special syntax to your favorite .NET testing framework. xUnit.NET - xUnit.net is a developer testing framework, built to support Test Driven Development, with a design goal of extreme simplicity and alignment with framework features. It is compatible with .NET Framework 2.0 and later, and offers several runners: console, GUI, MSBuild, and Visual Studio integration via TestDriven.net, CodeRush Test Runner and Resharper. It also offers test project integration for ASP.NET MVC. Getting started Well, as a first thing you need Visual Studio 2010. Then take a look at these resources: F# samples @ MSDN Microsoft F# Developer Center @ MSDN F# Language Reference @ MSDN F# blog F# forums Real World Functional Programming: With Examples in F# and C# (Amazon) Happy F#-ing! :)

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  • Bitmask data insertions in SSDT Post-Deployment scripts

    - by jamiet
    On my current project we are using SQL Server Data Tools (SSDT) to manage our database schema and one of the tasks we need to do often is insert data into that schema once deployed; the typical method employed to do this is to leverage Post-Deployment scripts and that is exactly what we are doing. Our requirement is a little different though, our data is split up into various buckets that we need to selectively deploy on a case-by-case basis. I was going to use a SQLCMD variable for each bucket (defaulted to some value other than “Yes”) to define whether it should be deployed or not so we could use something like this in our Post-Deployment script: IF ($(DeployBucket1Flag) = 'Yes')BEGIN   :r .\Bucket1.data.sqlENDIF ($(DeployBucket2Flag) = 'Yes')BEGIN   :r .\Bucket2.data.sqlENDIF ($(DeployBucket3Flag) = 'Yes')BEGIN   :r .\Bucket3.data.sqlEND That works fine and is, I’m sure, a very common technique for doing this. It is however slightly ugly because we have to litter our deployment with various SQLCMD variables. My colleague James Rowland-Jones (whom I’m sure many of you know) suggested another technique – bitmasks. I won’t go into detail about how this works (James has already done that at Using a Bitmask - a practical example) but I’ll summarise by saying that you can deploy different combinations of the buckets simply by supplying a different numerical value for a single SQLCMD variable. Each bit of that value’s binary representation signifies whether a particular bucket should be deployed or not. This is better demonstrated using the following simple script (which can be easily leveraged inside your Post-Deployment scripts): /* $(DeployData) is a SQLCMD variable that would, if you were using this in SSDT, be declared in the SQLCMD variables section of your project file. It should contain a numerical value, defaulted to 0. In this example I have declared it using a :setvar statement. Test the affect of different values by changing the :setvar statement accordingly. Examples: :setvar DeployData 1 will deploy bucket 1 :setvar DeployData 2 will deploy bucket 2 :setvar DeployData 3   will deploy buckets 1 & 2 :setvar DeployData 6   will deploy buckets 2 & 3 :setvar DeployData 31  will deploy buckets 1, 2, 3, 4 & 5 */ :setvar DeployData 0 DECLARE  @bitmask VARBINARY(MAX) = CONVERT(VARBINARY,$(DeployData)); IF (@bitmask & 1 = 1) BEGIN     PRINT 'Bucket 1 insertions'; END IF (@bitmask & 2 = 2) BEGIN     PRINT 'Bucket 2 insertions'; END IF (@bitmask & 4 = 4) BEGIN     PRINT 'Bucket 3 insertions'; END IF (@bitmask & 8 = 8) BEGIN     PRINT 'Bucket 4 insertions'; END IF (@bitmask & 16 = 16) BEGIN     PRINT 'Bucket 5 insertions'; END An example of running this using DeployData=6 The binary representation of 6 is 110. The second and third significant bits of that binary number are set to 1 and hence buckets 2 and 3 are “activated”. Hope that makes sense and is useful to some of you! @Jamiet P.S. I used the awesome HTML Copy feature of Visual Studio’s Productivity Power Tools in order to format the T-SQL code above for this blog post.

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  • Guessing Excel Data Types

    - by AjarnMark
    Note to Self HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\4.0\Engines\Excel: TypeGuessRows = 0 means scan everything. Note to Others About 10 years ago I stumbled across this bit of information just when I needed it and it saved my project.  Then for some reason, a few years later when it would have been nice, but not critical, for some reason I could not find it again anywhere.  Well, now I have stumbled across it again, and to preserve my future self from nightmares and sudden baldness due to pulling my hair out, I have decided to blog it in the hopes that I can find it again this way. Here’s the story…  When you query data from an Excel spreadsheet, such as with old-fashioned DTS packages in SQL 2000 (my first reference) or simply with an OLEDB Data Adapter from ASP.NET (recent task) and if you are using the Microsoft Jet 4.0 driver (newer ones may deal with this differently) then you can get funny results where the query reports back that a cell value is null even when you know it contains data. What happens is that Excel doesn’t really have data types.  While you can format information in cells to appear like certain data types (e.g. Date, Time, Decimal, Text, etc.) that is not really defining the cell as being of a certain type like we think of when working with databases.  But, presumably, to make things more convenient for the user (programmer) when you issue a query against Excel, the query processor tries to guess what type of data is contained in each column and returns it in an appropriate manner.  This is all well and good IF your data is consistent in every row and matches what the processor guessed.  And, for efficiency’s sake, when the query processor is trying to figure out each column’s data type, it does so by analyzing only the first 8 rows of data (default setting). Now here’s the problem, suppose that your spreadsheet contains information about clothing, and one of the columns is Size.  Now suppose that in the first 8 rows, all of your sizes look like 32, 34, 18, 10, and so on, using numbers, but then, somewhere after the 8th row, you have some rows with sizes like S, M, L, XL.  What happens is that by examining only the first 8 rows, the query processor inferred that the column contained numerical data, and then when it hits the non-numerical data in later rows, it comes back blank.  Major bummer, and a real pain to track down if you don’t know that Excel is doing this, because you study the spreadsheet and say, “the data is RIGHT THERE!  WHY doesn’t the query see it?!?!”  And the hair-pulling begins. So, what’s a developer to do?  One option is to go to the registry setting noted above and change the DWORD value of TypeGuessRows from the default of 8 to 0 (zero).  Setting this value to zero will force Jet to scan every row in the spreadsheet before making its determination as to what type of data the column contains.  And that means that in the example above, it would have treated the column as a string rather than as numeric, and presto! your query now returns all of the values that you know are in there. Of course, there is a caveat… if you are querying large spreadsheets, making Jet scan every row can be quite a performance hit.  You could enter a different number (more than 8) that you believe is a better sampling of rows to make the guess, but you still have the possibility that every row scanned looks alike, but that later rows are different, and that you might get blanks when there really is data there.  That’s the type of gamble, I really don’t like to take with my data. Anyone with a better approach, or with experience with more recent drivers that have a better way of handling data types, please chime in!

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  • List of objects or parallel arrays of properties?

    - by Headcrab
    The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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  • What is the preferred way in C++ for converting a builtin type (int) to bool?

    - by Martin
    When programming with Visual C++, I think every developer is used to see the warning warning C4800: 'BOOL' : forcing value to bool 'true' or 'false' from time to time. The reason obviously is that BOOL is defined as int and directly assigning any of the built-in numerical types to bool is considered a bad idea. So my question is now, given any built-in numerical type (int, short, ...) that is to be interpreted as a boolean value, what is the/your preferred way of actually storing that value into a variable of type bool? Note: While mixing BOOL and bool is probably a bad idea, I think the problem will inevitably pop up whether on Windows or somewhere else, so I think this question is neither Visual-C++ nor Windows specific. Given int nBoolean; I prefer this style: bool b = nBoolean?true:false; The following might be alternatives: bool b = !!nBoolean; bool b = (nBoolean != 0); Is there a generally preferred way? Rationale? I should add: Since I only work with Visual-C++ I cannot really say if this is a VC++ specific question or if the same problem pops up with other compilers. So it would be interesting to specifically hear from g++ or users how they handle the int-bool case. Regarding Standard C++: As David Thornley notes in a comment, the C++ Standard does not require this behavior. In fact it seems to explicitly allow this, so one might consider this a VC++ weirdness. To quote the N3029 draft (which is what I have around atm.): 4.12 Boolean conversions [conv.bool] A prvalue of arithmetic, unscoped enumeration, pointer, or pointer to member type can be converted to a prvalue of type bool. A zero value, null pointer value, or null member pointer value is converted to false; any other value is converted to true. (...)

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