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  • C: Pointers to any type?

    - by dragme
    I hear that C isn't so type-safe and I think that I could use that as an advantage for my current project. I'm designing an interpreter with the goal for the VM to be extremely fast, much faster than Ruby and Python, for example. Now I know that premature optimization "is the root of all evil" but this is rather a conceptual problem. I have to use some sort of struct to represent all values in my language (from number over string to list and map) Would the following be possible? struct Value { ValueType type; void* value; } I would store the actual values elsewhere, e.g: a separate array for strings and integers, value* would then point to some member in this table. I would always know the type of the value via the type variable, so there wouldn't be any problems with type errors. Now: Is this even possible in terms of syntax and typing?

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  • Define keyref selector based on element type in XPath

    - by Robert Sirre
    Let's say I have an XML file that will look like this: <a> <b d="value1"/> <c d="value2"/> </a> In the XSD file that defines the structure of this XML file I defined the elements by name 'b' and 'c' to be of the same type (and the type requires attribute 'd'). Let's say that I want to make a keyReference of all elements of the type that both 'b' and 'c' are, is there any way in XPath to do this? At the definition of the type of 'a' I would expect something like this: <xs:keyref name="myReferenceName" refer="keyToReferTo"> <xs:selector xpath="[@type='typenameof elements b and c?']"/> <xs:field xpath="@d"/> </xs:keyref> Is something like this possible, or is XPath, even in the XSD, schema-unaware?

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  • Is there a module that implements an efficient array type in Erlang?

    - by dsmith
    I have been looking for an array type with the following characteristics in Erlang. append(vector(), term()) O(1) nth(Idx, vector()) O(1) set(Idx, vector(), term()) O(1) insert(Idx, vector(), term()) O(N) remove(Idx, vector()) O(N) I normally use a tuple for this purpose, but the performance characteristics are not what I would want for large N. My testing shows the following performance characteristics... erlang:append_element/2 O(N). erlang:setelement/3 O(N). I have started on a module based on the clojure.lang.PersistentVector implementation, but if it's already been done I won't reinvent the wheel.

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  • GRUB reporting wrong partition type

    - by plok
    It all started when I had to replace one of the disks that the software RAID 1 on this machine currently uses. From that moment on I have not been able to boot to the Windows XP that is installed on the fourth hard drive, /dev/sdd. I am almost positive that the problem is related not to Windows but to GRUB, as if I unplug all the other hard drives so that the Windows XP disk is now /dev/sda it boots with no problem. The problem seems to be that GRUB detects a wrong partition type, which I understand suggest that something is really messed up. This is what I get when I try to follow the steps that until now had worked like a charm: grub> map (hd0) (hd3) grub> map (hd3) (hd0) grub> root (hd3,0) Filesystem type is ext2fs, partition type 0xfd 0xfd? That doesn't make sense. /dev/sdb and sdc are 0xfd (Linux raid), but not /dev/sdd: edel:~# fdisk -l [...] Disk /dev/sdd: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00048d89 Device Boot Start End Blocks Id System /dev/sdd1 * 1 30400 244187968+ 7 HPFS/NTFS edel:/boot/grub# cat device.map (hd0) /dev/sda (hd1) /dev/sdb (hd2) /dev/sdc (hd3) /dev/sdd I have been trying to work this out for hours, to no avail. Can anyone point me in the right direction?

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  • Is there any reason why someone would want to create an Core Data model programmatically?

    - by mystify
    I wonder in which cases it would be good to make an NSManagedObjectModel completely programmatically, with NSEntityDescription instances and all this stuff. I'm that kind of person who prefers to code programmatically, rejecting Interface Builder. But when it comes to Core Data, I have a hard time figuring out why I should kill my time NOT using the nice Xcode Data Modeler tool. And since data models are stuck to a given state (except when you want to do some ugly migration operations where thinks probably go wrong and users get mad, really mad), I see no big sense in a data model that's made programmatically for the purpose of changing it all the time. Did I miss something?

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  • MySQL Cluster data nodes - slow SELECTs

    - by Boyan Georgiev
    Hi to all. First off, I'm new to MySQL Cluster. This is my pain: I've managed to setup a MySQL Cluster with two data nodes, two SQL nodes and one management server. Everything works pretty well, except the following: my data nodes are spread across an intranet link which incurs latency into communications between the data nodes. Apparently, due to MySQL Cluster's internal partitioning schemes, when my PHP application pulls data from the cluster via SELECT queries, parts of the data are pulled from both data nodes. This makes the page appear onscreen REALLY slowly. If I bring one data node offline, the data can only be pulled from that single remaining data node, and thus, the final result (HTML output) appears on the screen in a very timely fashion. So, my question is this: can the data nodes/cluster be told to pull data from partitions stored only on a particular data node?

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  • How to structure a Visual Studio project for the data access layer

    - by Akk
    I currently have a project that uses various DB access technologies mainly for showcasing or for demos. Currently we have: Namespace App.Data (App.Data.dll) Folder NHibernate Folder EntityFramework Folder LinqToSql The above structure is ok as we only use Sql Server as the DB. But going forward we will be including Oracle, MySql etc. So what would be a better structure with this in mind? I thought about: Namespace App.Data.SqlServer (App.Data.SqlServer.dll) Folder NHibernate Folder EntityFramework Folder LinqToSql Or would it just be better to have separate assemblies for each database and access technology?: Namespace App.Data.SqlServer.NHibernate (App.Data.SqlServer.NHibernate.dll) Namespace App.Data.SqlServer.EntityFramework(App.Data.SqlServer.EntityFramework.dll) Namespace App.Data.Oracle.NHibernate (App.Data.Oracle.NHibernate.dll) Namespace App.Data.MySql.NHibernate (App.Data.MySql.Oracle.dll)

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  • AutoMapper determine what to map based on generic type

    - by Daz Lewis
    Hi, Is there a way to provide AutoMapper with just a source and based on the specified mapping for the type of that source automatically determine what to map to? So for example I have a type of Foo and I always want it mapped to Bar but at runtime my code can receive any one of a number of generic types. public T Add(T entity) { //List of mappings var mapList = new Dictionary<Type, Type> { {typeof (Foo), typeof (Bar)} {typeof (Widget), typeof (Sprocket)} }; //Based on the type of T determine what we map to...somehow! var t = mapList[entity.GetType()]; //What goes in ?? to ensure var in the case of Foo will be a Bar? var destination = AutoMapper.Mapper.Map<T, ??>(entity); } Any help is much appreciated.

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  • Are there any frameworks for data subscription and update?

    - by Timothy Pratley
    There is one server with multiple clients. The clients are viewing subsets of the servers entire data. If the data that a client is viewing changes, the client should be informed of the changes so that it displays the current data. Example: Two clients are viewing a list of users in an administration screen. One client adds a new user to the list and modifies the permissions of another user. The other client sees the changes propagated to their view.

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  • Create new Array of parameter type

    - by pimvdb
    I'm trying to create a function to parse out all values in a multidimensional Array with all but one dimension given. The details are not relevant, but for this function I need to return an one-dimensional Array containing values of the same type the original multidimensional Array has. To pass any Array with any dimension to my function, I declared the type of this parameter as Array. However, how would I create a new Array of that specific type (e.g. Integer)? Currently I have the following code: Function GetRow(ByVal arr As Array) As Array Dim result As (...) 'This should be Integer() if arr contains Integers, etc. Return result End Function How do I declare the type of result to make it having the same type of values as arr? New Array is not possible as it is declared MustInherit. Thanks a lot.

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  • Best way to migrate servers without losing any data and with no downtime(?)

    - by ina
    This is a methodology question from a freelancer, with a corollary on MySQL.. Is there a way to migrate from an old dedicated server to a new one without losing any data in-between - and with no downtime? In the past, I've had to lose MySQL data between the time when the new server goes up (i.e., all files transferred, system up and ready), and when I take the old server down (data still transferred to old until new one takes over). There is also a short period where both are down for DNS, etc., to refresh. Is there a way for MySQL/root to easily transfer all data that was updated/inserted between a certain time frame?

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  • Is there an difference between transient properties defined in the data model, or in the custom subc

    - by mystify
    I was reading that setting the value of a transient property always results in marking the managed object as "dirty". However, what I don't get is this: If I make a subclass of NSManagedObject and use some extra properties which I don't need to be persistet, how does Core Data know about them and how can it mark the object as dirty when I access these? Again, they're not defined in the data model, so Core Data has no really good hint that they are there. Or does Core Data use some kind of introspection to analyze my custom class and figure out what properties I have in there?

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  • R: How to write out a data.frame so that I can paste it into SO for others to read?

    - by John
    I have a large data.frame displaying some weird properties when plotted. I'd like to ask a question about it on Stackoverflow, to do that I'd like to write the data.frame out in a form that I can paste it into SO and somebody else can easily run it and have it back into a data.frame object again. Is there an easy way to accomplish this? Also, if it is really long, should I use paste bin instead of directly paste it here?

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  • Content Types in browsers, can we use the Mime??

    - by SoLoGHoST
    Ok, I am wondering which mime types are dangerous in browsers? That is to say setting the Content Type to that mime type?? Which mime types, if any would pose a security risk?? I am noticing that many forum software, when uploading files, use the application/octet-stream for any files other than images and place that into the Content Type of the header. I am wondering why don't they place the actual mime-type instead into the Content Type? Are there security risks involved with this? So far I have used text/css, text/plain, audio/mpeg, and many others and haven't noticed any difference between application/octet-stream and these others. Does anyone out there know the exact difference, and what makes application/octet-stream any better, or any worse...to use for the Content Type?? Thank You :)

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  • C# or windows equivalent of OS X's Core Data?

    - by Nektarios
    I'm late to the boat and have only just now started using Core Data in OS X / Cocoa - it's incredible and is really changing the way I look at things. Is there an equivalent technology in C# or the modern Windows frameworks? i.e. having managed data types where you get saving, data management, deleting, searching all for free? Also wondering if there's anything like this on Linux.

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  • Mass data store with SQL SERVER

    - by Leo
    We need management 10,000 GPS devices, each GPS device upload a GPS data every 30 seconds, these data need to store in the database(MS SQL Server 2005). Each GPS device daily data quantity is: 24 * 60 * 2 = 2,880 10 000 10,000 GPS devices daily data quantity is: 10000 * 2880 = 28,800,000 Each GPS data approximately 160Byte, the amount of data per day is: 28,800,000 * 160 = 4.29GB We need hold at least 3 months of GPS data in the database, My question is: 1, whether SQL Server 2005 can support such a large amount of data store? 2, How to plan data table? (all GPS data storage in one table? Daily table? Each GPS device with a GPS data table?) The GPS data: GPSID varchar(21), RecvTime datetime, GPSTime datetime, IsValid bit, IsNavi bit, Lng float, Lat float, Alt float, Spd smallint, Head smallint, PulseValue bigint, Oil float, TSW1 bigint, TSW1Mask bigint, TSW2 bigint, TSW2Mask, BSW bigint, StateText varchar(200), PosText varchar(200), UploadType tinyint

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  • What is the most efficient way to use Core Data?

    - by Eric
    I'm developing an iPad application using Core Data, and was hoping someone could clarify something about Core Data. Right now, I populate my table by making a fetch request for all of my data in viewDidLoad. I'd rather make individual fetch requests in my tableView:cellForRowAtIndexPath:. Can anyone tell me which is more efficient, and why? In other words, is it much less efficient to make lots of small requests as opposed to one big request?

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  • What happens if a user jumps over 10 versions before updating, and every version had a new data mode

    - by dontWatchMyProfile
    Example: User installs app v.1.0, adds data. Then the dev submits 10 updates in 10 weeks. After 11 weeks, the user wants v.11.0 and grabs a copy from the app store. Assuming that the app has got 11 .xcdatamodel versions inside, where ***11.xcdatamodel is the current one, what would happen now since the persistent store of the user is ages old? would the migration happen 10 times, step-by-step through every migration iteration? Or does the actual migration of data (lets assume gigabytes of data) happen exactly once, after Core Data (or the persistent store coordinator) has figured out precisely what to do to go from v.1.0 to v.11.0?

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  • is this possible: c# collection of Type with constrains, or collection of generic type?

    - by Jon
    I'm trying to store types in a collection, so that i can later instantiate objects of the types in the collection. But I'm not sure how to do this the best way. What i have so far: List<Type> list = new List<Type>(); list.Add(typeof(MyClass)); var obj = (MyClass)Activator.CreateInstance(list[0]); I would like to have some constrains on the Type, or better yet, just a generic type in the collection instead of an instantiated Type object. Is this possible?

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  • Where is the 'indeterminate type'?

    - by Daniel
    I'm defining the following type extension: type System.Reflection.MemberInfo with member x.GetAttribute<'T when 'T :> Attribute>(required, inherit') = match required, Attribute.GetCustomAttribute(x, typeof<'T>, inherit') with | true, null -> invalidOp (sprintf "Missing required attribute: %s" typeof<'T>.FullName) | _, attr -> attr :> 'T The last match expression (attr :> 'T) gives the error: The static coercion from Attribute to 'T involves an indeterminate type based on information prior to this program point. Static coercions are not allowed on some types. Further type annotations are needed. I've tried annotating the function return type, but got the same result. I would hate to change this to a dynamic cast. Is there a way to make the static cast work?

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  • Iterating over a large data set in long running Python process - memory issues?

    - by user1094786
    I am working on a long running Python program (a part of it is a Flask API, and the other realtime data fetcher). Both my long running processes iterate, quite often (the API one might even do so hundreds of times a second) over large data sets (second by second observations of certain economic series, for example 1-5MB worth of data or even more). They also interpolate, compare and do calculations between series etc. What techniques, for the sake of keeping my processes alive, can I practice when iterating / passing as parameters / processing these large data sets? For instance, should I use the gc module and collect manually? Any advice would be appreciated. Thanks!

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  • How do I inherit abstract unit tests in Ruby?

    - by Graeme Moss
    I have two unit tests that should share a lot of common tests with slightly different setup methods. If I write something like class Abstract < Test::Unit::TestCase def setup @field = create end def test_1 ... end end class Concrete1 < Abstract def create SomeClass1.new end end class Concrete2 < Abstract def create SomeClass2.new end end then Concrete1 does not seem to inherit the tests from Abstract. Or at least I cannot get them to run in eclipse. If I choose "Run all TestCases" for the file that contains Concrete1 then Abstract is run even though I do not want it to be. If I specify Concrete1 then it does not run any tests at all! If I specify test_1 in Concrete1 then it complains it cannot find it ("uncaught throw :invalid_test (ArgumentError)"). I'm new to Ruby. What am I missing here?

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  • Equivalent of #map in ruby in golang

    - by Oct
    I'm playing with Go and run into something I'm unable to find in Google, although there is certainly something that exists: I'm using the following struct: type Syntax struct { name string extensions *regexp.Regexp } type Scanner struct { classifier * bayesian.Classifier save_file string name_to_syntax map[string] *Syntax extensions_to_syntax map[*regexp.Regexp] *Syntax } I'd like to perform the following using Go and I'm quoting ruby because it's how I'd do that using ruby: test_regexpes = my_scanner.extensions_to_syntax.keys My goal is to get an array of *regexp.Regexp . Any idea on how to do that in a simple way ? Thank you !

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