Search Results

Search found 407 results on 17 pages for 'sequences'.

Page 10/17 | < Previous Page | 6 7 8 9 10 11 12 13 14 15 16 17  | Next Page >

• The clock problem - to if or not to if?

  - by trejder

  Let's say, we have a simple digital clock. To "power" it, we use a routine executed every second. We update seconds part in it. But, what about minutes and hours part? What is better / more professional / offers better performance: Ignore all checking and update hour, minute and seconds part each time, every second. Use if + a variable for checking, if 60 (or 3600) seconds passed and update minute / hour part only at that precise moments. This leads us to a question, what is better -- unnecessary drawings (first approach) or extra ifs? I've just spotted a Javascript digital clock, one of millions similar on one of billions pages. And I noticed that all three parts (hours, minutes and seconds) are updated every second, though first changes its value only once per 3600 seconds and second once per 60 seconds. I'm not to experienced developer, so I might me wrong. But everything, what I've learnt up until now, tells me, that if are far better then executing drawing / refreshing sequences only to draw the same content.

  Read the article

• When creating a GUI wizard, should all pages/tabs be of the same size? [closed]

  - by Job

  I understand that some libraries would force me to, but my question is general. If I have a set of buttons at the bottom: Back, Next, Cancel?, (other?), then should their location ever change? If the answer is no, then what do I do about pages with little content? Do I stretch things? Place them in the lone upper left corner? According to Steve Krug, it does not make sense to add anything to GUI that does not need to be there. I understand that there are different approaches to wizards - some have tabs, others do not. Some tabs are lined horizontally at the top; others - vertically on the left. Some do not show pages/tabs, and are simply sequences of dialogs. This is probably a must when the wizard is "non-linear", e.g. some earlier choices can result in branching. Either way the problem is the same - sacrifice on the consistency of the "big picture" (outline of the page/tab + location of buttons), or the consistency of details (some tabs might be somewhat packed; others having very little content). A third choice, I suppose is putting extra effort in the content in order to make sure that organizing the content such that it is more or less evenly distributed from page to page. However, this can be difficult to do (say, when the very first tab contains only a choice of three things, and then branches off from there; there are probably other examples), and hard to maintain this balance if any of the content changes later. Can you recommend a good approach? A link to a relevant good blog post or a chapter of a book is also welcome. Let me know if you have questions.

  Read the article

• Differences Between NHibernate and Entity Framework

  - by Ricardo Peres

  Introduction NHibernate and Entity Framework are two of the most popular O/RM frameworks on the .NET world. Although they share some functionality, there are some aspects on which they are quite different. This post will describe this differences and will hopefully help you get started with the one you know less. Mind you, this is a personal selection of features to compare, it is by no way an exhaustive list. History First, a bit of history. NHibernate is an open-source project that was first ported from Java’s venerable Hibernate framework, one of the first O/RM frameworks, but nowadays it is not tied to it, for example, it has .NET specific features, and has evolved in different ways from those of its Java counterpart. Current version is 3.3, with 3.4 on the horizon. It currently targets .NET 3.5, but can be used as well in .NET 4, it only makes no use of any of its specific functionality. You can find its home page at NHForge. Entity Framework 1 came out with .NET 3.5 and is now on its second major version, despite being version 4. Code First sits on top of it and but came separately and will also continue to be released out of line with major .NET distributions. It is currently on version 4.3.1 and version 5 will be released together with .NET Framework 4.5. All versions will target the current version of .NET, at the time of their release. Its home location is located at MSDN. Architecture In NHibernate, there is a separation between the Unit of Work and the configuration and model instances. You start off by creating a Configuration object, where you specify all global NHibernate settings such as the database and dialect to use, the batch sizes, the mappings, etc, then you build an ISessionFactory from it. The ISessionFactory holds model and metadata that is tied to a particular database and to the settings that came from the Configuration object, and, there will typically be only one instance of each in a process. Finally, you create instances of ISession from the ISessionFactory, which is the NHibernate representation of the Unit of Work and Identity Map. This is a lightweight object, it basically opens and closes a database connection as required and keeps track of the entities associated with it. ISession objects are cheap to create and dispose, because all of the model complexity is stored in the ISessionFactory and Configuration objects. As for Entity Framework, the ObjectContext/DbContext holds the configuration, model and acts as the Unit of Work, holding references to all of the known entity instances. This class is therefore not lightweight as its NHibernate counterpart and it is not uncommon to see examples where an instance is cached on a field. Mappings Both NHibernate and Entity Framework (Code First) support the use of POCOs to represent entities, no base classes are required (or even possible, in the case of NHibernate). As for mapping to and from the database, NHibernate supports three types of mappings: XML-based, which have the advantage of not tying the entity classes to a particular O/RM; the XML files can be deployed as files on the file system or as embedded resources in an assembly; Attribute-based, for keeping both the entities and database details on the same place at the expense of polluting the entity classes with NHibernate-specific attributes; Strongly-typed code-based, which allows dynamic creation of the model and strongly typing it, so that if, for example, a property name changes, the mapping will also be updated. Entity Framework can use: Attribute-based (although attributes cannot express all of the available possibilities – for example, cascading); Strongly-typed code mappings. Database Support With NHibernate you can use mostly any database you want, including: SQL Server; SQL Server Compact; SQL Server Azure; Oracle; DB2; PostgreSQL; MySQL; Sybase Adaptive Server/SQL Anywhere; Firebird; SQLLite; Informix; Any through OLE DB; Any through ODBC. Out of the box, Entity Framework only supports SQL Server, but a number of providers exist, both free and commercial, for some of the most used databases, such as Oracle and MySQL. See a list here. Inheritance Strategies Both NHibernate and Entity Framework support the three canonical inheritance strategies: Table Per Type Hierarchy (Single Table Inheritance), Table Per Type (Class Table Inheritance) and Table Per Concrete Type (Concrete Table Inheritance). Associations Regarding associations, both support one to one, one to many and many to many. However, NHibernate offers far more collection types: Bags of entities or values: unordered, possibly with duplicates; Lists of entities or values: ordered, indexed by a number column; Maps of entities or values: indexed by either an entity or any value; Sets of entities or values: unordered, no duplicates; Arrays of entities or values: indexed, immutable. Querying NHibernate exposes several querying APIs: LINQ is probably the most used nowadays, and really does not need to be introduced; Hibernate Query Language (HQL) is a database-agnostic, object-oriented SQL-alike language that exists since NHibernate’s creation and still offers the most advanced querying possibilities; well suited for dynamic queries, even if using string concatenation; Criteria API is an implementation of the Query Object pattern where you create a semi-abstract conceptual representation of the query you wish to execute by means of a class model; also a good choice for dynamic querying; Query Over offers a similar API to Criteria, but using strongly-typed LINQ expressions instead of strings; for this, although more refactor-friendlier that Criteria, it is also less suited for dynamic queries; SQL, including stored procedures, can also be used; Integration with Lucene.NET indexer is available. As for Entity Framework: LINQ to Entities is fully supported, and its implementation is considered very complete; it is the API of choice for most developers; Entity-SQL, HQL’s counterpart, is also an object-oriented, database-independent querying language that can be used for dynamic queries; SQL, of course, is also supported. Caching Both NHibernate and Entity Framework, of course, feature first-level cache. NHibernate also supports a second-level cache, that can be used among multiple ISessionFactorys, even in different processes/machines: Hashtable (in-memory); SysCache (uses ASP.NET as the cache provider); SysCache2 (same as above but with support for SQL Server SQL Dependencies); Prevalence; SharedCache; Memcached; Redis; NCache; Appfabric Caching. Out of the box, Entity Framework does not have any second-level cache mechanism, however, there are some public samples that show how we can add this. ID Generators NHibernate supports different ID generation strategies, coming from the database and otherwise: Identity (for SQL Server, MySQL, and databases who support identity columns); Sequence (for Oracle, PostgreSQL, and others who support sequences); Trigger-based; HiLo; Sequence HiLo (for databases that support sequences); Several GUID flavors, both in GUID as well as in string format; Increment (for single-user uses); Assigned (must know what you’re doing); Sequence-style (either uses an actual sequence or a single-column table); Table of ids; Pooled (similar to HiLo but stores high values in a table); Native (uses whatever mechanism the current database supports, identity or sequence). Entity Framework only supports: Identity generation; GUIDs; Assigned values. Properties NHibernate supports properties of entity types (one to one or many to one), collections (one to many or many to many) as well as scalars and enumerations. It offers a mechanism for having complex property types generated from the database, which even include support for querying. It also supports properties originated from SQL formulas. Entity Framework only supports scalars, entity types and collections. Enumerations support will come in the next version. Events and Interception NHibernate has a very rich event model, that exposes more than 20 events, either for synchronous pre-execution or asynchronous post-execution, including: Pre/Post-Load; Pre/Post-Delete; Pre/Post-Insert; Pre/Post-Update; Pre/Post-Flush. It also features interception of class instancing and SQL generation. As for Entity Framework, only two events exist: ObjectMaterialized (after loading an entity from the database); SavingChanges (before saving changes, which include deleting, inserting and updating). Tracking Changes For NHibernate as well as Entity Framework, all changes are tracked by their respective Unit of Work implementation. Entities can be attached and detached to it, Entity Framework does, however, also support self-tracking entities. Optimistic Concurrency Control NHibernate supports all of the imaginable scenarios: SQL Server’s ROWVERSION; Oracle’s ORA_ROWSCN; A column containing date and time; A column containing a version number; All/dirty columns comparison. Entity Framework is more focused on Entity Framework, so it only supports: SQL Server’s ROWVERSION; Comparing all/some columns. Batching NHibernate has full support for insertion batching, but only if the ID generator in use is not database-based (for example, it cannot be used with Identity), whereas Entity Framework has no batching at all. Cascading Both support cascading for collections and associations: when an entity is deleted, their conceptual children are also deleted. NHibernate also offers the possibility to set the foreign key column on children to NULL instead of removing them. Flushing Changes NHibernate’s ISession has a FlushMode property that can have the following values: Auto: changes are sent to the database when necessary, for example, if there are dirty instances of an entity type, and a query is performed against this entity type, or if the ISession is being disposed; Commit: changes are sent when committing the current transaction; Never: changes are only sent when explicitly calling Flush(). As for Entity Framework, changes have to be explicitly sent through a call to AcceptAllChanges()/SaveChanges(). Lazy Loading NHibernate supports lazy loading for Associated entities (one to one, many to one); Collections (one to many, many to many); Scalar properties (thing of BLOBs or CLOBs). Entity Framework only supports lazy loading for: Associated entities; Collections. Generating and Updating the Database Both NHibernate and Entity Framework Code First (with the Migrations API) allow creating the database model from the mapping and updating it if the mapping changes. Extensibility As you can guess, NHibernate is far more extensible than Entity Framework. Basically, everything can be extended, from ID generation, to LINQ to SQL transformation, HQL native SQL support, custom column types, custom association collections, SQL generation, supported databases, etc. With Entity Framework your options are more limited, at least, because practically no information exists as to what can be extended/changed. It features a provider model that can be extended to support any database. Integration With Other Microsoft APIs and Tools When it comes to integration with Microsoft technologies, it will come as no surprise that Entity Framework offers the best support. For example, the following technologies are fully supported: ASP.NET (through the EntityDataSource); ASP.NET Dynamic Data; WCF Data Services; WCF RIA Services; Visual Studio (through the integrated designer). Documentation This is another point where Entity Framework is superior: NHibernate lacks, for starters, an up to date API reference synchronized with its current version. It does have a community mailing list, blogs and wikis, although not much used. Entity Framework has a number of resources on MSDN and, of course, several forums and discussion groups exist. Conclusion Like I said, this is a personal list. I may come as a surprise to some that Entity Framework is so behind NHibernate in so many aspects, but it is true that NHibernate is much older and, due to its open-source nature, is not tied to product-specific timeframes and can thus evolve much more rapidly. I do like both, and I chose whichever is best for the job I have at hands. I am looking forward to the changes in EF5 which will add significant value to an already interesting product. So, what do you think? Did I forget anything important or is there anything else worth talking about? Looking forward for your comments!

  Read the article

• Sorting Algorithms

  - by MarkPearl

  General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

  Read the article

• Custom form designer, move/resize controls using WinAPI

  - by jonny

  I have to fix some problems and enchance form designer written long ago for a database project. In Design Panel class code I encountered these lines private void DesignPanel_MouseDown(object sender, MouseEventArgs e) { if (e.Button == MouseButtons.Left) { (sender as Control).Capture = false; switch (FMousePosition) { case MousePosition.mpNone: SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF009, 0); break;// Move case MousePosition.mpRightBottom: SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF008, 0); break;//RB case MousePosition.mpLeftBottom: SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF007, 0); // ... here are similar cases ... case MousePosition.mpLeft: SendMessage((sender as Control).Handle, WM_SYSCOMMAND, 0xF001, 0); break;//L } } } FMousePosition indicates whether mouse was over any edge of selected control. What confusing me is these windows messages: it seems there is no documentation on WM_SYSCOMMAND with parameters 0xF001-0xF009 (maybe it starts some kind of 'drag/resize sequence'). Any ideas? If my suggestion is right, then how can I cancel these sequences?

  Read the article

• Python Naming Conventions for Dictionaries/Maps/Hashes

  - by pokstad

  While other questions have tackled the broader category of sequences and modules, I ask this very specific question: "What naming convention do you use for dictionaries and why?" Some naming convention samples I have been considering: # 'value' is the data type stored in the map, while 'key' is the type of key value_for_key={key1:value1, key2,value2} value_key={key1:value1, key2,value2} v_value_k_key={key1:value1, key2,value2} Don't bother answering the 'why' with "because my work tells me to", not very helpful. The reason driving the choice is more important. Are there any other good considerations for a dictionary naming convention aside from readability?

  Read the article

• Advice? SSO in N-tiered SOA with mixture of REST and SOAP services

  - by Tyler

  Hi gang, We are moving to SSO in our N-tiered SOA applications. If all the services were SOAP, I'd be ok with just the WS-Security, WS-Trust, WS-Federation set of protocols. My problem is that many of the services are RESTful (ironic) and those protocols do not address REST services. What is your advice for SSO protecting the REST services in an N-tiered SOA architecture with the following requirements: ideally claims-based identity information available to the REST services original user (eg. bootstrap) information must flow through the tiers so that each service can "ActAs" or "OnBehalfOf" the user support sequences like: WebApp -- REST Svc -- SOAP Svc WebApp -- REST Svc1 -- REST Svc2 WebApp -- SOAP Svc -- REST Svc WebApp -- SOAP Svc1 -- SOAP Svc2 support SSO (and SSOff) service/web app platforms: ASP.Net and WCF Java end-user client platforms: .Net (WSE 3.0 and WCF) flash 10 java javascript and AJAX Normally I'm good at climbing / bashing my way through walls, but this one's knocked me flat. Hopefully with your help, we can get over this one. Thanks, Tyler

  Read the article

• Oracle custom sort

  - by Carter

  The query... select distinct name from myTable returns a bunch of values that start with the following character sequences... ADL* FG* FH* LAS* TWUP* Where '*' is the remainder of the string. I want to do an order by that sorts in the following manner... ADL* LAS* TWUP* FG* FH* But then I also want to sort within each name in the standard order by fashion. So, an example, if I have the following values LAS-21A TWUP-1 FG999 FH3 ADL99999 ADL88888 ADL77777 LAS2 I want it to be sorted like this... ADL77777 ADL88888 ADL99999 LAS2 TWUP-1 FG999 FH3 I initially thought I could accomplish this vias doing an order by decode(blah) with some like trickery inside of the decode but I've been unable to accomplish it. Any insights?

  Read the article

• How to get default Ctrl+Tab functionality in WinForms MDI app when hosting WPF UserControls

  - by jpierson

  I have a WinForms based app with traditional MDI implementation within it except that I'm hosting WPF based UserControls via the ElementHost control as the main content for each of my MDI children. This is the solution recommended by Microsoft for achieving MDI with WPF although there are various side effects unfortunately. One of which is that my Ctrl+Tab functionality for tab switching between each MDI child is gone because the tab key seems to be swallowed up by the WPF controls. Is there a simple solution to this that will let the Ctrl+tab key sequences reach my WinForms MDI parent so that I can get the built-in tab switching functionality?

  Read the article

• Constructing a hash table/hash function.

  - by nn

  Hi, I would like to construct a hash table that looks up keys in sequences (strings) of bytes ranging from 1 to 15 bytes. I would like to store an integer value, so I imagine an array for hashing would suffice. I'm having difficulty conceptualizing how to construct a hash function such that given the key would give an index into the array. Any assistance would be much appreiated. The maximum number of entries in the hash is: 4081*15 + 4081*14 + ... 4081 = 4081((15*(16))/2) = 489720. So for example: int table[489720]; int lookup(unsigned char *key) { int index = hash(key); return table[index]; } How can I compute hash(key). I'd preferably like to get a perfect hash function. Thanks.

  Read the article

• For a primary key of an integral type, why is it important to avoid gaps ?

  - by Jacques René Mesrine

  I am generating a surrogate key for a table & due to my hi/lo algorithm, everytime you reboot/restart the machine, gaps may appear. T1: current hi = 10000000 (sequence being dished out .. 1 to 100) Assume that current sequence is 10000050 T2: restart system. T3: System gives out the next_hi as 10000100 (sequence being dished out now ranges from 101 to 200) T4: Next request for a key returns 100001001 From a primary key or indexing internals perspective, why is it important that there be no gaps in the sequences ? I'm asking this for a deeper understanding of mysql specifically. Thanks

  Read the article

• JPA 2.0 Implementations comparison : Hibernate 3.5 vs EclipseLink 2 vs OpenJPA 2

  - by peperg

  What's your choice? Do You have any suggestions and experience? I'm developing an application with Hibernate 3.5 and Spring 3.0 Pros: Good documentation Easy configuration and helpful logs Popularity - wide community Some extensions to JPA Some additional Tools - JBoss Tools for Eclipse, hbm2ddl, generating static metamodel etc... Cons: Bugs! (Sequences, collections etc...) Lots of reatures are doubled with "pure" Hibernate. There's a mess in legacy Hibernate and JPA annotations. I'm considering to switch to EclipseLink. What do You think ? Edit: I've tried EclipseLink and have very bad experiences. It seems like EclipseLink needs LoadTimeWeaver and likes to run on OSGi platform rather than simple Jetty or Tomcat environment. I just don't have time for all this configuration stuff.

  Read the article

• Comparing (similar) images with Python/PIL

  - by Attila Oláh

  I'm trying to calculate the similarity (read: Levenshtein distance) of two images, using Python 2.6 and PIL. I plan to use the python-levenshtein library for fast comparison. Main question: What is a good strategy for comparing images? My idea is something like: Convert to RGB (transparent - white) (or maybe convert to monochrome?) Scale up the smaller one to the larger one's size Convert each channel (= the only channel, if converted to monochrome) to a sequence (item value = color value of the pixel) Calculate the Levenshtein distance between the two sequences Of course, this will not handle cases like mirrored images, cropped images, etc. But for basic comparison, this should be useful. Is there a better strategy documented somewhere?

  Read the article

• Writing to a new line of a file in Objective-C

  - by Kulpreet

  For some strange reason, the \n and \r escape sequences do not seem to be working in my code. I want to write each NSString on a new line of the file, but it just appends it the last string on one line. Here's the code: for (Entry *entry in self.entries) { NSString *path = @"/Users/me/File.txt"; NSString *string = (@"%@\r\n", [entry thisEntry]); NSFileHandle *fh = [NSFileHandle fileHandleForWritingAtPath:path]; [fh seekToEndOfFile]; [fh writeData:[string dataUsingEncoding:NSUnicodeStringEncoding]]; [fh closeFile]; } Am I doing something wrong? Forgive me as I am new to Objective-C.

  Read the article

• Deriving arrays in mathematics

  - by Gio Borje

  So I found some similarities between arrays and set notation while learning about sets and sequences in precalc e.g. set notation: {a | cond } = { a1, a2, a3, a4, ..., an} given that n is the domain (or index) of the array, a subset of Natural numbers (or unsigned integer). Most programming languages would provide similar methods to arrays that are applied to sets e.g. upperbounds & lowerbounds; possibly suprema and infima too. Where did arrays come from?

  Read the article

• BioPython: extracting sequence IDs from a Blast output file

  - by Jon

  Hi, I have a BLAST output file in XML format. It is 22 query sequences with 50 hits reported from each sequence. And I want to extract all the 50x22 hits. This is the code I currently have, but it only extracts the 50 hits from the first query. from Bio.Blast import NCBIXM blast_records = NCBIXML.parse(result_handle) blast_record = blast_records.next() save_file = open("/Users/jonbra/Desktop/my_fasta_seq.fasta", 'w') for alignment in blast_record.alignments: for hsp in alignment.hsps: save_file.write('>%s\n' % (alignment.title,)) save_file.close() Somebody have any suggestions as to extract all the hits? I guess I have to use something else than alignments. Hope this was clear. Thanks! Jon

  Read the article

• convert string to float without silent NaN/Inf conversion

  - by Peter Hansen

  I'd like convert strings to floats using Python 2.6 and later, but without silently converting things like 'NaN' and 'Inf'. Before 2.6, float("NaN") would raise a ValueError. Now it returns a float for which math.isnan() returns True, which is not useful behaviour for my application. Here's what I've got at the moment: import math def get_floats(source): for text in source.split(): try: val = float(text) if math.isnan(val) or math.isinf(val): raise ValueError yield val except ValueError: pass This is a generator, which I can supply with strings containing whitespace-separated sequences representing real numbers. I'd like it to yield only those fields which are purely numeric representations of floats, as in "1.23" or "-34e6", but not for example "NaN" or "-Inf". Test case: assert list(get_floats('1.23 -34e6 NaN -Inf')) == [1.23, -34000000.0] Please suggest alternatives you consider more elegant, even if they involve "look before you leap" (which is normally considered a lesser approach in Python).

  Read the article

• Sequence numbers best practice

  - by Abdullah Jibaly

  What's the best practice or well known methods to implement sequence numbers for business entities such as invoices, purchase orders, job numbers, etc? I want to be able to save the latest value in the database and be able to set it programatically. Is it OK to use a table for this purpose that has a SEQUENCE_NAME, SEQUENCE_NUMBER tuple? I know some databases have a first class sequence type but others (eg, MySQL) do not so it's not something I want to rely on. If a table is used to hold these sequences what is the right way to get and increment them in a synchronized fashion to ensure no data inconsistencies arise?

  Read the article

• Is there something like "if not exist create sequence ..." in Oracle SQL?

  - by Timo

  Very probably a noob question: For my application that uses an Oracle 8 DB, I am providing an SQL script to setup stuff like triggers, sequences etc., which can be copied and pasted into SQL*Plus. I would like the script to not stop with an error if a sequence that I am trying to create already exists. For a Trigger this can easily be done using "create or replace trigger ...", but for a sequence this does not work. Is there some alternative, like "if not exists mysequence then create sequence ..." (I tried this but it did not work :) ) Alternatively, if this is not possible, is there a way to do a "drop sequence mysequence" without SQL*Plus aborting the script if mysequence does not exist? Thanks. PS: I wish Oracle just had a simple Autoinc field type ... sigh.

  Read the article

• OpenCV in Python can't scan through pixels

  - by Marco L.

  Hi everyone, I'm stuck with a problem of the python wrapper for OpenCv. I have this function that returns 1 if the number of black pixels is greater than treshold def checkBlackPixels( img, threshold ): width = img.width height = img.height nchannels = img.nChannels step = img.widthStep dimtot = width * height data = img.imageData black = 0 for i in range( 0, height ): for j in range( 0, width ): r = data[i*step + j*nchannels + 0] g = data[i*step + j*nchannels + 1] b = data[i*step + j*nchannels + 2] if r == 0 and g == 0 and b == 0: black = black + 1 if black >= threshold * dimtot: return 1 else: return 0 The loop (scan each pixel of a given image) works good when the input is an RGB image...but if the input is a single channel image I get this error: for j in range( width ): TypeError: Nested sequences should have 2 or 3 dimensions The input single channel image (called 'rg' in the next example) is taken from an RGB image called 'src' processed with cvSplit and then cvAbsDiff cvSplit( src, r, g, b, 'NULL' ) rg = cvCreateImage( cvGetSize(src), src.depth, 1 ) # R - G cvAbsDiff( r, g, rg ) I've also already noticed that the problem comes from the difference image got from cvSplit... Anyone can help me? Thank you

  Read the article

• split a string based on pattern in java - capital letters and numbers

  - by rookie

  Hi all I have the following string "3/4Ton". I want to split it as -- word[1] = 3/4 and word[2] = Ton. Right now my piece of code looks like this:- Pattern p = Pattern.compile("[A-Z]{1}[a-z]+"); Matcher m = p.matcher(line); while(m.find()){ System.out.println("The word --> "+m.group()); } It carries out the needed task of splitting the string based on capital letters like:- String = MachineryInput word[1] = Machinery , word[2] = Input The only problem is it does not preserve, numbers or abbreviations or sequences of capital letters which are not meant to be separate words. Could some one help me out with my regular expression coding problem. Thanks in advance...

  Read the article

• Does any one know of a packet generator?

  - by Benoit

  We have a networked device, and we would like to perform some tests on how it handles malformed packets. Is there a product out there that can generate arbitrary packets and packet sequences? I would like to be able to specify a set of TCP/IP payloads and it would open a connection and send the data. Obviouly, the TCP/IP checksum should be calculated correctly, etc... Kind of like a wireshark in reverse. Note that I am not interested in network loading and blasting millions of packet.

  Read the article

• Intra-Unicode "lean" Encoding Converters

  - by Mystagogue

  Windows provides encoding conversion functions ("MultiByteToWideChar" and "WideCharToMultiByte") which are capable of UTF-8 to/from UTF-16 conversions, among other things. But I've seen people offer home-grown 30 to 40 line functions that claim also to perform UTF-8 / UTF-16 encoding conversions. My question is, how reliable are such tiny converters? Can such a tiny amount of code handle problems such as converting a UTF-16 surrogate pair (such as ) into a UTF-8 single four byte sequence (rather than making the mistake of converting into a pair of three byte sequences)? Can they correctly spot "unpaired" surrogate input, and provide an error? In short, are such tiny converters mere toys, or can they be taken seriously? For that matter, why does unicode.org seemingly offer no advice on an algorithm for accomplishing such conversions?

  Read the article

• problem with JMF !

  - by Razan

  Hi.. I have windows vista OS.. I Installed JMF to work with it.. but it seems I'm having some conflicts between Sound and JMF.. because after I installed JMF my projects that use Sound.. midi.. sequences.. are giving exceptions that they don't have some sound classes and so.. and when I removed JMF every thing went OK !! so what I'm gonna do?

  Read the article

• Specifying distinct sequence per table in Hibernate on subclasses

  - by gutch

  Is there a way to specify distinct sequences for each table in Hibernate, if the ID is defined on a mapped superclass? All entities in our application extend a superclass called DataObject like this: @MappedSuperclass public abstract class DataObject implements Serializable { @Id @GeneratedValue(strategy = GenerationType.SEQUENCE) @Column(name = "id") private int id; } @Entity @Table(name = "entity_a") public class EntityA extends DataObject { ... } @Entity @Table(name = "entity_b") public class EntityB extends DataObject { ... } This causes all entities to use a shared sequence, the default hibernate_sequence. What I would like to do is use a separate sequence for each entity, for example entity_a_sequence and entity_b_sequence in the example above. If the ID were specified on the subclasses then I could use the @SequenceGenerator annotation to specify a sequence for each entity, but in this case the ID is on the superclass. Given that ID is in the superclass, is there a way I can use a separate sequence for each entity — and if so, how? (We are using PostgreSQL 8.3, in case that's relevant)

  Read the article

< Previous Page | 6 7 8 9 10 11 12 13 14 15 16 17  | Next Page >