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• Method return type

  - by sarah xia

  Hi, In my company, a system is designed to have 3 layers. Layer1 is responsible for business logic handling. Layer3 is calling back end systems. Layer2 sits between the two layers so that layer1 doesn't need to know about the back end systems. To replay information from layer3, layer2 needs to define interface to layer1. For example, layer1 wants to check if a PIN from user is correct. It calls layer2 checkPin() method and then layer2 calls the relevant back end system. The checkPin() results could be: correctPin, inCorrectPin and internalError. At the moment, we defined the return type 'int'. So if layer2 returns 0, it means correctPin; if 1 is returned, it means inCorrectPin; if 9 is returned it means internalError. It works. However I feel a bit uneasy about this approach. Are there better ways to do it? For example define an enum CheckPinResult{CORRECT_PIN,INCORRECT_PIN,INTERNAL_ERROR}, and return CheckPinResult type? Thanks, Sarah

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• How does the last integer promotion rule ever get applied in C?

  - by SiegeX

  6.3.1.8p1: Otherwise, the integer promotions are performed on both operands. Then the following rules are applied to the promoted operands: If both operands have the same type, then no further conversion is needed. Otherwise, if both operands have signed integer types or both have unsigned integer types, the operand with the type of lesser integer conversion rank is converted to the type of the operand with greater rank. Otherwise, if the operand that has unsigned integer type has rank greater or equal to the rank of the type of the other operand, then the operand with signed integer type is converted to the type of the operand with unsigned integer type. Otherwise, if the type of the operand with signed integer type can represent all of the values of the type of the operand with unsigned integer type, then the operand with unsigned integer type is converted to the type of the operand with signed integer type. Otherwise, both operands are converted to the unsigned integer type corresponding to the type of the operand with signed integer type. For the bolded rule to be applied it would seem to imply you need to have have an unsigned interger type who's rank is less than the signed integer type and the signed integer type cannot hold all the values of the unsigned integer type. Is there a real world example of such a case or is this statement serving as a catch-all to cover all possible permutations?

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• Define a swig interface file for generation of wrapper to every type from some header file

  - by Dmitriy Matveev

  Hi! We're using some C library in our Java project. Several years ago some other developer which has retired few years ago (as always) has created all the wrappers for us. The wrappers were generated by the swig, but the interface file is lost now. The basic idea of library and the wrappers for it is following: There only one function which returns pointer to some complex object. And there are wrapper for that function. The complex object is a tree-like structure with dozens of node kinds and types (C structures) used to represent them. There are hundreds of wrappers for every field of every type and we're trying to use them all. The library was updated some time ago and now there are some new data we unaware of which yet, but would like to use. This data is contained in some of the objects indirectly contained or referenced from the object created by the function we call (Some new fields and types were added). I know that I shouldn't make any changes to the wrappers by hand and should rather modify the interface, but as I already wrote it's missing. For now I only want to generate wrappers some few types which are added/changed and them to our old wrappers, but later I want to start creation of interface file which will define "what and how should be wrapped". All the definitions necessary for us are defined in single header file. Is it possible to tell swig to generate wrappers for every type in this header? If so, how can I write such interface file?

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• WCF service with PHP client - complex type as parameter not working

  - by Matt F

  Hi, I have a WCF service with three methods. Two of the methods return custom types (these work as expected), and the third method takes a custom type as a parameter and returns a boolean. When calling the third method via a PHP soap client it returns an 'Object reference not set to an instance of an object' exception. Example Custom Type: _ Public Class MyClass Private _propertyA As Double <DataMember()> _ Public Property PropertyA() As Double Get Return _propertyA End Get Set(ByVal value As Double) _propertyA = value End Set End Property Private _propertyB As Double <DataMember()> _ Public Property PropertyB() As Double Get Return _propertyB End Get Set(ByVal value As Double) _propertyB = value End Set End Property Private _propertyC As Date <DataMember()> _ Public Property PropertyC() As Date Get Return _propertyC End Get Set(ByVal value As Date) _propertyC = value End Set End Property End Class Method: Public Function Add(ByVal param As MyClass) As Boolean Implements IService1.Add ' ... End Function PHP client call: $client-Add(array('param'=array( 'PropertyA' = 1, 'PropertyB' = 2, 'PropertyC' = "2009-01-01" ))); The WCF service works fine with a .Net client but I'm new to PHP and can't get this to work. Is it possible to create an instance of 'MyClass' in PHP. Any help would be appreciated. Note: I'm using PHP 5 (XAMPP 1.7.0 for Windows). Thanks Matt

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• Conversion type

  - by Ruben

  Hi, I've got the following question. I've got one class "Instellingen" that's a property in 3 other classes public class Instellingen { private int _ID; } public class Class1: Label { private Instellingen _Instellingen; } public class Class2 : Label { private Instellingen _Instellingen; } public class Class3 : Label { private Instellingen _Instellingen; } If I've got another class, that uses the other classes (but it can be anyone of this 3 classes) Do i have to use a switch? or is there an easier way? public class AnotherClass { public AnotherClass () { GetInstellingenFromClass(new Class1()); GetInstellingenFromClass(new Class2()); GetInstellingenFromClass(new Class3()); } private void GetInstellingenFromClass(Control c) { switch (c.GetType.ToString()) { case "Class1": Class1 klasse = (Class1) c; //Do something with the _Instellingen of this class break; case "Class2": Class2 klasse2 = (Class2) c; //Do something with the _Instellingen of this class break; case "Class3": Class3 klasse3 = (Class3)c; //Do something with the _Instellingen of this class break; } } } (does there exists something so i can just do something like c._Instellingen -- without converting it first to the right type, where it doesn't matter what type c is?) I hope you understand my question. Thanks

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• Strategy Pattern with Type Reflection affecting Performances ?

  - by Aurélien Ribon

  Hello ! I am building graphs. A graph consists of nodes linked each other with links (indeed my dear). In order to assign a given behavior to each node, I implemented the strategy pattern. class Node { public BaseNodeBehavior Behavior {get; set;} } As a result, in many parts of the application, I am extensively using type reflection to know which behavior a node is. if (node.Behavior is NodeDataOutputBehavior) workOnOutputNode(node) .... My graph can get thousands of nodes. Is type reflection greatly affecting performances ? Should I use something else than the strategy pattern ? I'm using strategy because I need behavior inheritance. For example, basically, a behavior can be Data or Operator, a Data behavior can IO, Const or Intermediate and finally an IO behavior can be Input or Output. So if I use an enumeration, I wont be able to test for a node behavior to be of data kind, I will need to test it to be [Input, Output, Const or Intermediate]. And if later I want to add another behavior of Data kind, I'm screwed, every data-testing method will need to be changed.

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• Adding a Taxonomy Filter to a Custom Post Type

  - by ken

  There is an amazing conversation from about two years ago on the Wordpress Answer site where a number of people came up with good solutions for adding a taxonomy filter to the admin screen for your custom post types (see URL for screen I'm referring to): http://[yoursite.com]/wp-admin/edit.php?s&post_status=all&post_type=[post-type] Anyway, I loved Michael's awesome contribution but in the end used Somatic's implementation with the hierarchy option from Manny. I wrapped it in a class - cuz that's how I like to do things -- and it ALMOST works. The dropdown appears but the values in the dropdown are all looking in the $_GET property for the taxonomies slug-name that you are filtering by. For some reason I don't get anything. I looked at the HTML of the dropdown and it appears ok to me. Here's a quick screen shot for some context: You can tell from this that my post-type is called "exercise" and that the Taxonomy I'm trying to use as a filter is "actions". Here then is the HTML surrounding the dropdown list: <select name="actions" id="actions" class="postform"> <option value="">Show all Actions</option> <option value="ate-dinner">Ate dinner(1)</option> <option value="went-running">Went running(1)</option> </select> I have also confirmed that all of the form elements are within the part of the DOM. And yet if I choose "Went running" and click on the filter button the URL query string comes back without ANY reference to what i've picked. More explicitly, the page first loads with the following URL: /wp-admin/edit.php?post_type=exercise and after pressing the filter button while having picked "Went Running" as an option from the actions filter: /wp-admin/edit.php?s&post_status=all&post_type=exercise&action=-1&m=0&actions&paged=1&mode=list&action2=-1 actually you can see a reference to an "actions" variable but it's set to nothing and as I now look in detail it appears that the moment I hit "filter" on the page it resets the filter dropdown to the default "Show All Actions". Can anyone help me with this?

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• VS2010 Implement Generic Interface expansion doesn't use specified type

  - by TJB

  Using the release version of Visual Studio 2010 I think there's a difference in the "Implement Interface" expansion from VS2008 If I speicify an interface and implement it in a class as so: public interface IRepository<T> where T : IModel { T Get<T>(int id); void Update<T>(); int Add<T>(T item); } public class MockRepository : IRepository<MockUser> { // ... } Then use the "Implement Interface" expansion and get this: public class MockRepository : IRepository<MockUser> { public T Get<T>(int id) { throw new NotImplementedException(); } public void Update<T>() { throw new NotImplementedException(); } public int Add<T>(T item) { throw new NotImplementedException(); } } Instead of what I expected public class MockRepository : IRepository<MockUser> { public MockUser Get<MockUser>(int id) { throw new NotImplementedException(); } public void Update<MockUser>() { throw new NotImplementedException(); } public int Add<MockUser>(MockUser item) { throw new NotImplementedException(); } } The IDE uses the type variable name from the generic interface definition T instead of the specified concrete type MockUser. Is this a bug? Or is something new just for VS2010 / .Net 4.0?

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• How to identify the type of socket data?

  - by Nitesh Panchal

  Hello, May be i am not able to express my doubt properly in this question but still i will try. Basically i created a simple socket based chat program and everything works fine. But i think i have made many patches in it from the design point of view. I have used ObjectInputStream and ObjectOutputStreams in my program. The question i want to ask is how do i identify the different type of data that i send across the network? say if it is simple String type object i directly add to List<String> chatMessages. Now if want to ban certain users i created an another class :- public class User{ private String name; private String id; //getters and setters } This User class means no importance to me till now but i only created it to properly identify the action. Thus if i receive an instanceOf User i can be sure that some user is to be banned. That way i dont have to hardcode strings. I mean first i thought of sending something like "Banned User :" + userName and then i used to check if string startsWith "Banned User :" then i take some action :p. I've created a User class but it means no importance to me in my program. I want to know whether directly sending strings is good way or create a class for every action that is good. If i am not clear please let me know. If i have hundreds of action do i have to create hundreds of classes so i can check via instanceOf? Say now if i plan to create a BUZZ like facility that is available in yahoo messenger. Should i again create an another class named BUZZ? so it can be identified easily?

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• Sql Exception: Error converting data type numeric to numeric

  - by Lucifer

  Hello We have a very strange issue with a database that has been moved from staging to production. The first time the database was moved it was by detaching, copying and reattaching, the second time we tried restoring from a backup of the staging. Both SQL Servers are the same version of MS SQL 2008, running on 64 bit hardware. The code accessing the database is the same build, built using the .net 2.0 framework. Here is the error message and some of the stack trace: Exception Details: System.Data.SqlClient.SqlException: Error converting data type numeric to numeric. Stack Trace: [SqlException (0x80131904): Error converting data type numeric to numeric.] System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +1953274 System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4849707 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194 System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +2392 System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) +204 System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) +954 System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +162 System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) +175 System.Data.SqlClient.SqlCommand.ExecuteNonQuery() +137 Version Information: Microsoft .NET Framework Version:2.0.50727.4200; ASP.NET Version:2.0.50727.4016

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• XmlAttribute/XmlText cannot be used to encode complex type

  - by Conrad C

  I want to serialize a class Ticket into xml. I get the error :"XmlAttribute/XmlText cannot be used to encode complex type" because of my customfield class. This is how the xml for customfields should look like ( the attribute array is nesseray but I don't understand how to create it): <custom_fields type="array"> <custom_field name="Standby Reason" id="6"> <value/> </custom_field> <custom_field name="Close Date" id="84"> Class Ticket public class Ticket { [XmlElement("custom_fields")] public CustomFields Custom_fields { get; set; } Class CustomFields [Serializable] public class CustomFields { [XmlAttribute("array")] public List<CustomField> custom_field { get; set; } Class CustomField [Serializable] public class CustomField { [XmlIgnore] public string Name { get; set; } [XmlElement] public int Id { get; set; } [XmlElement] public string Value { get; set; }

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• IE browser script to determine which (if any) ActiveX control will handle specific mime type

  - by Jay13

  I'm trying to figure out in an IE script (javascript or vbscript) which ActiveX control will handle a specific mime type, "image/tiff" in this case. This is easy to do in other browsers that use plugins with; navigator.mimeTypes["image/tiff"].enabledPlugin.name which would return something like QuickTime Plug-in X.X.X I've found plenty of examples to tell if a specific plugin is loaded but since there are several plugins available that can handle tiff images I need to know which, if any, is registered to handle this mime type. The problem I'm trying to deal with is that QuickTime always wants to register itself as the default tiff viewer but it does a terrible job of it resulting in lots of support calls. Unfortunately, simply detecting that QuickTime is installed isn't good enough since the user may also have another tiff viewer installed (like Alternatiff) as the default tiff viewer or the user may have configured QuickTime to not be the default viewer for tiff images so the browser could be using a helper app to display the image instead. Not meaning to be difficult but before anyone suggests reengineering workarounds; yes I know I could force the user to use a specific ActiveX viewer in IE or to use a Java tiff viewer but I'd rather let them use a viewer of their choice rather than forcing them to install a viewer of my choosing, especially since their viewer may be a helper app that loads the tiff image into a business workflow within their office yes I know there are other image formats that I could use but tiff is the defacto standard for document imaging and that's what the vast majority of these users prefer to use. The problem isn't the image format, it's that QuickTime just doesn't cut it as a tiff viewer Thanks in advance for any suggestions or solutions...

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• WCF RIA Services Custom Type with Collection of Custom Types

  - by Blakewell

  Is it possible to have a custom type within a custom type and have the result returned via WCF RIA services? I have the following two classes below, but I can't gain access to the Verticies property within the Polygon class. I assume it is because it is a custom class, or something to do with it being a List collection. Polygon Class public class Polygon { public Polygon() { _vertices = new List<Location>(); } private int _id; [Key] public int Id { get; set; } private List<Location> _vertices; public List<Location> Vertices { get { return _vertices; } set { _vertices = value; } } } Location Class public class Location { public Location() { } /// <summary> /// Default constructor for creating a Location object /// </summary> /// <param name="latitude"></param> /// <param name="longitude"></param> public Location( double latitude, double longitude ) { _latitude = latitude; _longitude = longitude; } private int _id; [Key] public int Id { get { return _id; } set { _id = value; } } private double _latitude; /// <summary> /// Latitude coordinate of the location /// </summary> public double Latitude { get { return _latitude; } set { _latitude = value; } } private double _longitude; /// <summary> /// Longitude coordiante of the location /// </summary> public double Longitude { get { return _longitude; } set { _longitude = value; } } }

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• Action property of interface type

  - by Daniel

  Hi, guys. With my understading, the nature of a Action is that properties can be pushed w/ request parameter values. And, one wonderful feature is that Struts2 allows you to directly populate parameter values against Class type property ;) Assuming there exists a Action and property class as below, class Action extends ActionSupport { User user; @Action(value="hello" {@result=(.......)}) public void execute() { ........ } ..... public void setUser(User user) { this.user = user; } public User getUser() { return this.user; } } class User { String name; ..... public void setName(String name) { this.name = name; } public String getName() { return this.name; } } you could populate User class property by doing like this. http://...../hello.action?user.name=John or via jsp page Then, I realize that there are actually people make an Action property as a Interface type. My question is what is the reason behind this. If there is a sample code demonstrating it will be great. Thanks in advance!

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• smallest mysql type that accomodates single decimal

  - by donpal

  Database newbie here. I'm setting up a mysql table. One of the fields will accept a value in increment of a 0.5. e.g. 0.5, 1.0, 1.5, 2.0, .... 200.5, etc. I've tried int but it doesn't capture the decimals. `value` int(10), What would be the smallest type that can accommodate this value, considering it's only a single decimal. I also was considering that because the decimal will always be 0.5 if at all, I could store it in a separate boolean field? So I would have 2 fields instead. Is this a stupid or somewhat over complicated idea? I don't know if it really saves me any memory, and it might get slower now that I'm accessing 2 fields instead of 1 `value` int(10), `half` bool, //or something similar to boolean What are your suggestions guys? Is the first option better, and what's the smallest data type in that case that would get me the 0.5?

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• [grails] setting cookies when render type is "contentType: text/json"

  - by Robin Jamieson

  Is it possible to set cookies on response when the return render type is set as json? I can set cookies on the response object when returning with a standard render type and later on, I'm able to get it back on the subsequent request. However, if I were to set the cookies while rendering the return values as json, I can't seem to get back the cookie on the next request object. What's happening here? These two actions work as expected with 'basicForm' performing a regular form post to the action, 'withRegularSubmit', when the user clicks submit. // first action set the cookie and second action yields the originally set cookie def regularAction = { // using cookie plugin response.setCookie("username-regular", "regularCookieUser123",604800); return render(view: "basicForm"); } // called by form post def withRegularSubmit = { def myCookie = request.getCookie("username-regular"); // returns the value 'regularCookieUser123' return render(view: "resultView"); } When I switch to setting the cookie just before returning from the response with json, I don't get the cookie back with the post. The request starts by getting an html document that contains a form and when doc load event is fired, the following request is invoked via javascript with jQuery like this: var someUrl = "http://localhost/jsonAction"; $.get(someUrl, function(jsonData) { // do some work with javascript} The controller work: // this action is called initially and returns an html doc with a form. def loadJsonForm = { return render(view: "jsonForm"); } // called via javascript when the document load event is fired def jsonAction = { response.setCookie("username-json", "jsonCookieUser456",604800); // using cookie plugin return render(contentType:'text/json') { 'pair'('myKey': "someValue") }; } // called by form post def withJsonSubmit = { def myCookie = request.getCookie("username-json"); // got null value, expecting: jsonCookieUser456 return render(view: "resultView"); } The data is returned to the server as a result of the user pressing the 'submit' button and not through a script. Prior to the submit of both 'withRegularSubmit' and 'withJsonSubmit', I see the cookies stored in the browser (Firefox) so I know they reached the client.

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• C# - Referencing a type in a dynamically generated assembly

  - by Ashley

  I'm trying to figure out if it's possible when you are dynamically generating assemblies, to reference a type in a previously dynamically generated assembly. For example: using System; using System.CodeDom.Compiler; using System.Reflection; using Microsoft.CSharp; CodeDomProvider provider = new CSharpCodeProvider(); CompilerParameters parameters = new CompilerParameters(); parameters.GenerateInMemory = true; CompilerResults results = provider.CompileAssemblyFromSource(parameters, @" namespace Dynamic { public class A { } } "); Assembly assem = results.CompiledAssembly; CodeDomProvider provider2 = new CSharpCodeProvider(); CompilerParameters parameters2 = new CompilerParameters(); parameters2.ReferencedAssemblies.Add(assem.FullName); parameters2.GenerateInMemory = true; CompilerResults results2 = provider2.CompileAssemblyFromSource(parameters, @" namespace Dynamic { public class B : A { } } "); if (results2.Errors.HasErrors) { foreach (CompilerError error in results2.Errors) { Console.WriteLine(error.ErrorText); } } else { Assembly assem2 = results2.CompiledAssembly; } This code prints the following on the console: The type or namespace name 'A' could not be found (are you missing a using directive or an assembly reference?) I've tried it lots of different ways, but nothing seems to be working. Am I missing something? Is this even possible?

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• Using generics in F# to create an EnumArray type

  - by Matthew

  I've created an F# class to represent an array that allocates one element for each value of a specific enum. I'm using an explicit constructor that creates a dictionary from enum values to array indices, and an Item property so that you can write expressions like: let my_array = new EnumArray<EnumType, int> my_array.[EnumType.enum_value] <- 5 However, I'm getting the following obscure compilation error at the line marked with '// FS0670' below. error FS0670: This code is not sufficiently generic. The type variable ^e when ^e : enum<int> and ^e : equality and ^e : (static member op_Explicit : ^e -> int) could not be generalized because it would escape its scope. I'm at a loss - can anyone explain this error? type EnumArray< 'e, 'v when 'e : enum<int> and 'e : equality and ^e : (static member op_Explicit : ^e -> int) > = val enum_to_int : Dictionary<'e, int> val a : 'v array new() as this = { enum_to_int = new Dictionary<'e, int>() a = Array.zeroCreate (Enum.GetValues(typeof<'e>).Length) } then for (e : obj) in Enum.GetValues(typeof<'e>) do this.enum_to_int.Add(e :?> 'e, int(e :?> 'e)) member this.Item with get (idx : 'e) : 'v = this.a.[this.enum_to_int.[idx]] // FS0670 and set (idx : 'e) (c : 'v) = this.a.[this.enum_to_int.[idx]] <- c

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• Incompatible types when assigning to type 'struct compartido'

  - by user1660559

  I have one problem with this code. I should create one structure and share it across 5 new process created from the father: #include <stdio.h> #include <stdlib.h> #include <sys/wait.h> #include <unistd.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/shm.h> #include <sys/sem.h> #include <time.h> struct compartido { int pid1, pid2, pid3, pid4, pid5; int propietario; int contador; int pidpadre; }; struct compartido var; int main(int argc, char *argv[]) { key_t llave1,llavesem; int idmem,idsem; llave1=ftok("/tmp",'a'); idmem=shmget(llave1,sizeof(int),IPC_CREAT|0600); if (idmem==-1) { perror ("shmget"); return 1; } var=shmat(idmem,0,0); /*This line is giving the error*/ /*rest of the code*/ } The exact error is giving is: error: incompatible types when assigning to type 'struct compartido' from type 'void *' I need to put this structure in the shared variable to be able to see and modify all those data from the 6 process (5 children and the father). What I'm doing bad? Thanks in advance and best regards,

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• How to define trees with more than one type in ML programing language

  - by user550413

  Well, I am asked to do the next thing: To define a binary tree which can contain 2 different types: ('a,'b) abtree and these are the requirements: Any inner vertex (not a leaf) must be of the type 'a or 'b and the leafs have no value. For every path in the tree all 'a values must appear before the 'b value: examples of paths: 'a->'a->'a-'b (legal) 'a->'b->'b (legal) 'a->'a->'a (legal) 'b->'b->'b (legal) 'a->'b->'a (ILLEGAL) and also I need to define another tree which is like the one described above but now I have got also 'c and in the second requirement it says that for every path I 'a values appear before the 'b values and all the 'b values appear before the 'c values. First, I am not sure how to define binary trees to have more than 1 type in them. I mean the simplest binary tree is: datatype 'a tree = leaf | br of 'a * 'a tree * 'a tree; And also how I can define a tree to have these requirements. Any help will be appreciated. Thanks.

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• How to index a table with a Type 2 slowly changing dimension for optimal performance

  - by The Lazy DBA

  Suppose you have a table with a Type 2 slowly-changing dimension. Let's express this table as follows, with the following columns: * [Key] * [Value1] * ... * [ValueN] * [StartDate] * [ExpiryDate] In this example, let's suppose that [StartDate] is effectively the date in which the values for a given [Key] become known to the system. So our primary key would be composed of both [StartDate] and [Key]. When a new set of values arrives for a given [Key], we assign [ExpiryDate] to some pre-defined high surrogate value such as '12/31/9999'. We then set the existing "most recent" records for that [Key] to have an [ExpiryDate] that is equal to the [StartDate] of the new value. A simple update based on a join. So if we always wanted to get the most recent records for a given [Key], we know we could create a clustered index that is: * [ExpiryDate] ASC * [Key] ASC Although the keyspace may be very wide (say, a million keys), we can minimize the number of pages between reads by initially ordering them by [ExpiryDate]. And since we know the most recent record for a given key will always have an [ExpiryDate] of '12/31/9999', we can use that to our advantage. However... what if we want to get a point-in-time snapshot of all [Key]s at a given time? Theoretically, the entirety of the keyspace isn't all being updated at the same time. Therefore for a given point-in-time, the window between [StartDate] and [ExpiryDate] is variable, so ordering by either [StartDate] or [ExpiryDate] would never yield a result in which all the records you're looking for are contiguous. Granted, you can immediately throw out all records in which the [StartDate] is greater than your defined point-in-time. In essence, in a typical RDBMS, what indexing strategy affords the best way to minimize the number of reads to retrieve the values for all keys for a given point-in-time? I realize I can at least maximize IO by partitioning the table by [Key], however this certainly isn't ideal. Alternatively, is there a different type of slowly-changing-dimension that solves this problem in a more performant manner?

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• Generic cast type to primitive.

  - by Nix

  Is there a way to do the below? Imagine a generic result wrapper class. Where you have a type and an associated error list. When there is no result to return to the user we will use boolean to indicate success failure. I want to create a constructor that takes in an error list, and if the list is null or count 0, AND the type is a bool/Boolean i want to set it to true.... Seemingly simple, but amazingly not possible. public class Result<T>{ private T valueObject { get;set;} private List<Error> errors{ get;set;} public Result(T valueObj, List<Error> errorList){ this.valueObject = valueObj; this.errors = errorList; } public Result(List<Error> errors) { this.valueObject = default(ReturnType); if (valueObject is Boolean) { //Wont work compile //(valueObject as Boolean) = ((errors == null) || errors.Count == 0); //Compiles but detaches reference //bool temp = ((bool)(valueObject as object)) ; //temp = ((errors == null) || errors.Count == 0); } this.errors = errors; } } } Am I missing something simple? And in general I would prefer to do it without reflection.

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• How to handle image/gif type response on client side using GWT

  - by user200340

  Hi all, I have a question about how to handle image/gif type response on client side, any suggestion will be great. There is a service which responds for retrieving image (only one each time at the moment) from database. The code is something like, JDBC Connection Construct MYSQL query. Execute query If has ResultSet, retrieve first one { //save image into Blob image, “img” is the only entity in the image table. image = rs.getBlob("img"); } response.setContentType("image/gif"); //set response type InputStream in = image.getBinaryStream(); //output Blob image to InputStream int bufferSize = 1024; //buffer size byte[] buffer = new byte[bufferSize]; //initial buffer int length =0; //read length data from inputstream and store into buffer while ((length = in.read(buffer)) != -1) { out.write(buffer, 0, length); //write into ServletOutputStream } in.close(); out.flush(); //write out The code on client side .... imgform.setAction(GWT.getModuleBaseURL() + "serviceexample/ImgRetrieve"); .... ClickListener { OnClick, then imgform.submit(); } formHandler { onSubmit, form validation onSubmitComplete ??????? //handle response, and display image **Here is my question, i had tried Image img = new Image(GWT.getHostPageBaseURL() +"serviceexample/ImgRetrieve"); mg.setSize("300", "300"); imgpanel.add(img); but i only got a non-displayed image with 300X300 size.** } So, how should i handle the responde in this case? Thanks,

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• Learning Java, how to type text on canvas?

  - by Voley

  I'm reading a book by Eric Roberts - Art and science of java and it got an excersise that I can't figure out - You have to make calendar, with GRect's, 7 by 6, that goes ok, the code part is easy, but also you have to type the numbers of the date on those rectangles, and it's kinda hard for me, there is nothing about it in the book. I tried using GLabel thing, but here arises the problem that I need to work on those numbers, and it says "can't convert from int to string and vice versa". GLabel (string, posX, posY) - it is not accepting int as a parameter, only string, I even tried typecasting, still not working. For example I want to make a loop int currentDate = 1; while (currentDate < 31) { add(new Glabel(currentDate, 100, 100); currentDate++; This code is saying that no man, can't convert int to string. If i try changing currentDate to string, it works, but I got a problem with calculation, as I can't manipulate with number in string, it doesn't even allow to typecast it into int. How can I fix it? Maybe there is another class or method to type the text over those rectangles? I know about println but it doen't have any x or y coordinates, so I can't work with it. And I think it's only for console programs.

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• Link error for user defined class type template parameter

  - by isurulucky

  Hi, I implemented a Simple STL map in C++. Factored out the comparison as a type as I was instructed to, then implemented the comparison as shown below: template <typename T> int KeyCompare<T>::operator () (T tKey1, T tKey2) { if(tKey1 < tKey2) return -1; else if(tKey1 > tKey2) return 1; else return 0; } here, tKey1 and tKet2 are the two keys I'm comparing. This worked well for all the basic data types and string. I added a template specialization to compare keys of a user defined type named Test and added a specialization as follows: int KeyCompare<Test>::operator () (Test tKey1, Test tKey2) { if(tKey1.a < tKey2.a) return -1; else if(tKey1.a > tKey2.a) return 1; else return 0; } when I run this, I get a linking error saying SimpleMap.obj : error LNK2005: "public: int __thiscall KeyCompare::operator()(class Test,class Test)" (??R?$KeyCompare@VTest@@@@QAEHVTest@@0@Z) already defined in MapTest.obj SimpleMap.obj : error LNK2005: "public: __thiscall KeyCompare::~KeyCompare(void)" (??1?$KeyCompare@VTest@@@@QAE@XZ) already defined in MapTest.obj SimpleMap.obj : error LNK2005: "public: __thiscall KeyCompare::KeyCompare(void)" (??0?$KeyCompare@VTester@@@@QAE@XZ) already defined in MapTest.obj MapTest.cpp is the test harness class in which I wrote the test case. I have used include guards as well, to stop multiple inclusions. Any idea what the matter is?? Thank you very much!!

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