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  • Using type aliases to Java enums

    - by oxbow_lakes
    I would like to achieve something similar to how scala defines Map as both a predefined type and object. In Predef: type Map[A, +B] = collection.immutable.Map[A, B] val Map = collection.immutable.Map //object Map However, I'd like to do this using Java enums (from a shared library). So for example, I'd have some global alias: type Country = my.bespoke.enum.Country val Country = my.bespok.enum.Country //compile error: "object Country is not a value" The reason for this is that I'd like to be able to use code like: if (city.getCountry == Country.UNITED_KINGDOM) //or... if (city.getCountry == UNITED_KINGDOM) Howver, this not possible whilst importing my type alias at the same time. Note: this code would work just fine if I had not declared a predefined type and imported it! Is there some syntax I can use here to achieve this?

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  • Context Free Language Question (Pumping Lemma)

    - by Maixy
    I know this isn't directly related to programming, but I was wondering if anyone know how to apply the pumping lemma to the following proof: Show that L={(a^n)(b^n)(c^m) : n!=m} is not a context free language I'm pretty confident with applying pumping lemmas, but this one is really irking me. What do you think?

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  • How change Subversion's default binary mime-type?

    - by lamcro
    Subversion sets a binary file's svn:mime-type property to application/octet-stream by default. I need to change this default to some other mime-type. When I import for the first time this code, I would like Subversion to set mime-type to the one I choose. The reason is that my code base contains code in binary files (proprietary format), and I have the applications necessary to emulate diff and diff3 for these. But Subversion does not let me due to their default mime-type. Please note: There is no default extension (*.jar, *.py, etc) for these code files. Some files don't even have an extension. So configuring mime-type by file extension is not possible.

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  • Convert a post-order binary tree traversal index to an level-order (breadth-first) index

    - by strfry
    Assuming a complete binary tree, each node can be adressed with the position it appears in a given tree traversal algorithm. For example, the node indices of a simple complete tree with height 3 would look like this: breadth first (aka level-order): 0 / \ 1 2 / \ / \ 3 4 5 6 post-order dept first: 6 / \ 2 5 / \ / \ 0 1 3 4 The height of the tree and an index in the post-order traversal is given. How can i calculate the breadth first index from this information?

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  • How do I create Ntlm Type 1 and Type 3 messages in .Net

    - by brj011
    I need to create Type 1 message and Type 3 message for NTLM handshaking. Is there any .Net API for this? Essentially, the application is WPF based, but Socket is used in order to stream data from the server. Use of socket is a technical requirement, but the problem is when user needs to connect to the server using a proxy server. Further, if the proxy authorization is based on Ntlm, the client application needs to create Type 1 and Type 3 messages in order to handshake with the proxy server. My question is: Is there any API already available in .NET libraries that can be consumed in order to create these different types of NTLM messages? Any help or alternatives will be greatly appreciated. Thanks in advance.

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  • PHP: SUBMIT Type vs IMAGE Type

    - by sebb
    I have noticed that when using a SUBMIT type its name attribute gets passed via POST , while an IMAGE type button do not have this data sent, can any one clear this up for me? In both instances the NAME attribute is present at HTML level, but only the SUMBIT type has the NAME sent via POST....is this right?

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  • Getting a Type variable knowing the name of type C#

    - by StuffHappens
    Hello! I'm developing a TypeTranslator class which has a method Type TranslateType(Type type). This method gets a type of an interface and if there's a class of interface name without leading I it creates it, otherwise an exception is raised. Here's some code to clearify what's written before: class Program { interface IAnimal { } class Animal : IAnimal { } void Function() { TypeTranslator typeTranslator = new TypeTranslator(); Assert(typeTranslator.TranslateType(typeof(IAnimal) == typeof(Animal))); } } Is it possible to get what I want? Thank you for your help!

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  • calling template function without <>; type inference

    - by Oops
    Hi, if I have a function template with typename T, where the compiler can set the type by itself, I do not have to write the type explicitely when I call the function like: template < typename T > T min( T v1, T v2 ) { return ( v1 < v2 ) ? v1: v2; } int i1 = 1, i2 = 2; int i3 = min( i1, i2 ); //no explicit <type> but if I have a function template with two different typenames like... template < typename TOut, typename TIn > TOut round( TIn v ) { return (TOut)( v + 0.5 ); } double d = 1.54; int i = round<int>(d); //explicit <int> Is it true that I have to specify at least 1 typename, always? I assume the reason is because C++ can not distinguish functions between different return types, true? but if I use a void function and handover a reference, again I must not explicitely specify the return typename: template < typename TOut, typename TIn > void round( TOut & vret, TIn vin ) { vret = (TOut)(vin + 0.5); } double d = 1.54; int i; round(i, d); //no explicit <int> should the conclusion be to avoid functions with return and more prefer void functions that return via a reference when writing templates? Or is there a possibility to avoid explicitely writing the return type? something like "type inference" for templates... is "type inference" possible in C++0x? I hope I was not too unclear. many thanks in advance Oops

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  • Scala path dependent return type from parameter

    - by Rich Oliver
    In the following code using 2.10.0M3 in Eclipse plugin 2.1.0 for 2.10M3. I'm using the default setting which is targeting JVM 1.5 class GeomBase[T <: DTypes] { abstract class NewObjs { def newHex(gridR: GridBase, coodI: Cood): gridR.HexRT } class GridBase { selfGrid => type HexRT = HexG with T#HexTr def uniformRect (init: NewObjs) { val hexCood = Cood(2 ,2) val hex: HexRT = init.newHex(selfGrid, hexCood)// won't compile } } } Error message: Description Resource Path Location Type type mismatch; found: GeomBase.this.GridBase#HexG with T#HexTr required: GridBase.this.HexRT (which expands to) GridBase.this.HexG with T#HexTr GeomBase.scala Why does the compiler think the method returns the type projection GridBase#HexG when it should be this specific instance of GridBase? Edit transferred to a simpler code class in responce to comments now getting a different error message. package rStrat class TestClass { abstract class NewObjs { def newHex(gridR: GridBase): gridR.HexG } class GridBase { selfGrid => def uniformRect (init: NewObjs) { val hex: HexG = init.newHex(this) //error here } class HexG { val test12 = 5 } } } . Error line 11:Description Resource Path Location Type type mismatch; found : gridR.HexG required: GridBase.this.HexG possible cause: missing arguments for method or constructor TestClass.scala /SStrat/src/rStrat line 11 Scala Problem Update I've switched to 2.10.0M4 and updated the plug-in to the M4 version on a fresh version of Eclipse and switched to JVM 1.6 (and 1.7) but the problems are unchanged.

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  • Is Haskell's type system an obstacle to understanding functional programming?

    - by FarmBoy
    I'm studying Haskell for the purpose of understanding functional programming, with the expectation that I'll apply the insight that I gain in other languages (Groovy, Python, JavaScript mainly.) I choose Haskell because I had the impression that it is very purely functional, and wouldn't allow for any reliance on state. I did not choose to learn Haskell because I was interested in navigating an extremely rigid type system. My question is this: Is a strong type system a necessary by-product of an extremely pure functional language, or is this an unrelated design choice particular to Haskell? If it is the latter, I'm curious what would be the most purely functional language that is dynamically typed. I'm not particularly opposed to strong typing, it has its place, but I'm having a hard time seeing how it benefits me in this educational endeavor.

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  • Is Haskell's type system an obstacle to understanding functional programming?

    - by Eric Wilson
    I'm studying Haskell for the purpose of understanding functional programming, with the expectation that I'll apply the insight that I gain in other languages (Groovy, Python, JavaScript mainly.) I choose Haskell because I had the impression that it is very purely functional, and wouldn't allow for any reliance on state. I did not choose to learn Haskell because I was interested in navigating an extremely rigid type system. My question is this: Is a strong type system a necessary by-product of an extremely pure functional language, or is this an unrelated design choice particular to Haskell? If it is the latter, I'm curious what would be the most purely functional language that is dynamically typed. I'm not particularly opposed to strong typing, it has its place, but I'm having a hard time seeing how it benefits me in this educational endeavor.

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  • Graph Theory: How to compute closeness centrality for each node in a set of data?

    - by Jordan
    I'd like to learn how to apply network theory to my own cache of relational data. I'm trying to build a demo of a new way of browsing a music library, using network theory, that I think would make for a very intuitive and useful way of finding the right song at any given time. I have all the data (artists as nodes, similarity from 0 to 1 between each artist and those it is related to) and I can already program, but I don't know how to actually calculate the centrality of a node from that. I've spent a while trying to email different professors at my school but no one seems to know where I can learn this. I hope someone's done something similar. Thanks in advance you guys! ~Jordan

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  • implementing type inference

    - by deepblue
    well I see some interesting discussions here about static vs. dynamic typing I generally prefer static typing, due to compile type checking, better documented code,etc. However I do agree that they do clutter up the code if done the way Java does it, for example. so Im about to start building a language of my own and type inference is one of the things that I want to implement, in a functional style language... I do understand that it is a big subject, and Im not trying to create something that has not been done before, just basic inferencing... any pointers on what to read up that will help me with this? preferably something more pragmatic/practical as oppose to more theoretical category theory/type theory texts. If there's a implementation discussion text out here, with data structures/algorithms, that would just be lovely much appreciated

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  • Thoughts on type aliases/synonyms?

    - by Rei Miyasaka
    I'm going to try my best to frame this question in a way that doesn't result in a language war or list, because I think there could be a good, technical answer to this question. Different languages support type aliases to varying degrees. C# allows type aliases to be declared at the beginning of each code file, and they're valid only throughout that file. Languages like ML/Haskell use type aliases probably as much as they use type definitions. C/C++ are sort of a Wild West, with typedef and #define often being used seemingly interchangeably to alias types. The upsides of type aliasing don't invoke too much dispute: It makes it convenient to define composite types that are described naturally by the language, e.g. type Coordinate = float * float or type String = [Char]. Long names can be shortened: using DSBA = System.Diagnostics.DebuggerStepBoundaryAttribute. In languages like ML or Haskell, where function parameters often don't have names, type aliases provide a semblance of self-documentation. The downside is a bit more iffy: aliases can proliferate, making it difficult to read and understand code or to learn a platform. The Win32 API is a good example, with its DWORD = int and its HINSTANCE = HANDLE = void* and its LPHANDLE = HANDLE FAR* and such. In all of these cases it hardly makes any sense to distinguish between a HANDLE and a void pointer or a DWORD and an integer etc.. Setting aside the philosophical debate of whether a king should give complete freedom to their subjects and let them be responsible for themselves or whether they should have all of their questionable actions intervened, could there be a happy medium that would allow the benefits of type aliasing while mitigating the risk of its abuse? As an example, the issue of long names can be solved by good autocomplete features. Visual Studio 2010 for instance will alllow you to type DSBA in order to refer Intellisense to System.Diagnostics.DebuggerStepBoundaryAttribute. Could there be other features that would provide the other benefits of type aliasing more safely?

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  • Using a user-defined type as a primary key

    - by Chris Kaminski
    Suppose I have a system where I have metadata such as: table: ====== key name address ... Then suppose I have a user-defined type described as so: datasource datasource-key A) are there systems where it's possible to have keys based on user-defined types? B) if so, how do you decompose the keys into a form suitable for querying? C) is this a case where I'm just better off with a composite primary key?

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  • HTTP Content-Type in ASP.Net SoapHttpClientProtocol

    - by Daniel Fone
    Hi there, I have a problem with a Web Service Consumer written in ASP.NET. The error message is: System.InvalidOperationException: Client found response content type of 'application/xml; charset=utf-8', but expected 'text/xml'. The client is based on System.Web.Services.Protocols.SoapHttpClientProtocol. We can't change the Content-Type given by the provider, this has to be 'application/xml; charset=utf-8'. Is there any way to change what Content-Type the SoapHttpClientProtocol expects? Unfortunately, we are probably limited to .NET 1.1. Thanks! Update: We found a way to change the Content-Type sent by the provider, and this solved the problem. I'd still be curious to know how to change the expectations of the consumer though.

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  • Getting ActiveRecord (Rails) to_xml to use xsi:nil and xsi:type instead of nil and type

    - by nbeyer
    The default behavior of XML serialization (to_xml) for ActiveRecord objects will emit 'type' and 'nil' attributes that are similar to XML Schema Instance attributes, but aren't set in a XML Namespace. For example, a model might produce an output like this: <user> <username nil="true" /> <first-name type="string">Name</first-name> </user> Is there anyway to get to_xml to utilize the XML Schema Instance namespace and prefix the attributes and the values? Using the above example, I'd like to produce the following: <user xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" xmlns:xs="http://www.w3.org/1999/XMLSchema"> <username xsi:nil="true" /> <first-name xsi:type="xs:string">Name</first-name> </user>

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  • Type attribute for text_field

    - by Koning Baard XIV
    I have this code: <%= f.text_field :email, :type => "email", :placeholder => "[email protected]" %> So people can enter their email on an iPhone with the email keyboard instead of the ASCII keyboard. However, the output is: <input id="user_email" name="user[email]" placeholder="[email protected]" size="30" type="text" /> which should be: <input id="user_email" name="user[email]" placeholder="[email protected]" size="30" type="email" /> Is there a way to force Rails to use the email type instead of text, or must I use HTML directly? Thanks

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  • wpf: design time error while writing Nested type in xaml

    - by viky
    I have created a usercontrol which accept type of enum and assign the values of that enum to a ComboBox control in that usercontrol. Very Simple. I am using this user control in DataTemplates. Problem comes when there comes nested type. I assign that using this notation EnumType="{x:Type myNamespace:ParentType + NestedType}" It works fine at runtime. but at design time it throws error saying Could not create an instance of type 'TypeExtension' Why? Due to this I am not able to see my window at design time. Any help?

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