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  • list permutations in haskell

    - by turingcomplete
    So I'm new to haskell and I've been playing with it for a while now. I want to get my function that outputs all list permutations to work. I have written 2 implementations, one works well, the other is giving me an error. Any help would be awesome. This is the first (working) implementation: permute [] = [[]] permute xs = [y| x <- xs, y <- map (x:) $ permute $ delete x xs] This one is giving me an error: permute [] = [[]] permute xs = map (\x -> map (x:) $ permute $ delete x xs) xs and here's the error message: Occurs check: cannot construct the infinite type: t0 = [t0] Expected type: [t0] Actual type: [[t0]] In the expression: map (x :) $ permute $ delete x xs In the first argument of `map', namely `(\ x -> map (x :) $ permute $ delete x xs)' I'd appreciate if someone could explain why I'm getting this error. Thanks

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  • check if a tree is complete standard ml

    - by aizen92
    I want to make a function in standard ml that checks if a tree is complete or not, the function somehow works, but its giving me the wrong type and a warning of non-exhaustive cases The tree code: datatype 'data tree = EMPTY | NODE of 'data tree * 'data * 'data tree; fun isComplete EMPTY = true | isComplete (NODE(x, y, z)) = if (x = EMPTY andalso z <> EMPTY) orelse (x <> EMPTY andalso z = EMPTY) then false else true; Now the above function's type is: ''a tree -> bool but the required type is 'a tree -> bool The warning I'm having is: stdIn:169.8 Warning: calling polyEqual stdIn:169.26 Warning: calling polyEqual stdIn:169.45-169.47 Warning: calling polyEqual stdIn:169.64-169.66 Warning: calling polyEqual stdIn:124.1-169.94 Warning: match nonexhaustive NODE (x,y,z) => ... What is the problem I'm having?

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  • Javascript push Object to cookies using JSON

    - by Hunkeone
    Hi All on click button I need to add object to array and then write array to cookies. From the start this array can be not empty so I parse cookie first. function addToBasket(){ var basket = $.parseJSON($.cookie("basket")) if (basket.length==0||!basket){ var basket=[]; basket.push( { 'number' : this.getAttribute('number'), 'type' : this.getAttribute('product') } ); } else{ basket.push( { 'number' : this.getAttribute('number'), 'type' : this.getAttribute('product') } ); } $.cookie("basket", JSON.stringify(basket)); } And HTML <button type="button" class="btn btn-success btn-lg" number="12" product="accs" onclick="addToBasket()">Add</button> Unfortunately I'm getting Uncaught ReferenceError: addToBasket is not defined onclick. Can't understand what am I doing wrong? Thanks!

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  • hook_form for multiple content types defined by the same module

    - by pao13gate
    A new module 'foo' implements foo_node_info() where one or more new content types can be defined. If foo_node_info() defines two content types, namely a content type 'footypea' and a content type 'footypeb', how does one go about implementing hook_form() (what should the name of the "hook" be?) to configure each node's editing form? In the drupal example, the name of the new content type is the same as the module name. What happens in the above described example where two new content types are defined by the module? Should the implemented hook_form() function be of the form: footypea_form() and footypeb_form() ? (this doesn't seem to work) Or should you implement a single foo_form() function and within this create and return an array $form with elements $form['footypea'] and $form['footypeb'] that are in turn arrays of the individual form field definitions?

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  • jQuery works on local host, but not on website

    - by Cortopasta
    Using Notepad++ and XAMPP to test stuff, then I upload it to the website over FTP. In the head of my code, I have this to call jQuery and the script: <script type="text/javascript" src="/jquery.js"></script> <script type="text/javascript" src="/portfolio.js"></script> and it works fine locally on my XAMPP server. But as soon as it's uploaded onto the host, it throws this error: Resource interpreted as script but transferred with MIME type text/html. Not sure what's going on, or why it's having a hard time using jQuery. Any ideas?

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  • jquery update div as text input is modified

    - by Piero
    Hi, So I have this text input in a form, and I want to update a div as the user types text in the text input. <p><label for="movie_name">Film: </label> <input type="text" name="movie_name" class="required" onkeydown="changediv2(this.value)" /></p> <p><div id="ajax_update"></div></p> My js method: function changediv2(str) { $('#ajax_update').html(geturl('http://url/search/movie?query='+str)); } If I type in a browser http://url/search/movie?query=someString, I get some html displayed. But when I call it via this ajax call, nothing happens... My geturl method: function geturl(addr) { var r = $.ajax({ type: 'GET', url: addr, async: false }).responseText; return r; } I cannot see what is wrong in there... Please help me! :)

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  • Using scope, defined in parent model, inside it's child (STI pattern)

    - by Anton
    I implement a class hierarchy using STI pattern class A scope :aaa, where([someField]:[someValue]) end class B < A end The problem is that when I try to call something like: B.limit(5).aaa => SELECT "[table]".* FROM "[table]" WHERE "[table]"."type" IN ('A') AND ([someField] = [someValue]) LIMIT 5 So I am getting 5 objects of type A, which satisfies scope :aaa But I need to do the same with rows where type = "B" Is there any way to use scopes from parent, without redifinning it in childs in STI pattern? Thanks in advance EDITED I just discussed it with my frind and he showed me one important thing. A in not the root class of STI. IN fact whole hierarchy looks like class O < ActiveRecord::Base end class A < O scope ..... ..... end class B < A end maybe the reason is in hierarchy itself?...

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  • Can I have fixed typed ArrayList in C#, just like C++?

    - by Kazoom
    I have an ArrayList which contains fixed type of objects. However everytime I need to extract an object a particular index, I need to typecast it to my user defined type from object type. Is there a way in C# to declare ArrayList of fixed types just like Java and C++, or is there a work around to avoid the typecasting everytime? Edit: I apologize I forgot mentioning that I require the datastructure to be thread-safe, which List is not. Otherwise I would have just used a normal Array. But I want to save myself from the effort of explicitly locking and unlocking while writing the array. So I thought of using ArrayList, synchronize it, but it requires typecasting every time.

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  • javascript---click copy the content to the clipboard

    - by runeveryday
    the following is the code. but it doesn't work. what's wrong with it? thank you. <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>no title</title> <script type="text/javascript"> function copyToClipBoard(content){ var clipBoardContent = ''; clipBoardContent = content; window.clipboardData.setData("Text",clipBoardContent); alert('have copied to the clipboard'); } <body> <textarea rows="4" cols="60" id="url">www.example.com</textarea> <input type="button" value="click me" onclick="copyToClibBoard (document.getElementById ('url').value);" /> </body>

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  • How to make sure a method returns an array, even when there is only one element in Ruby

    - by doctororange
    I have a Ruby method that searches an array of hashes and returns a subset of that array. def last_actions(type = 'all') actions = @actions if type == 'run' actions = actions.select {|a| a['type'] == "run" } end return actions end This works, except when there is only one action to return, in which case I don't think it is returning an array with one element, but just the element itself. This becomes problematic later. What's a good way to ensure it returns an array of 1 element in this case? Thanks.

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  • How do I change the list using mutable lists in Racket or Scheme?

    - by exOne
    I need your help Can anyone help me? first question This procedure should modify each element which’s index in the list is even. The value of the element should be equal to the new-element. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-indices number-list 10) The new list: 1 10 8 10 43 10 78 second question This problem is the extended version of Question 1. (modify-even-odd-indices my-list new-element modification-type) This procedure should modify each element according to the modification-type. The modification-type can be even or odd. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-odd-indices number-list 10 ‘even’) The new list: 1 10 8 10 43 10 78 (modify-even-odd-indices number-list 10 ‘odd’) The new list: 10 56 10 1 10 9 10

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  • Understanding the concept of Inodes

    - by darkie15
    Hi All, I am referring to the link: http://www.tux4u.nl/freedocs/unix/draw/inode.pdf I am confused on parts: 1 12 direct block pointers 2 1 single indirect block pointer 3 1 double indirect block pointer 4 1 triple indirect block pointer Now the diagram says that each pointer is 32/64 bits. [Query]: Why and how are these values inferred? I mean why specifically have only 32 or 64 bit pointers? The diagram says, One data block{8 KB} for each pointer {4 bytes/8 bytes} [Query]: How does this actually work out? i.e. 8*1024 bytes / 8 bytes = 1024 bytes? What is the logic behind having a 8 bytes pointer for 8KB block? Regards, darkie.

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  • Unable to access static var from Document Class in AS3

    - by omidomid
    I have a Document class called "CityModule", and an asset with class "City". Below is the coe for each. For some reason, I am unable to access the static variables of the City class from CityModule: CityModule.as: package { public class CityModule extends MovieClip { public function CityModule() { var buildings:Array = City.getBuildings(); } } } } City.as: package { import flash.display.MovieClip; public class City extends MovieClip { private static var _buildings:Array = [ {className:'City.Generic1', type:'generic'}, {className:'City.Generic2', type:'generic'}, {className:'City.Generic3', type:'generic'} ]; public function City(){ //empty } public static function getBuildings():Array{ return _buildings; } } } Doing this gives me a "Call to a possibly undefined method getBuildings" error. If I instantiate an instance of City, I can see any public/ getters/ setters perfectly fine. But static isn't working...

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  • display results of jquery in a label in asp.net

    - by Zoya
    I want to display result of this javascript in a label control on my asp.net page, instead of alert. how can i do so? <script type="text/javascript" language="Javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script> <!-- Require EasyJQuery After JQuery --><script type="text/javascript" language="Javascript" src="http://api.easyjquery.com/easyjquery.js"></script> <script type="text/javascript" language="Javascript"> // 1. Your Data Here function my_callback(json) { alert("IP :" + json.IP + " COUNTRY: " + json.COUNTRY); } function my_callback2(json) { alert("IP :" + json.IP + " COUNTRY: " + json.COUNTRY + " City: " + json.cityName + " Region Name: " + json.regionName); } // 2. Setup Callback Function // EasyjQuery_Get_IP("my_callback"); // fastest version EasyjQuery_Get_IP("my_callback2","full"); // full version </script>

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  • Writing .NET in dynamic language?

    - by tillda
    I'm confused by the possibility of writing .NET in dynamic languages, such as (Iron)Ruby. Particularly, I've seen code in IronRuby that used generics (...foo[String]), but I'm not aware of this feature in Ruby as it seems nonsense to me in dynamic languages. So, when I write .NET app in IronRuby, how is it with type safety and compilation? I thought that it is just as dynamic as Ruby everywhere else. I thought that if the Ruby syntax is OK all the type checking would be done at the runtime. Also, as far as I know, .NET itself is type-oriented - there are classes that heavily utilize the mentioned generics. How is this handled? And what about delegates? In dynamic languages I can have almost function-spaghetti and sometimes, its just fine (like hacking UI in javascript). Or do I have to care even about generic delegates?

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  • Can't export emacs display on ssh

    - by Humble Debugger
    local_machine:$> ssh myself@external_machine_ip_address -p specific_port -X external_machine:$> echo $DISPLAY localhost:10.0 external_machine:$> emacs Warning: Cannot convert string "-*-courier-medium-r-*-*-*-120-*-*-*-*-iso8859-*" to type FontStruct Warning: Cannot convert string "-*-helvetica-medium-r-*--*-120-*-*-*-*-iso8859-1" to type FontStruct I do see the emacs window, but I can't see any of the characters. What could be the error ?

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  • How to add new field(s) to the contact?

    - by user328302
    I want to add a Custom field to the ContactsContract content provider. I'm trying to build a Voip application and would like to add a SIP address(name@domain) field to it. What MIME type will I need to associate with it? Also I want to add a group address field which will have a list of group addresses in it (name@domain, name@domain,...). Wich MIME type will I have to associate with this type of field. I also want to add custom fields to the Call History like a session ID and SIP address(name@domain) field. How can I customize the call history? It'll be great if someone can give me an example.

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  • C++ - checking if a class has a certain method at compile time

    - by jetwolf
    Here's a question for the C++ gurus out there. Is there a way to check at compile time where a type has a certain method, and do one thing if it does, and another thing if it doesn't? Basically, I have a template function template <typename T> void function(T t); and I it to behave a certain way if T has a method g(), and another way if it doesn't. Perhaps there is something that can be used together with boost's enable_if? Something like this: template <typename T> enable_if<has_method<T, g, void ()>, void>::type function(T t) { // Superior implementation calling t.g() } template <typename T> disable_if<has_method<T, g, void ()>, void>::type function(T t) { // Inferior implementation in the case where T doesn't have a method g() } "has_method" would be something that preferably checks both that T has a method named 'g', and that the method has the correct signature (in this case, void ()). Any ideas?

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  • Rails - inheritance hierarchy of classes where an subtipe can play two roles

    - by Miquel
    I need to model Owners and Rentees in an application, so you have stuff that is always owned by someone and can be rented for someone else. I first approached this problem with Single Table Inheritance because both types of person will share all attributes, so you would have a model called Person associated to a table people with Owner and Rentee inheriting from Person. The problem is that Single type inheritance discerns subtypes using a field type and therefore a record in the table can represent either an Owner or a Rentee but not both at the same time, while in the real context you can have an Owner which is renting something from another Owner and therefore that person is at the same time an Owner and a Rentee. How would you approach this problem? Would you use separated tables fro owners and rentees? Is there any other type of table inheritance in Rails?

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  • manage date fields when are int in the db

    - by Luca Romagnoli
    Hi in my db there is a field "date_start" type integer. This is the part of form for this field <div class="editor-label"> <%: Html.LabelFor(model => model.date_start) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.date_start, new { @class = "calendar" })%> <%: Html.ValidationMessageFor(model => model.date_start) %> </div> In the form i want that the field's format is date type. and memorize it in int type after calling a my function for the convertion. How can i manage it? thanks

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  • Ranged integers in .NET (or C#)

    - by Mal Ross
    Am I being blind, or does the .NET framework not provide any kind of ranged integer class? That is, a type that would prevent you setting a value outside some given bounds that are not the full range of the basic data type. For example, an integer type that would restrict its values to between 1 and 100. Showing my age here, but back in '93, I remember using that sort of thing in Modula-2 (eeek!), but I've not seen explicit framework / language support for it since. Am I just missing something, or is it a case of "it's so simple to make your own that the framework doesn't bother"? Cheers.

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  • Can't update date in aspx to a MS-ACCESS table

    - by Bjork
    Hello I'm having problem with updating datatypes I insert the date in the C# part like this string strSQL = "INSERT into Frettir (CreatedBy,CreatedOn,Title,Description,Starts,Ends,CatId,SectionId,ArticleExt,Myndatexti,MyndUrAlbumi,NrMyndar) values(?,?,?,?,?,?,?,?,?,?,?,?)"; cmd.Parameters.Add("@Starts",OleDbType.Date).Value = dstartdate; but I update in the aspx part like this UpdateCommand="UPDATE [Frettir] SET [Title]=@Title,[Description]=@Description,[CreatedBy]=@notandaID,[ArticleExt]=@ArticleExt, [Myndatexti]=@Myndatexti,[Starts]=@Starts WHERE [ArticleID]=@id2 " I get an error Data type mismatch in criteria expression It seems that there are some type differences between the type that is input in the c# part and the aspx-part Can anyone help me with this?

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  • How is this input tag linking to another page?

    - by Matt
    Response.Write("<div><input type='submit' name='submit' value='Update Cart' /></div>") Response.Write("<div><input type='submit' name='submit' value='Shop More' /></div>") Response.Write("<div><input type='submit' name='submit' value='Checkout' /></div>") that is some example code from my teacher, but he hasn't answered my email in a couple days so I need some help. When you click the Update Cart button it just updates the cart page it's on, but when you click the Shop More button it links to Shop.aspx a different page, and the Checkout links to another page as well. I can't figure out how it is linking just from that code, anybody have any insights?

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  • C# - Why can't I enforce derived classes to have parameterless constructors?

    - by FrisbeeBen
    I am trying to do the following: public class foo<T> where T : bar, new { _t = new T(); private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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