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  • Why won't the following haskell code compile?

    - by voxcogitatio
    I'm in the process of writing a small lisp interpreter in haskell. In the process i defined this datatype, to get a less typed number; data Number = _Int Integer | _Rational Rational | _Float Double deriving(Eq,Show) Compiling this fails with the following error: ERROR "types.hs":16 - Syntax error in data type declaration (unexpected `|') Line 16 is the line w. the first '|' in the code above.

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  • How can I check the MIME type of an uploaded file using Perl CGI?

    - by FOOM
    I'm trying to get the MIME type of an <input type="file" /> element using Perl, but without actually examining the contents of the file itself, In other words, just using the HTTP headers. I have only been able to get the "multipart/form-type" Content-Type value, but my understanding is that each element will get its own MIME Type? How can I see the sub-MIME types using Perl?

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  • Object or primitive type

    - by John
    Hi, Can someone explain to me the usage of Integer, Boolean etc in place of their primitive types in JAVA? I can't seem to grasp the advantages their are providing. They seem to create unnecessary problems of handling null values. Thanks!

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  • Convolving two signals

    - by John Elway
    Calculate the convolution of the following signals (your answer will be in the form of an equation): h[n] = delta[n-1] + delta[n+1], x[n] = delta[n-a] + delta[n+b] I'm lost as to what I do with h and x. Do I simply multiply them? h[n]*x[n]? I programmed convolution with several types of blurs and edge detectors, but I don't see how to translate that knowledge to this problem. please help!

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  • Getting below error when trying to register a generic class with a implementation using .net 2.0

    - by Gaurav Saxena
    Code: StructureMapConfiguration.BuildInstancesOf().AsSingletons().TheDefaultIsConcreteType(); Error: StructureMap Exception Code: 190 Can not create a Generic PluginFamily for PluginFamily MIGExcel.Service.IPersistenceService1[[MIGExcel.Model.Contact, WizardModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]. Check that the basic type MIGExcel.Service.IPersistenceService1 is configured as a PluginFamily. These Generic types are configured within StructureMap as PluginFamily's: MIGExcel.Service.IPersistenceService`1[[MIGExcel.Model.Contact, WizardModel, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]],MIGExcel.Service;

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  • Keyboard Shortcuts you use when your typing code.

    - by Sagistic
    People use a variety of little shortcuts that make typing code easier and without the hassle of going back to your mouse. For example, when deleting, ctrl + backspace will delete the whole word. I was wondering what types of little nifty tricks you know that you would like to share!

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  • CSS: What is the proper way to deal with multiple classes of Text

    - by DavidR
    So I'm on commission for a website, and I'm trying to improve my code. When dealing with a website with multiple types of font (here it's large, there it's small, there it's bold, here it's underlined, etc.) is this where we use the h1-h6, or do we reserve those for times when there is a definite hierarchy, using instead <p class="xxx"> to define different classes for text?

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  • Effective Data Validation

    - by John Conde
    What's an effective way to handle data validation, say, from a form submission? Originally I had a bunch of if statements that checked each value and collected invalid values in an array for later retrieval (and listing). // Store errors here $errors = array(); // Hypothetical check if a string is alphanumeric if (!preg_match('/^[a-z\d]+$/i', $fieldvalue)) { $errors[$fieldname] = 'Please only use letters and numbers for your street address'; } // etc... What I did next was create a class that handles various data validation scenarios and store the results in an internal array. After data validation was complete I would check to see if any errors occurred and handle accordingly: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more methods here public function creditCard($cardNumber, $field, $msg = '') { // Validate credit card number } // more methods here public function hasErrors() { return count($this->errorList); } } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue1, $fieldname1, 'Please only use letters and numbers for your street address'); $validate->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Naturally it didn't take long before this class became bloated with the virtually unlimited types of data to be validated. What I'm doing now is using decorators to separate the different types of data into their own classes and call them only when needed leaving generic validations (i.e. isAlphaNumeric()) in the base class: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more generic methods here public function setError($field, $msg = '') { $this->errorList[$field] = $msg; } public function hasErrors() { return count($this->errorList); } } class ValidationCreditCard { protected $validate; public function __construct(Validation $validate) { $this->validate = $validate; } public function creditCard($cardNumber, $field, $msg = '') { // Do validation // ... // if there is an error $this->validate->setError($field, $msg); } // more methods here } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue, $fieldname, 'Please only use letters and numbers for your street address'); $validateCC = new ValidationCreditCard($validate); $validateCC->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Am I on the right track? Or did I just complicate data validation more then I needed to?

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  • Get name given by phone number on the iPhone

    - by ganti
    I'm using a TextField where the user types a phone number. When the TextField changes, it should check if this number is already in the phonebook and display the name. So far, my only way is to parse all names and number in a Dict and read it from there. Is there a simpler, more efficient and sophisticated way to do that?

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  • Is there a reason why a base class decorated with XmlInclude would still throw a type unknown exception when serialized?

    - by Tedford
    I will simplify the code to save space but what is presented does illustrate the core problem. I have a class which has a property that is a base type. There exist 3 dervived classes which could be assigned to that property. If I assign any of the derived classes to the container then the XmlSerializer throws dreaded "The type xxx was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically." exception when attempting to seralize the container. However my base class is already decorated with that attribute so I figure there must be an additional "hidden" requirement. The really odd part is that the default WCF serializer has no issues with this class hierarchy. The Container class [DataContract] [XmlRoot(ElementName = "TRANSACTION", Namespace = Constants.Namespace)] public class PaymentSummaryRequest : CommandRequest { /// <summary> /// Gets or sets the summary. /// </summary> /// <value>The summary.</value> /// <remarks></remarks> [DataMember] public PaymentSummary Summary { get; set; } /// <summary> /// Initializes a new instance of the <see cref="PaymentSummaryRequest"/> class. /// </summary> public PaymentSummaryRequest() { Mechanism = CommandMechanism.PaymentSummary; } } The base class [DataContract] [XmlInclude(typeof(xxxPaymentSummary))] [XmlInclude(typeof(yyyPaymentSummary))] [XmlInclude(typeof(zzzPaymentSummary))] [KnownType(typeof(xxxPaymentSummary))] [KnownType(typeof(xxxPaymentSummary))] [KnownType(typeof(zzzPaymentSummary))] public abstract class PaymentSummary { } One of the derived classes [DataContract] public class xxxPaymentSummary : PaymentSummary { } The serialization code var serializer = new XmlSerializer(typeof(PaymentSummaryRequest)); serializer.Serialize(Console.Out,new PaymentSummaryRequest{Summary = new xxxPaymentSummary{}}); The Exception System.InvalidOperationException: There was an error generating the XML document. --- System.InvalidOperationException: The type xxxPaymentSummary was not expected. Use the XmlInclude or SoapInclude attribute to specify types that are not known statically. at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriterPaymentSummaryRequest.Write13_PaymentSummary(String n, String ns, PaymentSummary o, Boolean isNullable, Boolean needType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriterPaymentSummaryRequest.Write14_PaymentSummaryRequest(String n, String ns, PaymentSummaryRequest o, Boolean isNullable, Boolean needType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationWriterPaymentSummaryRequest.Write15_TRANSACTION(Object o) --- End of inner exception stack trace --- at System.Xml.Serialization.XmlSerializer.Serialize(XmlWriter xmlWriter, Object o, XmlSerializerNamespaces namespaces, String encodingStyle, String id) at System.Xml.Serialization.XmlSerializer.Serialize(TextWriter textWriter, Object o, XmlSerializerNamespaces namespaces) at UserQuery.RunUserAuthoredQuery() in c:\Users\Tedford\AppData\Local\Temp\uqacncyo.0.cs:line 47

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  • Warning: newtype `CInt' is used in an FFI declaration,

    - by vivian
    When building gtk2hs-buildtools with ghc 7.4.2, I get the following warning: c2hs/toplevel/C2HSConfig.hs:110:1: Warning: newtype `CInt' is used in an FFI declaration, but its constructor is not in scope. This will become an error in GHC 7.6.1. When checking declaration: foreign import ccall safe "static bitfield_direction" bitfield_direction :: CInt I get similar warnings with FFI calls, even though I have import Foreign.C.Types(CInt). What is the correct way of getting rid of this warning?

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  • Is there a way to prevent an ASP.Net webapp from clearing out page variables on VB side?

    - by Chapso
    I have a webapp in ASP.Net with a VB codebehind. I need a List variable I have declared to persist as long as the person is on the page, but currently any time a control posts back to the code, everything is cleared out. I am completely new to ASP.net, so I have no idea if this is even possible. Can it be done with a Session variable? Those seem to me to be limited to base types, but I could be wrong.

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  • Looping on a closed range

    - by AProgrammer
    How would you fix this code? template <typename T> void closed_range(T begin, T end) { for (T i = begin; i <= end; ++i) { // do something } } T is constrained to be an integer type, can be the wider of such types and can be signed or unsigned begin can be numeric_limits<T>::min() end can be numeric_limits<T>::max() (in which case ++i will overflow in the above code) I've several ways, but none I really like.

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  • Regular Expression problem

    - by Yatendra Goel
    I want a regex to find the following types of strings: http://anything.abc.tld http://anything.abc.tld/ where abc - abc always remains abc anything - it could be any string tld - it could be any tld (top-level-domain) like .com .net .co.in .co.uk etc. Note: The url must not contain any other thing at the end, means http://anything.abc.tld/xyz is not acceptable.

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  • PHP curly string syntax question

    - by zildjohn01
    I'm running PHP 5.3.0. I've found that the curly string syntax only works when the first character of the expression is $. Is there a way to include other types of expressions (function calls, etc)? Trivial example: <?php $x = '05'; echo "{$x}"; // works as expected echo "{intval($x)}"; // hoped for "5", got "{intval(05)}"

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  • Multiple layouts in rails [Newbie Q]

    - by BriteLite
    Hi. As a newb, I decided to build a "home inventory" application. I am now stuck on how to programmatically select a layout based on what type of item it is when viewing it in a browser. According to my planning, so far I should have created a few models to represent types of items I can find in my home: Furniture, Electronics and Books. class Book < ActiveRecord::Base end class Furniture < ActiveRecord::Base end class Electronic < ActiveRecord::Base end Now the Books model has things like isbn, pages, address, and category. Furniture model has things like color, price, address, and category. Electronics has things like name, voltage, address, and category. Here is where I got confused. I know the property address is going to be the same for all of them. I also know that, I will need to create multiple "layouts" for 3 different types of items to show the different properties of said items with appropriate graphics and stylesheets. But how will I go about deciding which category the item is so I can determine which layout to render. According to me, this is how I will do it: class DisplayController < ApplicationController def display @item = Params[:item] if @item.category = "electronics" render :layout => 'electronics' end end In my routes.rb map.display ':item', :controller => 'display', :action => 'display' I only seem to have one concern with this, I probably will add a lot of categories later on and think there should be a more DRY-esque way of dealing, rather than hardcoding them. I understand that I need to add into my layout html tags to display relevant information for that particular category. ----Questions---- Is this the right way to approach this type of problem. Will this approach be compatible when I decide to add a gem like *thinking_sphinx* to run search. What issues do you see with my approach and how can I make it better. I was reading something about "Polymorphic Assoc", does that apply in this case, since category exist for all items? Also, I was trying to get a routes to render a URL like "http://localhost/living-room-tv"

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  • protected internal

    - by adfs
    The C# Language Reference on MSDN defines that protected internal as "Access is limited to the current assembly or types derived from the containing class". But from the semantic point of protected internal" sounds to me like both protected and internal which means the member will accessible only to those derived classes with in the same assembly. Is there any access modified that has a meaning to the same effect?

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