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• Parse a CSV file using python (to make a decision tree later)

  - by Margaret

  First off, full disclosure: This is going towards a uni assignment, so I don't want to receive code. :). I'm more looking for approaches; I'm very new to python, having read a book but not yet written any code. The entire task is to import the contents of a CSV file, create a decision tree from the contents of the CSV file (using the ID3 algorithm), and then parse a second CSV file to run against the tree. There's a big (understandable) preference to have it capable of dealing with different CSV files (I asked if we were allowed to hard code the column names, mostly to eliminate it as a possibility, and the answer was no). The CSV files are in a fairly standard format; the header row is marked with a # then the column names are displayed, and every row after that is a simple series of values. Example: # Column1, Column2, Column3, Column4 Value01, Value02, Value03, Value04 Value11, Value12, Value13, Value14 At the moment, I'm trying to work out the first part: parsing the CSV. To make the decisions for the decision tree, a dictionary structure seems like it's going to be the most logical; so I was thinking of doing something along these lines: Read in each line, character by character If the character is not a comma or a space Append character to temporary string If the character is a comma Append the temporary string to a list Empty string Once a line has been read Create a dictionary using the header row as the key (somehow!) Append that dictionary to a list However, if I do things that way, I'm not sure how to make a mapping between the keys and the values. I'm also wondering whether there is some way to perform an action on every dictionary in a list, since I'll need to be doing things to the effect of "Everyone return their values for columns Column1 and Column4, so I can count up who has what!" - I assume that there is some mechanism, but I don't think I know how to do it. Is a dictionary the best way to do it? Would I be better off doing things using some other data structure? If so, what?

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• Ruby and public_method_defined? : strange behaviour

  - by aXon

  Hi there Whilst reading through the book "The well grounded Rubyist", I came across some strange behaviour. The idea behind the code is using one's own method_missing method. The only thing I am not able to grasp is, why this code gets executed, as I do not have any Person.all_with_* class methods defined, which in turn means that the self.public_method_defined?(attr) returns true (attr is friends and then hobbies). #!/usr/bin/env ruby1.9 class Person PEOPLE = [] attr_reader :name, :hobbies, :friends def initialize(mame) @name = name @hobbies = [] @friends = [] PEOPLE << self end def has_hobby(hobby) @hobbies << hobby end def has_friend(friend) @friends << friend end def self.method_missing(m,*args) method = m.to_s if method.start_with?("all_with_") attr = method[9..-1] if self.public_method_defined?(attr) PEOPLE.find_all do |person| person.send(attr).include?(args[0]) end else raise ArgumentError, "Can't find #{attr}" end else super end end end j = Person.new("John") p = Person.new("Paul") g = Person.new("George") r = Person.new("Ringo") j.has_friend(p) j.has_friend(g) g.has_friend(p) r.has_hobby("rings") Person.all_with_friends(p).each do |person| puts "#{person.name} is friends with #{p.name}" end Person.all_with_hobbies("rings").each do |person| puts "#{person.name} is into rings" end The output is is friends with is friends with is into rings which is really understandable, as there is nothing to be executed.

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• Why does C# not provide the C++ style 'friend' keyword?

  - by Ash

  The C++ friend keyword allows a class A to designate class B as it's friend. This allows Class B to access the private/protected members of class A. I've never read anything as to why this was left out of C# (and VB.NET). Most answers to this earlier StackOverflow question seem to be saying it is a useful part of C++ and there are good reasons to use it. In my experience I'd have to agree. Another question seems to me to be really asking how to do something similar to friend in a C# application. While the answers generally revolve around nested classes, it doesn't seem quite as elegant as using the friend keyword. The original Design Patterns book uses the friend keyword regularly throughout its examples. So in summary, why is friend missing from C#, and what is the "best practice" way (or ways) of simulating it in C#? (By the way, the "internal" keyword is not the same thing, it allows ALL classes within the entire assembly to access internal members, friend allows you to give access to a class to just one other class.)

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• need help with Java solution /newbie

  - by Racket

  Hi, I'm new to programming in general so i'm trying to be as specific as possible in this question. There's this book that i'm doing some exercises on. I managed to do more than half of what they say, but it's just one input that I have been struggling to find out. I'll write the question and thereafter my code, "Write an application that creates and prints a random phone number of the form XXX-XXX-XXXX. Include the dashes in the output. Do not let the first three digits contain an 8 or 9 (but don't be more restrictive than that), and make sure that the second set of three digits is not greater than 742. Hint: Think through the easiest way to construct the phone number. Each diigit does not have to be determined separately." OK, the highlighted sentence is what i'm looking at. Here's my code: import java.util.Random; public class PP33 { public static void main (String[] args) { Random rand = new Random(); int num1, num2, num3; num1 = rand.nextInt(900) + 100; num2 = rand.nextInt(643) + 100; num3 = rand.nextInt(9000) + 1000; System.out.println(num1+"-"+num2+"-"+num3); } } How am I suppose to do this? I'm on chapter 3 so we have not yet discussed if statements etcetera, but Aliases, String class, Packages, Import declaration, Random Class, Math Class, Formatting output (decimal- & numberFormat), Printf, Enumeration & Wrapper classes + autoboxing. So consider answer the question based only on these assumptions, please. The code doesn't have any errors. Thank you!

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• how to check null value of Integer type field in ASP.NET MVC view?

  - by Vikas

  Hi, I have integer type field in database which is having property "Not Null". when i create a view & do a validation, if i left that field blank, it will consider it as 0 so i can not compare it with 0 because if someone insert a value 0 then it will be considered as error! one another problem is that i am using Model error as described in the book "ASP.NET MVC 1.0" @ Scott Gu blog. And I am checking the value in partial class of object (created by LINQ-To-SQL). i.e public partial class Person { public bool IsValid { get { return (GetRuleViolations().Count() == 0); } } public IEnumerable<RuleViolation> GetRuleViolations() { if (String.IsNullOrEmpty(Name)) yield return new RuleViolation("Name is Required", "Name"); if (Age == 0) yield return new RuleViolation("Age is Required", "Age"); yield break; } partial void OnValidate(ChangeAction action) { if (!IsValid) throw new ApplicationException("Rule violations prevent saving"); } } There is also problem with range. Like in database if i declared as smallint i.e. short in c#, now if i exceed that range then it gives error as "A Value is reguired". so finally is there any best way for validation in ASP.NET MVC?

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• How should rules for Aggregate Roots be enforced?

  - by MylesRip

  While searching the web, I came across a list of rules from Eric Evans' book that should be enforced for aggregates: The root Entity has global identity and is ultimately responsible for checking invariants Root Entities have global identity. Entities inside the boundary have local identity, unique only within the Aggregate. Nothing outside the Aggregate boundary can hold a reference to anything inside, except to the root Entity. The root Entity can hand references to the internal Entities to other objects, but they can only use them transiently (within a single method or block). Only Aggregate Roots can be obtained directly with database queries. Everything else must be done through traversal. Objects within the Aggregate can hold references to other Aggregate roots. A delete operation must remove everything within the Aggregate boundary all at once When a change to any object within the Aggregate boundary is committed, all invariants of the whole Aggregate must be satisfied. This all seems fine in theory, but I don't see how these rules would be enforced in the real world. Take rule 3 for example. Once the root entity has given an exteral object a reference to an internal entity, what's to keep that external object from holding on to the reference beyond the single method or block? (If the enforcement of this is platform-specific, I would be interested in knowing how this would be enforced within a C#/.NET/NHibernate environment.)

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• Object equality in context of hibernate / webapp

  - by bert

  How do you handle object equality for java objects managed by hibernate? In the 'hibernate in action' book they say that one should favor business keys over surrogate keys. Most of the time, i do not have a business key. Think of addresses mapped to a person. The addresses are keeped in a Set and displayed in a Wicket RefreshingView (with a ReuseIfEquals strategy). I could either use the surrogate id or use all fields in the equals() and hashCode() functions. The problem is that those fields change during the lifetime ob the object. Either because the user entered some data or the id changes due to JPA merge() being called inside the OSIV (Open Session in View) filter. My understanding of the equals() and hashCode() contract is that those should not change during the lifetime of an object. What i have tried so far: equals() based on hashCode() which uses the database id (or super.hashCode() if id is null). Problem: new addresses start with an null id but get an id when attached to a person and this person gets merged() (re-attached) in the osiv-filter. lazy compute the hashcode when hashCode() is first called and make that hashcode @Transitional. Does not work, as merge() returns a new object and the hashcode does not get copied over. What i would need is an ID that gets assigned during object creation I think. What would be my options here? I don't want to introduce some additional persistent property. Is there a way to explicitly tell JPA to assign an ID to an object? Regards

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• MySQL get point in time totals from related tables

  - by batfastad

  Hi everyone We have an order book and invoicing system and I've been tasked with trying to output monthly rolling totals from these tables. But I don't know really where to start with this. I think there's some SQL syntax that I don't even know about yet. I'm familiar with INNER/LEFT/JOINS and GROUP BY etc but grouping by date is confusing since I don't know how to limit the data to only the current date that's being grouped by at that point. I think this will involve joining the tables to themselves or possibly a sub-select. I always thought it best to avoid sub-selects apart from when absolutely necessary. Basically the system has 3 tables orders: order_id, currency, order_stamp orders_lines: order_line_id, invoice_id, order_id, price invoices: invoice_id, invoice_stamp order_stamp and invoice_stamp are UTC unix timestamps stored as integers, not MySQL timestamps. I'm trying to get a listing by year/month showing the total of current unbilled orders (sum of price), at that point in time. Current orders are ones where order_stamp is less than or equal to 00:00 on the 1st of the month. Unbilled orders are ones where invoice_stamp is null or invoice_stamp is greater than 00:00 on the 1st of the month. At that point in time there may not be a related invoice yet and invoice_id might be null. Anyone got any suggestions on what I should join to what and what I need to group by? Cheers, B

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• Java Concurrency in practice sample question

  - by andy boot

  I am reading "Java Concurrency in practice" and looking at the example code on page 51. This states that if a thread has references to a shared object then other threads may be able to access that object before the constructor has finished executing. I have tried to put this into practice and so I wrote this code thinking that if I ran it enough times a RuntimeException("World is f*cked") would occur. But it isn't doing. Is this a case of the Java spec not guaranting something but my particular implementation of java guaranteeing it for me? (java version: 1.5.0 on Ubuntu) Or have I misread something in the book? Code: (I expect an exception but it is never thrown) public class Threads { private Widgit w; public static void main(String[] s) throws Exception { while(true){ Threads t = new Threads(); t.runThreads(); } } private void runThreads() throws Exception{ new Checker().start(); w = new Widgit((int)(Math.random() * 100) + 1); } private class Checker extends Thread{ private static final int LOOP_TIMES = 1000; public void run() { int count = 0; for(int i = 0; i < LOOP_TIMES; i++){ try { w.checkMe(); count++; } catch(NullPointerException npe){ //ignore } } System.out.println("checked: "+count+" times out of "+LOOP_TIMES); } } private static class Widgit{ private int n; private int n2; Widgit(int n) throws InterruptedException{ this.n = n; Thread.sleep(2); this.n2 = n; } void checkMe(){ if (n != n2) { throw new RuntimeException("World is f*cked"); } } } }

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• Looking for a RESTful or SOAP pipeline between WordPress and InterWoven TeamSite

  - by deanpeters

  I've been Googling my brains out trying see if there's a simple way to bridge content to and from WordPress to and from TeamSite. I'm coming at this from the perspective of a WordPress developer. I see in the book "The Definitive Guide to Interwoven TeamSite" (http://bit.ly/d3z4wI) mention of objects for the Interwoven LiveSite product: com.interwoven.livesite.external.impl.RSS com.interwoven.livesite.external.impl.SOAP If I understand the above objects correctly, these allow me to instantiate objects of these data types, which after populating them via various method calls, allow me to render content using com.interwoven.livesite.external.ExternalCall ... but I'm not sure. Nor do I think this approach provides me the 2-way street I seek. As it stands now, from my limited understanding, it appears that the least path of resistance is deploying Interwoven's LiveSite with the existing TeamSite implementation so content can be both consumed and rendered via RSS ... an channel which WordPress can produce and consume; the latter with plugins such as wp-o-matic and/or feedpress. So the question is, does anyone out there have experience with a SOAP or RESTful API approach to InterWoven's TeamSite? If so, can I get some direction on documentation? Or is the addition of LiveSite + RSS the most feasible 2-way channel?

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• Why does grails use hsqldb when I ask for mysql?

  - by John

  I'm following the racetrack example from Jason Rudolph's book at InfoQ, using grails-1.2.1. I got up to the part where I was to switch from hsqldb to mysql. I think I've deleted every reference to hsqldb in the DataSource.groovy file, but I get an exception and the stack trace shows it's still using hsqldb. DataSource.groovy dataSource { boolean pooled = true String driverClassName = "com.mysql.jdbc.Driver" String url = "jdbc:mysql://localhost/dfpc2" String dbCreate = "create" String username = "dfpc2" String password = "dfpc2" dialect = org.hibernate.dialect.MySQL5InnoDBDialect } hibernate { cache.use_second_level_cache=true cache.use_query_cache=true cache.provider_class='net.sf.ehcache.hibernate.EhCacheProvider' } // environment specific settings environments { development { } test { } production { } } When I grails run-app it all starts up with no errors. I can navigate to the home page. But when I click on one of the links, I get a stack trace: java.sql.SQLException: Table not found in statement [select this_.id as id0_0_, this_.version as version0_0_, this_.name as name0_0_, this_.variant as variant0_0_ from domainObject this_ limit ?] at org.hsqldb.jdbc.Util.throwError(Unknown Source) at org.hsqldb.jdbc.jdbcPreparedStatement.<init>(Unknown Source) at org.hsqldb.jdbc.jdbcConnection.prepareStatement(Unknown Source) at dfpc2.domainObjectController$_closure2.doCall(script1269434425504953491149.groovy:13) at dfpc2.domainObjectController$_closure2.doCall(script1269434425504953491149.groovy) at java.lang.Thread.run(Thread.java:619) My mysql database shows no tables created. (I don't think groovy's connected to mysql yet.) Things I've checked: mysql-connector-java-5.1.6.jar is in lib directory. I've tried grails clean I tried putting the dataSource info in the development environment (I haven't graduated to test or prod yet), but it seemed to make no difference. The stdout shows I'm using development env. I've googled for solutions, but the only solution I've found is when people don't change the test or production environments.

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• Haskell Cons Operator (:)

  - by Carson Myers

  I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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• NUnit doesn't work well with Assert.AreEqual

  - by stasal

  Hi! I'm new to unit-testing and NUit in particular. I'm just typing some examples from the book which refers to Java and JUnit. But I'm using C# instead. The problem is: I've got a class with overriden methods such as Equals() and GetHashCode(), but when I am trying to compare two objects of this class with Assert.AreEqual() my code is not called, so I get an exception. Assert.True(MyClass.Equals(MyClass2)) does work well. But I don't wanna use this construction instead of Assert.AreEqual(). Where the problem can be? Here is the class: public class Money { public int amount; protected string currency; public Money(int amount, string currency) { this.amount = amount; this.currency = currency; } public new bool Equals(object obj) { if (obj == null) return false; Money money = (Money)obj; return (amount == money.amount) && (Currency().Equals(money.Currency())); } public new int GetHashCode() { return (string.Format("{0}{1}", amount, currency)).GetHashCode(); } public static Money Dollar(int amount) { return new Money(amount, "USD"); } public static Money Franc(int amount) { return new Money(amount, "CHF"); } public Money Times(int multiplier) { return new Money(amount * multiplier, currency); } public string Currency() { return currency; } } And the test method itself: [TestFixture] public class DollarTest { [Test] public void TestMultiplication() { Money five = Money.Dollar(5); Assert.True(Money.Dollar(10).Equals(five.Times(2))); // ok Assert.AreEqual(Money.Dollar(10), five.Times(2)); // fails } } Thanks.

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• jQuery and Ajax

  - by Banderdash

  Can anyone help with a jQuery snippet that would use Ajax to pull an XML file in on page load? Have really clunky way of doing it without jQuery here: <script type="text/javascript"> function loadXMLDoc() { if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); } else {// code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { xmlDoc=xmlhttp.responseXML; var txt=""; x=xmlDoc.getElementsByTagName("title"); for (i=0;i<x.length;i++) { txt=txt + x[i].childNodes[0].nodeValue + "<br />"; } document.getElementById("checkedIn").innerHTML=txt; } } xmlhttp.open("GET","ajax-response-data.xml",true); xmlhttp.send(); } </script> Ideally rather the having a click generate the list it would do so on page load, showing the fields from the XML (title, author, and whether it is checked in or not i.e. <book id="#" checked-in="0">) Would hug you for a solution.

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• Still Confused About Identifying vs. Non-Identifying Relationships

  - by Jason

  So, I've been reading up on identifying vs. non-identifying relationships in my database design, and a number of the answers on SO seem contradicting to me. Here are the two questions I am looking at: What's the Difference Between Identifying and Non-Identifying Relationships Trouble Deciding on Identifying or Non-Identifying Relationship Looking at the top answers from each question, I appear to get two different ideas of what an identifying relationship is. The first question's response says that an identifying relationship "describes a situation in which the existence of a row in the child table depends on a row in the parent table." An example of this that is given is, "An author can write many books (1-to-n relationship), but a book cannot exist without an author." That makes sense to me. However, when I read the response to question two, I get confused as it says, "if a child identifies its parent, it is an identifying relationship." The answer then goes on to give examples such as SSN (is identifying of a Person), but an address is not (because many people can live at an address). To me, this sounds more like a case of the decision between primary key and non-primary key. My own gut feeling (and additional research on other sites) points to the first question and its response being correct. However, I wanted to verify before I continued forward as I don't want to learn something wrong as I am working to understand database design. Thanks in advance.

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• Creation of Objects: Constructors or Static Factory Methods

  - by Rachel

  I am going through Effective Java and some of my things which I consider as standard are not suggested by the book, for instance creation of object, I was under the impression that constructors are the best way of doing it and books says we should make use of static factory methods, I am not able to few some advantages and so disadvantages and so am asking this question, here are the benefits of using it. Advantages: One advantage of static factory methods is that, unlike constructors, they have names. A second advantage of static factory methods is that, unlike constructors, they are not required to create a new object each time they’re invoked. A third advantage of static factory methods is that, unlike constructors, they can return an object of any subtype of their return type. A fourth advantage of static factory methods is that they reduce the verbosity of creating parameterized type instances. I am not able to understand this advantage and would appreciate if someone can explain this point Disadvantages: The main disadvantage of providing only static factory methods is that classes without public or protected constructors cannot be subclassed. A second disadvantage of static factory methods is that they are not readily distinguishable from other static methods.I am not getting this point and so would really appreciate some explanation. Reference: Effective Java, Joshua Bloch, Edition 2, pg: 5-10 Also, How to decide to use whether to go for Constructor or Static Factory Method for Object Creation ?

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• Problem with circular definition in Scheme

  - by user8472

  I am currently working through SICP using Guile as my primary language for the exercises. I have found a strange behavior while implementing the exercises in chapter 3.5. I have reproduced this behavior using Guile 1.4, Guile 1.8.6 and Guile 1.8.7 on a variety of platforms and am certain it is not specific to my setup. This code works fine (and computes e): (define y (integral (delay dy) 1 0.001)) (define dy (stream-map (lambda (x) x) y)) (stream-ref y 1000) The following code should give an identical result: (define (solve f y0 dt) (define y (integral (delay dy) y0 dt)) (define dy (stream-map f y)) y) (solve (lambda (x) x) 1 0.001) But it yields the error message: standard input:7:14: While evaluating arguments to stream-map in expression (stream-map f y): standard input:7:14: Unbound variable: y ABORT: (unbound-variable) So when embedded in a procedure definition, the (define y ...) does not work, whereas outside the procedure in the global environment at the REPL it works fine. What am I doing wrong here? I can post the auxiliary code (i.e., the definitions of integral, stream-map etc.) if necessary, too. With the exception of the system-dependent code for cons-stream, they are all in the book. My own implementation of cons-stream for Guile is as follows: (define-macro (cons-stream a b) `(cons ,a (delay ,b)))

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• Presenting collection of structures of strings in grid or similar in WPF - Example? Ideas?

  - by Andrew

  Hi, I have a collection of structures. The structure is just some strings. Example public struct ReportLine { public string Name; public string Address; public string Phone; ...// about 10 other strings } I can't change this part. What I want to do is display it in a simple grid or simlar in WPF. My only requirements are: a) need column headers b) rows must alternate in color c) columns big enough to hold largest datum (which is not know until run time) Can someone point me to an example to get me started? Is the GridView the way to go? Or DataGrid? Or perhaps just the grid? I have the book Pro WPF in C# 2008 and it covers binding ListBox's to collections, but the collections always seem to be collections of one field (ex. a collection of 40 names). Here I have a collection (an array in fact) of a structure. How do I setup the databinding? As you can see, I'm new to this and probably would most benefit from a reference to an article. I've found articles covering collections of 1 field, but no examples covering binding to an array of structures. Also, my intitial research indicates c) can't be easily done, if you demand that the column is big enough for all the data in that column, not just the visible data. Thanks, dave

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• Grails - Removing an item from a hasMany association List on data bind?

  - by ecrane

  Grails offers the ability to automatically create and bind domain objects to a hasMany List, as described in the grails user guide. So, for example, if my domain object "Author" has a List of many "Book" objects, I could create and bind these using the following markup (from the user guide): <g:textField name="books[0].title" value="the Stand" /> <g:textField name="books[1].title" value="the Shining" /> <g:textField name="books[2].title" value="Red Madder" /> In this case, if any of the books specified don't already exist, Grails will create them and set their titles appropriately. If there are already books in the specified indices, their titles will be updated and they will be saved. My question is: is there some easy way to tell Grails to remove one of those books from the 'books' association on data bind? The most obvious way to do this would be to omit the form element that corresponds to the domain instance you want to delete; unfortunately, this does not work, as per the user guide: Then Grails will automatically create a new instance for you at the defined position. If you "skipped" a few elements in the middle ... Then Grails will automatically create instances in between. I realize that a specific solution could be engineered as part of a command object, or as part of a particular controller- however, the need for this functionality appears repeatedly throughout my application, across multiple domain objects and for associations of many different types of objects. A general solution, therefore, would be ideal. Does anyone know if there is something like this included in Grails?

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• What does this structure actually do?

  - by LGTrader

  I found this structure code in a Julia Set example from a book on CUDA. I'm a newbie C programmer and cannot get my head around what it's doing, nor have I found the right thing to read on the web to clear it up. Here's the structure: struct cuComplex { float r; float i; cuComplex( float a, float b ) : r(a), i(b) {} float magnitude2( void ) { return r * r + i * i; } cuComplex operator*(const cuComplex& a) { return cuComplex(r*a.r - i*a.i, i*a.r + r*a.i); } cuComplex operator+(const cuComplex& a) { return cuComplex(r+a.r, i+a.i); } }; and it's called very simply like this: cuComplex c(-0.8, 0.156); cuComplex a(jx, jy); int i = 0; for (i=0; i<200; i++) { a = a * a + c; if (a.magnitude2() > 1000) return 0; } return 1; So, the code did what? Defined something of structure type 'cuComplex' giving the real and imaginary parts of a number. (-0.8 & 0.156) What is getting returned? (Or placed in the structure?) How do I work through the logic of the operator stuff in the struct to understand what is actually calculated and held there? I think that it's probably doing recursive calls back into the stucture float magnitude2 (void) { return return r * r + i * i; } probably calls the '*' operator for r and again for i, and then the results of those two operations call the '+' operator? Is this correct and what gets returned at each step? Just plain confused. Thanks!

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• MySQL " identify storage engine statement"

  - by sammysmall

  This IS NOT a Homework question! While building my current student database project I realized that I may want to identify comprehensive information about a database design in the future. More-so if I am fortunate enough to get a job in this field and were handed a database project how could I break down certain elements for identification... In all of my previous designs I have been using MySQL Community Server (GPL) 5.1.42, I thought (duh) that I was using the MyISAM based on most of my text-book instruction and MySQL 5.0 Reference Manual :: 13 Storage Engines :: 13.1 The MyISAM Storage Engine I determined that this was in fact incorrect for this version and the use of "SHOW ENGINES" at the console... No problem, figured out why they have "versions" the need to pay attention to what version is being used, and the need for a means to determine what I am about to mess up "if" I do not pay attention to detail... Q1. Specifically what statement will identify the version used by someone elses initial database creation? (since I created my own databases I know what version I used) Q2. Specifically what statement will identify the storage engine that the developer used when creating the database. (I specified a particular database in my collection then tried SHOW Engine, did not work, then tried to just get the metadata from one table in that database: mysql SELECT duck_cust, table_type, engine - FROM INFORMATION_SCHEMA.tables - WHERE table_schema = 'tp' - ORDER BY table_type ASC, table_name DESC; as this was not really what I wanted (and did not work) I am looking for some direction from the pros... Q3. (If you really have the inclination to continue helping) If I were to access a database from an earlier/later "version" are there backward/forward compatibility issues for maintaining/updating data between versions? Please and Thank you in advance for your time and efforts! sammysmall

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• Any suggestions to improve my PDO connection class?

  - by Scarface

  Hey guys I am pretty new to pdo so I basically just put together a simple connection class using information out of the introductory book I was reading but is this connection efficient? If anyone has any informative suggestions, I would really appreciate it. class PDOConnectionFactory{ public $con = null; // swich database? public $dbType = "mysql"; // connection parameters public $host = "localhost"; public $user = "user"; public $senha = "password"; public $db = "database"; public $persistent = false; // new PDOConnectionFactory( true ) <--- persistent connection // new PDOConnectionFactory() <--- no persistent connection public function PDOConnectionFactory( $persistent=false ){ // it verifies the persistence of the connection if( $persistent != false){ $this->persistent = true; } } public function getConnection(){ try{ $this->con = new PDO($this->dbType.":host=".$this->host.";dbname=".$this->db, $this->user, $this->senha, array( PDO::ATTR_PERSISTENT => $this->persistent ) ); // carried through successfully, it returns connected return $this->con; // in case that an error occurs, it returns the error; }catch ( PDOException $ex ){ echo "We are currently experiencing technical difficulties. We have a bunch of monkies working really hard to fix the problem. Check back soon: ".$ex->getMessage(); } } // close connection public function Close(){ if( $this->con != null ) $this->con = null; } }

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• How do I count how many arrays have the same name within a multidimensional array with php?

  - by zeckdude

  I have a multidimensional array, and I would have multiple arrays within it. Some of those arrays contain multiple arrays within them as well, and I would like to count how many arrays are within the second array(the date). This is an example of the structure of the multidimensional array: $_SESSION['final_shipping'][04/03/2010][book] $_SESSION['final_shipping'][04/12/2010][magazine] $_SESSION['final_shipping'][04/12/2010][cd] This is the foreach statement I am currently using to count how many of the second array(the one with the dates) exists. foreach($_SESSION['final_shipping'] as $date_key => $date_value) { foreach ($date_value as $product_key => $product_value) { echo 'There are ' . count($date_key) . ' of the ' . $date_key . ' selection.<br/>'; } } It is currently outputting this: There are 1 of the 04/03/2010 selection. There are 1 of the 04/12/2010 selection. There are 1 of the 04/12/2010 selection. I would like it to output this: There are 1 of the 04/03/2010 selection. There are 2 of the 04/12/2010 selection.

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• Generic <T> how cast ?

  - by Kris-I

  Hi, I have a "Product" base class, some other classes "ProductBookDetail","ProductDVDDetail" inherit from this class. I use a ProductService class to make operation on these classes. But, I have to do some check depending of the type (ISBN for Book, languages for DVD). I'd like to know the best way to cast "productDetail" value, I receive in SaveOrupdate. I tried GetType() and cast with (ProductBookDetail)productDetail but that's not work. Thanks, var productDetail = new ProductDetailBook() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailBook>>(); service.SaveOrUpdate(productDetail); var productDetail = new ProductDetailDVD() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailDVD>>(); service.SaveOrUpdate(productDetail); public class ProductServiceGeneric<T> : IProductServiceGeneric<T> { private readonly ISession _session; private readonly IProductRepoGeneric<T> _repo; public ProductServiceGeneric() { _session = UnitOfWork.CurrentSession; _repo = IoC.Resolve<IProductRepoGeneric<T>>(); } public void SaveOrUpdate(T productDetail) { using (ITransaction tx = _session.BeginTransaction()) { //here i'd like ot know the type and access properties depending of the class _repo.SaveOrUpdate(productDetail); tx.Commit(); } } }

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• PHP gettext on Windows

  - by Axsuul

  There's some tutorials out there for gettext (w/ Poedit)... unfortunately, it's mostly for a UNIX environment. And even more unfortunate is that I am running my WAMP server on Windows XP (but I am developing for a UNIX environment) and none of the tutorials can get gettext working properly for me. From the man page (http://us3.php.net/manual/en/book.gettext.php), it appears that it's a different process on a Windows environment. I've tried out some of the solutions in the comments but I still can't get it to work! Please, I've spent many hours on this, hopefully someone can point me in the right direction to get this thing to work! (and I'm sure there are others out there who share my frustration). So far with my setup, I'm only getting output "Hello World!" whereas I should be getting the translated string. Here is my setup/code so far: <?php // test.php if (!defined('LC_MESSAGES')) { define('LC_MESSAGES', 6); } $locale = "deu_DEU"; // apparently the locales are different on a WINDOWS platform putenv("LC_ALL=$locale"); setlocale(LC_ALL, $locale); bindtextdomain("greetings", ".\locale"); textdomain("greetings"); echo _("Hello World"); ?> Folder structure root: C:\Program Files\WampServer 2\www test.php: C:\Program Files\WampServer 2\www\site .po: C:\Program Files\WampServer 2\www\site\locale\deu_DEU\LC_MESSAGES\greetings.po .mo: C:\Program Files\WampServer 2\www\site\locale\deu_DEU\LC_MESSAGES\greetings.mo Please advise! Thanks for your time :)

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