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• Some questions regarding Flex

  - by Rachel

  For what real time scenarios/use cases one should go to Flex Technology ? What real time problems you have solved using Flex Technology ? What real time problems have you faced because of using Flex Technology and what was your work around for that use case ?

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• What is an index in MySQL?

  - by Eric

  http://i.imgur.com/JdsUK.jpg I created a table like the picture above. What are the "Indexes"? primary key? unique? It works well without setting indexes.. What do they do? why do I need them? Also, I set all String fields to TEXT because I didn't know how many characters I need. Is this a good idea? I don't see any difference. Thanks!

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• Bad method names and what it says about code structure.

  - by maxfridbe

  (Apologies in advance if this is a re-post but I didn't find similar posts) What bad method name patterns have you seen in code and what did it tell you about the code. For instance, I keep seeing: public void preform___X___IfNecessary(...); I believe that this is bad because the operation X has an inversion of conditions. Note that this is a public method because classes methods might legitimately require private helpers like this

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• Are these jobs for developer or designers or for client itself?

  - by jitendra

  Spell checking grammar checking Descriptive alt text for big chart , graph images, technical images To write Table summary and caption Descriptive Link text Color Contrast checking Deciding in content what should be H2 ,H3, H4... and what should be <strong> or <span class="boldtext"> Meta Description and keywords for each pages Image compression To decide Filenames for images,PDf etc To decide Page's <title> for each page

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• Refactor/rewrite code or continue?

  - by Dan

  I just completed a complex piece of code. It works to spec, it meets performance requirements etc etc but I feel a bit anxious about it and am considering rewriting and/or refactoring it. Should I do this (spending time that could otherwise be spent on features that users will actually notice)? The reasons I feel anxious about the code are: The class hierarchy is complex and not obvious Some classes don't have a well defined purpose (they do a number of unrelated things) Some classes use others internals (they're declared as friend classes) to bypass the layers of abstraction for performance, but I feel they break encapsulation by doing this Some classes leak implementation details (eg, I changed a map to a hash map earlier and found myself having to modify code in other source files to make the change work) My memory management/pooling system is kinda clunky and less-than transparent They look like excellent reasons to refactor and clean code, aiding future maintenance and extension, but could be quite time consuming. Also, I'll never be perfectly happy with any code I write anyway... So, what does stackoverflow think? Clean code or work on features?

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• Start thread with two parameters

  - by Matt

  I've got a method that gets called on an event, which presents me with two variables varA, varB (both strings). This method gets called with new information quite frequently, thus I have created a separate method that takes in the two parameters. I want to run this method in a thread, however have struck the issue that Thread.Start will not accept parameters. I've tried a few supposed methods, but have so far had no luck.. I think my best bet is to create a separate class, and handle it there.. However I have a List which I am inserting data into, and hit a dead end when the separate class tried to access that list, since it was in a different class. Can someone help me out here please?

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• Business Applications: What are the fundemental features of a search form?

  - by Jonathan Allen

  In a typical business application it is quite common to have forms that are used for searching. Some basic features are: A pane that contains the search criteria A grid to display the results Sorting on the grid A detail page that opens when an item is selected in the results grid What other features would you expect in a business application's search functionality?

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• Help required in adding new methods, properties into existing classes dynamically

  - by Bepenfriends

  Hi All, I am not sure whether it is possible to achieve this kind of implementation in Dot Net. Below are the information Currently we are on an application which is done in COM+, ASP, XSL, XML technologies. It is a multi tier architecture application in which COM+ acts as the BAL. The execution steps for any CRUD operation will be defined using a seperate UI which uses XML to store the information. BAL reads the XML and understands the execution steps which are defined and executes corresponding methods in DLL. Much like EDM we have our custom model (using XML) which determines which property of object is searchable, retrievable etc. Based on this information BAL constructs queries and calls procedures to get the data. In the current application both BAL and DAL are heavily customizable without doing any code change. the results will be transmitted to presentation layer in XML format which constructs the UI based on the data recieved. Now I am creating a migration project which deals with employee information. It is also going to follow the N Tier architecture in which the presentation layer communicates with BAL which connects to DAL to return the Data. Here is the problem, In our existing version we are handling every information as XML in its native form (no converstion of object etc), but in the migration project, Team is really interested in utilizing the OOP model of development where every information which is sent from BAL need to be converted to objects of its respective types (example employeeCollection, Address Collection etc). If we have the static number of data returned from BAL we can have a class which contains those nodes as properties and we can access the same. But in our case the data returned from our BAL need to be customized. How can we handle the customization in presentation layer which is converting the result to an Object. Below is an example of the XML returned <employees> <employee> <firstName>Employee 1 First Name</firstName> <lastName>Employee 1 Last Name</lastName> <addresses> <address> <addressType>1</addressType> <StreetName>Street name1</StreetName> <RegionName>Region name</RegionName> <address> <address> <addressType>2</addressType> <StreetName>Street name2</StreetName> <RegionName>Region name</RegionName> <address> <address> <addressType>3</addressType> <StreetName>Street name3</StreetName> <RegionName>Region name</RegionName> <address> <addresses> </employee> <employee> <firstName>Employee 2 First Name</firstName> <lastName>Employee 2 Last Name</lastName> <addresses> <address> <addressType>1</addressType> <StreetName>Street name1</StreetName> <RegionName>Region name</RegionName> <address> <address> <addressType>2</addressType> <StreetName>Street name2</StreetName> <RegionName>Region name</RegionName> <address> <addresses> </employee> </employees> If these are the only columns then i can write a class which is like public class Address{ public int AddressType {get;set;}; public string StreetName {get;set;}; public string RegionName {get;set;}; } public class Employee{ public string FirstName {get; set;} public string LastName {get; set;} public string AddressCollection {get; set;} } public class EmployeeCollection : List<Employee>{ public bool Add (Employee Data){ .... } } public class AddressCollection : List<Address>{ public bool Add (Address Data){ .... } } This class will be provided to customers and consultants as DLLs. We will not provide the source code for the same. Now when the consultants or customers does customization(example adding country to address and adding passport information object with employee object) they must be able to access those properties in these classes, but without source code they will not be able to do those modifications.which makes the application useless. Is there is any way to acomplish this in DotNet. I thought of using Anonymous classes but, the problem with Anonymous classes are we can not have methods in it. I am not sure how can i fit the collection objects (which will be inturn an anonymous class) Not sure about datagrid / user control binding etc. I also thought of using CODEDom to create classes runtime but not sure about the meory, performance issues. also the classes must be created only once and must use the same till there is another change. Kindly help me out in this problem. Any kind of help meterial/ cryptic code/ links will be helpful.

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• Three level database - foreign keys

  - by poke

  I have a three level database with the following structure (simplified to only show the primary keys): Table A: a_id Table B: a_id, b_id Table C: a_id, b_id, c_id So possible values for table C would be something like this: a_id b_id c_id 1 1 1 1 1 2 1 1 3 1 2 1 1 2 2 2 1 1 2 2 1 2 2 2 ... I am now unsure, how foreign keys should be set; or if they should be set for the primary keys at all. My idea was to have a foreign key on table B B.a_id -> A.a_id, and two foreign key on C C.a_id -> A.a_id and ( C.a_id, C.b_id ) -> ( B.a_id, B.b_id ). Is that the way I should set up the foreign keys? Is the foreign key from C->A necessary? Or do I even need foreign keys at all given that all those columns are part of the primary keys? Thanks.

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• Dealing with dependencies between WCF services when using Castle Windsor

  - by Georgia Brown

  I have several WCF services which use castle windsor to resolve their dependencies. Now I need some of these services to talk to each other. The typical structure is service -- Business Logic -- DAL The calls to the other services need to occur at Business Logic level. What is the best approach for implementing this? Should I simply inject a service proxy into the business logic? Is this wasteful if for example, only one of two method from my service need to use this proxy? What if the services need to talk to each other? - Will castle windsor get stuck in a loop trying to resolve each services dependencies?

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• Pros and Cons on where to place business logic: app level or DB

  - by Juri

  Hi, I always again encounter discussions about where to place the business logic: inside a business layer in the application code or down in the DB in terms of stored procedures. Personally I'd tend to the 1st approach, but I'd like to hear some opinions from your part first, without influencing you with my personal views. I know there doesn't exist a one-size-fits-all solution and it often depends on many factors, but we can discuss about that. Btw, we are in the context of web applications and our current approach is to have UI layer which accepts UI input and does a first, client-side validation Business layer with a number of service-classes which contains the business logic including validation for user input (server-side) Data Access Layer which calls stored procedures from the DB for doing persistency/read operations Many people however tend to move the business layer stuff (especially regarding the validation) down to the DB in terms of stored procedures. What do you think about it? I'd like to discuss.

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• how do simple SQLAlchemy relationships work?

  - by Carson Myers

  I'm no database expert -- I just know the basics, really. I've picked up SQLAlchemy for a small project, and I'm using the declarative base configuration rather than the "normal" way. This way seems a lot simpler. However, while setting up my database schema, I realized I don't understand some database relationship concepts. If I had a many-to-one relationship before, for example, articles by authors (where each article could be written by only a single author), I would put an author_id field in my articles column. But SQLAlchemy has this ForeignKey object, and a relationship function with a backref kwarg, and I have no idea what any of it MEANS. I'm scared to find out what a many-to-many relationship with an intermediate table looks like (when I need additional data about each relationship). Can someone demystify this for me? Right now I'm setting up to allow openID auth for my application. So I've got this: from __init__ import Base from sqlalchemy.schema import Column from sqlalchemy.types import Integer, String class Users(Base): __tablename__ = 'users' id = Column(Integer, primary_key=True) username = Column(String, unique=True) email = Column(String) password = Column(String) salt = Column(String) class OpenID(Base): __tablename__ = 'openid' url = Column(String, primary_key=True) user_id = #? I think the ? should be replaced by Column(Integer, ForeignKey('users.id')), but I'm not sure -- and do I need to put openids = relationship("OpenID", backref="users") in the Users class? Why? What does it do? What is a backref?

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• ASP.NET sets of technologies/components

  - by Maxim Gueivandov

  Just a question of pure curiosity. It happens that development teams tend to stick to the same technological set(s) for some time, for various reasons (obviously, the lack of time, money, necessity and/or willingless to adopt new technologies). So, what are your usual sets of technologies/components to build an ASP.NET application (e.g., WebForms / MVC, Automapper, NInject, NHibernate / LinqToSql, JQuery / ASP.NET Ajax, ...) or architectural frameworks (Arch#, Catharsis, ...) and in which context do you use them (site size, speed/availability requirements, etc.)?

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• Using Doctrine to abstract CRUD operations

  - by TomWilsonFL

  This has bothered me for quite a while, but now it is necessity that I find the answer. We are working on quite a large project using CodeIgniter plus Doctrine. Our application has a front end and also an admin area for the company to check/change/delete data. When we designed the front end, we simply consumed most of the Doctrine code right in the controller: //In semi-pseudocode function register() { $data = get_post_data(); if (count($data) && isValid($data)) { $U = new User(); $U->fromArray($data); $U->save(); $C = new Customer(); $C->fromArray($data); $C->user_id = $U->id; $C->save(); redirect_to_next_step(); } } Obviously when we went to do the admin views code duplication began and considering we were in a "get it DONE" mode so it now stinks with code bloat. I have moved a lot of functionality (business logic) into the model using model methods, but the basic CRUD does not fit there. I was going to attempt to place the CRUD into static methods, i.e. Customer::save($array) [would perform both insert and update depending on if prikey is present in array], Customer::delete($id), Customer::getObj($id = false) [if false, get all data]. This is going to become painful though for 32 model objects (and growing). Also, at times models need to interact (as the interaction above between user data and customer data), which can't be done in a static method without breaking encapsulation. I envision adding another layer to this (exposing web services), so knowing there are going to be 3 "controllers" at some point I need to encapsulate this CRUD somewhere (obviously), but are static methods the way to go, or is there another road? Your input is much appreciated.

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• PHP MVC Framework Structure

  - by bigstylee

  I am sorry about the amount of code here. I have tried to show enough for understanding while avoiding confusion (I hope). I have included a second copy of the code at Pastebin. (The code does execute without error/notice/warning.) I am currently creating a Content Management System while trying to implement the idea of Model View Controller. I have only recently come across the concept of MVC (within the last week) and trying to implement this into my current project. One of the features of the CMS is dynamic/customisable menu areas and each feature will be represented by a controller. Therefore there will be multiple versions of the Controller Class, each with specific extended functionality. I have looked at a number of tutorials and read some open source solutions to the MVC Framework. I am now trying to create a lightweight solution for my specific requirements. I am not interested in backwards compatibility, I am using PHP 5.3. An advantage of the Base class is not having to use global and can directly access any loaded class using $this->Obj['ClassName']->property/function();. Hoping to get some feedback using the basic structure outlined (with performance in mind). Specifically; a) Have I understood/implemented the concept of MVC correctly? b) Have I understood/implemented Object Orientated techniques with PHP 5 correctly? c) Should the class propertise of Base be static? d) Improvements? Thank you very much in advance! <?php /* A "Super Class" that creates/stores all object instances */ class Base { public static $Obj = array(); // Not sure this is the correct use of the "static" keyword? public static $var; static public function load_class($directory, $class) { echo count(self::$Obj)."\n"; // This does show the array is getting updated and not creating a new array :) if (!isset(self::$Obj[$class]) && !is_object(self::$Obj[$class])) //dont want to load it twice { /* Locate and include the class file based upon name ($class) */ return self::$Obj[$class] = new $class(); } return TRUE; } } /* Loads general configuration objects into the "Super Class" */ class Libraries extends Base { public function __construct(){ $this->load_class('library', 'Database'); $this->load_class('library', 'Session'); self::$var = 'Hello World!'; //testing visibility /* Other general funciton classes */ } } class Database extends Base { /* Connects to the the database and executes all queries */ public function query(){} } class Session extends Base { /* Implements Sessions in database (read/write) */ } /* General functionality of controllers */ abstract class Controller extends Base { protected function load_model($class, $method) { /* Locate and include the model file */ $this->load_class('model', $class); call_user_func(array(self::$Obj[$class], $method)); } protected function load_view($name) { /* Locate and include the view file */ #include('views/'.$name.'.php'); } } abstract class View extends Base { /* ... */ } abstract class Model extends Base { /* ... */ } class News extends Controller { public function index() { /* Displays the 5 most recent News articles and displays with Content Area */ $this->load_model('NewsModel', 'index'); $this->load_view('news', 'index'); echo $this->var; } public function menu() { /* Displays the News Title of the 5 most recent News articles and displays within the Menu Area */ $this->load_model('news/index'); $this->load_view('news/index'); } } class ChatBox extends Controller { /* ... */ } /* Lots of different features extending the controller/view/model class depending upon request and layout */ class NewsModel extends Model { public function index() { echo $this->var; self::$Obj['Database']->query(/*SELECT 5 most recent news articles*/); } public function menu() { /* ... */ } } $Libraries = new Libraries; $controller = 'News'; // Would be determined from Query String $method = 'index'; // Would be determined from Query String $Content = $Libraries->load_class('controller', $controller); //create the controller for the specific page if (in_array($method, get_class_methods($Content))) { call_user_func(array($Content, $method)); } else { die('Bad Request'. $method); } $Content::$var = 'Goodbye World'; echo $Libraries::$var . ' - ' . $Content::$var; ?> /* Ouput */ 0 1 2 3 Goodbye World! - Goodbye World

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• How to use yahoo UI in my page.

  - by Ayyappan.Anbalagan

  I need to include any dll in my asp.net project?.Is that good to use in web page my page..

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• actionscript-3: refactor interface inheritance to get rid of ambiguous reference error

  - by maxmc

  hi! imagine there are two interfaces arranged via composite pattern, one of them has a dispose method among other methods: interface IComponent extends ILeaf { ... function dispose() : void; } interface ILeaf { ... } some implementations have some more things in common (say an id) so there are two more interfaces: interface ICommonLeaf extends ILeaf { function get id() : String; } interface ICommonComponent extends ICommonLeaf, IComponent { } so far so good. but there is another interface which also has a dispose method: interface ISomething { ... function dispose() : void; } and ISomething is inherited by ICommonLeaf: interface ICommonLeaf extends ILeaf, ISomething { function get id() : String; } As soon as the dispose method is invoked on an instance which implements the ICommonComponent interface, the compiler fails with an ambiguous reference error because ISomething has a method called dispose and ILeaf also has a dispose method, both living in different interfaces (IComponent, ISomething) within the inheritace tree of ICommonComponent. I wonder how to deal with the situation if the IComponent, the ILeaf and the ISomething can't change. the composite structure must also work for for the ICommonLeaf & ICommonComponent implementations and the ICommonLeaf & ICommonComponent must conform to the ISomething type. this might be an actionscript-3 specific issue. i haven't tested how other languages (for instance java) handle stuff like this.

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• What is the best database structure for this scenario?

  - by Ricketts

  I have a database that is holding real estate MLS (Multiple Listing Service) data. Currently, I have a single table that holds all the listing attributes (price, address, sqft, etc.). There are several different property types (residential, commercial, rental, income, land, etc.) and each property type share a majority of the attributes, but there are a few that are unique to that property type. My question is the shared attributes are in excess of 250 fields and this seems like too many fields to have in a single table. My thought is I could break them out into an EAV (Entity-Attribute-Value) format, but I've read many bad things about that and it would make running queries a real pain as any of the 250 fields could be searched on. If I were to go that route, I'd literally have to pull all the data out of the EAV table, grouped by listing id, merge it on the application side, then run my query against the in memory object collection. This also does not seem very efficient. I am looking for some ideas or recommendations on which way to proceed. Perhaps the 250+ field table is the only way to proceed. Just as a note, I'm using SQL Server 2012, .NET 4.5 w/ Entity Framework 5, C# and data is passed to asp.net web application via WCF service. Thanks in advance.

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• Need to work out database structure

  - by jim smith

  Hi, Just need a little kickstart with this. I have Mysql/PHP, and I have 5,000 products. I have 30 companies I need to store some data for those 30 companies for each product as follows: a) prices b) stock qty I also need to store data historically on a daily basis. So the table... It makes sense that the records will be the products because there's 5000, and if I put the companies as the columns, I can store the prices, but what about the stock quantities? I could create two columns for each compoany, one for prices, one for qty. Then make the tablename the date for that day...so theer would be a new table for every day with 5000 products in it? is this the correct way? Some idea on how I'll be retreiving data the top 5 lowest prices (and the company) by product for a certain date the price and stock changes in the past 7 days by product

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• Drop Shadow Center Column Website web page

  - by hagope

  How can I add a drop shadow effect to a website that has one center column? Some examples of what I mean: lala.com mint.com

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• Custom language - FOR loop in a clojure interpeter?

  - by Mark

  I have a basic interpreter in clojure. Now i need to implement for (initialisation; finish-test; loop-update) { statements } Implement a similar for-loop for the interpreted language. The pattern will be: (for variable-declarations end-test loop-update do statement) The variable-declarations will set up initial values for variables.The end-test returns a boolean, and the loop will end if end-test returns false. The statement is interpreted followed by the loop-update for each pass of the loop. Examples of use are: (run ’(for ((i 0)) (< i 10) (set i (+ 1 i)) do (println i))) (run ’(for ((i 0) (j 0)) (< i 10) (seq (set i (+ 1 i)) (set j (+ j (* 2 i)))) do (println j))) inside my interpreter. I will attach my interpreter code I got so far. Any help is appreciated. Interpreter (declare interpret make-env) ;; needed as language terms call out to 'interpret' (def do-trace false) ;; change to 'true' to show calls to 'interpret' ;; simple utilities (def third ; return third item in a list (fn [a-list] (second (rest a-list)))) (def fourth ; return fourth item in a list (fn [a-list] (third (rest a-list)))) (def run ; make it easy to test the interpreter (fn [e] (println "Processing: " e) (println "=> " (interpret e (make-env))))) ;; for the environment (def make-env (fn [] '())) (def add-var (fn [env var val] (cons (list var val) env))) (def lookup-var (fn [env var] (cond (empty? env) 'error (= (first (first env)) var) (second (first env)) :else (lookup-var (rest env) var)))) ;; for terms in language ;; -- define numbers (def is-number? (fn [expn] (number? expn))) (def interpret-number (fn [expn env] expn)) ;; -- define symbols (def is-symbol? (fn [expn] (symbol? expn))) (def interpret-symbol (fn [expn env] (lookup-var env expn))) ;; -- define boolean (def is-boolean? (fn [expn] (or (= expn 'true) (= expn 'false)))) (def interpret-boolean (fn [expn env] expn)) ;; -- define functions (def is-function? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'lambda (first expn))))) (def interpret-function ; keep function definitions as they are written (fn [expn env] expn)) ;; -- define addition (def is-plus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '+ (first expn))))) (def interpret-plus (fn [expn env] (+ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define subtraction (def is-minus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '- (first expn))))) (def interpret-minus (fn [expn env] (- (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define multiplication (def is-times? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '* (first expn))))) (def interpret-times (fn [expn env] (* (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define division (def is-divides? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '/ (first expn))))) (def interpret-divides (fn [expn env] (/ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define equals test (def is-equals? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '= (first expn))))) (def interpret-equals (fn [expn env] (= (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define greater-than test (def is-greater-than? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '> (first expn))))) (def interpret-greater-than (fn [expn env] (> (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define not (def is-not? (fn [expn] (and (list? expn) (= 2 (count expn)) (= 'not (first expn))))) (def interpret-not (fn [expn env] (not (interpret (second expn) env)))) ;; -- define or (def is-or? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'or (first expn))))) (def interpret-or (fn [expn env] (or (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define and (def is-and? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'and (first expn))))) (def interpret-and (fn [expn env] (and (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define print (def is-print? (fn [expn] (and (list? expn) (= 2 (count expn)) (= 'println (first expn))))) (def interpret-print (fn [expn env] (println (interpret (second expn) env)))) ;; -- define with (def is-with? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'with (first expn))))) (def interpret-with (fn [expn env] (interpret (third expn) (add-var env (first (second expn)) (interpret (second (second expn)) env))))) ;; -- define if (def is-if? (fn [expn] (and (list? expn) (= 4 (count expn)) (= 'if (first expn))))) (def interpret-if (fn [expn env] (cond (interpret (second expn) env) (interpret (third expn) env) :else (interpret (fourth expn) env)))) ;; -- define function-application (def is-function-application? (fn [expn env] (and (list? expn) (= 2 (count expn)) (is-function? (interpret (first expn) env))))) (def interpret-function-application (fn [expn env] (let [function (interpret (first expn) env)] (interpret (third function) (add-var env (first (second function)) (interpret (second expn) env)))))) ;; the interpreter itself (def interpret (fn [expn env] (cond do-trace (println "Interpret is processing: " expn)) (cond ; basic values (is-number? expn) (interpret-number expn env) (is-symbol? expn) (interpret-symbol expn env) (is-boolean? expn) (interpret-boolean expn env) (is-function? expn) (interpret-function expn env) ; built-in functions (is-plus? expn) (interpret-plus expn env) (is-minus? expn) (interpret-minus expn env) (is-times? expn) (interpret-times expn env) (is-divides? expn) (interpret-divides expn env) (is-equals? expn) (interpret-equals expn env) (is-greater-than? expn) (interpret-greater-than expn env) (is-not? expn) (interpret-not expn env) (is-or? expn) (interpret-or expn env) (is-and? expn) (interpret-and expn env) (is-print? expn) (interpret-print expn env) ; special syntax (is-with? expn) (interpret-with expn env) (is-if? expn) (interpret-if expn env) ; functions (is-function-application? expn env) (interpret-function-application expn env) :else 'error))) ;; tests of using environment (println "Environment tests:") (println (add-var (make-env) 'x 1)) (println (add-var (add-var (add-var (make-env) 'x 1) 'y 2) 'x 3)) (println (lookup-var '() 'x)) (println (lookup-var '((x 1)) 'x)) (println (lookup-var '((x 1) (y 2)) 'x)) (println (lookup-var '((x 1) (y 2)) 'y)) (println (lookup-var '((x 3) (y 2) (x 1)) 'x)) ;; examples of using interpreter (println "Interpreter examples:") (run '1) (run '2) (run '(+ 1 2)) (run '(/ (* (+ 4 5) (- 2 4)) 2)) (run '(with (x 1) x)) (run '(with (x 1) (with (y 2) (+ x y)))) (run '(with (x (+ 2 4)) x)) (run 'false) (run '(not false)) (run '(with (x true) (with (y false) (or x y)))) (run '(or (= 3 4) (> 4 3))) (run '(with (x 1) (if (= x 1) 2 3))) (run '(with (x 2) (if (= x 1) 2 3))) (run '((lambda (n) (* 2 n)) 4)) (run '(with (double (lambda (n) (* 2 n))) (double 4))) (run '(with (sum-to (lambda (n) (if (= n 0) 0 (+ n (sum-to (- n 1)))))) (sum-to 100))) (run '(with (x 1) (with (f (lambda (n) (+ n x))) (with (x 2) (println (f 3))))))

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• Just wondering what is the reason of InvalidOperationException in Enumerable.Aggregate<TSource>?

  - by the_joric

  Why only one overload throws this exception?

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• Active Record/ORM vs Normal Forms?

  - by Arsenal

  Hello, I've been playing around with Active Record a bit, and I have noticed that A.C./ORM always uses the following database model when creating a one-to-one relationship Person id | country_id | name | ... Country id | tld | name | ... No I wondered, isn't this a violiation of the third Normal Form? This clearly states "Every non-prime attribute is non-transitively dependent on every key of the table". Well this country_id isn't dependent of personid is it? So is this wrong or am I just not getting the point?

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• How to maintain an ordered table with Core Data (or SQL) with insertions/deletions?

  - by Jean-Denis Muys

  This question is in the context of Core Data, but if I am not mistaken, it applies equally well to a more general SQL case. I want to maintain an ordered table using Core Data, with the possibility for the user to: reorder rows insert new lines anywhere delete any existing line What's the best data model to do that? I can see two ways: 1) Model it as an array: I add an int position property to my entity 2) Model it as a linked list: I add two one-to-one relations, next and previous from my entity to itself 1) makes it easy to sort, but painful to insert or delete as you then have to update the position of all objects that come after 2) makes it easy to insert or delete, but very difficult to sort. In fact, I don't think I know how to express a Sort Descriptor (SQL ORDER BY clause) for that case. Now I can imagine a variation on 1): 3) add an int ordering property to the entity, but instead of having it count one-by-one, have it count 100 by 100 (for example). Then inserting is as simple as finding any number between the ordering of the previous and next existing objects. The expensive renumbering only has to occur when the 100 holes have been filled. Making that property a float rather than an int makes it even better: it's almost always possible to find a new float midway between two floats. Am I on the right track with solution 3), or is there something smarter?

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• Domain model: should things like Logging, Audit, Persistence be in it

  - by hom.tanks

  I'm having a hard time convincing our architect that a Domain model should only have the essential elements of the business domain on it. Things like the fact that a class is persistable, that it needs logging and auditing and that it has a RESTful URI should not drive the domain model. They can be added later on, by using interfaces. Ours is a healthcare information management system. At the very coarse level, its a system where users login and access their healthcare information. They can share this information with others and be custodian for others' information (think Roles). But because of a few sound bytes that caught on early like "Everything should be a REST resource" the model now has a top level class called Resource that every other class extends from. I'm trying to make him see that the domain model should have well defined concepts like User Account, HealthDocument, UserRole etc which are distinct entities of the business , with specific associations between them. Clubbing everything under Resource class lets our model be inflexible besides being potentially incorrect. But he wants me to show him why its a bad idea to do it his way. I don't know how to articulate that properly but all my OO instincts tell me that its just not right. Any thoughts?

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