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• Are there programming languages that allow you to do set arithmetic on types?

  - by Will Brown

  Out of curiosity, are there languages that allow you to do set arithmetic on types to create new types? Something like: interface A { void a(); void b(); } interface B { void b(); void c(); } interface C = A & B; // has b() interface D = A | B; // has a(), b() and c() interface E = (A & B) ^ B; // has c() I know that in some languages these ideas can be expressed (i.e., Java has List<Comparable & Serializable> for the union of the interfaces) but I've never heard of a language that supports type arithmetic. Thanks!

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• What should one keep in mind when switching from traditional to RESTful routing in Rails?

  - by Brian Holder-Chow

  What should one keep in mind when switching from traditional to RESTful routing in Rails? From a typical Rails routes.rb file: # This is a legacy wild controller route that's not recommended for RESTful applications. # Note: This route will make all actions in every controller accessible via GET requests. match ':controller(/:action(/:id))(.:format)' As switching away from this means that I will have to create routes for each controller individually, does anyone have any advice on the best way to migrate this safely?

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• What is the ideal length of a method?

  - by iPhoneDeveloper

  In object-oriented programming, there is no exact rule on the maximum length of a method , but I still found these two qutes somewhat contradicting each other, so I would like to hear what you think. In Clean Code: A Handbook of Agile Software Craftsmanship, Robert Martin says: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long. and he gives an example from Java code he sees from Kent Beck: Every function in his program was just two, or three, or four lines long. Each was transparently obvious. Each told a story. And each led you to the next in a compelling order. That’s how short your functions should be! This sounds great, but on the other hand, in Code Complete, Steve McConnell says something very different: The routine should be allowed to grow organically up to 100-200 lines, decades of evidence say that routines of such length no more error prone then shorter routines. And he gives a reference to a study that says routines 65 lines or long are cheaper to develop. So while there are diverging opinions about the matter, is there a functional best-practice towards determining the ideal length of a method for you?

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• Requesting feedback on my OO design

  - by Prog

  I'm working on an application that creates music by itself. I'm seeking feedback for my OO design so far. This question will focus on one part of the program. The application produces Tune objects, that are the final musical products. Tune is an abstract class with an abstract method play. It has two subclasses: SimpleTune and StructuredTune. SimpleTune owns a Melody and a Progression (chord sequence). It's play implementation plays these two objects simultaneously. StructuredTune owns two Tune instances. It's own play plays the two Tunes one after the other according to a pattern (currently only ABAB). Melody is an abstract class with an abstract play method. It has two subclasses: SimpleMelody and StructuredMelody. SimpleMelody is composed of an array of notes. Invoking play on it plays these notes one after the other. StructuredMelody is composed of an array of Melody objects. Invoking play on it plays these Melodyies one after the other. I think you're starting to see the pattern. Progression is also an abstract class with a play method and two subclasses: SimpleProgression and StructuredProgression, each composed differently and played differently. SimpleProgression owns an array of chords and plays them sequentially. StructuredProgression owns an array of Progressions and it's play implementation plays them sequentially. Every class has a corresponding Generator class. Tune, Melody and Progression are matched with corresponding abstract TuneGenerator, MelodyGenerator and ProgressionGenerator classes, each with an abstract generate method. For example MelodyGenerator defines an abstract Melody generate method. Each of the generators has two subclasses, Simple and Structured. So for example MelodyGenerator has a subclasses SimpleMelodyGenerator, with an implementation of generate that returns a SimpleMelody. (It's important to note that the generate methods encapsulate complex algorithms. They are more than mere factory method. For example SimpleProgressionGenerator.generate() implements an algorithm to compose a series of Chord objects, which are used to instantiate the returned SimpleProgression). Every Structured generator uses another generator internally. It is a Simple generator be default, but in special cases may be a Structured generator. Parts of this design are meant to allow the end-user through the GUI to choose what kind of music is to be created. For example the user can choose between a "simple tune" (SimpleTuneGenerator) and a "full tune" (StructuredTuneGenerator). Other parts of the system aren't subject to direct user-control. What do you think of this design from an OOD perspective? What potential problems do you see with this design? Please share with me your criticism, I'm here to learn. Apart from this, a more specific question: the "every class has a corresponding Generator class" part feels very wrong. However I'm not sure how I could design this differently and achieve the same flexibility. Any ideas?

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• TTS on App Engine

  - by yati sagade

  I have written a small front-end to the Festival TTS system using Python/Django. I wish to deploy it on the Google App Engine cloud. A few questions: My application uses the Festival app 'text2wave'. Will is work on the cloud? I have used Python primitives like subprocess.call() to invoke the aforementioned program. Will that work? If your answer to any or both of (1) and (2) is no, is there a free api on the web that I can use (from the appengine)? I read somewhere about placing calls from Phono to a Voxeo backend, but I'm not sure what that means. I am aware of the Google Translate extension that allows translation using an HTTP GET (REST) request, but here the text is limited to 100 chars. Bad. Plus, they may take it down any point of time.

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• Distributed transactions and queues, ruby, erlang

  - by chrispanda

  I have a problem that involves several machines, message queues, and transactions. So for example a user clicks on a web page, the click sends a message to another machine which adds a payment to the user's account. There may be many thousands of clicks per second. All aspects of the transaction should be fault tolerant. I've never had to deal with anything like this before, but a bit of reading suggests this is a well known problem. So to my questions. Am I correct in assuming that secure way of doing this is with a two phase commit, but the protocol is blocking and so I won't get the required performance? It appears that DBs like redis and message queuing system like Rescue, RabbitMQ etc don't really help me a lot - even if I implement some sort of two phase commit, the data will be lost if redis crashes because it is essentially memory-only. All of this has led me to look at erlang - but before I wade in and start learning a new language, I would really like to understand better if this is worth the effort. Specifically, am I right in thinking that because of its parallel processing capabilities, erlang is a better choice for implementing a blocking protocol like two phase commit, or am I confused?

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• Handling Deployment to Multiple Environments

  - by JayGee

  How should I handle deploying web applications to multiple servers? Constraints I have a dev, test and prod environment. No build server is available. Developers can't deploy to prod. The people that do deploy to prod copy files from test to prod. They don't have VS installed. Currently The way it's handled is using web.config transform. However, to deploy to prod involves putting prod code on the test server where it's copied over. Problem Sometimes simple mistakes are made, such as forgetting to change test back to the right environment after deployment. Or the test config gets moved to prod instead of the prod config. Solution So the question is, what is the best way to prevent mistakes from happening? My first thought is let the app determine which server it's on at runtime and use the appropriate settings/connection strings/etc... However, the server names could change in the not too distant future. So if multiple apps are hard coded, that would mean updating all of them. The easiest way to handle that situation would be to place a DLL in the GAC that determines the environment. Are there any drawbacks or possible complications that this would cause? Or is there a better solution to the problem than this?

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• What's the relationship between meta-circular interpreters, virtual machines and increased performance?

  - by Gomi

  I've read about meta-circular interpreters on the web (including SICP) and I've looked into the code of some implementations (such as PyPy and Narcissus). I've read quite a bit about two languages which made great use of metacircular evaluation, Lisp and Smalltalk. As far as I understood Lisp was the first self-hosting compiler and Smalltalk had the first "true" JIT implementation. One thing I've not fully understood is how can those interpreters/compilers achieve so good performance or, in other words, why is PyPy faster than CPython? Is it because of reflection? And also, my Smalltalk research led me to believe that there's a relationship between JIT, virtual machines and reflection. Virtual Machines such as the JVM and CLR allow a great deal of type introspection and I believe they make great use it in Just-in-Time (and AOT, I suppose?) compilation. But as far as I know, Virtual Machines are kind of like CPUs, in that they have a basic instruction set. Are Virtual Machines efficient because they include type and reference information, which would allow language-agnostic reflection? I ask this because many both interpreted and compiled languages are now using bytecode as a target (LLVM, Parrot, YARV, CPython) and traditional VMs like JVM and CLR have gained incredible boosts in performance. I've been told that it's about JIT, but as far as I know JIT is nothing new since Smalltalk and Sun's own Self have been doing it before Java. I don't remember VMs performing particularly well in the past, there weren't many non-academic ones outside of JVM and .NET and their performance was definitely not as good as it is now (I wish I could source this claim but I speak from personal experience). Then all of a sudden, in the late 2000s something changed and a lot of VMs started to pop up even for established languages, and with very good performance. Was something discovered about the JIT implementation that allowed pretty much every modern VM to skyrocket in performance? A paper or a book maybe?

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• Merge two different API calls into One

  - by dhilipsiva

  I have two different apps in my django project. One is "comment" and an other one is "files". A comment might save some file attached to it. The current way of creating a comment with attachments is by making two API calls. First one creates an actual comment and replies with the comment ID which serves as foreign key for the Files. Then for each file, a new request is made with the comment ID. Please note that file is a generic app, that can be used with other apps too. What is the cleanest way of making this into one API call? I want to have this as a single API call because I am in a situation where I need to send user an email with all the files as attachment when a comment is made. I know Queueing is the ideal way to do it. But I don't have the liberty to add queing to our stack now. So this was the only way I could think of.

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• What benefits can I get upgrading my ASP.NET (Webform) + DAL(EF) + Repository + BLL structure to MVC?

  - by Etienne

  I'm in the process of defining an approach that may best fit our needs for a big web application development. For now, I'm thinking going with an ASP.NET Architecture with a DAL using Entity Framework, a Repository concept to not access DAL directly from BLL and a BLL that call the repository and make every manipulations necessary to prepare data to push in a presentation layer (.aspx files). I don't plan to use ASP.Net controls and prefer to keep things simple and lightweight using plain html, jQuery UI controls and do most of the server calls with jQuery Ajax. Sometimes, when needed, I plan to use handlers (.ashx) to call BLL methods that will return JSON or HTML to client for dynamic stuff. My solution also has a test project that Mock the Repository with in-memory data to not repose on database for testing BLL methods... It may be usefull to add that we will build a big application over this architecture with hundreds of tables and store procedures with a lot of reading and writing to database. My question is, having this architecture in mind, Is there any evident advantages that I can obtain by using an MVC3 project instead of the described architecture base on Webform? Do you see any problem in this architecture that may cause us problem during the next steps of development? I know the MVC pattern for using it in others projects with Django... but the Microsoft MVC implementation look so much more complex and verbose than Django MVC and it's why I'm hesitating (or waiting for a little push?) right now before jumping into it... We are in a real project with deadlines and don't want to slow the development process without any real benefits.

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• What's the best way to create a static utility class in python? Is using metaclasses code smell?

  - by rsimp

  Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common code needs to reference the state of the module using it so simple imports wouldn't work well. I don't like singletons, and classes that use the classmethod decorator do not have proper support for python properties. One pattern I see used a lot is creating an internal python class prefixed with an underscore and creating a single instance which is then explicitly imported or set as the module itself. This is also used by fabric to create a common environment object (fabric.api.env). I've realized another way to accomplish this would be with metaclasses. For example: #util.py class MetaFooBase(type): @property def file_path(cls): raise NotImplementedError def inherited_method(cls): print cls.file_path #foo.py from util import * import env class MetaFoo(MetaFooBase): @property def file_path(cls): return env.base_path + "relative/path" def another_class_method(cls): pass class Foo(object): __metaclass__ = MetaFoo #client.py from foo import Foo file_path = Foo.file_path I like this approach better than the first pattern for a few reasons: First, instantiating Foo would be meaningless as it has no attributes or methods, which insures this class acts like a true single interface utility, unlike the first pattern which relies on the underscore convention to dissuade client code from creating more instances of the internal class. Second, sub-classing MetaFoo in a different module wouldn't be as awkward because I wouldn't be importing a class with an underscore which is inherently going against its private naming convention. Third, this seems to be the closest approximation to a static class that exists in python, as all the meta code applies only to the class and not to its instances. This is shown by the common convention of using cls instead of self in the class methods. As well, the base class inherits from type instead of object which would prevent users from trying to use it as a base for other non-static classes. It's implementation as a static class is also apparent when using it by the naming convention Foo, as opposed to foo, which denotes a static class method is being used. As much as I think this is a good fit, I feel that others might feel its not pythonic because its not a sanctioned use for metaclasses which should be avoided 99% of the time. I also find most python devs tend to shy away from metaclasses which might affect code reuse/maintainability. Is this code considered code smell in the python community? I ask because I'm creating a pypi package, and would like to do everything I can to increase adoption.

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• How were the first compilers made?

  - by Sauron

  I always wonder this, and perhaps I need a good history lesson on programming languages. But....since most compilers nowadays are made in C......how were the very first compilers made (AKA before C) or were all the languages just interpreted. With that being said, I still don't understand how even the first assembly language was done, I understand what assembly language is......but I don't see how they got the VERY first assembly language working (like.....how did they make the first commands (like mov R21) or w/e set to the binary equivalent.

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• what's included in a typical computer architecture class? [closed]

  - by sq1020

  Does this description fit what's usually included in a computer architecture class? Computer Organization and Assembly Language An introduction to the hardware organization and assembly language of the Intel processor. Topics include memory hierarchy and design- CPU design- pipelining- addressing modes- subroutine linkage- polled input/output- interrupts- high level language interfacing and macros.

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• Does it help to be core programmer of a product (meant for social good) for getting into a PhD program at a top university?

  - by Maddy.Shik

  Hey i am working upon a product as core developer which will be launched in USA market in few months if successful. Can this factor improve my chances for getting accepted into a PhD program at a top university (say top 20 in US)? Normally good universities like CMU, Standford, MIT, Cornell are more interested in student's profile like research work, undergraduate school, etc. I am now passed out from very good university it's ranked in top 20 of India only. Neither did I do research work till now. But being one of founding member of company and developing product for same, I want to know if this factor can help and to what extent.

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• Innovation on CS

  - by guiman

  Hi all, its been some time that i've been thinking about creating something that could help the web community and leave some mark, but the problem that there are no ideas poping out of my head. So 2 questions comes to my mind: First, how did projects like Twitter, Google or any other big project that had changed our way of living in the internet get started? Secondly, do we have to force it or just keep doing what we do best and wait to that idea that could change things? While writting this question, one quote come to mind: Imagination is more important than knowledge Albert Einstein

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• a little code to allow word substitution depending on user

  - by Fred Quimby

  Can anyone help? I'm creating a demo web app in html in order for people to physically see and comment on the app prior to committing to a proper build. So whilst the proper app will be database driven, my demo is just standard html with some javascript effects. What I do want to demonstrate is that different user group will see different words. For example, imagine I have an html sentence that says 'This will cost £100 to begin'. What I need to some way of identifying that if the user has deemed themselves to be from the US, the sentence says 'This will cost $100 to begin'. This requirement is peppered throughtout the pages but I'm happy to add each one manually. So I envisage some code along the lines of 'first, remove the [boot US] trunk' where the UK version is 'first remove the boot' but the code is saying that the visitor needs the US version. It then looks up boot (in an Access database perhaps) and sees that the table says for boot for US, display 'trunk'. I'm not a programmer but I can normally cobble together scripts so I'm hoping someone may have a relatively easy solution in javascrip, CSS or asp. To recap; I have a number of words or short sentences that need to appear differently and I'm happy to manually insert each one if necessary (but would be even better if the words were automatically changed). And I need a device which allows me to tell the pages to choose the US version, or for example, the New Zealand version. Thanks in advance. Fred

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• Javascript Rookie Question: Define Variables Inline

  - by Dylan Kinnett

  I'm proficient with HTML and CSS but I'm still pretty shaky when it comes to Javascript. That said, I've been able to build a site using the Internet Archive Book Reader, which relies on reader.js Here's a copy of one of my versions of reader.js https://gist.github.com/dylan-k/ed4efed2384e221d46cc It's a good site, but I find I have to repeat things a lot. Basically, I have one copy of reader.js for every page/book featured on the site. It seems there must be a better way. I re-use the script, making copies, just so that I can change lines 28, 80, 83, 84. Is there a way I could include just one copy of reader.js and then use a <script> tag to define these 4 lines for the individual pages?

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• PHP rand function (or not so rand)

  - by Badr Hari

  I was testing PHP rand function to write on a image. Of course the output shows that it's not so random. The code I used: <?php header('Content-Type: image/png'); $lenght = 512; $im = imagecreatetruecolor($lenght, $lenght); $blue = imagecolorallocate($im, 0, 255, 255); for ($y = 0; $y < $lenght; $y++) { for ($x = 0; $x < $lenght; $x++) { if (rand(0,1) == 0) { imagesetpixel($im, $x, $y, $blue); } } } imagepng($im); imagedestroy($im); ?> My question is, if I use image width/lenght (variable $lenght in this example) number like 512, 256 or 1024, it is very clear that it's not so random. When I change the variable to 513 for an example, it is so much harder for human eye to detect it. Why is that? What is so special about these numbers? 512: 513: Edit: I'm running xampp on Windows to test it.

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• I'm a CS student, and honestly I don't understand Knuth's books..

  - by Raymond Ho

  I stumbled this quote from Bill Gates: "You should definitely send me a resume if you can read the whole thing." He was talking about The Art of Programming books.. So I was pretty curious and want to read it all but honestly, I don't understand it at all.. I'm really not that highly intellectual being.. So this should be the reason why I can't understand it, but I am eager to learn.. I'm currently reading volume 1 about fundamental algo.. So is there any books out there that are friendly to novice/slow people like me? So I can build up myself and hopefully in the future I can read Knuth's book at ease..

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• Starting web development with ASP.Net [closed]

  - by nayef harb

  Possible Duplicate: Fastest way to get up to speed on webapp development with ASP.NET? If you develop with ASP.NET, which other technologies do you use? How much do i need to learn in order to get an entry level asp.net job? training plan for asp.net and c# Trying to learn ASP.NET What should every programmer know about web development? I learned web development in ASP.Net couple of month ago in college, nothing serious just couple of general lessons. But now I am confused where to start, should I start with HTML and JavaScript before ASP.Net?

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• Preffered lambda syntax?

  - by Roger Alsing

  I'm playing around a bit with my own C like DSL grammar and would like some oppinions. I've reserved the use of "(...)" for invocations. eg: foo(1,2); My grammar supports "trailing closures" , pretty much like Ruby's blocks that can be passed as the last argument of an invocation. Currently my grammar support trailing closures like this: foo(1,2) { //parameterless closure passed as the last argument to foo } or foo(1,2) [x] { //closure with one argument (x) passed as the last argument to foo print (x); } The reason why I use [args] instead of (args) is that (args) is ambigious: foo(1,2) (x) { } There is no way in this case to tell if foo expects 3 arguments (int,int,closure(x)) or if foo expects 2 arguments and returns a closure with one argument(int,int) - closure(x) So thats pretty much the reason why I use [] as for now. I could change this to something like: foo(1,2) : (x) { } or foo(1,2) (x) -> { } So the actual question is, what do you think looks best? [...] is somewhat wrist unfriendly. let x = [a,b] { } Ideas?

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• On-the-fly graphical representation of code

  - by dukeofgaming

  I know about Omondo's plugin for live code-UML synchronization in Eclipse, but I was wondering if there was any other tool/IDE/IDE-extension that has some form of live graphical code representaiton (structural, flow, call-stacks, dependencies, etc.). I'm essentially looking for richer visual feedback on code while programming, not really looking for purely graphical code editors, though round-trips would be nice (edit graphically, code gets modified; edit code, representation gets modified). If you don't know about any graphical live documentation tool for code, maybe someone that can coexist with code, such as MySQL Workbench or Enterprise Architect.

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• Software Tester to Developer [closed]

  - by Mayu Mayooresan

  Possible Duplicate: How do I become a developer? Its not a question related to programming but related to career. Last 2 and half year I've been working as a Software Tester and i'm seriously considering a track change to programmer. but the problems I think of is.. 1. My age (28) 2. My IT experience with Testing 3. Salary wont match if I change the track as I have to start from scrach. Wot do you think guys?? Please advice me. Is it better to change track or stay in Tester job?? I think I dont seem to like tester job. Please advice. Thanks in advance.

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• Transiltion from maintenance programing to design

  - by andrew wang

  What to do guys do develop a design for a s/w for a given set of requirements? I like many people joined a Semiconductor MNC and got stuck in maintenance for quite a couple of years. My work was usually changing a lines of code for windows drivers supplied by my company or a couple of small script (style like) C programs for validating h/w. As a result I developed the bad habit of 'programming by coincidence'. I have not developed the ability for designing tools/programs from scratch. I was the only s/w member of the local team and thus some grunt work from the well established other site of the company came to be done by me. Now I have moved to a different company and thus finding developing from scratch very difficult. How do I unlearn my bad habit and develop this ability of designing s/w and then coding it ?

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• How to Mentor a Junior Developer

  - by Josh Johnson

  This title is a little broad but I may need to give a little background before I can ask my question properly. I know that similar questions have been asked here already. But in my case I'm not asking if I should be mentoring someone or if the person is a good fit for being a software developer. That is not my place to judge. I have not been asked outright, but it is apparent that myself and other fellow senior developers are to mentor the new developers that start here. I have no problem with this whatsoever and, in many cases, it lends me a fresh perspective on things and I end up learning in the process. Also, I remember how beneficial it was in the beginning of my career when someone would take some time to teach me something. When I say "new developer" they could be anywhere from fresh out of college to having a year or two of experience. Recently and in the past we've had people start here who seem to have an attitude toward development/programming which is different from mine and hard for me to reconcile; they seem to extract just enough information to get the task done but not really learn from it. I find myself going over and over the same issues with them. I understand that part of this could be a personality thing, but I feel it's my job to do my best and sort of push them out of the nest while they're under my wing, so to speak. How can I impart just enough information so that they will learn but not give so much as to solve the problem for them? Or perhaps: What's the proper response to questions that are designed to take the path of least resistance and, in essence, force them to learn instead of take the easy way out? These questions are probably more general teaching questions and don't have that much to do specifically with software development. Note: I do not get a say in what tasks they are working on. Management doles the task out and it could be anything from a very simple bug fix to starting an entire application by themselves. While this is not ideal by any means and obviously presents its own gauntlet of challenges, I feel it's a topic best left for another question. So the best I can do is help them with the problem at hand and try to help them break it down into simpler problems and also check their commit logs and point out mistakes that they made. My main objectives are to: Help them out and give them the tools they need to start becoming more self-reliant. Steer them in the right direction and break bad development habits early on. Lessen the amount of time I spend with them (the personality type described above seems to need much more one-on-one time and does not do well over IM or email. While that's generally fine, I can't always stop what I'm working on, break my stride, and help them debug an error on a moments notice; I have my own projects that need to get done).

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