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  • How can this C and PHP programmer learn Ruby and Rails?

    - by Winston
    I came from a C, php and bash background, it was easy to learn because they all have the same C structure, which I can associate with what I already know. Then 2 years ago I learned Python and I learned it quite well, Python is easier for me to learn than Ruby. Then since last year, I was trying to learn Ruby, then Rails, and I admit, until now I still couldn't get it, the irony is that those are branded as easy to learn, but for a seasoned programmer like me, I just couldn't associate it with what I learned before, I have 2 books on both Ruby and Rails, and when I'm reading it nothing is absorbed into my mind, and I'm close to giving up... In ruby, I'm having a hard time grasping the concepts of blocks, and why there's @variables that can be accessed by other functions, and what does $variable and :variable do? And in Rails, why there's function like this_is_another_function_that_do_this, so thus ruby, is it just a naming convention or it's auto-generated with thisvariable _can_do_this_function. I'm still puzzled that where all those magic concepts and things came from? And now, 1 year of trying and absorbing, but still no progress... Edit: To summarize: How can I learn about blocks, and how can it be related to concepts from PHP/C? Variables, what does does it mean when a variable is prefixed with: @ $ : "Magic concepts", suchs as rails declarations of Records, what happens behind the scenes when I write has_one X OK so, bear with me with my confusion, at least I'm honest with myself, and it's over a year now since I first trying to learn ruby, and I'm not getting younger.. so I learned this in Bash/C/PHP solve_problem($problem) { if [ -e $problem == "trivial" ]; then write_solution(); else breakdown_problem_into_N_subproblems(\; define_relationship_between_subproblems; for i in $( command $each_subproblem ); do solve_problem $i done fi } write_solution(problem) { some_solution=$(command <parameters> "input" | command); command | command $some_solution > output_solved_problem_to_file } breakdown_problem_into_N_subproblems($problems) { for i in $problems; do command $i | command > i_can_output_a_file_right_away done } define_relationship_between_subproblems($problems) { if [ -e $problem == "relationship" ]; then relationship=$(command; command | command; command;) elsif [ -e $problem == "another_relationship" ]; relationship=$(command; command | command; command;) fi } In C/PHP is something like this solve_problem(problem) { if (problem == trivial) write_solution; else { breakdown_problem_into_N_subproblems; define_relationship_between_subproblems; for (each_subproblem) solve_problems(subproblem); } } And now, I just couldn't connect the dots with Ruby, |b|{ blocks }, using @variables, :variables, and variables_with_this_things..

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  • Statistical approach to chess?

    - by Chinmay Kanchi
    Reading about how Google solves the translation problem got me thinking. Would it be possible to build a strong chess engine by analysing several million games and determining the best possible move based largely (completely?) on statistics? There are several such chess databases (this is one that has 4.5 million games), and one could potentially weight moves in identical (or mirrored or reflected) positions using factors such as the ratings of the players involved, how old the game is (to factor in improvements in chess theory) etc. Any reasons why this wouldn't be a feasible approach to building a chess engine?

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  • Kohonen SOM Maps: Normalizing the input with unknown range

    - by S.N
    According to "Introduction to Neural Networks with Java By Jeff Heaton", the input to the Kohonen neural network must be the values between -1 and 1. It is possible to normalize inputs where the range is known beforehand: For instance RGB (125, 125, 125) where the range is know as values 0 and 255: 1. Divide by 255: (125/255) = 0.49 (0.49,0.49,0.49) 2. Multiply by two and subtract one: ((0.49*2)-1)=-0.02 (-0.02,-0.02,-0.02) The question is how can we normalize the input where the range is unknown like our height or weight. Also, some other papers mention that the input must be normalized to the values between 0 and 1. Which is the proper way, "-1 and 1" or "0 and 1"?

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  • getting started with nosql

    - by radi
    hi , i am new to nosql world i know sql and rdbms very well , i want to get start with nosql so i need to know : where i can start read about nosql (books , online tutorials )? what is the most simple nosql engine i can start with (i am using java)? thanks .

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  • What are the primitive Forth operators?

    - by Barry Brown
    I'm interested in implementing a Forth system, just so I can get some experience building a simple VM and runtime. When starting in Forth, one typically learns about the stack and its operators (DROP, DUP, SWAP, etc.) first, so it's natural to think of these as being among the primitive operators. But they're not. Each of them can be broken down into operators that directly manipulate memory and the stack pointers. Later one learns about store (!) and fetch (@) which can be used to implement DUP, SWAP, and so forth (ha!). So what are the primitive operators? Which ones must be implemented directly in the runtime environment from which all others can be built? I'm not interested in high-performance; I want something that I (and others) can learn from. Operator optimization can come later. (Yes, I'm aware that I can start with a Turing machine and go from there. That's a bit extreme.) Edit: What I'm aiming for is akin to bootstrapping an operating system or a new compiler. What do I need do implement, at minimum, so that I can construct the rest of the system out of those primitive building blocks? I won't implement this on bare hardware; as an educational exercise, I'd write my own minimal VM.

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  • Is it worth moving from stored procedures to linq ?

    - by Josef
    I'm looking at standardizing programming in an organisaiton. Half uses stored procedures and the other half Linq. From what i've read there is still some debate going on on this topic. My concern is that MS is trying to slip in it's own proprietry query language 'linq' to make SQL redundant. If a few years back microsoft had tried to win customers from oracle and sybase with their MSSQL database and stated that it didn't use SQL by their own proprietry query langues ie linq. I doubt many would have switched. I believe that is exactly what is happening now by introducting it into the applicaiton business layer. I have used MS for many years but there is one gripe that I have with them and that is that they change their direction a lot. By a lot I mean new releases of .net, silverlight etc are more than 30% different from previous version. So by the time you become productive a new release is on the way. As things stand now a web developer using .net would need to know either vb.net or c#, xml, xaml,javascript,html, sql and now linq. That doesn't make for good productivity in my books. My concern is that once we all start using linq MS will start changing it between releases. and it will become an ever changing landscape. I believe that 'linq to sql' has already been deprecated. At leas with SQL we are dealing with a more stable and standardized language. Are we looking at a programming revolution or a marketing campaign? As far as I know other languages like Cobol have stayed the same for years. A cobol program from 20 years ago could pick up todays code and start working on it. Could a Vb3 person work on a modern .net web app ? Would these large changes need to be made if the underlying original foundation had been sound ? I worry about following MS shaking roadmap with it's deadends and double backs. are there any architects out there who feel the same ? regards Josef

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  • How do people know so much about programming?

    - by Luciano
    I see people in this forums with a lot of points, so I assume they know about a lot of different programming stuff. When I was young I knew about basic (commodore) and the turbo pascal (pc). Then in college I learnt about C, memory management, x86 set, loop invariants, graphs, db query optimization, oop, functional, lambda calculus, prolog, concurrency, polymorphism, newton method, simplex, backtracking, dynamic programming, heuristics, np completeness, LR, LALR, neural networks, static & dynamic typing, turing, godel, and more in between. Then in industry I started with Java several years ago and learnt about it, and its variety of frameworks, and also design patterns, architecture patterns, web development, server development, mobile development, tdd, bdd, uml, use cases, bug trackers, process management, people management if you are a tech lead, profiling, security concerns, etc. I started to forget what I learnt in college... And then there is the stuff I don't know yet, like python, .net, perl, JVM stuff like groovy or scala.. Of course Google is a must for rapid documentation access to know if a problem has been solved already and how, and to keep informed about new stuff by blogs and places like this one. It's just too much or I just have a bad memory.. how do you guys manage it?

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  • The advantages and disadvantages of using ORM

    - by JHarley1
    Good Morning, I would like to discuss today the advantages and disadvantages of using ORM (such as ADO.NET). Advantages: Speeds-up Development - eliminates the need for repetitive SQL code. Reduces Development Time. Reduces Development Costs. Overcomes vendor specific SQL differences - the ORM knows how to write vendor specific SQL so you don't have to. Disadvantages: Loss in developer productivity whilst they learn to program with ORM. Developers loose understanding of what the code is actually doing - the developer is more in control using SQL. ORM has a tendency to be slow. ORM fail to compete against SQL queries for complex queries. In summary, I believe that the disadvantages of using an ORM (mainly the reduced time taken to perform repetitive tasks) is far outweighed by the disadvantages of ORM e.g. its difficulty to get to grips with. Can people point out were I am going wrong and suggest any further advantages/disadvantages. Many Thanks, J

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  • What is a database file system?

    - by Ravi
    I have a very little idea about what database file system is. Can somebody out here explain to me what actually a database file system is, and what its applications are? How is it different from a conventional file system? How I can build it?

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  • Python2 or Python3?

    - by Michael
    I'm just starting to learn Python, but just to use my time more efficiently, would you recommend to read Python2 or start directly from Python3? I'm about "Dive into Python". Is it similar to start reading PHP4 or PHP5? I'm trying to understand whether it's worth spending time on Python2 literature.

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  • Question on multi-probe Local Sensitive Hashing

    - by Yijinsei
    Hey guys sorry to be asking this kind noob question, but because I really need some guidance on how to use Multi probe LSH pretty urgently, so I did not do much research myself. I realize there is a lib call LSHKIT available that implemented that algorithm, but I have trouble trying to figure out how to use it. Right now, I have a few thousand feature vector 296 dimension, each representing an image. The vector is used to query an user input image, to retrieve the most similar image. The method I used to derive the distance between vector is euclidean distance. I know this might be a rather noob question, but do you guys have knowledge on how should i implement multi probe LSH? I am really very grateful to any answer or response.

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  • Clarification How CRF(Conditional random Field) works using examples

    - by Moges.A
    I read different documents how CRF(conditional random field) works but all the papers puts the formula only. Is there any one who can send me a paper that describes about CRF with examples like if we have a sentence "Mr.Smith was born in New York. He has been working for the last 20 years in Microsoft company." if the above sentence is given as an input to train, how does the Model works during the training taking in to consideration for the formula for CRF? Moges.A

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  • Implementing a linear, binary SVM (support vector machine)

    - by static_rtti
    I want to implement a simple SVM classifier, in the case of high-dimensional binary data (text), for which I think a simple linear SVM is best. The reason for implementing it myself is basically that I want to learn how it works, so using a library is not what I want. The problem is that most tutorials go up to an equation that can be solved as a "quadratic problem", but they never show an actual algorithm! So could you point me either to a very simple implementation I could study, or (better) to a tutorial that goes all the way to the implementation details? Thanks a lot!

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  • Starting work on a Pre-existing Project

    - by Toymakerii
    So this is more of a generic question. I seem to keep finding myself being put on larger and larger projects. Recently I have been assigned to a very large project written in C and VHDL. The goal is for me to become familiar with the code and eventually take the lead on the project. This is by far the largest project I have been assigned to work on that I didn't start. So here is my question: What methods/tools do you use to learn how everything works? Do you just increase and expand on comments? Do you make a UML representation of the project? Any tips would be great! Thanks

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  • Good books on Sybase ASE 15?

    - by Ilya Kochetov
    We need to get some good books on Sybase ASE 15 for our developers. The people in the team have previous experience with different SQL flavors (MS SQL, MySQL, Informix and Oracle) but no one worked with Sybase before. Therefore I am looking for two kinds of books: Book for developers on how to use Sybase for queries,sprocs, views etc. Has to be a book for professionals and not something like 'learn SQL in 21 day' Book for the DB administrator on how to maintain the database. This could be on any level and a dummy guide would not go wrong :) Thank you

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  • computing z-scores for 2D matrices in scipy/numpy in Python

    - by user248237
    How can I compute the z-score for matrices in Python? Suppose I have the array: a = array([[ 1, 2, 3], [ 30, 35, 36], [2000, 6000, 8000]]) and I want to compute the z-score for each row. The solution I came up with is: array([zs(item) for item in a]) where zs is in scipy.stats.stats. Is there a better built-in vectorized way to do this? Also, is it always good to z-score numbers before using hierarchical clustering with euclidean or seuclidean distance? Can anyone discuss the relative advantages/disadvantages? thanks.

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  • What every web developer should know?

    - by arikfr
    Let's say you got a new intern, who's a third-year CS student. He has firm knowledge of the basics, has some experience with C/Java from the courses he took and a lot of desire to learn more. What would you teach him in order to become a good web developer? What I had in mind is: HTML/CSS and the importance of writing semantic markup Javascript, some JS framework (jQuery), JSON Basics of Git/Subversion (whatever you use) The language we use (Ruby, Python, PHP, C#, whatever) Introduction the web framework we use (Rails, Django, ASP.NET MVC...) MVC - what/why/who RESTful web services - how to consume them and how to create one What's on your list?

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  • plotting results of hierarchical clustering ontop of a matrix of data in python

    - by user248237
    How can I plot a dendrogram right on top of a matrix of values, reordered appropriately to reflect the clustering, in Python? An example is in the bottom of the following figure: http://www.coriell.org/images/microarray.gif I use scipy.cluster.dendrogram to make my dendrogram and perform hierarchical clustering on a matrix of data. How can I then plot the data as a matrix where the rows have been reordered to reflect a clustering induced by the cutting the dendrogram at a particular threshold, and have the dendrogram plotted alongside the matrix? I know how to plot the dendrogram in scipy, but not how to plot the intensity matrix of data with the right scale bar next to it. Any help on this would be greatly appreciated.

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  • using Multi Probe LSH with LSHKIT

    - by Yijinsei
    Hi Guys, I have read through the source code for mplsh, but I still unsure on how to use the indexes generated by lshkit to speed up the process in comparing feature vector in Euclidean Distance. Do you guys have any experience regarding this?

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  • Object Orientated PHP books

    - by user275074
    Hi, I've realised just how rusty my knowledge of PHP 5 and advanced PHP programming is after completing some questions for a test. I seriously need to read a book or something. Any recommendations for PHP 5 books?

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  • Will be self-taught limit me?

    - by Isaiah
    I'm 21 and am pretty efficient in html/css, python, and javascript. I also know my way around lisp languages and enjoy programing in them. My problem is that I'm extremely self-taught and not quite confident that I could land a job programing, but I really need a job soon as I've just become a father. I haven't even created a resume yet because I'm not really sure what to put on it except my lone experience. So I wanted to ask, will being primarily self-taught with some experience on small projects I've done for a few clients limit me too much? I mean I know I need some kind of education so I've enrolled part time in a community college to work on a degree in computer science, but it's years till then. And if it will limit me a lot, what kind of skills would be good to work on to make my chances any better? Thank You

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  • Going from a math career to a cs career: how to do it?

    - by Joseph
    Hey, I'm looking for some advice on how to successfully make the transition from mathematics to CS. My academic background is in mathematics (BS and MSc), and I've taken loads of math courses as well. You name it, and I took it: Measure Theory, Algebra, PDES, Manifolds, Complex Analysis, etc. I progressed quite far along this track, and at one point, I thought I would be a professional mathematician...But around the time I was finishing my MSc, I really got sick of it. Studying very abstract mathematics was fun, but it really lost it's appeal to me. Outside of a couple hundred people, I'm not sure if anybody would understand my research. I did not want to be 60 years old and say that my only contribution to the world consisted of published papers. Anyways, I've been an off and on hobbyist programmer since 2002. I've programmed in C and Java (just small projects), and I really started to be drawn to the area as time passed. There's a real appeal to CS work because, well, it actually means something to other people out there! I enjoy all parts of it: designing webpages (a real artistic appeal). On the other end, I do enjoy toying with compilers and more nitty-gritty stuff as well. Suffice to say, I have broad interests out there. Anyways, I know it's a bit late, but I was wondering if there were other folks out there who made the change, and if so, how I could do so. I know I have some fairly big gaps to fill in terms of data structures, lack of internship experience, etc. But I really would like to make this work. So my question is simply: How can I make the switch from math to CS? To pay the bills, I'll be doing financial analysis for a company, but I'd like to eventually transition into a developer type position. I've been reading "Algorithm Design" by Tardos and doing all the problems. It's not hard to make progress since the problems are far more concrete than the stuff I've been doing the past six years. I feel I can make fairly rapid progress in picking up all the materials from data structures, etc. but none of it can substitute the past several years I've lost. Anyways, I'm eager to learn but would love some advice/concrete direction. Thanks, Joseph

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