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• What resources are there for facial recognition

  - by Zintinio

  I'm interested in learning the theory behind facial recognition software so that I can hopefully implement it in the future. Not just face tracking, but being able to recognize individuals. What papers, books, libraries, or source is available so that I can learn more about the subject? I have found libface which seems to use eigenfaces for recognition. If there are any practitioners out there, please share any information that you can.

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• Recommened design pattern to handle multiple compression algorithms for a class hierarchy

  - by sgorozco

  For all you OOD experts. What would be the recommended way to model the following scenario? I have a certain class hierarchy similar to the following one: class Base { ... } class Derived1 : Base { ... } class Derived2 : Base { ... } ... Next, I would like to implement different compression/decompression engines for this hierarchy. (I already have code for several strategies that best handle different cases, like file compression, network stream compression, legacy system compression, etc.) I would like the compression strategy to be pluggable and chosen at runtime, however I'm not sure how to handle the class hierarchy. Currently I have a tighly-coupled design that looks like this: interface ICompressor { byte[] Compress(Base instance); } class Strategy1Compressor : ICompressor { byte[] Compress(Base instance) { // Common compression guts for Base class ... // if( instance is Derived1 ) { // Compression guts for Derived1 class } if( instance is Derived2 ) { // Compression guts for Derived2 class } // Additional compression logic to handle other class derivations ... } } As it is, whenever I add a new derived class inheriting from Base, I would have to modify all compression strategies to take into account this new class. Is there a design pattern that allows me to decouple this, and allow me to easily introduce more classes to the Base hierarchy and/or additional compression strategies?

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• Why does F. Wagner consider "NOT (AI_LARGER_THAN_8.1)" to be ambiguous?

  - by oosterwal

  In his article on Virtual Environments (a part of his VFSM specification method) Ferdinand Wagner describes some new ways of thinking about Boolean Algebra as a software design tool. On page 4 of this PDF article, when describing operators in his system he says this: Control statements need Boolean values. Hence, the names must be used to produce Boolean results. To achieve this we want to combine them together using Boolean operators. There is nothing wrong with usage of AND and OR operators with their Boolean meaning. For instance, we may write: DI_ON OR AI_LARGER_THAN_8.1 AND TIMER_OVER to express the control situation: digital input is on or analog input is larger than 8.1 and timer is over. We cannot use the NOT operator, because the result of the Boolean negation makes sense only for true Boolean values. The result of, for instance, NOT (AI_LARGER_THAN_8.1) would be ambiguous. If "AI_LARGER_THAN_8.1" is acceptable, why would he consider "NOT (AI_LARGER_THAN_8.1)" to be ambiguous?

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• How to decide whether to implement an operation as Entity operation vs Service operation in Domain Driven Design?

  - by Louis Rhys

  I am reading Evans's Domain Driven Design. The book says that there are entity and there are services. If I were to implement an operation, how to decide whether I should add it as a method on an entity or do it in a service class? e.g. myEntity.DoStuff() or myService.DoStuffOn(myEntity)? Does it depend on whether other entities are involved? If it involves other entities, implement as service operation? But entities can have associations and can traverse it from there too right? Does it depend on stateless or not? But service can also access entities' variable, right? Like in do stuff myService.DoStuffOn, it can have code like if(myEntity.IsX) doSomething(); Which means that it will depend on the state? Or does it depend on complexity? How do you define complex operations?

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• What is the difference between development and R&D?

  - by MainMa

  I was asked by a colleague to explain clearly the difference between ordinary development and research and development (R&D) and was unable to do it. After reading Wikipedia, I still don't have the precise answer. According to Wikipedia (slightly modified): There are two primary models: In one model, the primary function is to develop new products; in the other model, the primary function is to discover and create new knowledge about scientific and technological topics for the purpose of uncovering and enabling development of valuable new products, processes, and services. The first model is confusing. Does it mean that development (not R&D) consists exclusively in adding new features to a product, solving bugs and doing maintenance? What if something which was previously developed as a new feature becomes a separate product? The second model is less confusing, but still, how to qualify whether something is new knowledge or existent knowledge which is just rediscovered? Later, Wikipedia adds that ordinary development is different from R&D because of its: nearly immediate profit or immediate improvement. It's still not clear enough. How to qualify "nearly immediate profit"? What if a task has an immediate profit but requires heavy research? Or if it is basic but has uncertain profit, like the enforcement of a common style over the codebase? For example, does it belong to development or R&D to: Develop an engine which abstracts the access to the database, simplifying and shortening enormously the code of other applications (existent or ones which will be written in future) which should access to the database? Establish a new service-oriented architecture for the entire organization of company resources, in order to move from a bunch of separate and autonomous applications to a set of well-organized, interconnected web services, like what is used by Amazon? Design a new communication protocol to allow faster replication of data between two data centers of the company? Conceive a new type of software testing while working on a specific product, knowing that this type of testing will improve/simplify the testing process? Prove that Functional programming is more appropriate than OOP for a specific application, based on evidence, logic and previous experience? Enhance the existent application by adding gestures on tactile screens, after doing studies and testing that shows that those gestures improve the productivity of the users by a ratio of at least 1.4 for a precise set of tasks? Find a way to strongly enhance the Power usage effectiveness (PUE) of a data center? Create a Domain-Specific Language (DSL)? In short, how could I determine whether I'm doing R&D while working on something?

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• Algorithm to reduce calls to mapping API

  - by aidan

  A random distribution of points lies on a map. This data lies behind an API, and I want to grab the complete set of points within a given bounding box. I can query the API with the bounding box and the API will return the set of points that fall within that box. The problem is that the API will limit the result set to 10 items, with no pagination and no indication if there are more points that have been omitted. So I made a recursive algorithm that takes a bounding box and requests the points that lie within it. If the result set is exactly 10 items, then I split the bounding box into four quadrants and recurse. It works fine but my question is this: if want to minimize the number of API calls, what is the optimal way to split the bounding box? Splitting it into quadrants was just an arbitrary decision. When there are a lot of points on the map, I have to drill down many levels before I start getting meaningful results. So I imagine it might be faster to split the box into, say, 9, 16, or more sections. But if I do that, then I eventually get to a point where a lot of requests are returning 0 results which isn't so efficient. Also, does the size of the limit on the results set affect the answer? (This is all assuming that I have no prior knowledge of nominal point density in the bounding box)

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• Started wrong with a project. Should I start over?

  - by solidsnake

  I'm a beginner web developer (one year of experience). A couple of weeks after graduating, I got offered a job to build a web application for a company whose owner is not much of a tech guy. He recruited me to avoid theft of his idea, the high cost of development charged by a service company, and to have someone young he can trust onboard to maintain the project for the long run (I came to these conclusions by myself long after being hired). Cocky as I was back then, with a diploma in computer science, I accepted the offer thinking I can build anything. I was calling the shots. After some research I settled on PHP, and started with plain PHP, no objects, just ugly procedural code. Two months later, everything was getting messy, and it was hard to make any progress. The web application is huge. So I decided to check out an MVC framework that would make my life easier. That's where I stumbled upon the cool kid in the PHP community: Laravel. I loved it, it was easy to learn, and I started coding right away. My code looked cleaner, more organized. It looked very good. But again the web application was huge. The company was pressuring me to deliver the first version, which they wanted to deploy, obviously, and start seeking customers. Because Laravel was fun to work with, it made me remember why I chose this industry in the first place - something I forgot while stuck in the shitty education system. So I started working on small projects at night, reading about methodologies and best practice. I revisited OOP, moved on to object-oriented design and analysis, and read Uncle Bob's book Clean Code. This helped me realize that I really knew nothing. I did not know how to build software THE RIGHT WAY. But at this point it was too late, and now I'm almost done. My code is not clean at all, just spaghetti code, a real pain to fix a bug, all the logic is in the controllers, and there is little object oriented design. I'm having this persistent thought that I have to rewrite the whole project. However, I can't do it... They keep asking when is it going to be all done. I can not imagine this code deployed on a server. Plus I still know nothing about code efficiency and the web application's performance. On one hand, the company is waiting for the product and can not wait anymore. On the other hand I can't see myself going any further with the actual code. I could finish up, wrap it up and deploy, but god only knows what might happen when people start using it. What do you think I should do?

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• How to remove java.sql.BatchUpdateException in Grails? [closed]

  - by aman.nepid

  I have a domain like this: class BusinessOrganization { static hasMany = [organizationBusinessTypes:OrganizationBusinessType] String name String icon static constraints = { name(blank:false,unique:true) icon(unique:true) } String toString() { return "${name}" } } When I save some data for first time it works fine. But when by the next time it shows this error : Error 500: Internal Server Error URI /nLocatePortal/businessOrganization/save Class java.sql.BatchUpdateException Message Batch entry 0 insert into business_organization (version, icon, name, id) values ('0', '', 'dddd', '2') was aborted. Call getNextException to see the cause. **Around line 24 of grails-app/controllers/com/nlocate/portal/BusinessOrganizationController.groovy** 21: 22: def save() { 23: def businessOrganizationInstance = new BusinessOrganization(params) 24: if (!businessOrganizationInstance.save(flush: true)) { 25: render(view: "create", model: [businessOrganizationInstance: businessOrganizationInstance]) 26: return 27: } Please someone help me why this is happening. I am new to Grails. I have not modified the controllers but still I get this error.

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• Just interviewed, turned down, now got an email asking to chat with recruiter. No response. What should I do? [closed]

  - by Lambert

  I was turned down after two interviews by a prominent company for an internship, and only a couple days later, I was asked when I had 10-15 minutes to chat today. Of course, I loved to, so I emailed within just 10 minutes of their email and let them know what times I was available at, and asked them when the best time should be, and if I should go somewhere or expect a phone call. No reply has come from them since yesterday afternoon, the recruiter wanted to talk to me today. I don't want to lose this opportunity, but I have no way to contact the recruiter other than by email, and the recruiter hasn't responded to my emails from yesterday, even though we were supposed to talk today. What's the best thing I can do (preferably within the next few hours!) to get the job? Is that even probably why she emailed me, or was a different reason likely? Any ideas?

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• How to avoid mediocre CV.

  - by QriousCat

  Though in every project we (testers) face different set challenges, when it comes to CV, more or less we have same responsibilities. For example responsibilities like understanding requirements, preparing and executing test cases, creating defects, liaising with dev, BA teams will be repeated for every project we involve. If we keep writing same responsibilities for every role, CV becomes mediocre and a yarn. In fact most of the testing resumes I have come across are like that. How do I avoid repetition of responsibilities in my resume and make it more interesting? If this is not the correct forum for this question let me know. Thanks in advance for your suggestions.

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• Software development magazines [closed]

  - by Sebastian

  Ive spent the last hour or so browsing the web for professional development magazines. I am mostly interested in the java platform, agile methods, "programming in general" (tutorials on languages or whatever, "hot new stuff" etc) and software craftmanship. My best finding yet was pragpub and maybe MSDN magazine. I am willing to pay and have a Zinio account if anyone knows a magazine about programming that is distributed by them. Ive already browsed a couple of related threads here on stackexchange. ACM and IEEE does not seem relevant, as Im not interested in research articles. Maybe conferences like OOPSLA as somebody mentioned in another thread. PS. I prefer if they are in pdf or readable on kindle or a tablet. DS. BR Sebastian

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• Ways to break the "Syndrome of the perfect programmer"

  - by Rushino

  I am probably not the only one that feel that way. But I have what I tend to call "The syndrome of the perfect programmer" which many might say is the same as being perfectionist but in this case it's in the domain of programming. However, the domain of programming is a bit problematic for such a syndrome. Have you ever felt that when you are programming you're not confident or never confident enought that your code is clean and good code that follows most of the best practices ? There so many rules to follow that I feel like being overwhelmed somehow. Not that I don't like to follow the rules of course I am a programmer and I love programming, I see this as an art and I must follow the rules. But I love it too, I mean I want and I love to follow the rules in order to have a good feeling of what im doing is going the right way.. but I only wish I could have everything a bit more in "control" regarding best practices and good code. Maybe it's a lack of organization? Maybe it's a lack of experience? Maybe a lack of practice? Maybe it's a lack of something else someone could point out? Is there any way to get rid of that syndrome somehow ?

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• Should I use the cool, new and awesome stuff [closed]

  - by Ieyasu Sawada

  I'm in the field of Web Development. I follow a lot of awesome people on Twitter(Paul Irish, Alex Sexton, David Walsh, Rebecca Murphey, etc.) By following these people I'm constantly updated of the new and cool stuff in web development(backbone.js, angular.js, require.js, ember.js, jasmine, etc.) Now I'm creating a web application for a client and because of the different tools, libraries, plugins that I'm aware of I don't even know anymore when do I need to use those or do I even need those, or how do I even implement it in a sane way where I won't have to repeat myself(DRY). What's your advice on what I really need to do in order to become better. Do I really need to use these cool new tools or should I just stick with what I know for now and try to make my code better. Should I unfollow these people in order to not pollute my mind with stuff that I can't really use now because I don't have the necessary experience in order to use it. What sort of things should I really be focusing on for someone like me who has only about 2 years of experience in the field of web development.

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• What are the algorithms that are used for working with large data in popular web applications

  - by Moss Farmer

  I am looking for some well known algorithms that can be considered while handling very large amount of data.(Edit- By large amount of data I refer to records in a database excluding blobs). These algorithms if not in totality but in parts may be used in big web applications like Twitter, Last.fm , Amazon ,etc. Specifically, I'm looking for names or links to such algorithms. My primary interest lies in developing a very deep understanding on working with large database records and writing efficient code for working with the same.

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• What is a user-friendly solution to editing email templates with replacement variables?

  - by Daniel Magliola

  I'm working on a system where we rely a lot of "admins / managers" emailing users from the database. One of the key features is being able to email several people at the same time, with specific information relevant to each of them. Another key feature is to be able to hand-craft emails, because it tends to be be necessary to slightly modify them each time, but having a basic template saves a lot of time. For this, we have the typical "templates" solution, where we have a template that looks kind of like this: Hello {{recipient.full_name}}, Your application to {{activity.title}} has been accepted. You have requested to participate on dates {{application.dates}}, in role {{application.role}} Blah blah blah The problem we are having is obviously that (as we expected), managers don't get the whole "variables" idea, and they do things like overwriting them, which doesn't let them email more than one person at a time, assuming those are not going to get replaced and that the system is broken, or even inexplicable things like "Hello {{John}}". The big problem is that this isn't relegated, as usual, to an "admin" section where only a few power users have access to editing the templates that are automatically send out, and they're expected to know what they are doing. Every user of the system gets exposed to this problem. The obvious solution would be to replace the variables before showing this template for the user to edit, but that doesn't work when emailing several people. This seems like a reasonably common problem, and we are kind of hoping that someone has already solved it. Have you seen anywhere/created/can think of good solutions to this problem?

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• How to write constructors which might fail to properly instantiate an object

  - by whitman

  Sometimes you need to write a constructor which can fail. For instance, say I want to instantiate an object with a file path, something like obj = new Object("/home/user/foo_file") As long as the path points to an appropriate file everything's fine. But if the string is not a valid path things should break. But how? You could: 1. throw an exception 2. return null object (if your programming language allows constructors to return values) 3. return a valid object but with a flag indicating that its path wasn't set properly (ugh) 4. others? I assume that the "best practices" of various programming languages would implement this differently. For instance I think ObjC prefers (2). But (2) would be impossible to implement in C++ where constructors must have void as a return type. In that case I take it that (1) is used. In your programming language of choice can you show how you'd handle this problem and explain why?

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• how to save and load the state of a game in scheme

  - by user3667664

  I'm creating the game of chess in scheme, but do not know how to save and load game state is a part I have this code (define-struct ficha(color se-movio? tipo-ficha )) ;;tablero lista de listas de fichas (define-struct estado (tablero turno fichaSel)) (define bpawn (bitmap "b-peon.png")) (define brook (bitmap "b-torre.png")) (define bcaballo (bitmap "b-caballo.png")) (define bbish (bitmap "b-arfil.png")) (define bquee (bitmap "b-reina.png")) (define bking (bitmap "b-rey.png")) (define wpawn (bitmap "w-peon.png")) (define wrook (bitmap "w-torre.png")) (define wcaballo (bitmap "w-caballo.png")) (define wbish (bitmap "w-arfil.png")) (define wquee (bitmap "w-reina.png")) (define wking (bitmap "w-rey.png")) (define board (bitmap "board.jpg")) This is the board that is a list of lists (define tableroini (list (list torreb caballob arfilb reinab reyb arfilb caballob torreb) (list peonb peonb peonb peonb peonb peonb peonb peonb) (list empty empty empty empty empty empty empty empty) (list empty empty empty empty empty empty empty empty) (list empty empty empty empty empty empty empty empty) (list empty empty empty empty empty empty empty empty) (list peonw peonw peonw peonw peonw peonw peonw peonw) (list torrew caballow arfilw reinaw reyw arfilw caballow torrew))) I did this to save the state of the game: (define (Guardar-en-archivo archivo) (write-file (string-append Subcarpeta archivo ".txt") "game state" )) But not as you insert the game state on "game state" for me to save the game How I can do this ?

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• Is it a good pattern that no objects should know more than what it needs to know?

  - by Jim Thio

  I am implementing a viewController class. The view controller class got NSNotification when the Grabbing class start or finish updating. I have 2 choices. I can make the grabbing class to provide a public read only property so all other classes can know whether it is still uploading. Or I can let view Controller to listen to 2 different events. Start updating and finish updating events. The truth is the viewController do need to know whether the grabbing class is still updating or not at any other time. So I am thinking of creating 2 events would be a better way to go. Actually, what do you think?

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• How do you name your projects?

  - by Corey

  Naming is hard. Really, really hard. Even StackExchange is a prime example of this -- remember the huge domain name controversy that occurred when SE sites first started graduating? Anyway, I've got a project I'm working on but I have no idea what to name it! This simple fact has caused production to cease, because I'm at the point where I want to create repositories and database tables, and I don't want to name everything "Untitled project" and have to change potentially hundreds of lines of code in the future. Also, I would like to collaborate with others but it's difficult to be taken seriously if I refer to this as "some project I'm working on." It makes it seem like a new project in its infancy and doesn't garner a lot of interest. Just the simple fact act of having a name will make a huge impact in how it registers in others' minds. How do you guys name your projects? This particular one is a website, so not only do I need to find a good name, I need to find one with an available domain, which is next to impossible these days. How do you brainstorm? Who do you talk to (or not talk to)? Is there an "eureka!" moment when you stumble across something that works?

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• How many copies are needed to enlarge an array?

  - by user10326

  I am reading an analysis on dynamic arrays (from the Skiena's algorithm manual). I.e. when we have an array structure and each time we are out of space we allocate a new array of double the size of the original. It describes the waste that occurs when the array has to be resized. It says that (n/2)+1 through n will be moved at most once or not at all. This is clear. Then by describing that half the elements move once, a quarter of the elements twice, and so on, the total number of movements M is given by: This seems to me that it adds more copies than actually happen. E.g. if we have the following: array of 1 element +--+ |a | +--+ double the array (2 elements) +--++--+ |a ||b | +--++--+ double the array (4 elements) +--++--++--++--+ |a ||b ||c ||c | +--++--++--++--+ double the array (8 elements) +--++--++--++--++--++--++--++--+ |a ||b ||c ||c ||x ||x ||x ||x | +--++--++--++--++--++--++--++--+ double the array (16 elements) +--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--+ |a ||b ||c ||c ||x ||x ||x ||x || || || || || || || || | +--++--++--++--++--++--++--++--++--++--++--++--++--++--++--++--+ We have the x element copied 4 times, c element copied 4 times, b element copied 4 times and a element copied 5 times so total is 4+4+4+5 = 17 copies/movements. But according to formula we should have 1*(16/2)+2*(16/4)+3*(16/8)+4*(16/16)= 8+8+6+4=26 copies of elements for the enlargement of the array to 16 elements. Is this some mistake or the aim of the formula is to provide a rough upper limit approximation? Or am I missunderstanding something here?

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• How important is using the same language for client and server?

  - by Makita

  I have been evaluating architecture solutions for a mobile project that will have a web-service/app in addition to native apps and have been looking at various libraries, frameworks, and stacks like Meteor, this being a sort of "open stack package framework", is tightly bound with Node.js. There is a lot of talk about the benefits of using the same language both client and server side, and I'm not getting it. I could understand if you want to mirror the entire state of a web application on both client and server but struggling to find other wins... Workflow efficiency? I'm trying to understand why client/server language parity is considered to be a holy grail. Why does client/server language parity matter in software development?

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• Popular programming books which have been translated into Russian

  - by arikfr

  I'm looking for recommendations of popular programming books that have been translated into Russian. I'm talking about books like: Test-Driven Development by Example by Kent Beck Code Complete The Pragmatic Programmer And other books like them. Also, recommendations for books in Russian by other authors but about similar topics (TDD, BDD, general programming methodologies) will be appreciated.

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• What follows after lexical analysis?

  - by madflame991

  I'm working on a toy compiler (for some simple language like PL/0) and I have my lexer up and running. At this point I should start working on building the parse tree, but before I start I was wondering: How much information can one gather from just the string of tokens? Here's what I gathered so far: One can already do syntax highlighting having only the list of tokens. Numbers and operators get coloured accordingly and keywords also. Autoformatting (indenting) should also be possible. How? Specify for each token type how many white spaces or new line characters should follow it. Also when you print tokens modify an alignment variable (when the code printer reads "{" increment the alignment variable by 1, and decrement by 1 for "}". Whenever it starts printing on a new line the code printer will align according to this alignment variable) In languages without nested subroutines one can get a complete list of subroutines and their signature. How? Just read what follows after the "procedure" or "function" keyword until you hit the first ")" (this should work fine in a Pascal language with no nested subroutines) In languages like Pascal you can even determine local variables and their types, as they are declared in a special place (ok, you can't handle initialization as well, but you can parse sequences like: "var a, b, c: integer") Detection of recursive functions may also be possible, or even a graph representation of which subroutine calls who. If one can identify the body of a function then one can also search if there are any mentions of other function's names. Gathering statistics about the code, like number of lines, instructions, subroutines EDIT: I clarified why I think some processes are possible. As I read comments and responses I realise that the answer depends very much on the language that I'm parsing.

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

  - by Raymond Ho

  I stumbled upon 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. I'm really not that intellectual. 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 algorithms. Are there any books out there that are friendly for novices/slow people like me, which would help to build up my knowledge so that I can read Knuth's book with ease in the future?

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• Is Haskell worth learning?

  - by Jason K

  I am looking at this question primarily from a career point of view, so I hope you answer it accordingly. I am fairly proficient with Python, can write C++ and I am a final year student of computer science engineering I am looking to learn Haskell because I have heard a lot about it. My question is: apart from learning it because of all the good I have heard about it, is it any good for my career? Is it used in the industry? I am curious to learn it but unless it helps me somehow in my career, I am not willing to make that change at this stage. Looking for some personal experiences here. Thanks!

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