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  • Design pattern for isomorphic trees

    - by Peregring-lk
    I want to create a data structure to work with isomorphic tree. I don't search for a "algorithms" or methods to check if two or more trees are isomorphic each other. Just to create various trees with the same structure. Example: 2 - - - - - - - 'a' - - - - - - - 3.5 / \ / \ / \ 3 3 'f' 'y' 1.0 3.1 / \ / \ / \ 4 7 'e' 'f' 2.3 7.7 The first "layer" or tree is the "natural tree" (a tree with natural numbers), the second layer is the "character tree" and the third one is the "float tree". The data structure has a method or iterator to traverse the tree and to make diferent operations with its values. These operations could change the value of nodes, but never its structure (first I create the structure and then I configure the tree with its diferent layers). In case of that I add a new node, this would be applied to each layer. Which known design pattern fits with this description or is related with it?

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  • What are some best practices for cookie based web authentication?

    - by rdasxy
    I'm working on a small side project using CGI and Python (scalability is not an issue and it needs to be a VERY simple system. I was thinking of implementing authentication using cookies, and was wondering if there were any established best practices. When the user successfully authenticates, I want to use cookies to figure out who is logged on. What, according to the best practices, should be stored in such a cookie?

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  • How to protect a peer-to-peer network from inappropriate content?

    - by Mike
    I’m developing a simple peer-to-peer app in .Net which should enable users to share specific content (text and picture files). As I've learned with my last question, inappropriate content can “relatively” easily be identified / controlled in a centralized environment. But what about a peer-to-peer network, what are the best methods to protect a decentralized system from unwanted (illegal) content? At the moment I only see the following two methods: A protocol (a set of rules) defines what kind of data (e.g. only .txt and jpg-files, not bigger than 20KB etc.) can be shared over the p2p-network and all clients (peers) must implement this protocol. If a peer doesn’t, it gets blocked by other peers. Pro: easy to implement. Con: It’s not possible to define the perfect protocol (I think eMail-Spam filters have the same problem) Some kind of rating/reputation system must be implemented (similar to stackoverflow), so “bad guys” and inappropriate content can be identified / blocked by other users. Pro: Would be very accurate. Con: Would be slow and in my view technically very hard to implement. Are there other/better solutions? Any answer or comment is highly appreciated.

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  • Multi-lingual error messages and error numbers

    - by Jon Hopkins
    So we're looking at the possibility of porting our software to support multiple languages and one of the areas we're going to have to deal with is error messages and other notifications. These obviously have to be reported to the users in their own language. Our team (largely) only speak English and even if we were all multi-lingual we're looking at selling to a wide range of countries and could never expect to have a reasonable number of people speaking all languages (we're a small company). The obvious way to get round the language issue when errors or other messages we may get asked about which are being reported is error numbers which would be consistent across language. While these are going to exist in the backend (if only as key on the error message), I'd really rather not throw them at users if we don't have to but I don't have any other solution. Anyone have any useful suggestions for alternatives?

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  • Successful technical communities except for open-source?

    - by Joshua Fox
    Have you ever seen a successful technical community -- e.g. user group, industry organization? Am I asking about a group of software engineers who get together F2F (or maybe online) and discuss technical and industry issues with deep zeal and interest -- a place where meaningful connections are made. Here are the only examples I have ever seen: Open source Maybe the Silicon Valley Java Users' Group Homebrew Computing Club in the '70's This sort of thing does exist in academia. Of course, there are lots of conferences and attempts at user's groups. However, almost all committed, serious software engineers, when asked about this, say "I don't have the time", which means that the organizations are not worthwhile to the best in our profession. Has anyone seen any organizations with an ongoing spirit of enthusiasm from top software engineers?

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  • How to sync files between local dir and remote dir without using an IDE?

    - by Moe Sweet
    I'm running windows 7 and I have a working dir in my PC. I have my staging server that I only have FTPS (Explicit) access to. What I want... Everytime I change something in my local dir, I want my remote dir synced via FTPS method alone. SVN, CVS, GIT is not an option. I tried notepad++, eclipse and Netbeans and all couldn't work. In general, I don't want to rely on an IDE to achieve this task. And I don't want to install anything funny like rsync and I don't want to write scripts.

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  • Vectorization of matlab code for faster execution

    - by user3237134
    My code works in the following manner: 1.First, it obtains several images from the training set 2.After loading these images, we find the normalized faces,mean face and perform several calculation. 3.Next, we ask for the name of an image we want to recognize 4.We then project the input image into the eigenspace, and based on the difference from the eigenfaces we make a decision. 5.Depending on eigen weight vector for each input image we make clusters using kmeans command. Source code i tried: clear all close all clc % number of images on your training set. M=1200; %Chosen std and mean. %It can be any number that it is close to the std and mean of most of the images. um=60; ustd=32; %read and show images(bmp); S=[]; %img matrix for i=1:M str=strcat(int2str(i),'.jpg'); %concatenates two strings that form the name of the image eval('img=imread(str);'); [irow icol d]=size(img); % get the number of rows (N1) and columns (N2) temp=reshape(permute(img,[2,1,3]),[irow*icol,d]); %creates a (N1*N2)x1 matrix S=[S temp]; %X is a N1*N2xM matrix after finishing the sequence %this is our S end %Here we change the mean and std of all images. We normalize all images. %This is done to reduce the error due to lighting conditions. for i=1:size(S,2) temp=double(S(:,i)); m=mean(temp); st=std(temp); S(:,i)=(temp-m)*ustd/st+um; end %show normalized images for i=1:M str=strcat(int2str(i),'.jpg'); img=reshape(S(:,i),icol,irow); img=img'; end %mean image; m=mean(S,2); %obtains the mean of each row instead of each column tmimg=uint8(m); %converts to unsigned 8-bit integer. Values range from 0 to 255 img=reshape(tmimg,icol,irow); %takes the N1*N2x1 vector and creates a N2xN1 matrix img=img'; %creates a N1xN2 matrix by transposing the image. % Change image for manipulation dbx=[]; % A matrix for i=1:M temp=double(S(:,i)); dbx=[dbx temp]; end %Covariance matrix C=A'A, L=AA' A=dbx'; L=A*A'; % vv are the eigenvector for L % dd are the eigenvalue for both L=dbx'*dbx and C=dbx*dbx'; [vv dd]=eig(L); % Sort and eliminate those whose eigenvalue is zero v=[]; d=[]; for i=1:size(vv,2) if(dd(i,i)>1e-4) v=[v vv(:,i)]; d=[d dd(i,i)]; end end %sort, will return an ascending sequence [B index]=sort(d); ind=zeros(size(index)); dtemp=zeros(size(index)); vtemp=zeros(size(v)); len=length(index); for i=1:len dtemp(i)=B(len+1-i); ind(i)=len+1-index(i); vtemp(:,ind(i))=v(:,i); end d=dtemp; v=vtemp; %Normalization of eigenvectors for i=1:size(v,2) %access each column kk=v(:,i); temp=sqrt(sum(kk.^2)); v(:,i)=v(:,i)./temp; end %Eigenvectors of C matrix u=[]; for i=1:size(v,2) temp=sqrt(d(i)); u=[u (dbx*v(:,i))./temp]; end %Normalization of eigenvectors for i=1:size(u,2) kk=u(:,i); temp=sqrt(sum(kk.^2)); u(:,i)=u(:,i)./temp; end % show eigenfaces; for i=1:size(u,2) img=reshape(u(:,i),icol,irow); img=img'; img=histeq(img,255); end % Find the weight of each face in the training set. omega = []; for h=1:size(dbx,2) WW=[]; for i=1:size(u,2) t = u(:,i)'; WeightOfImage = dot(t,dbx(:,h)'); WW = [WW; WeightOfImage]; end omega = [omega WW]; end % Acquire new image % Note: the input image must have a bmp or jpg extension. % It should have the same size as the ones in your training set. % It should be placed on your desktop ed_min=[]; srcFiles = dir('G:\newdatabase\*.jpg'); % the folder in which ur images exists for b = 1 : length(srcFiles) filename = strcat('G:\newdatabase\',srcFiles(b).name); Imgdata = imread(filename); InputImage=Imgdata; InImage=reshape(permute((double(InputImage)),[2,1,3]),[irow*icol,1]); temp=InImage; me=mean(temp); st=std(temp); temp=(temp-me)*ustd/st+um; NormImage = temp; Difference = temp-m; p = []; aa=size(u,2); for i = 1:aa pare = dot(NormImage,u(:,i)); p = [p; pare]; end InImWeight = []; for i=1:size(u,2) t = u(:,i)'; WeightOfInputImage = dot(t,Difference'); InImWeight = [InImWeight; WeightOfInputImage]; end noe=numel(InImWeight); % Find Euclidean distance e=[]; for i=1:size(omega,2) q = omega(:,i); DiffWeight = InImWeight-q; mag = norm(DiffWeight); e = [e mag]; end ed_min=[ed_min MinimumValue]; theta=6.0e+03; %disp(e) z(b,:)=InImWeight; end IDX = kmeans(z,5); clustercount=accumarray(IDX, ones(size(IDX))); disp(clustercount); Running time for 50 images:Elapsed time is 103.947573 seconds. QUESTIONS: 1.It is working fine for M=50(i.e Training set contains 50 images) but not for M=1200(i.e Training set contains 1200 images).It is not showing any error.There is no output.I waited for 10 min still there is no output. I think it is going infinite loop.What is the problem?Where i was wrong?

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  • Stored procedure Naming conventions?

    - by Chris
    One of our senior developers has stated that we should be using a naming convention for stored procedures with an "objectVerb" style of naming such as ("MemberGetById") instead of a "verbObject" type of naming ("GetMemberByID"). The reasoning for this standard is that all related stored procedures would be grouped together by object rather than by the action. While I see the logic for this way of naming things, this is the first time that I have seen stored procedures named this way. My opinion of the naming convention is that the name can not be read naturally and takes some time to determine what the words are saying and what the procedure might do. What are your takes on this? Which way is the more common way of naming a stored proc, and does a what types of stored proc naming conventions have you used or go by?

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  • Design for a plugin based application

    - by Varun Naik
    I am working on application, details of which I cannot discuss here. We have core framework and the rest is designed as plug in. In the core framework we have a domain object. This domain object is updated by the plugins. I have defined an interface in which I have function as DomainObject doProcessing(DomainObject object) My intention here is I pass the domain object, the plug in will update it and return it. This updated object is then passed again to different plugin to be updated. I am not sure if this is a good approach. I don't like passing the DomainObject to plugin. Is there a better way I can achieve this? Should I just request data from plugin and update the domain object myself?

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  • When are Getters and Setters Justified

    - by Winston Ewert
    Getters and setters are often criticized as being not proper OO. On the other hand most OO code I've seen has extensive getters and setters. When are getters and setters justified? Do you try to avoid using them? Are they overused in general? If your favorite language has properties (mine does) then such things are also considered getters and setters for this question. They are same thing from an OO methodology perspective. They just have nicer syntax. Sources for Getter/Setter Criticism (some taken from comments to give them better visibility): http://www.javaworld.com/javaworld/jw-09-2003/jw-0905-toolbox.html http://typicalprogrammer.com/?p=23 http://c2.com/cgi/wiki?AccessorsAreEvil http://www.darronschall.com/weblog/2005/03/no-brain-getter-and-setters.cfm http://www.adam-bien.com/roller/abien/entry/encapsulation_violation_with_getters_and To state the criticism simply: Getters and Setters allow you to manipulate the internal state of objects from outside of the object. This violates encapsulation. Only the object itself should care about its internal state. And an example Procedural version of code. struct Fridge { int cheese; } void go_shopping(Fridge fridge) { fridge.cheese += 5; } Mutator version of code: class Fridge { int cheese; void set_cheese(int _cheese) { cheese = _cheese; } int get_cheese() { return cheese; } } void go_shopping(Fridge fridge) { fridge.set_cheese(fridge.get_cheese() + 5); } The getters and setters made the code much more complicated without affording proper encapsulation. Because the internal state is accessible to other objects we don't gain a whole lot by adding these getters and setters. The question has been previously discussed on Stack Overflow: http://stackoverflow.com/questions/565095/java-are-getters-and-setters-evil http://stackoverflow.com/questions/996179

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  • I'm creating my own scalable, rapid prototyping web server. How should I design it?

    - by Mike Willliams
    I'm going to create my own web server that focuses on scalability, rapid prototyping and the use of JavaScript as the server's scripting language, much like node.js. It will use a Model-View-Controller design pattern so a web application can support more concurrent users just by adding hardware -- and not having to redesign the software. Basically, I'm aiming to produce a framework that allows for fast and easy development of cloud applications without the need to write lots of boiler plate code. I've got some questions about this... How hard will it be to put MySQL in the cloud? How could I go about implementing this and make the resulting product free? Will I have to write my own engine or modify an existing one, if I do what should I watch out for? To make this scalable I need to adjust from one server to hundreds of servers this creates the requirement for the servers to be load balancing, how should I do this? If I balance based on the work load per server I would need gateway to handle all the incoming requests. Is it the right idea to have all the servers check into the gateway and update there status. By having the servers run through a gateway if the gateway dies all the incoming requests are ignored. I'm thinking that having all the servers maintain a list of each other, or at least a few I could rebuild the list of servers and establish a new gateway. Is it worth it? Or should I have a backup gateway that could switch out? Should I let the user choose? How should I pick which server handles the database and which handles the page serving? Should I spread the database so that queries are preformed on multiple servers? Which would theoretically improve performance. The servers would need to mirror the database at least once so that if a server goes down the database isn't corrupted. So this brings up writing another question, should I broadcast SQL queries so that all the servers can take a bit of the work load? If I do it that way wouldn't a query clog up the network so that other queries couldn't be preformed? What are my alternatives? Finally, is there a free solution already out there that might need a little modification that suits my needs?

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  • Web application framework for embedded systems?

    - by datenwolf
    I'm currently developing the software for a measurement and control system. In addition to the usual SCPI interface I'd also give it a nice HTTP frontend. Now I don't want to reinvent the wheel all over again. I already have a simple HTTPD running, but I don't want to implement all the other stuff. So what I'm looking for is a web application toolkit targeted at embedded system development. In particular this has to run on a ARM Cortex-M4, and I have some 8k of RAM available for this. It must be written in C. Is there such a thing or do I have to implement this myself?

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  • Handling Errors In PHP When Using MVC

    - by James Jeffery
    I've been using Codeigniter a lot recently, but one thing that gets on my nerves is handling errors and displaying them to the user. I've never been good at handling errors without it getting messy. My main concern is when returning errors to the user. Is it good practice to use exceptions and throw/catch exceptions rather than returning 0 or 1 from functions and then using if/else to handle the errors. Thus, making it easier to inform the user about the issue. I tend to go away from exceptions. My Java tutor at university some years ago told me "exceptions shouldn't be used in production code it's more for debugging". I get the feeling he was lying. But, an example, I have code that adds a user to a database. During the process more than 1 thing could go wrong, such as a database issue, a duplicate entry, a server issue, etc. When an issue happens during registration the user needs to know about it. What's the best way to handle errors in PHP, keeping in mind that I'm using an MVC framework.

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  • Does relying on intellisense and documentation a lot while coding makes you a bad programmer? [duplicate]

    - by sharp12345
    This question already has an answer here: Forgetting basic language functions due to use of IDE, over reliance? [duplicate] 4 answers Is a programmer required to learn and memorize all syntax, or is it ok to keep handy some documentation? Would it affect the way that managers look at coders? What are the downside of depending on intellisense and auto-complete technologies and pdf documentation?

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  • Would learning any (linguistic) language in particular further your programming career?

    - by Anonymous
    It seems apparent that English is the dominant international language for programming based on previous P.SE questions (though a highly upvoted comment correctly points out that asking a question like that on a predominantly English site will skew the results). However, is there benefit in learning a foreign language for software development? For example, do the Chinese have completely different software tools, languages, technologies, etc? How about Japanese, Russian, and other non-latin based languages? Is there an entire world of software development languages, tools and so on that only exist in these other languages? Or do people that know these languages use the tools and languages we know and love?

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  • Is it bad to have an "Obsessive Refactoring Disorder"?

    - by Rachel
    I was reading this question and realized that could almost be me. I am fairly OCD about refactoring someone else's code when I see that I can improve it. For example, if the code contains duplicate methods to do the same thing with nothing more than a single parameter changing, I feel I have to remove all the copy/paste methods and replace it with one generic one. Is this bad? Should I try and stop? I try not to refactor unless I can actually make improvements to the code performance or readability, or if the person who did the code isn't following our standard naming conventions (I hate expecting a variable to be local because of the naming standard, only to discover it is a global variable which has been incorrectly named)

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  • What is the difference between WCF service and a simple Web service in developing using .NET Framework?

    - by Steve Johnson
    My questions are: What is the difference between WCF service and a simple Web service in .NET Framework? What a WCF Service can do which a .NET Web service cant? In other words, what are the limitation of .NET Web services which were overcome in WCF services? I understand that WCF are REST based and .NET web services are SOAP based. But I need to know more than that. How a developer will make a design decision whether to developer a Web service or a WCF service?

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  • Development environment to manage multiple Oracle databases

    - by jkohlhepp
    I am in an enterprise environment where we have applications that need to run against multiple Oracle databases. Developers may need to manage multiple vintages of these databases to support different test data or diagnose bugs against different versions of the code. Right now, we have a limited set of test environments set up on "real" Oracle servers within the data center. We juggle these among development and QA groups and there is a lot of conflicts and inefficiencies that arise because of it. I am taking a look at Oracle Express Edition which would allow me to spin up a local Oracle database. This is similar to the workflow I most often see with SQL Server. Devs work on their location machine until they are ready to integration and then they push their DB changes to integration / QA environments. However, from what I read it seems that Oracle XE only supports one database instance at a time. So if I have an application that utilizes two different databases, I can't have both of them running on my local machine. Is that correct? Does Oracle Standard or Personal editions get around this limitation? If I had one of those installed locally, how difficult would it be to get multiple databases working on the same development machine? How do dev shops handle developing against Oracle where they need to be using several different Oracle instances for their applications?

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  • Softpedia published some of my open source projects — how to react?

    - by polarblau
    (FYI: I've just moved this question over from Stackoverflow on recommendation.) I just received a few emails, informing me that softpedia.com has added some of my "products" to their "database of scripts, code snippets and web applications". My products are in this case some smaller open source projects, which I have hosted and published on github. Now I'm wondering how to react to this. This site is indirectly making money of my free work through ads on three pages before the actual download. They also seem to "invent" version numbers and I can't find out if they're hosting the latest or all versions of my projects. — I can see how this could lead to problems in the future, since I don't control what's "the latest" everywhere. On the other hand I don't mind some extra publicity. I want as many people as possible to know about the projects, use them, fork them and hopefully improve them. The projects in questions are really fairly small, but this might not be the case in the future for me and/or other people reading this question. I'm sure that this must have happened to others around here. What's your opinion? Should I try to get the downloads removed? Update 1 I've requested the removal and mentioned that I don't feel that Softpedia can provide the right environment for this kind of project. Their team got back to me instantly with a friendly email saying, that they'll remove the links for now: If you are worried that your projects won't be updated, then I must tell you that I have them bookmarked in my RSS reader, so any version changes will be forwarded to me when needed. So I promise I'll keep your script up to date as soon as I see an update in the repository. I have to say, that I appreciate this kind of reaction quite a lot and so I sent them another email, describing in more detail what I'm worried about and what bothers me. I also stated, that I'm aware that my license clearly permits them to host the projects in any case, but that I'd be even happy if they would host the projects as long as they could convince me of a few details and maybe make some small changes to the way the projects are represented. — Let's see where this goes. Update 2 After discussing with their contact and requesting some changes regarding display of version (they had given the possibility to do so) and authorship they put the projects back up on their site. All in all a positive and definitely interesting experience.

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  • Some Insight on the Field of Knowledge Representations and Reasoning

    - by picmate
    I started following an MS in computer sciences after about two years of work for a software company. I worked primarily in data warehousing and business intelligence related software development during my previous occupation. There is a high chance for me to select a research in knowledge representations, ontologies and reasoning, as there are no other research available in any other interesting fields, such as pattern recognition and navigation. I developed an interest towards knowledge representation with what I learnt from the courses I am taking currently. But I do not have a deep understanding of it in terms of which areas such a field would have an impact in a real life scenario, and how it will help me when I am hunting for a job in the near future. Some thought about this would be greatly appreciated.

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  • What's a good, quick algorithms refresh?

    - by Casey Patton
    I have programming interviews coming up in a couple weeks. I took an algorithms class a while ago but likely forgot some key concepts. I'm looking for something like a very short book (< 100 pages) on algorithms to get back up to speed. Sorting algorithms, data structures, and any other essentials should be included. It doesn't have to be a book...just looking for a great way to get caught up in about a week. What's the best tool for a quick algorithms intro or refresher?

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  • Purpose of NOP instruction and align statement in x86 assembly

    - by alvonellos
    It has been a year or so since I last took an assembly class. In that class, we were using MASM with the Irvine libraries to make it easier to program in. After we'd gone through most of the instructions, he said that the NOP instruction essentially did nothing and not to worry about using it. Anyway, it was about midterm and he has some example code that wouldn't run properly, so he told us to add a NOP instruction and it worked fine. I asked I'm after class why and what it actually did, and he said he didn't know. Anybody know?

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  • Backward compatibility with event-sourcing

    - by Tomas Jansson
    How do you stay backward compatible with event-sourcing? Let say you release a version that has one kind of event, let call it X. You know how to handle that event in all the systems that extracts the events from the event source. In a later release you make a change to event X or delete it, how do you stay backward compatible with that? To have a fully functional system you need to be able to handle the old event as the same time as you need to handle the updated version. Or if you delete that event type, then you will be stuck with code that is only there to handle legacy events which in my head can be a little bit messy in the long run.

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  • Using a :default for file names on include templates in SMARTY 3 [closed]

    - by Yohan Leafheart
    Hello everyone, Although I don't think the question was as good as it could be, let me try to explain better here. I have a site using SMARTY 3 as the template system. I have a template structure similar to the below one: /templates/place1/inner_a.tpl /templates/place1/inner_b.tpl /templates/place2/inner_b.tpl /templates/place2/inner_c.tpl /templates/default/inner_a.tpl /templates/default/inner_b.tpl /templates/default/inner_c.tpl These are getting included on the parent template using {include file="{$temp_folder}/{$inner_template}"} So far great. What I wanted to do is having a default for, in the case that the file "{$temp_folder}/{$inner_template}" does not exists, it uses the equivalent file at "default/{$inner_template}". i.e. If I do {include file="place1/inner_c.tpl"}, since that file does not exists it in fact includes "default/inner_c.tpl" Is it possible?

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  • High Salaried Investment Banking Jobs for Developers — What are the pitfalls?

    - by Jaywalker
    This question might make more sense to somebody having multi-threaded programming experience in Java/ C++ with some job experience in London / Singapore. There is a huge market of Investment Banking development jobs with astonishingly high salaries (sometimes more than 100K pounds per year). Can someone with experience as a front office/trading developer tell what are the requirements to land this type job? What are the downside that i should be ready for?

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