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• Is it reasonable to expect knowing the whole stack bottom up?

  - by Vaibhav Garg

  I am an Sr. developer/architect/Product Manager for embedded systems. The systems that I have had experience with have typically been small to medium size codebases - typically close to 25-30K LOC in C, using 8-16 and 32 bit low end microcontrollers. The systems have been entirely bootstrapped by our team - meaning right from the start-up code to the end application code has either been written by the team, or at the very least, is thoroughly understood and maintained by us. Now, if we were to start developing more complex systems with complex peripherals, such as USB OTG et al. (think, low end cell phones), there are libraries and stacks available commercially and from chip vendors that reduce the task to just calling the right APIs and being able to use those peripherals. Now, from a habit point of view, this does not give me and the team a comfortable feeling, not being able to comprehend the entire code tree, with virtual black boxes at the lower layers. Is it reasonable to devote, and reserve, time getting into the details of how the APIs are implemented, assuming that the same would also entail getting into details of relevant standards (again, for USB as an example)? Or, alternatively, should a thorough understanding of the top level usage of the APIs be sufficient? This of course assumes that the source codes to all libraries are available, which they are, in almost all cases. Edit: In partial response to @Abhi Beckert, the documentation is refreshingly very comprehensive and meticulously maintained, AFAIK and been able to judge. I have not had a long experience with the same.

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• Strategies for browser compatibility on web applications in a corporate environment

  - by TiagoBrenck

  With the new CSS 3 and HTML 5 technology, web applications have gained a lot of new tools for a better UI (user interface) interaction, beautiful templates and even responsive layout to fit into tablets and smartphones. Within a corporate environment, those new technologies are required so the company can "follow" the IT evolution and their concurrent, but they also want that those new web applications supports old browsers. How should I deal with this situation? By one side we are asked to follow the the evolution of technology, create responsive layouts and use a lot of cool jQuery plugins. On the other hand, we are asked to support old browsers that do not support those new responsive features, plugins or components. I would like advice and strategies on how to create "modern" web applications that are also supported on old browsers. How does your company deal with this situation? Is it possible to have the same web application run well and beautifully on old browsers, and be responsive and interactive on newer browsers?

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• Are CK Metrics still considered useful? Is there an open source tool to help?

  - by DeveloperDon

  Chidamber & Kemerer proposed several metrics for object oriented code. Among them, depth of inheritance tree, weighted number of methods, number of member functions, number of children, and coupling between objects. Using a base of code, they tried to correlated these metrics to the defect density and maintenance effort using covariant analysis. Are these metrics actionable in projects? Perhaps they can guide refactoring. For example weighted number of methods might show which God classes needed to be broken into more cohesive classes that address a single concern. Is there approach superseded by a better method, and is there a tool that can identify problem code, particularly in moderately large project being handed off to a new developer or team?

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• Do you develop with security in mind?

  - by MattyD

  I was listening to a podcast on Security Now and they mentioned about how a lot of the of the security problems found in Flash were because when flash was first developed it wasdn't built with security in mind because it didn't need to thus flash has major security flaws in its design etc. I know best practices state that you should build secure first etc. Some people or companies don't always follow 'best practice'... My question is do you develop to be secure or do you build with all the desired functionality etc then alter the code to be secure (Whatever the project maybe) (I realise that this question could be a possible duplicate of Do you actively think about security when coding? but it is different in the fact of actually process of building the software/application and design of said software/application)

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• Project structure: where to put business logic

  - by Mister Smith

  First of all, I'm not asking where does business logic belong. This has been asked before and most answers I've read agree in that it belongs in the model: Where to put business logic in MVC design? How much business logic should be allowed to exist in the controller layer? How accurate is "Business logic should be in a service, not in a model"? Why put the business logic in the model? What happens when I have multiple types of storage? However people disagree in the way this logic should be distributed across classes. There seem to exist three major currents of thought: Fat model with business logic inside entity classes. Anemic model and business logic in "Service" classes. It depends. I find all of them problematic. The first option is what most Fowlerites stick to. The problem with a fat model is that sometimes a business logic funtion is not only related to a class, and instead uses a bunch of other classes. If, for example, we are developing a web store, there should be a function that calcs an order's total. We could think of putting this function inside the Order class, but what actually happens is that the logic needs to use different classes, not only data contained in the Order class, but also in the User class, the Session class, and maybe the Tax class, Country class, or Giftcard, Payment, etc. Some of these classes could be composed inside the Order class, but some others not. Sorry if the example is not very good, but I hope you understand what I mean. Putting such a function inside the Order class would break the single responsibility principle, adding unnecesary dependences. The business logic would be scattered across entity classes, making it hard to find. The second option is the one I usually follow, but after many projects I'm still in doubt about how to name the class or classes holding the business logic. In my company we usually develop apps with offline capabilities. The user is able to perform entire transactions offline, so all validation and business rules should be implemented in the client, and then there's usually a background thread that syncs with the server. So we usually have the following classes/packages in every project: Data model (DTOs) Data Access Layer (Persistence) Web Services layer (Usually one class per WS, and one method per WS method). Now for the business logic, what is the standard approach? A single class holding all the logic? Multiple classes? (if so, what criteria is used to distribute the logic across them?). And how should we name them? FooManager? FooService? (I know the last one is common, but in our case it is bad naming because the WS layer usually has classes named FooWebService). The third option is probably the right one, but it is also devoid of any useful info. To sum up: I don't like the first approach, but I accept that I might have been unable to fully understand the Zen of it. So if you advocate for fat models as the only and universal solution you are welcome to post links explaining how to do it the right way. I'd like to know what is the standard design and naming conventions for the second approach in OO languages. Class names and package structure, in particular. It would also be helpful too if you could include links to Open Source projects showing how it is done. Thanks in advance.

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• How do you keep code with continuations/callbacks readable?

  - by Heinzi

  Summary: Are there some well-established best-practice patterns that I can follow to keep my code readable in spite of using asynchronous code and callbacks? I'm using a JavaScript library that does a lot of stuff asynchronously and heavily relies on callbacks. It seems that writing a simple "load A, load B, ..." method becomes quite complicated and hard to follow using this pattern. Let me give a (contrived) example. Let's say I want to load a bunch of images (asynchronously) from a remote web server. In C#/async, I'd write something like this: disableStartButton(); foreach (myData in myRepository) { var result = await LoadImageAsync("http://my/server/GetImage?" + myData.Id); if (result.Success) { myData.Image = result.Data; } else { write("error loading Image " + myData.Id); return; } } write("success"); enableStartButton(); The code layout follows the "flow of events": First, the start button is disabled, then the images are loaded (await ensures that the UI stays responsive) and then the start button is enabled again. In JavaScript, using callbacks, I came up with this: disableStartButton(); var count = myRepository.length; function loadImage(i) { if (i >= count) { write("success"); enableStartButton(); return; } myData = myRepository[i]; LoadImageAsync("http://my/server/GetImage?" + myData.Id, function(success, data) { if (success) { myData.Image = data; } else { write("error loading image " + myData.Id); return; } loadImage(i+1); } ); } loadImage(0); I think the drawbacks are obvious: I had to rework the loop into a recursive call, the code that's supposed to be executed in the end is somewhere in the middle of the function, the code starting the download (loadImage(0)) is at the very bottom, and it's generally much harder to read and follow. It's ugly and I don't like it. I'm sure that I'm not the first one to encounter this problem, so my question is: Are there some well-established best-practice patterns that I can follow to keep my code readable in spite of using asynchronous code and callbacks?

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• What is the advantage of currying?

  - by Mad Scientist

  I just learned about currying, and while I think I understand the concept, I'm not seeing any big advantage in using it. As a trivial example I use a function that adds two values (written in ML). The version without currying would be fun add(x, y) = x + y and would be called as add(3, 5) while the curried version is fun add x y = x + y (* short for val add = fn x => fn y=> x + y *) and would be called as add 3 5 It seems to me to be just syntactic sugar that removes one set of parentheses from defining and calling the function. I've seen currying listed as one of the important features of a functional languages, and I'm a bit underwhelmed by it at the moment. The concept of creating a chain of functions that consume each a single parameter, instead of a function that takes a tuple seems rather complicated to use for a simple change of syntax. Is the slightly simpler syntax the only motivation for currying, or am I missing some other advantages that are not obvious in my very simple example? Is currying just syntactic sugar?

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• Improving performance of fuzzy string matching against a dictionary [closed]

  - by Nathan Harmston

  Hi, So I'm currently working for with using SecondString for fuzzy string matching, where I have a large dictionary to compare to (with each entry in the dictionary has an associated non-unique identifier). I am currently using a hashMap to store this dictionary. When I want to do fuzzy string matching, I first check to see if the string is in the hashMap and then I iterate through all of the other potential keys, calculating the string similarity and storing the k,v pair/s with the highest similarity. Depending on which dictionary I am using this can take a long time ( 12330 - 1800035 entries ). Is there any way to speed this up or make it faster? I am currently writing a memoization function/table as a way of speeding this up, but can anyone else think of a better way to improve the speed of this? Maybe a different structure or something else I'm missing. Many thanks in advance, Nathan

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• Documenting and enforcing programming standards and guidelines for shared library

  - by dreza

  Myself and another developer with the go ahead from our IT director have started a general purpose library in .NET with the intention that it will provide many common purpose classes that we use in our day to day development. During discussions and design of the library we have come up with a set of standards that we want the library to follow to ensure it is maintained and expanded on in a consistent manner. What is the best way to ensure these decisions we made for the library get feed to the other developers who might be using and adding to this library in the future. One of our decisions was to ensure we review all checked in code so we expect initially there to be some differences in coding styles of individuals not fitting in with the project standards. Some ideas I had were: Add a Read-me.txt to the project that outline the guidelines and standards Send an email out to everyone in the team to let them know about the project etc Call a team meeting to go through this new project and our expectations and standards we were aiming to follow Try and enforce the standards via Visual Studio (not sure if this would be possible or how just an idea) At the moment there is no general company programming standards so this would be a first really insofar as we are creating a standard that different project teams would need to adhere to.

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• Is a code review which uses only code comments a good idea?

  - by gaRex

  Preconditions Team uses DVCS IDE supports comments parsing (like TODO and etc.) Tools like CodeCollaborator are expensive for budget Tools like gerrit are too complex for install or not usable Workflow Author publishes somewhere on central repo feature branch Reviewer fetch it and start review In case of some question/issue reviewer create comment with special label, like "REV". Such label MUST not be in production code -- only on review stage: $somevar = 123; // REV Why do echo this here? echo $somevar; When reviewer finish post comments -- it just commits with stupid message "comments" and pushes back Author pulls feature branch back and answer comments in similar way or improve code and push it back When "REV" comments have gone we can think, that review has successfully finished. Author interactively rebases feature branch, squashes it to remove those "comment" commits and now is ready to merge feature to develop or make any action that usualy could be after successful internal review IDE support I know, that custom comment tags are possible in eclipse & netbeans. Sure it also should be in blablaStorm family. Questions Do you think this methodology is viable? Do you know something similar? What can be improved in it?

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• Is eval the defmacro of javascript?

  - by Florian Margaine

  In Common Lisp, defmacro basically allows us to build our own DSL. I read this page today and it explains something cleverly done: But I wasn't about to write out all these boring predicates myself, so I defined a function that, given a list of words, builds up the text for such a predicate automatically, and then evals it to produce a function. Which just looks like defmacro to me. Is eval the defmacro of javascript? Could it be used as such?

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• Web Application Tasks Estimation

  - by Ali

  I know the answer depends on the exact project and its requirements but i am asking on the avarage % of the total time goes into the tasks of the web application development statistically from your own experiance. While developing a web application (database driven) How much % of time does each of the following activities usually takes: -- database creation & all related stored procedures -- server side development -- client side development -- layout settings and designing I know there are lots of great web application developers around here and each one of you have done fair amount of web development and as a result there could be an almost fixed percentage of time going to each of the above activities of web developments for standard projects Update : I am not expecting someone to tell me number of hours i am asking about the average percentage of time that goes on each of the activities as per your experience i.e. server side dev 50%, client side development 20% ,,,,, I repeat there will be lots of cases that differs from the standard depending on the exact requirments of each web application project but here i am asking about Avarage for standard (no special requirment) web project

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• Implementation details of database synchronisation API

  - by Daniel

  I want to achieve a database synchronisation between my server database and a client application. The server would run MySQL and the applications may run different database technologies, their implementation isn't important. I have a MySQL database online and web accessible via an API I wrote in PHP (just a detail). My client application ships with a copy of the online data. As time passes my goal is to check for any changes in the online database and make these updates available to the client app via an API call, by sending a date to an API endpoint corresponding to the last date the app was updated, the response would be a JSON filled with all new objects and updated objects, and delete IDs, this makes possible to update the local store appropriately. Essentially I want to do this: http://dbconvert.com/synchronization.php My question is about the implementation details. Would I need to add a column to my database tables with a "last modified" date? Since the client app could be very out of date if it's been offline for a long time, does that also mean I shouldn't delete data from the online database but instead have another column called "delete" set to 1 and a modified date updated appropriately? Would my SQL query simply check for all data with a modified date superior then the date passed into the API request by the client? I feel like there's a lot more to it then having a ton of dates everywhere. And also, worry that I will need to persist a lot of old data in order to ensure that old versions of the client app always have the opportunity to delete parts of their data when they are able to sync.

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• What are algorithmic paradigms?

  - by Vaibhav Agarwal

  We generally talk about paradigms of programming as functional, procedural, object oriented, imperative etc but what should I reply when I am asked the paradigms of algorithms? For example are Travelling Salesman Problem, Dijkstra Shortest Path Algorithm, Euclid GCD Algorithm, Binary search, Kruskal's Minimum Spanning Tree, Tower of Hanoi paradigms of algorithms? Should I answer the data structures I would use to design these algorithms?

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• Question about casting a class in Java with generics

  - by Florian F

  In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ArrayList<?>>)ArrayList.class; gives a warning. Why is (a) an error? What is it, that Java needs to do in the assignment, if not the cast shown in (b)? And why isn't ArrayList compatible with ArrayList? I know one is "raw" and the other is "generic", but what is it you can do with an ArrayList and not with an ArrayList, or the other way around?

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• Great Debugging skills weak problem solving

  - by Mahmoud

  For the 5 years I worked for various companies, I worked in large software like computer vision kits, embedded, games. I found myself very good at debuggins skills, I've even found and fixed bugs in frameworks and I solved them. The problem is that I'm very weak at problem solving. I got interview with Qualcomm, and they said you're fine at software, but you have a limited problem solving, I also had the same results with Google. I'm very bad at solving puzzles and brain teasers. During the interviews I solve all of the software related problems on the blackboard, but when I went to the GM and face math problems and probabilities, I struggle. How can I improve my problem solving skills? Edit Some of the problems: A cake that is cut from anywhere and needs just one cut to halved in equal. I told him cut it horizontally, he said No, consider it as a 2D Problem!. Consider a concenteric 3 circles, each one can get a color, but not matched with the other circle, how many blobs you can make out of those circles ? this was with the GM ( Augmented Reality SDK) Consider a train, an infinite one, and you looked at the window, and there are two cars, one big, and one small, what is the probability of having only a big car, I said 50%, he said, what if that two cars you dont know their length, and you want to get the probability of getting the biggest one, I struggled, didn't solve it... I was really exahusted after long day of interviews prob of having a number divisible by 5 in numbers from 1 to 100.. struggled!! All coding questions I solved them like reverse a string, detect a cycle in a linked list,..etc.

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• Developing JSON API for a Carpool Engine

  - by Siddharth

  I am developing a new set of API methods for carpooling/cab booking, so if a developer needs to develop an app or webportal for carpooling, he can call my JSON API. Basically making it easy for developers. My API current has: AddVehicle AddJourney SearchJourney SubscribeToThisJourney(journey) SubscriberList(journey) to get list of people who have subscribed for this journey AcceptSubscription(subscriber) AcceptedSubcriberList SubscriberList to get list of providers I have subscribed to I need help with replacing subscriber with something else. It's difficult to remember, and confusing when you see 3 methods that mean very different things: SubscriberList, SubscribedToThisJourneyList and AcceptedSubscriberList. Confusing to remember. One is a list of who I have subscribed to Who has subscribed to me Whose subscription I have accepted How can I name these methods to make them easier to understand and remember?

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• org.apache.sling.scripting.jsp.jasper.JasperException: Unable to load tag handler class [migrated]

  - by Babak Behzadi

  I'm developing an Apache Sling WCMS and using java tag libs to rendering some data. I defined a jsp tag lib with following descriptor and handler class: TLD file contains: <?xml version="1.0" encoding="UTF-8"?> <taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"> <tlib-version>1.0</tlib-version> <short-name>taglibdescriptor</short-name> <uri>http://bob/taglibs</uri> <tag> <name>testTag</name> <body-content>tagdependent</body-content> <tag-class>org.bob.taglibs.test.TestTagHandler</tag-class> </tag> </taglib> Tag handler class: package org.bob.taglibs.test; import javax.servlet.jsp.tagext.TagSupport; public class TestTagHandler extends TagSupport{ @Override public int doStartTag(){ try { pageContext.getOut().print("<h1>Helloooooooo</h1>"); } catch(Exception e) { return SKIP_BODY; } return EVAL_BODY_INCLUDE; } } I packaged the tag lib as BobTagLib.jar and deployed it as a bundle using Sling Web Console. I used this tag lib in a jsp page deployed in my Sling repository: index.jsp: <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="bob" uri="http://bob/taglibs" %> <html> <head><title>Simple jsp page</title></head> <body> <bob:testTag/> </body> </html> Calling the page cause the following exception: org.apache.sling.scripting.jsp.jasper.JasperException: /apps/TagTest/index.jsp(7,5) Unable to load tag handler class "org.bob.taglibs.test.TestTagHandler" for tag "bob:testTag" ... Can any one get me a solution? In advance, any help is apreciated.

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• How to name an subclass that add a minor, detailed thing?

  - by Louis Rhys

  What is the most concise (yet descriptive) way of naming a subclass that only add a specific minor thing to the parent? I encountered this case a lot in WPF, where sometime I have to add a small functionality to an out-of-the-box control for specific cases. Example: TreeView doesn't change the SelectedItem on right-click, but I have to make one that does in my application. Some possible names are TreeViewThatChangesSelectedItemOnRightClick (way too wordy and maybe difficult to read because there is so many words concantenated together) TreeView_SelectedItemChangesOnRightClick (slightly more readable, but still too wordy and the underscore also breaks the normal convention for class names) TreeViewThatChangesSIOnRC (non-obvious acronym), ExtendedTreeView (more concise, but doesn't describe what it is doing. Besides, I already found a class called this in the library, that I don't want to use/modify in my application). LouisTreeView, MyTreeView, etc. (doesn't describe what it is doing). It seems that I can't find a name which sounds right. What do you do in situation like this?

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• TDD/Tests too much an overhead/maintenance burden?

  - by MeshMan

  So you've heard it many times from those who do not truly understand the values of testing. Just to start things out, I'm a follower of Agile and Testing... I recently had a discussion about performing TDD on a product re-write where the current team does not practice unit testing on any level, and probably have never heard of the dependency injection technique or test patterns/design etc (we won't even get on to clean code). Now, I am fully responsible for the rewrite of this product and I'm told that attempting it in the fashion of TDD, will merely make it a maintenance nightmare and impossible for the team maintain. Furthermore, as it's a front-end application (not web-based), adding tests is pointless, as the business drive changes (by changes they mean improvements of course), the tests will become out of date, other developers who come on to the project in the future will not maintain them and become more of a burden for them to fix etc. I can understand that TDD in a team that does not currently hold any testing experience doesn't sound good, but my argument in this case is that I can teach my practice to those around me, but further more, I know that TDD makes BETTER software. Even if I was to produce the software using TDD, and throw all the tests away on handing it over to a maintenance team, it surely would be a better approach than not using TDD at all from the start? I've been shot down as I've mentioned doing TDD on most projects for a team that have never heard of it. The thought of "interfaces" and strange looking DI constructors scares them off... Can anyone please help me in what is normally a very short conversation of trying to sell TDD and my approach to people? I usually have a very short window of argument before falling at the knees to the company/team.

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• How to dealing with the "programming blowhard"?

  - by Peter G.

  (Repost, I posted this in the wrong section before, sorry) So I'm sure everyone has run into this person at one point or another, someone catches wind of your project or idea and initially shows some interest. You get to talking about some of your methods and usually around this time they interject stating how you should use method X instead, or just use library Y. But not as a friendly suggestion, but bordering on a commandment. Often repeating the same advice over and over like a overzealous parrot. Personally, I like to reinvent the wheel when I'm learning, or even just for fun, even if it turns out worse than what's been done before. But this person apparently cannot fathom recreating ANY utility for such purposes, or possibly try something that doesn't strictly follow traditional OOP practices, and will settle for nothing except their sense of perfection, and thus naturally heave their criticism sludge down my ears full force. To top it off, they eventually start justifying their advice (retardation) by listing all the incredibly complex things they've coded single-handedly (usually along the lines of "trust me, I've made/used program X for a long time, blah blah blah"). Now, I'm far from being a programming master, I'm probably not even that good, and as such I value advice and critique, but I think advice/critique has a time and place. There is also a big difference between being helpful and being narcissistic. In the past I probably would have used a somewhat stronger George Carlin style dismissal, but I don't think burning bridges is the best approach anymore. Maybe I'm just an asshole, but do you have any advice on how to deal with this kind of verbal flogging?

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• Obtaining Embedded Linux Experience

  - by Thomas Matthews

  As an embedded firmware developer, I have used operating systems such as WinCE, Nucleus, ThreadX, VRTX and some background loops. There are more opportunities for me if I had Linux OS experience, or perhaps some certification. In my research, the only way to get Linux experience is to have your company move to a Linux OS. All the recruiters and HR folks won't let you in the door unless you have Linux experience. I haven't found any Universities that teach Linux. Recruiters and HR want some tangible proof (starting up your own Ubuntu box or playing with it doesn't count). So, how does one get into the area of Embedded Linux without Linux experience (I have Unix and Cygwin experience, but not Linux)?

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• Is there a measure of code rot?

  - by DarenW

  I'm dealing, again, with a messy C++ application, tons of classes with confusing names, objects have pointers into each other and all over, longwinded Boost and STL data types, etc. (Pause and consider your favorite terror of messy legacy code. We probably have it.) The phrase "code rot" oft comes to mind when I work on this project. Is there a quantitative way to measure code rot? I wouldn't expect anything highly meaningful or scientific, since no other measure of code productivity or quality is so fine. I'm not looking for a mere opposite of measures of code quality, but specifically a measure of how many bad things happened after a series of maintenance software "engineers" have had turns hacking at the code. A general measure applying to any language, or many languages, would be great. If there's no such thing, at least for C++, which is a better than average language for creating messes. Maybe something involving a measure of topology of how objects connect during runtime, a count of chunks of commented out code, how mane files a typical variable's usage is scattered over, I don't know... but surely now, a decade into the 21st Century, someone has attempted to define some sort of rot measure. It would be especially interesting to automate a series of svn checkouts, measure the "rottenosity" of each, and plot the decay over time.

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• Is there an established convention for separating Windows file names in a string?

  - by Heinzi

  I have a function which needs to output a string containing a list of file paths. I can choose the separation character but I cannot change the data type (e.g. I cannot return a List<string> or something like that). Wanting to use some well-established convention, my first intuition was to use the semicolon, similar to what Windows's PATH and Java's CLASSPATH (on Windows) environment variables do: C:\somedir\somefile.txt;C:\someotherdir\someotherfile.txt However, I was surprised to notice that ; is a valid character in an NTFS file name. So, is the established best practice to just ignore this fact (i.e. "no sane person should use ; in a file name and if they do, it's their own fault") or is there some other established character for separating Windows paths or files? (The pipe (|) might be a good choice, but I have not seen it used anywhere yet for this purpose.)

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• scrapy cannot find div on this website [on hold]

  - by Jaspal Singh Rathour

  I am very new at this and have been trying to get my head around my first selector can somebody help? i am trying to extract data from page http://groceries.asda.com/asda-webstore/landing/home.shtml?cmpid=ahc--ghs-d1--asdacom-dsk-_-hp#/shelf/1215337195041/1/so_false all the info under div class = listing clearfix shelfListing but i cant seem to figure out how to format response.xpath(). I have managed to launch scrapy console but no matter what I type in response.xpath() i cant seem to select the right node. I know it works because when I type response.xpath('//div[@class="container"]') I get a response but don't know how to navigate to the listsing cleardix shelflisting. I am hoping that once i get this bit I can continue working my way through the spider. Thank you in advance! PS I wonder if it is not possible to scan this site - is it possible for the owners to block spiders?

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