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• Actor based concurrency and cancellation

  - by Akash

  I'm reading about actor based concurrency and I appreciate the simplicity of actors sequentially processing messages on a single thread. However there is one scenario that doesn't seen possible. Suppose that actor A sends a message to actor B, who then performs some long running task and returns a completion message to actor A. How can actor A force actor B to cancel the long running task after it has started? If actor B is running the task in its message queue thread, it won't pick up the cancellation message until it had completed the task; if actor B runs the task in a background thread then it seems to be violating the principle of actors. Is there a common way that this scenario is handled with actors? Or does each actor language/framework take a different approach? Or is this not a suitable problem to tackle via actors?

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• Proper way to measure the scalability of web Application

  - by Jorge

  Let's say that I have a web Application where i'm going to have 300 users and each one have to see data on real time, imagine that each client make an ajax call to the server to see in real time what's happens with the changes of the data, this calls are made each 300 ms per user. I know that i can run a simulation to see if the hardware of my server supports this example. But what happen's if the number of users start to grow up. Is there a way that i can measure the hardware needed to handle this growing behavior, a software, a formula, algorithm or maybe recommend me if i need to implement an distributed application with multiplies servers and balance the loads.

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• A new mission statement for my school's algorithms class

  - by Eric Fode

  The teacher at Eastern Washington University that is now teaching the algorithms course is new to eastern and as a result the course has changed drastically mostly in the right direction. That being said I feel that the class could use a more specific, and industry oriented (since that is where most students will go, though suggestions for an academia oriented class are also welcome) direction, having only worked in industry for 2 years I would like the community's (a wider and much more collectively experienced and in the end plausibly more credible) opinion on the quality of this as a statement for the purpose an algorithms class, and if I am completely off target your suggestion for the purpose of a required Jr. level Algorithms class that is standalone (so no other classes focusing specifically on algorithms are required). The statement is as follows: The purpose of the algorithms class is to do three things: Primarily, to teach how to learn, do basic analysis, and implement a given algorithm found outside of the class. Secondly, to teach the student how to model a problem in their mind so that they can find a an existing algorithm or have a direction to start the development of a new algorithm. Third, to overview a variety of algorithms that exist and to deeply understand and analyze one algorithm in each of the basic algorithmic design strategies: Divide and Conquer, Reduce and Conquer, Transform and Conquer, Greedy, Brute Force, Iterative Improvement and Dynamic Programming. The Question in short is: do you agree with this statement of the purpose of an algorithms course, so that it would be useful in the real world, if not what would you suggest?

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• What are some cool git or .gitignore tricks & best practices? [closed]

  - by 01walid

  Git is just awesome and fast VCS, however, knowing better this tool will help you incredibly increase your productivity and save your time. Here we can try to make a collection of tips, tricks and useful links to better take advantage of git, this question can have some more sub-questions, I mean: what are some usefull commands that reverse or rectify commits/adding/removing mistakes? what are .gitignore & Global .gitignore best practices? especially with private/secure files that contains passwords, api keys, local config and so on ... .gitignore first or git add <files> first? what are the advantages/disadvantages of both being the first/last. links to blog post, articles, would be sufficient. I thought every sub-question is not worthy opening a whole post each alone, I think centralizing these tips in one question post would help many people.

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• Can throwing the iPhone high in the air launch my app or trigger desired function in iOS 7 or later

  - by aMother

  My app is an emergency app. It will be used by people in emergency and disasters. It's possible that they got stuck in situations where they just don't have the time to enter or draw their password, launch the appp and push a button. Is it possible that ask the OS to launch the app if user throw their iphone up in the air or shake it vigrously or something else. PS: I think it's possible with the accelerometer.

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• Data migration - dangerous or essential?

  - by MRalwasser

  The software development department of my company is facing with the problem that data migrations are considered as potentially dangerous, especially for my managers. The background is that our customers are using a large amount of data with poor quality. The reasons for this is only partially related to our software quality, but rather to the history of the data: Most of them have been migrated from predecessor systems, some bugs caused (mostly business) inconsistencies in the data records or misentries by accident on the customer's side (which our software allowed by error). The most important counter-arguments from my managers are that faulty data may turn into even worse data, the data troubles may awake some managers at the customer and some processes on the customer's side may not work anymore because their processes somewhat adapted to our system. Personally, I consider data migrations as an integral part of the software development and that data migration can been seen to data what refactoring is to code. I think that data migration is an essential for creating software that evolves. Without it, we would have to create painful software which somewhat works around a bad data structure. I am asking you: What are your thoughts to data migration, especially for the real life cases and not only from a developer's perspecticve? Do you have any arguments against my managers opinions? How does your company deal with data migrations and the difficulties caused by them? Any other interesting thoughts which belongs to this topics?

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• What can procs and lambdas do that functions can't in ruby

  - by SecurityGate

  I've been working in Ruby for the last couple weeks, and I've come to the subject of procs, lambdas and blocks. After reading a fair share of examples from a variety of sources, I don't how they're much different from small, specialized functions. It's entirely possible that the examples I've read aren't showing the power behind procs and lambdas. def zero_function(x) x = x.to_s if x.length == 1 return x = "0" + x else return x end end zero_lambda = lambda {|x| x = x.to_s if x.length == 1 return x = "0" + x else return x end } zero_proc = Proc.new {|x| x = x.to_s if x.length == 1 puts x = "0" + x else puts x end } puts zero_function(4) puts zero_lambda.call(3) zero_proc.call(2) This function, proc, and lambda do the exact same thing, just slightly different. Is there any reason to choose one over another?

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• Can a NodeJS webserver handle multiple hostnames on the same IP?

  - by Matthew Patrick Cashatt

  I have just begun learning NodeJS and LOVE it so far. I have set up a Linux box to run it and, in learning to use the event-driven model, I am curious if I can use a common IP for multiple domain names. Could I point, for example, www.websiteA.com, www.websiteB.com, and www.websiteC.com all to the same IP (node webserver) and then route to the appropriate source files based on the request? Would this cause certain doom when it came to scaling to any reasonable size?

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• To branch or not to branch?

  - by Idsa

  Till recently my development workflow was the following: Get the feature from product owner Make a branch (if feature is more than 1 day) Implement it in a branch Merge changes from main branch to my branch (to reduce conflicts during backward merging) Merge my branch back to main branch Sometimes there were problems with merging, but in general I liked it. But recently I see more and more followers of idea to not make branches as it makes more difficult to practice continuous integration, continuous delivery, etc. And it sounds especially funny from people with distributed VCS background who were talking so much about great merging implementations of Git, Mercurial, etc. So the question is should we use branches nowadays?

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• Access functions from user control without events?

  - by BornToCode

  I have an application made with usercontrols and a function on main form that removes the previous user controls and shows the desired usercontrol centered and tweaked: public void DisplayControl(UserControl uControl) I find it much easier to make this function static or access this function by reference from the user control, like this: MainForm mainform_functions = (MainForm)Parent; mainform_functions.DisplayControl(uc_a); You probably think it's a sin to access a function in mainform, from the usercontrol, however, raising an event seems much more complex in such case - I'll give a simple example - let's say I raise an event from usercontrol_A to show usercontrol_B on mainform, so I write this: uc_a.show_uc_b+= (s,e) => { usercontrol_B uc_b = new usercontrol_B(); DisplayControl(uc_b); }; Now what if I want usercontrol_B to also have an event to show usercontrol_C? now it would look like this: uc_a.show_uc_b+= (s,e) => { usercontrol_B uc_b = new usercontrol_B(); DisplayControl(uc_b); uc_b.show_uc_c += (s2,e2) => {usercontrol_C uc_c = new usercontrol_C(); DisplayControl(uc_c);} }; THIS LOOKS AWFUL! The code is much simpler and readable when you actually access the function from the usercontrol itself, therefore I came to the conclusion that in such case it's not so terrible if I break the rules and not use events for such general function, I also think that a readable usercontrol that you need to make small adjustments for another app is preferable than a 100% 'generic' one which makes my code look like a pile of mud. What is your opinion? Am I mistaken?

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• Updating password hashing without forcing a new password for existing users

  - by Willem

  You maintain an existing application with an established user base. Over time it is decided that the current password hashing technique is outdated and needs to be upgraded. Furthermore, for UX reasons, you don't want existing users to be forced to update their password. The whole password hashing update needs to happen behind the screen. Assume a 'simplistic' database model for users that contains: ID Email Password How does one go around to solving such a requirement? My current thoughts are: create a new hashing method in the appropriate class update the user table in the database to hold an additional password field Once a user successfully logs in using the outdated password hash, fill the second password field with the updated hash This leaves me with the problem that I cannot reasonable differentiate between users who have and those who have not updated their password hash and thus will be forced to check both. This seems horribly flawed. Furthermore this basically means that the old hashing technique could be forced to stay indefinitely until every single user has updated their password. Only at that moment could I start removing the old hashing check and remove the superfluous database field. I'm mainly looking for some design tips here, since my current 'solution' is dirty, incomplete and what not, but if actual code is required to describe a possible solution, feel free to use any language.

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• Branching and CI Builds with Agile

  - by Bob Horn

  We follow many agile processes, including automated tests, continuous integration, sprint reviews, etc... We're currently having a debate about how often we should branch release builds. We've been doing two-week sprints and trying to deploy to production at the end of each sprint. Some of us think we should be branching every sprint. Some of us think that's overkill. If a project encompasses three Visual Studio solutions, and we branch every sprint, then that's three branches, and three CI builds to create every two weeks. If we do this for six months, we'll end up with 36 branches and 36 CI builds. There is overhead involved in that. For those of us that think that branching every sprint is overkill, we don't have a very good alternative. On my last project, we deployed some solutions from the Main trunk. Yeah, that's not good, but it saved on some of the overhead. What's the right way to manage branching/releasing and CI builds, using agile, when we have such short (two-week) sprint cycles?

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• Distributed Transaction Framework across webservices

  - by John Petrak

  I am designing a new system that has one central web service and several site web services which are spread across the country and some overseas. It has some data that must be identical on all sites. So my plan is to maintain that data in the central web service and then "sync" the data to sites. This includes inserts, edits and deletes. I see a problem when deleting, if one site has used the record, then I need to undo the delete that has happened on the other servers. This lead me to idea that I need some sort of transaction system that can work across different web servers. Before I design one from scratch, I would like to know if anyone has come across this sort of problem and if there are any frame works or even design patterns that might aid me?

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• Proper Method name for XML builder

  - by Wesley

  I think this is the right stack for this. I have a helper class which builds CAML queries (SharePoint XML for getting list items from SQL) There is one method that is flexibly used to build the queries that get all related votes and comments for a social item. I don't want to call it BuildVoteorCommentXML or something long winded like that. Is there a good naming convention for getting all Join/Foreign Key objects from a core object?

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• Does a mobile app need more access than the public API of a site?

  - by Iain

  I have a site with a public API, and some mobile app developers have been brought in to produce an iPhone app for the site. They insist they need to see the database schema, but as I understand it, they should only need access to the documented public API. Am I right? Is there something I've missed? I've told them that if there's a feature missing or data they require I can extend the API so that they can access it. I thought a web service API held to much the same principles as OOP object API's, in that the implementation details should be hidden as much as possible. I'm not a mobile app developer so if there is something I don't quite see then please let me know. Any insight or help will be much appreciated.

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• How can I sell a legacy program rewrite to the business?

  - by Wil

  We have a legacy classic ASP application that's been around since 2001. It badly needs to be re-written, but it's working fine from an end user perspective. The reason I feel like a rewrite is necessary is that when we need to update it (which is admittedly not that often) then it takes forever to go through all the spaghetti code and fix problems. Also, adding new features is also a pain since it was architect-ed and coded badly. I've run cost analysis for them on maintenance but they are willing to spend more for the small maintenance jobs than a rewrite. Any suggestions on convincing them otherwise?

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• How do I write code that doesn't suck? [closed]

  - by Afnan

  My friends and I would like to write a C# desktop application, and would like some guidance on how to make sure the code base is professional and well-kept. Should we use classes or interfaces for our inheritance patterns (which is better)? What are the best practices for professional applications? How do we know what sloppy code looks like, and how do we avoid creating sloppy code? Are there any best practices regarding the design of Winforms applications?

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• What's the best way to move to linux from windows for web development ?

  - by rajesh pillai

  I am primarily a programmer developing on windows based OS using c# as my primary language. I am evaluating Ubuntu Linux as an alternate platform and would like to know the best stack for doing web development on this. I had gone through the following thread Moving development from Windows to Linux but it doesn't answer my questions fully. Some of the points I am interested are outlined below PHP/Ruby/Python (What would you recommend?) Is Mono mature enough for any large scale development? Has anyone any real experience using Mono. IDE (including debugging support, intellisense, source control integration,Unit testing) Unit testing framework based on the language recommended Web framework if any. Load Testing tools Web server (I know there are many webservers, but would like to know which one is primarily used by most people) Your inputs is greatly appreciated. Thanks.

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• Which programming language do you think is the most beautiful and which the ugliest? [closed]

  - by user1598390

  I would like to hear opinions about what programming language do you consider to produce the most legible, self-documenting, intention-transparent, beautiful-looking code ? And which produces the most messy-looking, unintentionally obfuscated, ugly code, regardless of it being good code ? Let me clarify: I'm talking about the syntax, "noise vs signal", structure of the language. Assignment operators. De-referencing. Whether it's dot syntax or "-" syntax. What languages do you think are inherently harder to read than others, given all other things being equal like, say, code quality, absence of code smells, etc. ?

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• Why would I want to install node.js in my Rails Application?

  - by Crazy JIm

  Okay guys, I'm super confused. I thought node.js was a sever side framwork, basically the js version of Ruby's Rails or PHP's Zend. However, I'm having some difficulty with turbolinks, and it seems to be the way to fix it is through installing node.js I mean, I don't understand this at all. How can two frameworks work together like this? Also, it's not a gem (that REALLY would have confused me), you have to install node.js it onto your local machine by running (in the case of Ubuntu) sudo apt-get install nodejs Firstly, how does this totally separate framwork have any bearing on rails? Secondly, surely this isn't fixing the problem forever? When you specify a gem in your gemfile, the server knows what external libraries to install. How does the server know to install nodejs?

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• How important are unit tests in software development?

  - by Lo Wai Lun

  We are doing software testing by testing a lot of I/O cases, so developers and system analysts can open reviews and test for their committed code within a given time period (e.g. 1 week). But when it come across with extracting information from a database, how to consider the cases and the corresponding methodology to start with? Although that is more likely to be a case studies because the unit-testing depends on the project we have involved which is too specific and particular most of the time. What is the general overview of the steps and precautions for unit-testing?

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• JUnit Testing in Multithread Application

  - by e2bady

  This is a problem me and my team faces in almost all of the projects. Testing certain parts of the application with JUnit is not easy and you need to start early and to stick to it, but that's not the question I'm asking. The actual problem is that with n-Threads, locking, possible exceptions within the threads and shared objects the task of testing is not as simple as testing the class, but testing them under endless possible situations within threading. To be more precise, let me tell you about the design of one of our applications: When a user makes a request several threads are started that each analyse a part of the data to complete the analysis, these threads run a certain time depending on the size of the chunk of data (which are endless and of uncertain quality) to analyse, or they may fail if the data was insufficient/lacking quality. After each completed its analysis they call upon a handler which decides after each thread terminates if the collected analysis-data is sufficient to deliver an answer to the request. All of these analysers share certain parts of the applications (some parts because the instances are very big and only a certain number can be loaded into memory and those instances are reusable, some parts because they have a standing connection, where connecting takes time, ex.gr. sql connections) so locking is very common (done with reentrant-locks). While the applications runs very efficient and fast, it's not very easy to test it under real-world conditions. What we do right now is test each class and it's predefined conditions, but there are no automated tests for interlocking and synchronization, which in my opionion is not very good for quality insurances. Given this example how would you handle testing the threading, interlocking and synchronization?

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• Calling COM from Intel Fortran?

  - by user57460

  I'm trying to get COM working from my Fortran application. I do a "COMINITIALIZE" followed by a "COMCreateObjectByProgID". Both of these appear to be successful and return a status of zero. However, when I try to use the COM object, I get "Unhandled exception at 0x00000000 in FortranProg01.exe: 0xC0000005: Access violation." I realize that this error can mean almost anything, but has anyone got some suggestions of common problems with COM that produce this problem? Here are some more details. My program code: program FortranProg01 use myolepg implicit none integer*4 comInitStatus integer:: comCreateStatus INTEGER(INT_PTR_KIND()) $OBJECT INTEGER(4) funcResult REAL(8) pkgVersion call COMINITIALIZE(comInitStatus) print *, comInitStatus call COMCreateObjectByProgID('MyOlePg.MyOlePkg', $OBJECT, comCreateStatus) print *, comCreateStatus funcResult = IMyOlePkg_GetPackageVersion($OBJECT, pkgVersion) print *, funcResult call COMUNINITIALIZE() end program FortranProg01 The wizard-generated interface code: INTERFACE !property PackageVersion INTEGER(4) FUNCTION IMyOlePkg_GetPackageVersion($OBJECT, pVal) INTEGER(INT_PTR_KIND()), INTENT(IN) :: $OBJECT ! Object Pointer !DEC$ ATTRIBUTES VALUE :: $OBJECT REAL(8), INTENT(OUT) :: pVal !DEC$ ATTRIBUTES REFERENCE :: pVal !DEC$ ATTRIBUTES STDCALL :: IMyOlePkg_GetPackageVersion END FUNCTION IMyOlePkg_GetPackageVersion END INTERFACE Any help would be much appreciated! Thanks! Brad.

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• Sorting a Linked List [closed]

  - by Mohit Sehgal

  I want to sort a linked list. Here Node is class representing a node in a Linked List I have written a code to bubble sort a linked list. Program does not finishes execution. Kindly point out the mistakes. class Node { public: int data; public: Node *next; Node() { data=0;next=0; } Node(int d) { data=d; } void setData(int d) { data=d; } void print() { cout<<data<<endl; } bool operator==(Node n) { return this->data==n.data; } bool operator >(Node d) { if((this->data) > (d.data)) return true; return false; } }; class LList { public: int noOfNodes; Node *start;/*Header Node*/ LList() { start=new Node; noOfNodes=0;start=0; } void addAtFront(Node* n) { n->next=(start); start=n; noOfNodes++; } void addAtLast(Node* n) { Node *cur=(start); n->next=NULL; if(start==NULL) { start=n; noOfNodes++; return; } while(cur->next!=NULL) { cur=cur->next; } cur->next=n; noOfNodes++; } void addAtPos(Node *n,int pos) { if(pos==1) { addAtFront(n);return; } Node *cur=(start); Node *prev=NULL; int curPos=0; n->next=NULL; while(cur!=NULL) { curPos++; if(pos==curPos+1) { prev=cur; } if(pos==curPos) { n->next=cur; prev->next=n; break; } cur=cur->next; } noOfNodes++; } void removeFirst() { Node *del=start; start=start->next; delete del; noOfNodes--; return; } void removeLast() { Node *cur=start,*prev=NULL; while(cur->next!=NULL) { prev=cur; cur=cur->next; } prev->next=NULL; Node *del=cur->next; delete del; noOfNodes--; return; } void removeNodeAt(int pos) { if(pos<1) return; if(pos==1) { removeFirst();return;} int curPos=1; Node* cur=start->next; Node* prev=start; Node* del=NULL; while(curPos<pos&&cur!=NULL) { curPos++; if(curPos==pos) { del=cur; prev->next=cur->next; cur->next=NULL; delete del; noOfNodes--; break; } prev=prev->next; cur=cur->next; } } void removeNode(Node *d) { Node *cur=start; if(*d==*cur) { removeFirst();return; } cur=start->next; Node *prev=start,*del=NULL; while(cur!=NULL) { if(*cur==*d) { del=cur; prev->next=cur->next; delete del; noOfNodes--; break; } prev=prev->next; cur=cur->next; } } int getPosition(Node data) { int pos=0; Node *cur=(start); while(cur!=NULL) { pos++; if(*cur==data) { return pos; } cur=cur->next; } return -1;//not found } Node getNode(int pos) { if(pos<1) return -1;// not a valid position else if(pos>noOfNodes) return -1; // not a valid position Node *cur=(start); int curPos=0; while(cur!=NULL) { if(++curPos==pos) return *cur; cur=cur->next; } } void reverseList()//reverse the list { Node* cur=start->next; Node* d=NULL; Node* prev=start; while(cur!=NULL) { d=cur->next; cur->next=start; start=cur; prev->next=d; cur=d; } } void sortBubble() { Node *i=start,*j=start,*prev=NULL,*temp=NULL,*after=NULL; int count=noOfNodes-1;int icount=0; while(i->next!=NULL) { j=start; after=j->next; icount=0; while(++icount!=count) { if((*j)>(*after)) { temp=after->next; after->next=j; prev->next=j->next; j->next=temp; prev=after; after=j->next; } else{ prev=j; j=after; after=after->next; } } i=i->next; count--; } } void traverse() { Node *cur=(start); int c=0; while(cur!=NULL) { // cout<<"start"<<start; c++; cur->print(); cur=cur->next; } noOfNodes=c; } ~LList() { delete start; } }; int main() { int n; cin>>n; int d; LList list; Node *node; Node *temp=new Node(2123); for(int i=0;i<n;i++) { cin>>d; node=new Node(d); list.addAtLast(node); } list.addAtPos(temp,1); cout<<"traverse\n"; list.traverse(); temp=new Node(12); list.removeNode(temp); cout<<"12 removed"; list.traverse(); list.reverseList(); cout<<"\nreversed\n"; list.traverse(); cout<<"bubble sort\n"; list.sortBubble(); list.traverse(); getch(); delete node; return 0; }

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• Very simple OOP question

  - by Mosty Mostacho

  I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works on constructions that are quite different one from each other but are still constructions. Note I've added one field for each class but there should be many more. Now, I thought this was the way to go but my partner told me that if in the future new construction classes appear we would have to modify the Company class, which is correct. So the new proposed class diagram would be this: Now I've been wondering: Should the fact that in no place of the application will there be mixed lists of planes and bridges affect the design in any way? When we have to list only planes for a company, how are we supposed to distinguish them from the other elements in the list without checking for their class names? Related to the previous question, is it correct to assume that this type of diagram should be high-level and this is something it shouldn't matter at this stage but rather be thought and decided at implementation time? Any comment will be appreciated.

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