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• Avoid Postfix Increment Operator

  - by muntoo

  I've read that I should avoid the postfix increment operator because of performance reasons (in certain cases). But doesn't this affect code readability? In my opinion: for(int i = 0; i < 42; i++); /* i will never equal 42! */ Looks better than: for(int i = 0; i < 42; ++i); /* i will never equal 42! */ But this is probably just out of habit. Admittedly, I haven't seen many use ++i. Is the performance that bad to sacrifice readability, in this case? Or am I just blind, and ++i is more readable than i++?

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• Motivation and use of move constructors in C++

  - by Giorgio

  I recently have been reading about move constructors in C++ (see e.g. here) and I am trying to understand how they work and when I should use them. As far as I understand, a move constructor is used to alleviate the performance problems caused by copying large objects. The wikipedia page says: "A chronic performance problem with C++03 is the costly and unnecessary deep copies that can happen implicitly when objects are passed by value." I normally address such situations by passing the objects by reference, or by using smart pointers (e.g. boost::shared_ptr) to pass around the object (the smart pointers get copied instead of the object). What are the situations in which the above two techniques are not sufficient and using a move constructor is more convenient?

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• Comparison of languages by usage type? [closed]

  - by Tom

  Does anyone know of a good place to go find comparisons of programming languages by the intended platform/usage? Basically, what I want to know, is of the more popular languages, which ones are meant for high level application development, low level system development, mobile development, web, etc. If there's a good listing out there already, I'm not finding it so far. Does anyone know of a place that would have this? Thanks.

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• Help to understand the abstract factory pattern

  - by Chobeat

  I'm learning the 23 design patterns of the GoF. I think I've found a way to understand and simplify how the Abstract Factory works but I would like to know if this is a correct assumption or if I am wrong. What I want to know is if we can see the result of the Abstract Factory method as a matrix of possible products where there's a Product for every "Concrete Factory" x "AbstractProduct" where the Concrete Factory is a single implementation among the implementations of an AbstractFactory and an AbstractProduct is an interface among the interfaces to create Products. Is this correct or am I missing something?

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• Are there any concerns with using a static read-only unit of work so that it behaves like a cache?

  - by Rowan Freeman

  Related question: How do I cache data that rarely changes? I'm making an ASP.NET MVC4 application. On every request the security details about the user will need to be checked with the area/controller/action that they are accessing to see if they are allowed to view it. The security information is stored in the database. For example: User Permission UserPermission Action ActionPermission A "Permission" is a token that is applied to an MVC action to indicate that the token is required in order to access the action. Once a user is given the permission (via the UserPermission table) then they have the token and can therefore access the action. I've been looking in to how to cache this data (since it rarely changes) so that I'm only querying in-memory data and not hitting a database (which is a considerable performance hit at the moment). I've tried storing things in lists, using a caching provider but I either run in to problems or performance doesn't improve. One problem that I constantly run in to is that I'm using lazy loading and dynamic proxies with EntityFramework. This means that even if I ToList() everything and store them somewhere static, the relationships are never populated. For example, User.Permissions is an ICollection but it's always null. I don't want to Include() everything because I'm trying to keep things simple and generic (and easy to modify). One thing I know is that an EntityFramework DbContext is a unit of work that acts with 1st-level caching. That is, for the duration of the unit of work, everything that is accessed is cached in memory. I want to create a read-only DbContext that will exist indefinitely and will only be used to read about permission data. Upon testing this it worked perfectly; my page load times went from 200ms+ to 20ms. I can easily force the data to refresh at certain intervals or simply leave it to refresh when the application pool is recycled. Basically it will behave like a cache. Note that the rest of the application will interact with other contexts that exist per request as normal. Is there any disadvantage to this approach? Could I be doing something different?

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• Understanding clojure keywords

  - by tjb1982

  I'm taking my first steps with Clojure. Otherwise, I'm somewhat competent with JavaScript, Python, Java, and a little C. I was reading this artical that describes destructuring vectors and maps. E.g. => (def point [0 0]) => (let [[x y] point] => (println "the coordinates are:" x y)) the coordinates are: 0 0 but I'm having a difficult time understanding keywords. At first glance, they seem really simple, as they just evaluate to themselves: => :test :test But they seem to be used is so many different ways and I don't understand how to think about them. E.g., you can also do stuff like this: => (defn full-name [& {first :first last :last}] => (println first last)) => (full-name :first "Tom" :last "Brennan") Tom Brennan nil This doesn't seem intuitive to me. I would have guessed the arguments should have been something more like: (full-name {:first "Tom" :last "Brennan"}) because it looks like in the function definition that you're saying "no required arguments, but a variable number of arguments comes in the form of a single map". But it seems more like you're saying "no required arguments, but a variable number of arguments comes which should be a list of alternating keywords and values... ?" I'm not really sure how to wrap my brain around this. Also, things like this confuse me too: => (def population {:humans 5 :zombies 1000}) => (:zombies population) 1000 => (population :zombies) 1000 How do maps and keywords suddenly become functions? If I could get some clarification on the use of keywords in these two examples, that would be really helpful. Update I've also seen http://stackoverflow.com/questions/3337888/clojure-named-arguments and while the accepted answer is a great demonstration of how to use keywords with destructuring and named arguments, I'm really looking more for understanding how to think about them--why the language is designed this way and how I can best internalize their use.

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• Is there a good example of the difference between practice and theory?

  - by a_person

  There has been a lot of posters advising that the best way to retain knowledge is to apply it practically. After ignoring said advice for several years in a futile attempt to accumulate enough theoretical knowledge to be prepared for every possible case scenario, the process which lead me to assembling a library that's easily worth ~6K, I finally get it. I would like to share my story in the hopes that others will avoid taking the same route that was taken by me. I've selected graphical format (photos with caption to be exact) as my media. Help me with your ideas, maybe a fragment of code, or other imagery that would convey a message of the inherent difference between practice and theory.

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• Writing drivers for a printer?

  - by user828584

  My goal is to be able to fax 20 page pdf documents for free. I've looked online, and there are some free fax services, but all of them have their limits. I do have an old fax machine, but the documents that need to be faxed are on the computer, and to print them would be far from free. Unfortunately, the only way to send a fax with the machine is by scanning it. What's strange is that it can scan to the computer and print from it, but it won't fax from it... :(. Is it possible to write something (preferably C#, but it's going to take some learning anyway) that will allow me to send a fax from the computer? I have very little software experience, and none in anything like this, so I have no idea where to start. If it is possible, where can I find all the information needed to write the program?

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• lowering the use of the memory controller in OpenCL based applications

  - by user827992

  With my first experiments I noticed that OpenCL is a good technology but often hampered by the X86 architecture and finding a mid-range VGA driven by a low-end chipset is not that unusual in the real world scenarios, sometimes this can happen with some high-end VGA too. Are there some caching techniques? Something that can bypass this inconvenience in some ways. The amount of dedicated memory on today's VGA is usually high, it's possible to use this memory to create some kind of buffer with instructions.

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• KISS principle applied to programming language design?

  - by Giorgio

  KISS ("keep it simple stupid", see e.g. here) is an important principle in software development, even though it apparently originated in engineering. Citing from the wikipedia article: The principle is best exemplified by the story of Johnson handing a team of design engineers a handful of tools, with the challenge that the jet aircraft they were designing must be repairable by an average mechanic in the field under combat conditions with only these tools. Hence, the 'stupid' refers to the relationship between the way things break and the sophistication available to fix them. If I wanted to apply this to the field of software development I would replace "jet aircraft" with "piece of software", "average mechanic" with "average developer" and "under combat conditions" with "under the expected software development / maintenance conditions" (deadlines, time constraints, meetings / interruptions, available tools, and so on). So it is a commonly accepted idea that one should try to keep a piece of software simple stupid so that it easy to work on it later. But can the KISS principle be applied also to programming language design? Do you know of any programming languages that have been designed specifically with this principle in mind, i.e. to "allow an average programmer under average working conditions to write and maintain as much code as possible with the least cognitive effort"? If you cite any specific language it would be great if you could add a link to some document in which this intent is clearly expressed by the language designers. In any case, I would be interested to learn about the designers' (documented) intentions rather than your personal opinion about a particular programming language.

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• Book about tcp, http, named pipe, shared memory, wcf and other inter-process communication protocol

  - by Samuel

  Recently, I had to create a program to send messages between two winforms executable. I used a tool with simple built-in functionalities to prevent having to figure out all the ins and outs of this vast quantity of protocols that exist. But now, I'm ready to learn more about the internals difference between each of theses protocols. I googled a couple of them but it would be greatly appreciate to have a good reference book that gives me a clean idea of how each protocol works and what are the pros and cons in a couple of context. Here is a list of nice protocols that I found: Shared memory TCP List item Named Pipe File Mapping Mailslots MSMQ (Microsoft Queue Solution) WCF I know that all of these protocols are not specific to a language, it would be nice if example could be in .net. Thank you very much.

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• Books / blogs that discuss service excellence? [closed]

  - by Bogdan Gavril

  I'm looking for information about service excellence topics such as: 0 downtime deployment how to deal with versioning (backward and forward compatibility) environment strategies (how many staging envs ? etc.) performance testing testing in production monitoring I am looking at the Microsoft stack, but the concepts should be the same everywhere. Do you have any recommendations of books or blogs on the subject? PS: I have found some good articles from I.M.Wright's "Hard Code" blog. Anything else?

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• Randomly generate directed graph on a grid

  - by Talon876

  I am trying to randomly generate a directed graph for the purpose of making a puzzle game similar to the ice sliding puzzles from Pokemon. This is essentially what I want to be able to randomly generate: http://bulbanews.bulbagarden.net/wiki/Crunching_the_numbers:_Graph_theory. I need to be able to limit the size of the graph in an x and y dimension. In the example given in the link, it would be restricted to an 8x4 grid. The problem I am running into is not randomly generating the graph, but randomly generating a graph, which I can properly map out in a 2d space, since I need something (like a rock) on the opposite side of a node, to make it visually make sense when you stop sliding. The problem with this is that sometimes the rock ends up in the path between two other nodes or possibly on another node itself, which causes the entire graph to become broken. After discussing the problem with a few people I know, we came to a couple of conclusions that may lead to a solution. Including the obstacles in the grid as part of the graph when constructing it. Start out with a fully filled grid and just draw a random path and delete out blocks that will make that path work. The problem then becomes figuring out which ones to delete to avoid introducing an additional, shorter path. We were also thinking a dynamic programming algorithm may be beneficial, though none of us are too skilled with creating dynamic programming algorithms from nothing. Any ideas or references about what this problem is officially called (if it's an official graph problem) would be most helpful. Here are some examples of what I have accomplished so far by just randomly placing blocks and generating the navigation graph from the chosen start/finish. The idea (as described in the previous link) is you start at the green S and want to get to the green F. You do this by moving up/down/left/right and you continue moving in the direction chosen until you hit a wall. In these pictures, grey is a wall, white is the floor, and the purple line is the minimum length from start to finish, and the black lines and grey dots represented possible paths. Here are some bad examples of randomly generated graphs: http://i.stack.imgur.com/9uaM6.png Here are some good examples of randomly generated (or hand tweaked) graphs: i.stack.imgur.com/uUGeL.png (can't post another link, sorry) I've also seemed to notice the more challenging ones when actually playing this as a puzzle are ones which have lots of high degree nodes along the minimum path.

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• Different ways of solving problems in code.

  - by Erin

  I now program in C# for a living but before that I programmed in python for 5 years. I have found that I write C# very differently than most examples I see on the web. Rather then writing things like: foreach (string bar in foo) { //bar has something doen to it here } I write code that looks like this. foo.ForEach( c => c.someActionhere() ) Or var result = foo.Select( c => { //Some code here to transform the item. }).ToList(); I think my using code like above came from my love of map and reduce in python - while not exactly the same thing, the concepts are close. Now it's time for my question. What concepts do you take and move with you from language to language; that allow you to solve a problem in a way that is not the normal accepted solution in that language?

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• Advancing my Embedded knowledge.....with a CS degree.

  - by Mercfh

  So I graduated last December with a B.S. in Computer Science, in a pretty good well known engineering college. However towards the end I realized that I actually like Assembly/Lower level C programming more than I actually enjoy higher level abstracted OO stuff. (Like I Programmed my own Device Drivers for USB stuff in Linux, stuff like that) But.....I mean we really didn't concentrate much on that in college, perhaps an EE/CE degree would've been better, but I knew the classes......and things weren't THAT much different. I've messed around with Atmel AVR's/Arduino stuff (Mostly robotics) and Linux Kernals/Device Drivers. but I really want to enhance my skills and maybe one day get a job doing embedded stuff. (I have a job now, it's An entry level software dev/tester job, it's a good job but not exactly what my passion lies in) (Im pretty good with C and certain ASM's for specific microcontrollers) Is this even possible with a CS degree? or am I screwed? (since technically my degree usually doesn't involve much embedded stuff) If Im NOT screwed then what should I be studying/learning? How would I even go about it........ I guess I could eventually say "Experienced with XXXX Microcontrollers/ASM/etc...." but still, it wouldn't be the same as having a CE/EE degree. Also....going back to college isn't an option. just fyi. edit: Any book recommendations for "getting used to this stuff" I have ARM System-on-Chip Architecture (2nd edition) it's good.....for ARM stuff lol

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• Using an open source non-free license

  - by wagglepoons

  Are there any projects/products out there that use an open source license that basically says "free for small companies" and "cost money for larger companies" in addition to "make modifications available"? (And are there any standard licenses with such a wording?) If I were to release a project under such a license, would it be automatically shunned by every developer on the face of the earth, or, assuming it is actually a useful project, does it have a fair chance at getting contributions from Joe Programmer? The second part of this question can easily become subjective, but any well argued point of view will be highly appreciated. For example, do dual licensed projects made by commercial entities have success with the open source communities?

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• flat files vs. RDBMS database, few read/writes, few changes

  - by Bob Lapique

  I have to handle data from long term (years, decades) climate monitoring stations. The data flow usually starts with raw data (voltages, etc.) plus quality check information (pressure, temperature, flow rate, etc.) generally recorded @ 1Hz. Then, the data are assigned a quality flag (human and/or program), processed (apply calibration curves) and flagged. So, we basically end up with 2 datasets : raw and processed data. New data are typically added once a day (~500Ko/day/instrument). Simultaneous queries are not likely to ever happen. I wanted to go for a RDBMS (we have a MySQL server) and have some experience in database design, but the IT guy keeps telling me that flat files will to the job just as well. I suspect him to try to make his life easier when it comes to backup/upgrade the MySQL. There are not so many links between data, they don't change much, but the quality flags will change. A RDBMS is easier to compare data from different instruments on a "many days" scale, compared to daily text files. Well, what would you advise ? Thanks.

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• The best way to have a pointer to several methods - critique requested

  - by user827992

  I'm starting with a short introduction of what i know from the C language: a pointer is a type that stores an adress or a NULL the * operator reads the left value of the variable on its right and use this value as address and reads the value of the variable at that address the & operator generate a pointer to the variable on its right so i was thinking that in C++ the pointers can work this way too, but i was wrong, to generate a pointer to a static method i have to do this: #include <iostream> class Foo{ public: static void dummy(void){ std::cout << "I'm dummy" << std::endl; }; }; int main(){ void (*p)(); p = Foo::dummy; // step 1 p(); p = &(Foo::dummy); // step 2 p(); p = Foo; // step 3 p->dummy(); return(0); } now i have several questions: why step 1 works why step 2 works too, looks like a "pointer to pointer" for p to me, very different from step 1 why step 3 is the only one that doesn't work and is the only one that makes some sort of sense to me, honestly how can i write an array of pointers or a pointer to pointers structure to store methods ( static or non-static from real objects ) what is the best syntax and coding style for generating a pointer to a method?

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• Design Patterns for these scenarios

  - by user1899749

  Please help me to find design patterns for following situations. Situation 1: how can a smart robot use Wi-Fi? Situation 2: How can a Smart robot automatically go to rechargeable unit while there is no remote signal? Situation 3: Voice recognition component (If homeowner itself at home and motion detection is off then how can Smart Robot voice recognition component will recognize those very sensitive sentences) Situation 4: Motion detection component (How can Smart Robot send video stream on cell phone while homeowner/resident driving) I am looking for the design patterns for above Situations to answer following question. if not using design patterns, then what’re the difficulties?

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• Tips for achieving "continual" delivery

  - by Ben

  A team is experiencing difficulty releasing software on a frequent basis (once every week). What follows is a typical release timeline: During the iteration: Developers work on stories on the backlog on short-lived (this is enthusiastically enforced) feature branches based on the master branch. Developers frequently pull their feature branches into the integration branch, which is continually built and tested (as far as the test coverage goes) automatically. The testers have the ability to auto-deploy integration to a staging environment and this occurs multiple times per week, enabling continual running of their test suites. Every Monday: there is a release planning meeting to determine which stories are "known good" (based on the testers' work), and hence will be in the release. If there is a known issue with a story, the source branch is pulled out of integration. no new code (only bug fixes requested by the testers) may be pulled into integration on this Monday to ensure the testers have a stable codebase to cut a release from. Every Tuesday: The testers have tested the integration branch as much as they possibly can have given the time available and there are no known bugs so a release is cut and pushed out to the production nodes slowly. This sounds OK in practise, but we have found that it is incredibly difficult to achieve. The team sees the following symptoms "subtle" bugs are found on production that were not identified on the staging environment. last minute hot-fixes continue into the Tuesday. problems on the production environment require roll-backs which blocks continued development until a successful live deployment is achieved and the master branch can be updated (and hence branched from). I think test coverage, code quality, ability to regression test quickly, last minute changes and environmental differences are at play here. Can anyone offer any advice regarding how best to achieve "continual" delivery?

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• Personal Software Process (PSP1)

  - by gentoo_drummer

  I'm trying to figure out an exercise but it doesn't really makes to much sense.. I'm not asking someone to provide the solution. just to try and analyse what needs to be done in order to solve this. I'm trying to understand which PSP 1.0 1.1 process I should use. PROBE? Or something else? I would greatly appreciate some help on this one from someone that has experience with the Personal Software Process Methodology.. Here is the question. For the reference case (“code1.c”), the following s/w metrics are provided: man-hours spent in implementation phase (per-module): 2,7 mh/file man-hours spent in testing phase (per-module): 4,3 mh/file estimated number of bugs remaining (per-module): 0,3 errors/function, 4 errors/module (remaining) Based on the corresponding values provided for the reference case, each of the following tasks focus on some s/w metrics to be estimated for the test case (“code2.c”): [25 marks] (estimated) man-hours required in implementation phase (per-module) [8 marks] (estimated) man-hours required in testing phase (per-module) [8 marks] (estimated) number of bugs remaining at the end of testing phase (per-module) [9 marks] Tasks 4 through 6 should use the data provided for the reference case within the context of Personal Software Process level-1 (PSP-1), using them as a single-point historic data log. Specifically, the same s/w metrics are to be estimated for the test case (“code2.c”), using PSP as the basic estimation model. In order to perform the above listed tasks, students are advised to consider all phases of the PSP software development process, especially at levels PSP0 and PSP1. Both cases are to be treated as separate case-studies in the context of classic s/w development.

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• Implementing a bit shift using AND, NOT, ADD [closed]

  - by fdart17

  I'm implementing a 16-bit left bit shift by r bits, and I only have access to AND, NOT and ADD. There are 3 condition codes, negative, zero and positive, which are set when you use any of these operations. How I went about it was : (1) And the number with 1000 0000 0000 0000 to set condition codes to positive if the most significant bit is 1. (2) Add the number with itself. This shifts bits one to the left. (3) If the MSB was 1, add 1 to the result. (4) Loop threw (1)-(3) r times. I'm wondering if anyone has any hints to some more efficient methods? Thanks!

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• COM INTEROP Support - which is better? C# or VB

  - by dot

  I keep hearing that c# is "better" than vb... but as far as I can see, aside from syntactical differences, both compile down to the same IL. I've found some good articles by googling that explain what the differences are between the two and so I feel comfortable in "diffusing" conversations between developers arguing over vb / c#. =) But I did read an article that said vb.net 2005 had better support for com interop stuff. But i'm wondering if this is still the case? This is of interest to me because we are in the middle of redesigning an old vb6 app that communicates with some older COM components. Does anyone have recent experience with .NET and COM interop? Thanks.

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• Reasons for Pair Programming

  - by Jeff Langemeier

  I've worked in a few shops where management has passed the idea of pair programming either to me or another manager/developer, and I can't get behind it at all. From a developer stand-point I can't find a reason why moving to this coding style would be beneficial, nor as a manager of a small team have I seen any benefit. I understand that it helps on basic syntax errors and can be helpful if you need to hash something out, but managers that are out of the programming loop seem to keep seeing it as a way of keeping their designers from going to Facebook or Reddit than as a design tool. As someone close to the development floor that apparently can't quite understand from a book tossed my way or a wiki page on the subject... from a high level management position, what are the benefits of Pair Programming when dealing with Scrum or Agile environments?

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• Python response parse [migrated]

  - by Pavel Shevelyov

  When I'm sending some data on host: r = urllib2.Request(url, data = data, headers = headers) page = urllib2.urlopen(r) print page.read() I have something like this: [{"command":"settings","settings":{"basePath":"\/","ajaxPageState":{"theme":"spsr","theme_token":"kRHUhchUVpxAMYL8Y8IoyYIcX0cPrUstziAi8gSmMYk","css":[]},"ajax":{"edit-submit":{"callback":"spsr_calculator_form_ajax","wrapper":"calculator_form","method":"replaceWith","event":"mousedown","keypress":true,"url":"\/ru\/system\/ajax","submit":{"_triggering_element_name":"submit"}}}},"merge":true},{"command":"insert","method":null,"selector":null,"data":"\u003cdiv id=\"calculator_form\"\u003e\u003cform action=\"\/ru\/service\/calculator\" method=\"post\" id=\"spsr-calculator-form\" accept-charset=\"UTF-8\"\u003e\u003cdiv\u003e\u003cinput id=\"edit-from-ship-region-id\" type=\"hidden\" name=\"from_ship_region_id\" value=\"\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_build_id\" value=\"form-0RK_WFli4b2kUDTxpoqsGPp14B_0yf6Fz9x7UK-T3w8\" \/\u003e\n\u003cinput type=\"hidden\" name=\"form_id\" value=\"spsr_calculator_form\" \/\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"bg_p\"\u003e \n\u0421\u0435\u0439\u0447\u0430\u0441 \u0412\u044b... bla bla bla but I want have something, like this: <html><h1>bla bla bla</h1></html> How can I do it?

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