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  • Theory of computation - Using the pumping lemma for CFLs

    - by Tony
    I'm reviewing my notes for my course on theory of computation and I'm having trouble understanding how to complete a certain proof. Here is the question: A = {0^n 1^m 0^n | n>=1, m>=1} Prove that A is not regular. It's pretty obvious that the pumping lemma has to be used for this. So, we have |vy| = 1 |vxy| <= p (p being the pumping length, = 1) uv^ixy^iz exists in A for all i = 0 Trying to think of the correct string to choose seems a bit iffy for this. I was thinking 0^p 1^q 0^p, but I don't know if I can obscurely make a q, and since there is no bound on u, this could make things unruly.. So, how would one go about this?

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  • Data Quality Check - SQL Server

    - by user319384
    I am trying to find a good mechanism where I can check whether the data being entered by a group of people is grammatically correct, has correct spellings, etc, etc. I also would like to compute words per minute and accuracy. Is there any process to do this so that I do not have to re-invent the wheel? Thanks in advance.

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  • Why is this c# snippet legal?

    - by Sir Psycho
    Silly question, but why does the following line compile? int[] i = new int[] {1,}; As you can see, I haven't entered in the second element and left a comma there. Still compiles even though you would expect it not to.

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  • The Definition of Regular Languages

    - by AraK
    Good Day, I have tried, and burned my brain to understand the definition of Regular Languages in Discrete Mathematics and its Applications(Rosen) without reaching the goal of understanding why the definition is like that in this book. On page(789), I am rephrasing the definition: Type 3 grammars are defined as: w1 --> w2 Where w1 is a non-terminal, and w2 is of the form: w2 = aB w2 = a Where B is a non-terminal, and a is a terminal. A special case is when w1 is the starting symbol and w2 is lambda(the empty string): w1 = S S --> lambda Two questions I couldn't find an answer for. First, Why can't w2 be of the form Ba. Second, Why lambda is only allowed for the starting symbol only. The book states that, regular languages are equivalent to Finite State Automaton, and we can easily see that a we can build FSA for both cases. I took a look at other resources, and these restrictions don't exist in these resources. Thanks,

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  • rhino embedding

    - by neheh
    Anyone understands the rhino javascript Contexts? I cannot find any useful documentation about it. My main problem is the Context.exit() (really should be cx.exit()) which from what I understand exits the context associated with the current thread? Does that mean I need to keep track of what which thread does? main thread: Context cx; cx.evaluateReader( ... ) // load some function start thread 2 thread 2: Object o= scope.get("methodname", scope); ((Function)o).call( ... ) I do not plan on doing multithreading but what if the different setups comes from different threads?

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  • How do I best do balanced quoting with Perl's Regexp::Grammars?

    - by Evan Carroll
    Using Damian Conway's Regexp::Grammars, I'm trying to match different balanced quoting ('foo', "foo", but not 'foo") mechanisms -- such as parens, quotes, double quotes, and double dollars. This is the code I'm currently using. <token: pair> \'<literal>\'|\"<literal>\"|\$\$<literal>\$\$ <token: literal> [\S]+ This generally works fine and allows me to say something like: <rule: quote> QUOTE <.as>? <pair> My question is how do I reform the output, to exclude the needles notation for the pair token? { '' => 'QUOTE AS \',\'', 'quote' => { '' => 'QUOTE AS \',\'', 'pair' => { 'literal' => ',', '' => '\',\'' } } }, Here, there is obviously no desire to have pair in between, quote, and the literal value of it. Is there a better way to match 'foo', "foo", and $$foo$$, and maybe sometimes ( foo ) without each time creating a needless pair token? Can I preprocess-out that token or fold it into the above? Or, write a better construct entirely that eliminates the need for it?

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  • Unable to free const pointers in C

    - by lego69
    How can I free a const char*? I allocated new memory using malloc, and when I'm trying to free it I always receive the error "incompatible pointer type" The code that causes this is something like: char* name="Arnold"; const char* str=(const char*)malloc(strlen(name)+1); free(str); // error here

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  • Using $this when not in object context

    - by Ken
    I'm creating a function to show blog's. So I made a show blog function but it keeps giving "Using $this when not in object context" error Class Blog{ public function getLatestBlogsBig($cat = null){ $sqlString = "SELECT blog_id FROM jab_blog"; if($cat != null) $sqlString .= " WHERE blog_cat = " . $cat; $sqlString .= " ORDER BY blog_id DESC LIMIT 5"; $blog = mysql_query($sqlString); while($id = mysql_result($blog,"blog_id")){ $this->showBlog($id); //Error is on this line } } function showBlog($id,$small = false){ $sqlString = "SELECT blog_id FROM jab_blog WHERE blog_id=" . $id . ";"; $blog = mysql_query($sqlString); if($small = true){ echo "<ul>"; while($blogItem = mysql_fetch_array($blog)){ echo '<a href="' . $_SESSION['JAB_LINK'] . "blog/" . $blogItem['blog_id'] . "/" . SimpleUrl::toAscii($blogItem['blog_title']) .'">' . $blogItem['blog_title'] . '</a></li>'; } echo "</ul>"; }else{ while($blogItem = mysql_fetch_array($blog)){ ?> <div class="post"> <h2 class="title"><a href="<?php echo $_SESSION['JAB_LINK'] . "blog/" . $blogItem['blog_id'] . "/" . SimpleUrl::toAscii($blogItem['blog_title']);?>"><?php echo $blogItem['blog_title'];?></a></h2> <p class="meta"><span class="date">The date implement</span><span class="posted">Posted by <a href="#">Someone</a></span></p> <div style="clear: both;">&nbsp;</div> <div class="entry"> <?php echo $blogItem['blog_content'];?> </div> </div> <?php } } } }

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  • Detecting use after free() on windows.

    - by The Rook
    I'm trying to detect "Use after free()" bugs, otherwise known as "Dangling pointers". I know Valgrind can be used to detect "Use after free" bugs on the *nix platform, but what about windows? What if I don't have the source? Is there a better program than Valgrind for detecting all dangling pointers in a program? A free and open source would be preferred , but I'll use a commercial solution if it will get the job done.

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  • How do LL(*) parsers work?

    - by freezer878
    I cannot find any complete description about LL(*) parser, such as ANTLR, on Internet. I'm wondering what is the difference between an LL(k) parser and an LL(*) one and why they can't support left-recusrive grammars despite their flexibility.

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  • .NET Free memory usage (how to prevent overallocation / release memory to the OS)

    - by Ronan Thibaudau
    I'm currently working on a website that makes large use of cached data to avoid roundtrips. At startup we get a "large" graph (hundreds of thouthands of different kinds of objects). Those objects are retrieved over WCF and deserialized (we use protocol buffers for serialization) I'm using redgate's memory profiler to debug memory issues (the memory didn't seem to fit with how much memory we should need "after" we're done initializing and end up with this report Now what we can gather from this report is that: 1) Most of the memory .NET allocated is free (it may have been rightfully allocated during deserialisation, but now that it's free, i'd like for it to return to the OS) 2) Memory is fragmented (which is bad, as everytime i refresh the cash i need to redo the memory hungry deserialisation process and this, in turn creates large object that may throw an OutOfMemoryException due to fragmentation) 3) I have no clue why the space is fragmented, because when i look at the large object heap, there are only 30 instances, 15 object[] are directly attached to the GC and totally unrelated to me, 1 is a char array also attached directly to the GC Heap, the remaining 15 are mine but are not the cause of this as i get the same report if i comment them out in code. So my question is, what can i do to go further with this? I'm not really sure what to look for in debugging / tools as it seems my memory is fragmented, but not by me, and huge amounts of free spaces are allocated by .net , which i can't release. Also please make sure you understand the question well before answering, i'm not looking for a way to free memory within .net (GC.Collect), but to free memory that is already free in .net , to the system as well as to defragment said memory. Note that a slow solution is fine, if it's possible to manually defragment the large heap i'd be all for it as i can call it at the end of RefreshCache and it's ok if it takes 1 or 2 second to run. Thanks for your help! A few notes i forgot: 1) The project is a .net 2.0 website, i get the same results running it in a .net 4 pool, idem if i run it in a .net 4 pool and convert it to .net 4 and recompile. 2) These are results of a release build, so debug build can not be the issue. 3) And this is probably quite important, i do not get these issues at all in the webdev server, only in IIS, in the webdev i get memory consumption rather close to my actual consumption (well more, but not 5-10X more!)

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  • Detecting use after free() on windows. (dangling pointers)

    - by The Rook
    I'm trying to detect "Use after free()" bugs, otherwise known as "Dangling pointers". I know Valgrind can be used to detect "Use after free" bugs on the *nix platform, but what about windows? What if I don't have the source? Is there a better program than Valgrind for detecting all dangling pointers in a program? A free and open source would be preferred , but I'll use a commercial solution if it will get the job done.

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  • Is it possible to start an activity from a regular java class?

    - by Yotam
    In my ActionBarSherlock I have the same menu items for all activities, so it seems unwise to define onClick handlers in each activity - they all do the same. Instead I created a class called MyClickListener that implements com.actionbarsherlock.view.MenuItem.OnMenuItemClickListener, and in there I have a simple switch block that starts the appropriate activity. Problem is that Intent constructor's first argument is of type Context, and even when I pass this to MyClickListener's constructor, I can't start any activity. The same goes for every method that has a Context object as a parameter. Is there a way to work around it? What is a context object? Thanks

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  • How to free control inside its event handler?

    - by lyborko
    Hi, Does anybody know the trick, how to free control inside its event handler ? According delphi help it is not possible... I want to free dynamicaly created TEdit, when Self.Text=''. TAmountEdit = class (TEdit) . . public procedure KeyUp(var Key: Word; Shift :TShiftState); end; procedure TAmountEdit.KeyUp(var Key: Word; Shift :TShiftState); begin inherited; if Text='' then Free; // after calling free, an exception arises end; How should do to achieve the same effect? Thanx

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  • Regular Expression

    - by equilibrium
    Ohh! this regular expression thing is eating my brain up. I have been reading it from Introduction to Automata Theory, Languages and Computer by Hopcroft, Motwani and Ullman. I have solved a few exercises too but could not solve the following even after trying for almost one hr. The problem is to write a regular expression that defines a language consisting of all strings of 0s and 1s except the substring 011. Is the answer (0+1)* - 011 correct ? If not what should be the correct answer for this?

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  • problems with 'free' in C

    - by lego69
    hello, can somebody please explain can I free const char* ? I allocated new memory using malloc and when I'm trying to free it I always receive an error incompatible pointer type thanks in advance something like this char* name="Arnold"; const char* str=malloc(stlen(name)+1); free(str); <- here bug

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  • Looking for WebAii Framework free edition online - before the Telerik merge

    - by jdk
    Art of Test produced a nice UI testing tool for free -- WebAii Framework-- that I've been using to add client-side DOM unit tests to my projects. Recently they merged with Telerik and it's now a commercial product. From free to $1500 is suddenly very expensive. Does anybody know if the community edition is still available, or even the last free version is available for download? At least I can finish off with that.

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  • regular expression for bit strings with even number of 1s

    - by equilibrium
    Let L= { w in (0+1)* | w has even number of 1s}, i.e. L is the set of all bit strings with even number of 1s. Which one of the regular expressions below represents L? A) (0*10*1)* B) 0*(10*10*)* C) 0*(10*1)* 0* D) 0*1(10*1)* 10* According to me option D is never correct because it does not represent the bit string with zero 1s. But what about the other options? We are concerned about the number of 1s(even or not) not the number of zeros doesn't matter. Then which is the correct option and why?

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