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  • Fatal error with php code

    - by basma
    hello i have a problem in my php code that use recursion: <?php solveTowers(5, "A", "B", "C"); function solveTowers($count, $src, $dest, $spare) { if (count == 1) { echo "Move a disk from ".$src." to ".$dest ; } else { solveTowers($count - 1, $src, $spare, $dest); solveTowers(1, $src, $dest, $spare); solveTowers($count - 1, $spare, $dest, $src); } } ?> but it doesnt run !! this error accures : Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 261904 bytes) in C:\xampp\htdocs\cap492\towers.php on line 13 line 13 is the first call to the function in the else statment can you please help me with that ?!

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  • Building 'flat' rather than 'tree' LINQ expressions

    - by Ian Gregory
    I'm using some code (available here on MSDN) to dynamically build LINQ expressions containing multiple OR 'clauses'. The relevant code is var equals = values.Select(value => (Expression)Expression.Equal(valueSelector.Body, Expression.Constant(value, typeof(TValue)))); var body = equals.Aggregate<Expression>((accumulate, equal) => Expression.Or(accumulate, equal)); This generates a LINQ expression that looks something like this: (((((ID = 5) OR (ID = 4)) OR (ID = 3)) OR (ID = 2)) OR (ID = 1)) I'm hitting the recursion limit (100) when using this expression, so I'd like to generate an expression that looks like this: (ID = 5) OR (ID = 4) OR (ID = 3) OR (ID = 2) OR (ID = 1) How would I modify the expression building code to do this?

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  • C# two classes with static members referring to each other

    - by Jerry
    Hi, I wonder why this code doesn't end up in endless recursion. I guess it's connected to the automatic initialization of static members to default values, but can someone tell me "step by step" how does 'a' get the value of 2 and 'b' of 1? public class A { public static int a = B.b + 1; } public class B { public static int b = A.a + 1; } static void Main(string[] args) { Console.WriteLine("A.a={0}, B.b={1}", A.a, B.b); //A.a=2, B.b=1 Console.Read(); }

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  • MS SQL replace sequence of same characters inside Text Field (TSQL only)

    - by zmische
    I have a text column varchar(4000) with text: 'aaabbaaacbaaaccc' and I need to remove all duplicated chars - so only one from sequence left: 'abacbac' It should not be a function, Procedure or CLR - Regex solution. Only true SQL select. Currently I think about using recursive WITH clause with replace 'aa'-'a', 'bb'-'b', 'cc'-'c'. So recursion should cycle until all duplicated sequences of that chars would be replaced. DO you have another solution, perhaps more Permormant one? PS: I searched through this site about different replace examples - they didnt suit to this case.

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  • How do you solve this Haskell problem using a fold map and take?

    - by Linda Cohen
    Define a function replicate which given a list of numbers returns a list with each number duplicated its value. Use a fold, map, and take .. replicate [5,1,3,2,8,1,2] output: [5,5,5,5,5,1,3,3,3,2,2,8,8,8,8,8,8,8,8,1,2,2] I've figure this out using List comprehension and recursion: replicate2 [] = [] replicate2 (n:nn) = take n(repeat n) ++ replicate2 nn but how would you use fold and map to do this? so far I have: replicate n = map (foldl1 (take n(repeat n)) n) n which is obviously wrong, but I think I am close.. so any help would be nice, THANKS!

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  • Calling same function until it connect to server

    - by user171523
    I am in the process of designing a system where i need to keep on trying to connect to MQ server unitl i get a connection. By default if the MQ is not availlble it will thorugh exception. How can call the same method again and again until i get the connection. I know i can use recursion, is there any better way to do it . Becuase i would like to avoid infinite loops. I also want to wait the the furthere processing until i get connection. I am using .net 2.0 with C#. It is window Service application.

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  • How does functional programming work?

    - by Headcrab
    I'm used to imperative/OO programming (know C, C++, Python, PHP, etc.). I wanted to get into functional programming but there are some things unclear to me. Take for example the languages F# and Haskell: How do you implement loops? By recursion? Eew. What about conditions? How can you get by without variables? I mean.. What do we have RAM for.. storing variables, right?

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  • A Simulator for a non-deterministic Push-Down Automaton

    - by shake
    Well, i need to make simulator for non-deterministic Push-Down Automaton. Everything is okey, i know i need to do recursion or something similar. But i do not know how to make that function which would simulate automaton. I got everything else under control, automaton generator, stack ... I am doing it in java, so this is maybe only issue that man can bump on, and i did it. So if anyone have done something similar, i could use advices. This is my current organisation of code: C lasses: class transit: list -contains non deterministic transitions state input sign stack sign class generator it generate automaton from file clas NPA public boolean start() - this function i am having trouble with Of course problem of separate stacks, and input for every branch. I tried to solve it with collection of objects NPA and try to start every object, but it doesn work :((..

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  • Is ReaderWriterLockSlim.EnterUpgradeableReadLock() essentially the same as Monitor.Enter()?

    - by Neil Barnwell
    So I have a situation where I may have many, many reads and only the occasional write to a resource shared between multiple threads. A long time ago I read about ReaderWriterLock, and have read about ReaderWriterGate which attempts to mitigate the issue where many writes coming in trump reads and hurt performance. However, now I've become aware of ReaderWriterLockSlim... From the docs, I believe that there can only be one thread in "upgradeable mode" at any one time. In a situation where the only access I'm using is EnterUpgradeableReadLock() (which is appropriate for my scenario) then is there much difference to just sticking with lock(){}? Here's the excerpt: A thread that tries to enter upgradeable mode blocks if there is already a thread in upgradeable mode, if there are threads waiting to enter write mode, or if there is a single thread in write mode. Or, does the recursion policy make any difference to this?

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  • Why do SQL connection leave parameters in?

    - by acidzombie24
    While coding with sqlite everytime i always had the exact number of parameters and when i executed the query i always had 0 parameters after it. I kept using the cmd object and it worked fine. Now while porting to use sql server (2008) my SqlConnection has parameters left over from a successful command. Why? I seem to be able to create tables without the problem (then again i may have use a clone of an empty cmd since i use recursion). Does SqlCommand always leave the parameters in after a query? This always breaks the following query unless i do parameter.clear(). Should i create a new SqlCommand object? or use parameter.clear() each time? I'm somewhat confused.

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  • Bind can only work for the DNS server inside zone

    - by Bob
    I got a big problem when I added a new zone to my current Bind configuration. ===============/etc/named.conf=============== include "/etc/rndc.key"; controls { inet 127.0.0.1 port 953 allow { 127.0.0.1; } keys { "rndckey"; }; }; acl "trusted" { 127.0.0.1; 208.43.81.157; 69.4.236.88; }; options { directory "/var/named"; allow-query { any; }; recursion yes; allow-recursion { trusted; }; }; zone "." { type hint; file "root.hints"; }; zone "2comu.com" { type master; file "2comu.com.db"; allow-update { none; }; }; zone "usa-diamond.com" { type master; file "usa-diamond.com.db"; allow-update { none; }; }; ===============/var/named/2comu.com.db=============== $TTL 86400 @ IN SOA ns1.2comu.com. root.2comu.com. ( 2011011101 3600 300 3600000 3600 ) IN NS ns1.2comu.com. IN NS ns2.2comu.com. IN MX 10 email.2comu.com. ns1.2comu.com. IN A 208.43.81.157 ns2.2comu.com. IN A 69.4.236.88 www.2comu.com. IN A 208.43.81.157 ftp.2comu.com. IN A 208.43.81.157 email.2comu.com. IN A 208.43.81.157 ===============/var/named/usa-diamond.com=============== $TTL 86400 @ IN SOA ns1.2comu.com. root.usa-diamond.com. ( 2011011115 3600 300 3600000 3600 ) IN NS ns1.2comu.com. IN NS ns2.2comu.com. www.usa-diamond.com. IN A 208.43.81.157 ================================================================ All of the configurations inside domain 2comu.com work well. But when www.usa-diamond.com doesn't work at all. When I tried "dig +trace www.usa-diamond.com", I got the following message ================================================================ ; <<>> DiG 9.3.6-P1-RedHat-9.3.6-4.P1.el5_4.2 <<>> +trace usa-diamond.com ;; global options: printcmd . 517603 IN NS c.root-servers.net. . 517603 IN NS d.root-servers.net. . 517603 IN NS e.root-servers.net. . 517603 IN NS f.root-servers.net. . 517603 IN NS g.root-servers.net. . 517603 IN NS h.root-servers.net. . 517603 IN NS i.root-servers.net. . 517603 IN NS j.root-servers.net. . 517603 IN NS k.root-servers.net. . 517603 IN NS l.root-servers.net. . 517603 IN NS m.root-servers.net. . 517603 IN NS a.root-servers.net. . 517603 IN NS b.root-servers.net. ;; Received 500 bytes from 208.43.81.157#53(208.43.81.157) in 0 ms com. 172800 IN NS j.gtld-servers.net. com. 172800 IN NS d.gtld-servers.net. com. 172800 IN NS e.gtld-servers.net. com. 172800 IN NS i.gtld-servers.net. com. 172800 IN NS f.gtld-servers.net. com. 172800 IN NS m.gtld-servers.net. com. 172800 IN NS b.gtld-servers.net. com. 172800 IN NS k.gtld-servers.net. com. 172800 IN NS l.gtld-servers.net. com. 172800 IN NS c.gtld-servers.net. com. 172800 IN NS h.gtld-servers.net. com. 172800 IN NS a.gtld-servers.net. com. 172800 IN NS g.gtld-servers.net. ;; Received 505 bytes from 192.33.4.12#53(c.root-servers.net) in 3 ms usa-diamond.com. 172800 IN NS ns1.2comu.com. usa-diamond.com. 172800 IN NS ns2.2comu.com. ;; Received 107 bytes from 192.48.79.30#53(j.gtld-servers.net) in 177 ms ;; Received 33 bytes from 208.43.81.157#53(ns1.2comu.com) in 0 ms ========================================================================= It seems I can't get any answer from ns1.2comu.com. Can anyone give some suggestions? Thanks a lot. Bob

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  • What, if any, is wrong with this definition of letrec in Scheme?

    - by Lajla
    R5RS gives proposed macro definitions for library forms of syntax: http://schemers.org/Documents/Standards/R5RS/HTML/r5rs-Z-H-10.html#%_sec_7.3 Which also defines letrec, in a very complicated way, certainly not how I would define it, I would simply use: (define-syntax letrec2 (syntax-rules () ((letrec2 ((name val) ...) body bodies ...) ((lambda () (define name val) ... body bodies ...))))) As far as I understand the semantics of letrec, which I use very often as a named let. It works in this way, however as I've had my fair share of debates with philosophers who think they can just disprove special relativity or established phonological theories, I know that when you think you have a simple solution to a complex problem, it's probably WRONG. There has got to be some point where this macro does not satify the semantics of letrec else they'd probably have used it. In this definition, the definitions are local to the body of the letrec, they can refer to each other for mutual recursion, I'm not quite sure what (if any) is wrong.

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  • What is it about Fibonacci numbers?

    - by Ian Bishop
    Fibonacci numbers have become a popular introduction to recursion for Computer Science students and there's a strong argument that they persist within nature. For these reasons, many of us are familiar with them. They also exist within Computer Science elsewhere too; in surprisingly efficient data structures and algorithms based upon the sequence. There are two main examples that come to mind: Fibonacci heaps which have better amortized running time than binomial heaps. Fibonacci search which shares O(log N) running time with binary search on an ordered array. Is there some special property of these numbers that gives them an advantage over other numerical sequences? Is it a density quality? What other possible applications could they have? It seems strange to me as there are many natural number sequences that occur in other recursive problems, but I've never seen a Catalan heap.

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  • generate all subsets of size k from a set

    - by Kumar
    hi, i want to generate all the subsets of size k from a set. eg:-say i have a set of 6 elements, i have to list all the subsets in which the cardinality of elements is 3. I tried looking for solution,but those are code snippets. Its been long since I have done coding,so I find it hard to understand the code and construct a executable program around it. A complete executable program in C or C++ will be quite helpful. Hoping of an optimal solution using recursion. Thanks in advance. Kumar.

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  • F# script to application

    - by sudaly
    I have written two small scripts, First one maintains a dictionary of current stock prices for a set of securities. I am using recursion to listen to a named pipe. Whenever there is something available on the name pipe, it updates the security price and goes right back and start listening to the pipe. The second one periodically reads the stock price of some security from the price cache of the first program and performs come calculation. But I have no idea how to make these two programs communicate. I somehow need to make my second programs start the first program and let it run in the background and get the price whenever it needs it. Can someone point me in the right direction? Thank you, -Niran

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  • Efficient bitshifting an array of int?

    - by nn
    Hi, To be on the same page, let's assume sizeof(int)=4 and sizeof(long)=8. Given an array of integers, what would be an efficient method to bitshift the array to either the left or right? I am contemplating an auxiliary variable such as a long, that will compute the bitshift for the first pair of elements (index 0 and 1) and set the first element (0). Continuing in this fashion the bitshift for elements (index 1 and 2) will be computer, and then index 1 will be set. I think this is actually a fairly efficient method, but there are drawbacks. I cannot bitshift greater than 32 bits. I think using multiple auxiliary variables would work, but I'm envisioning recursion somewhere along the line.

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  • Enumerating all hamiltonian paths from start to end vertex in grid graph

    - by Eric
    Hello, I'm trying to count the number of Hamiltonian paths from a specified start vertex that end at another specified vertex in a grid graph. Right now I have a solution that uses backtracking recursion but is incredibly slow in practice (e.g. O(n!) / 3 hours for 7x7). I've tried a couple of speedup techniques such as maintaining a list of reachable nodes, making sure the end node is still reachable, and checking for isolated nodes, but all of these slowed my solution down. I know that the problem is NP-complete, but it seems like some reasonable speedups should be achievable in the grid structure. Since I'm trying to count all the paths, I'm sure that the search must be exhaustive, but I'm having trouble figuring out how to prune out paths that aren't promising. Does anyone have some suggestions for speeding the search up? Or an alternate search algorithm?

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  • Which is the best Linux C/C++ debugger (or front-end to gdb) to help teaching programming?

    - by omer.gimenez
    I teach a sort of "lite" C++ programming course to novices ("lite" meaning no pointers, no classes, just plain old C, plus references and STL string and vectors). Students have no previous experience in programming, so I believe that using an interactive debugger would help them understand program flow, variables, and recursion. The course is taught in Linux. Teaching them to use gdb is just overkill (they will not use nor understand most features). I just need something simple but easy to use: to see at which line the program is now, what is in the stack (local variables, previous calls, etc.). I look something similar to old Turbo Pascal or Turbo C++ Borland's debugger, or Visual Studio debugger. Thank you,

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  • Pattern matching for lambda expressions

    - by alphomega
    21 --Primitive recursion constructor 22 pr :: ([Int] -> Int) -> ([Int] -> Int) -> ([Int] -> Int) 23 pr f g = \xs 0 -> f xs 24 pr f g = \xs (y+1) -> g xs y ((pr f g) xs y) I want the function this function creates to act differently on different inputs, so that it can create a recursive function. As expected, the above code doesn't work. How do I do something like pattern matching, but for the function it creates? Thanks

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  • Implementing a recursive menu system a'la Joomla in CodeIgniter

    - by pettersolberg
    Hi I have some sites powered by Joomla, but with my current assignment I wanted to try something new and created with CodeIgniter a really basic CMS (just to suit my client's needs). Everything works fine except menus - multilevel menus like in Joomla, Drupal etc. with items and subitems... My question is: do you know of any tutorials or texts abut implementing such a structure. I've tried the recursion thinggy with while getting children's IDs move downwards from the parent while searching for the currently displayed item's ID. I've tried also the Drupalish way with having a path parameter enclosing ID's all the way from top to bottom '1/23/123/3'. But all in all it was just too chaotic - code something, try it out. If you have some idea on this topic - thanks in advice.

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  • Another Permutation Word Conundrum... With Linq?

    - by CraigF
    I have seen many examples of getting all permutations of a given set of letters. Recursion seems to work well to get all possible combinations of a set of letters (though it doesn't seem to take into account if 2 of the letters are the same). What I would like to figure out is, could you use linq (or not) to get all possible combinations of letters down to 3 letter combinations. For example, given the letters: P I G G Y I want an array of all possible cominations of these letters so I can check against a word list (scrabble?) and eventually get a list of all possible words that you can make using those letters (from 3 letters up to the total, in this case 5 letters).

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  • 'Recursive' LINQ calls

    - by Sir Psycho
    Hi, I'm trying to build an XML tree of some data with a parent child relationship, but in the same table. The two fields of importance are CompetitionID ParentCompetitionID Some data might be CompetitionID=1, ParentCompetitionID=null CompetitionID=2, ParentCompetitionID=1 CompetitionID=3, ParentCompetitionID=1 The broken query I have simply displays results in a flat format. Seeing that I'm working with XML, some sort of recursive functionality is required. I can do this using recursion, but would like to see the linq version. Any help appreciated. var results = from c1 in comps select new { c.CompetitionID, SubComps= from sc in comps.Where (c2 => c2.CompetitionID == c1.CompetitionID) select sc };

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  • Write the longest possible loop.

    - by Abhay
    Hello Group, Recently I was asked this question in a technical discussion. What is the longest possible loop that can be written in a programming language? This loop has to be as long as possible and yet not an infinite loop and should not end-up crashing the program (Recursion etc...) I honestly did not know how to attack this problem, so I asked him if is it practically possible. He said using some computer science concepts, you can arrive at a hypothetical number which may not be practical but nevertheless it will still not be infinite. Anyone here; knows how to analyse / attack this problem. P.S. Choosing some highest limit for a type that can store the highest numerical value is apparently not an answer. Thanks in advance,

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  • Binding in ContentControl Crash

    - by ImJames
    Can anyone tell me why this crashes my app? There seems to be some endless recursion by I can't figure out why. I get this exception Logical tree depth exceeded while traversing the tree. This could indicate a cycle in the tree <ContentControl Content="{Binding}"> <ContentControl.ContentTemplate> <DataTemplate> <Button Content="{Binding MyString}"/> </DataTemplate> </ContentControl.ContentTemplate> </ContentControl> And this is all I have as Source public MainWindow() { InitializeComponent(); MyString = "Test"; this.DataContext = this; } public string MyString { get; set; }

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  • How to hash and check for equality of objects with circular references

    - by mfya
    I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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