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• Getting a "for each" loop in Java to run in different order everytime

  - by R Stokes

  Hi, Basically my problem is that I'm trying to write a method that finds a random path in a graph of strings, which takes as it's parameters a start string, an integer length and a Vector of strings that will store the path. I'm attempting to do this by first adding the starting string to our blank vector, recursing through its neighbors until the vector's length (not including the start node) is the same as the integer length specified in the parameters. I've provided my code so far here: public Vector<String> findRandomPathFrom(String n, int len, Vector<String> randomPath){ randomPath.add(n); if (randomPath.size() == len + 1) return randomPath; for (String m : this.neighbours(n)){ if (!randomPath.contains(m) && findRandomPathFrom(m, len, randomPath) != null) return randomPath; } path.setSize(path.size() - 1); return null; } It seems to be working fine, returning a path with exactly the number of strings specified after the given start string. However, for any given starting string it generates the EXACT same path everytime, which kind of defeats the purpose of it being a random path generator. I'm guessing this problem is related to my "for each" loop, which loops through all the neighbouring strings of your current string. It seems to just be going with the first string in the neighbours vector every single time. Can anyone help me fix this problem so that it will choose a random neighbour instead of going in order? tl;dr - Any way of getting a "for each" loop in java to process a collection in a random order as oppoosed to start-to-finsih? Thanks in advance

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• Mutually exclusive regular expressions

  - by CaptnCraig

  If I have a list of regular expressions, is there an easy way to determine that no two of them will both return a match for the same string? That is, the list is valid if and only if for all strings a maximum of one item in the list will match the entire string. It seems like this will be very hard (maybe impossible?) to prove definitively, but I can't seem to find any work on the subject. The reason I ask is that I am working on a tokenizer that accepts regexes, and I would like to ensure only one token at a time can match the head of the input.

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• Recursive Iterators

  - by soandos

  I am having some trouble making an iterator that can traverse the following type of data structure. I have a class called Expression, which has one data member, a List<object>. This list can have any number of children, and some of those children might be other Expression objects. I want to traverse this structure, and print out every non-list object (but I do want to print out the elements of the list of course), but before entering a list, I want to return "begin nest" and after I just exited a list, I want to return "end nest". I was able to do this if I ignored the class wherever possible, and just had List<object> objects with List<object> items if I wanted a subExpression, but I would rather do away with this, and instead have an Expressions as the sublists (it would make it easier to do operations on the object. I am aware that I could use extension methods on the List<object> but it would not be appropriate (who wants an Evaluate method on their list that takes no arguments?). The code that I used to generate the origonal iterator (that works) is: public IEnumerator GetEnumerator(){ return theIterator(expr).GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is List<object>)){ yield return " begin nest "; foreach (var item in (List<object>)root){ foreach (var item2 in theIterator(item)){ yield return item2; } } yield return " end nest "; } else yield return root; } A type swap of List<object> for expression did not work, and lead to a stackOverflow error. How should the iterator be implemented? Update: Here is the swapped code: public IEnumerator GetEnumerator() { return this.GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is Expression)) { yield return " begin nest "; foreach (var item in (Expression)root) { foreach (var item2 in theIterator(item)) yield return item2; } yield return " end nest "; } else yield return root; }

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• Base Case in a recursive method

  - by Shaza

  Hey all, About my question, I'm asking a theoretical question here about Base case or the halting case in a recursive method, what's its standards? I mean, is it standard not to have body in it, just a return statement? Is it always like the following: If(input operation value) return sth; Do you have different thoughts about it??

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• Lambda recursive PHP functions.

  - by Kendall Hopkins

  Is it possible to have a PHP function that is both recursive and anonymous (lambda). This is my attempt to get it to work, but it doesn't pass in the function name. $factorial = function( $n ) use ( $factorial ) { if( $n == 1 ) return 1; return $factorial( $n - 1 ) * $n; }; print $factorial( 5 ); I'm also aware that this is a bad way to implement factorial, it's just an example.

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• recursive program

  - by wilson88

  I am trying to make a recursive program that calculates interest per year.It prompts the user for the startup amount (1000), the interest rate (10%)and number of years(1).(in brackets are samples) Manually I realised that the interest comes from the formula YT(1 + R)----- interest for the first year which is 1100. 2nd year YT(1 + R/2 + R2/2) //R squared 2nd year YT(1 + R/3 + R2/3 + 3R3/) // R cubed How do I write a recursive program that will calculate the interest? Below is the function which I tried //Latest after editing double calculateInterest2(double start, double rate, int duration) { if (0 == duration) { return start; } else { return (1+rate) * calculateInterest2(start, rate, duration - 1); } }

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• AngularJS recursive directive with a dynamic HTML template (bounty)

  - by Nazar Sobchuk

  I have a realy hard task here. I am working on an AngularJS web app, which is capable of sending different HTTP methods to our project's Restful Web Service and receiving responses in JSON. Basicaly it looks like this: You can create some REST resource from this application. Let's say an exam. To create an exam - you pick a resource from a list of available resources. This triggers a function, that sends a request to localhost:8080/STEP/api/explain/resorceName and gets a description for this resource. Description looks like this: http://jsonblob.com/534fc022e4b0bb44248d6460 After receiving a response - I start building input fields like follows (allFields - array of field objects for this resource, enumValues - enum values for resource's field if it's property isEnum = true): <div ng-repeat="field in allFields"> <div ng-show={{!field.isEnum}}> <p ng-show={{field.isRequired}}>{{field.name}}*: </p> <p ng-show={{!field.isRequired}}>{{field.name}}: </p> <input type="text" ng-model="updateEntityResource[field.name]" ng-change="getUpdateEntityAsText()" class="form-control" placeholder="{{parseClassName(field.type)}}"> </div> <div ng-show={{field.isEnum}}> <p ng-show={{field.isRequired}}>{{field.name}}*: </p> <p ng-show={{!field.isRequired}}>{{field.name}}: </p> <select ng-model="updateEntityResource[field.name]" ng-change="getUpdateEntityAsText()" class="form-control"> <option></option> <option ng-repeat="enumValue in field.enumValues" label={{enumValue.name}}>{{enumValue.ordinal}}</option> </select> </div> </div> Now, the problem. I need to create a recursive directive, which would be capable of generating fields in such maner as described above for every resource's field that has "restResourceName" not null. To get all it's fields you just send a request to localhost:8080/STEP/api/explain/restResourceName and get similar JSON response as shown above, which is then used to build HTML elements for inputing values into model. Does anyone know how this can be achieved using angular recursive directive? Every useful answer is highly appreciated and evaluated. The correct answer will get +50 or I will start a bounty, because I'm realy stuck with this for 2 days. If you need any additional info - let me know. Thank you.

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• How to detect the root recursive call?

  - by ahmadabdolkader

  Say we're writing a simple recursive function fib(n) that calculates the nth Fibonacci number. Now, we want the function to print that nth number. As the same function is being called repeatedly, there has to be a condition that allows only the root call to print. The question is: how to write this condition without passing any additional arguments, or using global/static variables. So, we're dealing with something like this: int fib(int n) { if(n <= 0) return 0; int fn = 1; if(n > 2) fn = fib(n-2) + fib(n-1); if(???) cout << fn << endl; return fn; } int main() { fib(5); return 0; } I thought that the root call differs from all children by returning to a different caller, namely the main method in this example. I wanted to know whether it is possible to use this property to write the condition and how. Update: please note that this is a contrived example that only serves to present the idea. This should be clear from the tags. I'm not looking for standard solutions. Thanks.

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• recursively reverse linked list.

  - by Amanda

  I am implementing a function to recursively reverse a linked-list, but getting seg-fault. typedef struct _node { int data; struct _node *next; } Node, *NodeP; NodeP recursiveReverseList(NodeP first){ if(first == NULL) return NULL; if(first->next == NULL) return head; NodeP rest = recursiveReverseList(head->next); rest->next = first; first->next = NULL; return first; } Can you please help. P.S. The iterative version is working fine though. Its not homework. Just practicing C.

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• Getting HIERARCHY_REQUEST_ERR when using Javascript to recursively generate a nested list

  - by Mark

  I have a method that is trying to take in a list. This list can contain data and other lists. The end goal is to try to convert something like this ["a", "b", ["c", "d"]] into <ol> <li> <b>a</a> </li> <li> <b>b</a> </li> <ol> <li> <b>c</a> </li> <li> <b>d</a> </li> </ol> </ol> The code is: function $(tagName) { return document.createElement(tagName); } //returns an html element representing data //data should be an array or some sort of value function tagMaker(data) { tag = null; if(data instanceof Array) { //data is an array, represent using <ol> tag = $("ol"); for(i=0; i<data.length; i++) { //construct one <li> for each item in the array listItem = $("li"); //get the html element representing this particular item in the array child = tagMaker(data[i]); //<li>*html for child*</li> listItem.appendChild(child); //add this item to the list tag.appendChild(listItem); } } else { //data is not an array, represent using <b>data</b> tag = $("b"); tag.innerHTML = data.toString(); } return tag; } Calling tagMaker throws HIERARCHY_REQUEST_ERR: DOM Exception 3, rather than generating a helpful HTML element object which I was planning to append to document.body.

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• solving problems recursively in C

  - by Harry86

  Our professor gave us the following assignment: A "correct" series is one inwhich the sum of its members equals to the index of its first member. The program is supposed to find the length of the LONGEST "correct" series within a series of n numbers. for example: if the input series would be arr[4]={1, 1, 0, 0} the output (longest "correct" series) would be 3. arr[0]=1. 0!=1 therefore the longest series here is 0. arr[1]=1,and 1=1. but the follwing members also sum up to 1 as shown below: 1=arr[1]+arr[2]+arr[3] = 1+ 0 + 0, therefore the longest series here is 3. the output in this example is 3. That's what I got so far: int solve(int arr[], int index, int length,int sum_so_far) { int maxwith,maxwithout; if(index==length) return 0; maxwith = 1+ solve(arr,index+1,length,sum_so_far+arr[index]); maxwithout = solve(arr,index+1,length,arr[index+1]); if(sum_so_far+arr[index]==index) if(maxwith>maxwithout) return maxwith; return maxwithout; return 0; } int longestIndex(int arr[], int index,int length) { return solve(arr,0,length,0); } What am I doing wrong here? Thanks a lot for your time... Harry

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• Haskell Add Function Return to List Until Certain Length

  - by kienjakenobi

  I want to write a function which takes a list and constructs a subset of that list of a certain length based on the output of a function. If I were simply interested in the first 50 elements of the sorted list xs, then I would use fst (splitAt 50 (sort xs)). However, the problem is that elements in my list rely on other elements in the same list. If I choose element p, then I MUST also choose elements q and r, even if they are not in the first 50 elements of my list. I am using a function finderFunc which takes an element a from the list xs and returns a list with the element a and all of its required elements. finderFunc works fine. Now, the challenge is to write a function which builds a list whose total length is 50 based on multiple outputs of finderFunc. Here is my attempt at this: finish :: [a] -> [a] -> [a] --This is the base case, which adds nothing to the final list finish [] fs = [] --The function is recursive, so the fs variable is necessary so that finish -- can forward the incomplete list to itself. finish ps fs -- If the final list fs is too small, add elements to it | length fs < 50 && length (fs ++ newrs) <= 50 = fs ++ finish newps newrs -- If the length is met, then add nothing to the list and quit | length fs >= 50 = finish [] fs -- These guard statements are currently lacking, not the main problem | otherwise = finish [] fs where --Sort the candidate list sortedps = sort ps --(finderFunc a) returns a list of type [a] containing a and all the -- elements which are required to go with it. This is the interesting -- bit. rs is also a subset of the candidate list ps. rs = finderFunc (head sortedps) --Remove those elements which are already in the final list, because -- there can be overlap newrs = filter (`notElem` fs) rs --Remove the elements we will add to the list from the new list -- of candidates newps = filter (`notElem` rs) ps I realize that the above if statements will, in some cases, not give me a list of exactly 50 elements. This is not the main problem, right now. The problem is that my function finish does not work at all as I would expect it to. Not only does it produce duplicate elements in the output list, but it sometimes goes far above the total number of elements I want to have in the list. The way this is written, I usually call it with an empty list, such as: finish xs [], so that the list it builds on starts as an empty list.

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• How can i optimize this recursive method

  - by Tirdyr

  Hi there. I'm trying to make a word puzzle game, and for that i'm using a recursive method to find all possible words in the given letters. The letters is in a 4x4 board. Like this: ABCD EFGH HIJK LMNO The recursive method is called inside this loop: for (int y = 0; y < width; y++) { for (int x = 0; x < height; x++) { myScabble.Search(letters, y, x, width, height, "", covered, t); } } letters is a 2D array of chars. y & x is ints that shows where in the board width & height is also int, that tells the dimensions of the board "" is the string we are trying to make (the word) covered is an array of bools, to check if we allready used that square. t is a List (wich contains all the words to check against). The recursive method that need optimizing: public void Search(char[,] letters, int y, int x, int width, int height, string build, bool[,] covered, List<aWord> tt) { // Dont get outside the bounds if (y >= width || y < 0 || x >= height || x < 0) { return; } // Dont deal with allrady covered squares if (covered[x, y]) { return; } // Get Letter char letter = letters[x, y]; // Append string pass = build + letter; // check if its a possibel word //List<aWord> t = myWords.aWord.Where(w => w.word.StartsWith(pass)).ToList(); List<aWord> t = tt.Where(w => w.word.StartsWith(pass)).ToList(); // check if the list is emphty if (t.Count < 10 && t.Count != 0) { //stop point } if (t.Count == 0) { return; } // Check if its a complete word. if (t[0].word == pass) { //check if its allrdy present in the _found dictinary if (!_found.ContainsKey(pass)) { //if not add the word to the dictionary _found.Add(pass, true); } } // Check to see if there is more than 1 more that matches string pass // ie. are there more words to find. if (t.Count > 1) { // make a copy of the covered array bool[,] cov = new bool[height, width]; for (int i = 0; i < width; i++) { for (int a = 0; a < height; a++) { cov[a, i] = covered[a, i]; } } // Set the current square as covered. cov[x, y] = true; // Continue in all 8 directions. Search(letters, y + 1, x, width, height, pass, cov, t); Search(letters, y, x + 1, width, height, pass, cov, t); Search(letters, y + 1, x + 1, width, height, pass, cov, t); Search(letters, y - 1, x, width, height, pass, cov, t); Search(letters, y, x - 1, width, height, pass, cov, t); Search(letters, y - 1, x - 1, width, height, pass, cov, t); Search(letters, y - 1, x + 1, width, height, pass, cov, t); Search(letters, y + 1, x - 1, width, height, pass, cov, t); } } The code works as i expected it to do, however it is very slow.. it takes about 2 mins to find the words. EDIT: i clarified that the letters array is 2D

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• Python 3: Recursivley find if number is even

  - by pythonhack

  I am writing a program that must find if a number is even or not. It needs to follow this template. I can get it to find if a number is even or not recursively (call function and subtract 2, base case zero), but I am having a hard time following this template, based on how the isEven function is called in the main function. Any help would be greatly appreciated. Write a recursive function called isEven that finds whether a number is even or not: def isEven() #recursivley determine whether number is even or not def main(): number=int(input(“Enter a number : “)) if (isEven(number)): print(“Number is even”) else: print(“Number is not even”) main() Thank you! Appreciate it.

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• How do I find the millionth number in the series: 2 3 4 6 9 13 19 28 42 63 ... ?

  - by HH

  It takes about minute to achieve 3000 in my comp but I need to know the millionth number in the series. The definition is recursive so I cannot see any shortcuts except to calculate everything before the millionth number. How can you fast calculate millionth number in the series? Series Def n_{i+1} = \floor{ 3/2 * n_{i} } and n_{0}=2. Interestingly, only one site list the series according to Google: this one. Too slow Bash code #!/bin/bash function series { n=$( echo "3/2*$n" | bc -l | tr '\n' ' ' | sed -e 's@\\@@g' -e 's@ @@g' ); # bc gives \ at very large numbers, sed-tr for it n=$( echo $n/1 | bc ) #DUMMY FLOOR func } n=2 nth=1 while [ true ]; #$nth -lt 500 ]; do series $n # n gets new value in the function through global value echo $nth $n nth=$( echo $nth + 1 | bc ) #n++ done

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• How can I make a recursive version of my iterative method?

  - by user247679

  Greetings. I am trying to write a recursive function in Java that prints the numbers one through n. (n being the parameter that you send the function.) An iterative solution is pretty straightforward: public static void printNumbers(int n){ for(int i = 1; i <= n; i++){ System.out.println(i); i++; } As a novice programmer, I'm having troubles figuring out how a recursive version of this method would work. Any bright ideas? Thanks for reading my problem!

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• How to handle recursive parent/child problems like this?

  - by lsdude

  In web dev I come across these problems a lot. For example, we have a giant list of URLs that are in this format: /businesses /businesses/food /businesses/food/wendys /businesses/food/wendys/chili /businesses/food/wendys/fries /businesses/food/wendys/chicken-nuggets /businesses/pharmacy/cvs /businesses/pharmacy/cvs/toothpaste /businesses/pharmacy/cvs/toothpaste/brand ... and then we need to output each one, where the parent category is in h1 tags, the child is in h2 tags, and the children of that are in h3 tags. I can handle this but I feel my code is messy. I'm sure there is a design pattern I can use? Langs are ruby/php usually. how would you handle this?

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• C++ Filling an 1D array to represent a n-dimensional object based on a straight line segment

  - by Ben

  I'm struggling to find a good way to put this question but here goes. I'm making a system that uses a 1D array implemented as double * parts_ = new double[some_variable];. I want to use this to hold co-ordinates for a particle system that can run in various dimensions. What I want to be able to do is write a generic fill algorithm for filling this in n-dimensions with a common increment in all direction to a variable size. Examples will serve best I think. Consider the case where the number of particles stored by the array is 4 In 1D this produces 4 elements in the array because each particle only has one co-ordinate. 1D: {0, 25, 50, 75}; In 2D this produces 8 elements in the array because each particle has two co-ordinates.. 2D: {0, 0, 0, 25, 25, 0, 25, 25} In 3D this produces 12 elements in the array because each particle now has three co-ordinates {0, 0, 0, 0, 0, 25, 0, 0, 50, ... } These examples are still not quite accurate, but they hopefully will suffice. The way I would do this normally for two dimensions: int i = 0; for(int x = 0; x < parts_size_ / dims_ / dims_ * 25; x += 25) { for(int y = 0; y < parts_size_ / dims_ / dims_ * 25; y += 25) { parts_[i] = x; parts_[i+1] = y; i+=2; // Indentation hates me today .< How can I implement this for n-dimensions where 25 can be any number? The straight line part is because it seems to me logical that a line is a somewhat regular shape in 1D, as is a square in 2D, and a cube in 3D. It seems to me that it would follow that there would be similar shapes in this family that could be implemented for 4D and higher dimensions via a similar fill pattern. This is the shape I wish to set my array to represent.

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• Recursively looping through a drive and replacing illegal characters

  - by yeahumok

  Hi I have to create an app that drills into a specific drive, reads all file names and replaces illegal SharePoint characters with underscores. The illegal characters I am referring to are: ~ # % & * {} / \ | : <> ? - "" Can someone provide either a link to code or code itself on how to do this? I am VERY new to C# and need all the help i can possibly get. I have researched code on recursively drilling through a drive but i am not sure how to put the character replace and the recursive looping together. Please help!

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• passing back answers in prolog

  - by AhmadAssaf

  i have this code than runs perfectly .. returns a true .. when tracing the values are ok .. but its not returning back the answer .. it acts strangely when it ends and always return empty list .. uninstantiated variable .. test :- extend(4,12,[4,3,1,2],[[1,5],[3,4],[6]],_ExtendedBins). %printing basic information about the extend(NumBins,Capacity,RemainingNumbers,BinsSoFar,_ExtendedBins) :- getNumberofBins(BinsSoFar,NumberOfBins), msort(RemainingNumbers,SortedRemaining),nl, format("Current Number of Bins is :~w\n",[NumberOfBins]), format("Allowed Capacity is :~w\n",[Capacity]), format("maximum limit in bin is :~w\n",[NumBins]), format("Trying to fit :~w\n\n",[SortedRemaining]), format("Possible Solutions :\n\n"), fitElements(NumBins,NumberOfBins, Capacity,SortedRemaining,BinsSoFar,[]). %this is were the creation for possibilities will start %will check first if the number of bins allowed is less than then %we create a new list with all the possible combinations %after that we start matching to other bins with capacity constraint fitElements(NumBins,NumberOfBins, Capacity,RemainingNumbers,Bins,ExtendedBins) :- ( NumberOfBins < NumBins -> print('Creating new set: '); print('Sorry, Cannot create New Sets')), createNewList(Capacity,RemainingNumbers,Bins,ExtendedBins). createNewList(Capacity,RemainingNumbers,Bins,ExtendedBins) :- createNewList(Capacity,RemainingNumbers,Bins,[],ExtendedBins), print(ExtendedBins). createNewList(0,Bins,Bins,ExtendedBins,ExtendedBins). createNewList(_,[],_,ExtendedBins,ExtendedBins). createNewList(Capacity,[Element|Rest],Bins,Temp,ExtendedBins) :- conjunct_to_list(Element,ListedElement), append(ListedElement,Temp,NewList), sumlist(NewList,Sum), (Sum =< Capacity, append(ListedElement,ExtendedBins,Result); Capacity = 0), createNewList(Capacity,Rest,Bins,NewList,Result). fit(0,[],ExtendedBins,ExtendedBins). fit(Capacity,[Element|Rest],Bin,ExtendedBins) :- conjunct_to_list(Element,Listed), append(Listed,Bin,NewBin), sumlist(NewBin,Sum), (Sum =< Capacity -> fit(Capacity,Rest,NewBin,ExtendedBins); Capacity = 0, append(NewBin,ExtendedBins,NewExtendedBins), print(NewExtendedBins), fit(0,[],NewBin,ExtendedBins)). %get the number of bins provided getNumberofBins(List,NumberOfBins) :- getNumberofBins(List,0,NumberOfBins). getNumberofBins([],NumberOfBins,NumberOfBins). getNumberofBins([_List|Rest],TempCount,NumberOfBins) :- NewCount is TempCount + 1, %calculate the count getNumberofBins(Rest,NewCount,NumberOfBins). %recursive call %Convert set of terms into a list - used when needed to append conjunct_to_list((A,B), L) :- !, conjunct_to_list(A, L0), conjunct_to_list(B, L1), append(L0, L1, L). conjunct_to_list(A, [A]). Greatly appreciate the help

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• slowing down a loop in a recursive function

  - by eco_bach

  I have a difficult problem with a recursive function. Essentially I need to 'slow down' a for loop within a function that repeatedly calls itself(the function); Is this possible, or do I need to somehow extract the recursive nature of the function? function callRecursiveFuncAgain(ob:Object):void{ //do recursive stuff; for (var i:int = 0; i < 4; i++) { _nextObj=foo callRecursiveFuncAgain(_nextObj); } }

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• MySql stored procedure not found in PHP

  - by kaupov

  Hello, I have a trouble with MySql stored procedure that calls itself recursively using PHP (CakePHP). Calling it I receive following error: SQL Error: 1305: FUNCTION dbname.GetAdvertCounts does not exist The procedure itself is following: delimiter // DROP PROCEDURE IF EXISTS GetAdvertCounts// CREATE PROCEDURE GetAdvertCounts(IN category_id INT) BEGIN DECLARE no_more_sub_categories, advert_count INT DEFAULT 0; DECLARE sub_cat_id INT; DECLARE curr_sub_category CURSOR FOR SELECT id FROM categories WHERE parent_id = category_id; DECLARE CONTINUE HANDLER FOR NOT FOUND SET no_more_sub_categories = 1; SELECT COUNT(*) INTO advert_count FROM adverts WHERE category_id = category_id; OPEN curr_sub_category; FETCH curr_sub_category INTO sub_cat_id; REPEAT SELECT advert_count + GetAdvertCounts(sub_cat_id) INTO advert_count; FETCH curr_sub_category INTO sub_cat_id; UNTIL no_more_sub_categories = 1 END REPEAT; CLOSE curr_sub_category; SELECT advert_count; END // delimiter ; If I remove or comment out the recursive call, the procedure is working. Any idea what I'm missing here? The categories are 2 level deep.

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• Java - StackOverflow Error on recursive 2D boolean array method that shouldn't happen.

  - by David W.

  Hey everyone, I'm working on a runnable java applet that has a fill feature much like the fill method in drawing programs such as Microsoft Paint. This is how my filling method works: 1.) The applet gets the color that the user clicked on using .getRGB 2.) The applet creates a 2D boolean array of all the pixels in the window, with the value "true" if that pixel is the same color as the color clicked on or "false" if not. The point of this step is to keep the .getRGB method out of the recursive method to hopefully prevent this error. 3.) The applet recursively searches the 2D array of booleans where the user clicked, recording each adjacent point that is "true" in an ArrayList. The method then changes each point it records to false and continues. 4.) The applet paints every point stored in the ArrayList to a user selected color. All of the above steps work PERFECTLY if the user clicks within a small area, where only a few thousand pixels or so have their color changed. If the user selects a large area however (such as about 360,000 / the size of the applet window), the applet gets to the recursive stage and then outputs this error: Exception in thread "AWT-EventQueue-1" java.lang.StackOverflowError at java.util.ArrayList.add(ArrayList.java:351) at paint.recursiveSearch(paint.java:185) at paint.recursiveSearch(paint.java:190) at paint.recursiveSearch(paint.java:190) at paint.recursiveSearch(paint.java:190) at paint.recursiveSearch(paint.java:190) at paint.recursiveSearch(paint.java:190) at paint.recursiveSearch(paint.java:190) (continues for a few pages) Here is my recursive code: public void recursiveSearch(boolean [][] list, Point p){ if(isValid(p)){ if(list[(int)p.y][(int)p.x]){ fillPoints.add(p); list[(int)p.y][(int)p.x] = false; recursiveSearch(list, new Point(p.x-1,p.y));//Checks to the left recursiveSearch(list, new Point(p.x,p.y-1));//Checks above recursiveSearch(list, new Point(p.x+1,p.y));//Checks to the right recursiveSearch(list, new Point(p.x,p.y+1));//Checks below } } } Is there any way I can work around an error like this? I know that the loop will never go on forever, it just could take a lot of time. Thanks in advance.

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• Python recursive program

  - by mathboy

  I'm relatively newcomer on programming as I'm educated a mathematician and have no experience on Python. I would like to know how to solve this problem in Python which appeared as I was studying one maths problem on my own: Program asks a positive integer m. If m is of the form 2^n-1 it returns T(m)=n*2^{n-1}. Otherwise it writes m to the form 2^n+x, where -1 < x < 2^n, and returns T(m)=T(2^n-1)+x+1+T(x). Finally it outputs the answer.

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• Recurssion Question : Revision

  - by stan

  My slides say that A recurssive call should always be on a smaller data structure than the current one There must be a non recurssive option if the data structure is too small You need a wrapper method to make the recurssive method accessible Just reading this from the slides makes no sence, especially seeing as it was a topic from before christmas! Could anyone try and clear up what it means please? Thank you

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