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  • PHP: Recursive array function

    - by Industrial
    Hi everybody, I want to create a function that returns the full path from a set node, back to the root value. I tried to make a recursive function, but ran out of luck totally. What would be an appropriate way to do this? I assume that a recursive function is the only way? Here's the array: Array ( [0] => Array ( [id] => 1 [name] => Root category [_parent] => ) [1] => Array ( [id] => 2 [name] => Category 2 [_parent] => 1 ) [2] => Array ( [id] => 3 [name] => Category 3 [_parent] => 1 ) [3] => Array ( [id] => 4 [name] => Category 4 [_parent] => 3 ) ) The result I want my function to output when getting full path of node id#4: Array ( [0] => Array ( [id] => 1 [name] => Root category [_parent] => ) [1] => Array ( [id] => 3 [name] => Category 3 [_parent] => 1 ) [2] => Array ( [id] => 4 [name] => Category 4 [_parent] => 3 ) ) The notoriously bad example of my recursive skills: function recursive ($id, $array) { $innerarray = array(); foreach ($array as $k => $v) { if ($v['id'] === $id) { if ($v['_parent'] !== '') { $innerarray[] = $v; recursive($v['id'], $array); } } } return $innerarray; } Thanks!

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  • Difference between an LL and Recursive Descent parser?

    - by Noldorin
    I've recently being trying to teach myself how parsers (for languages/context-free grammars) work, and most of it seems to be making sense, except for one thing. I'm focusing my attention in particular on LL(k) grammars, for which the two main algorithms seem to be the LL parser (using stack/parse table) and the Recursive Descent parser (simply using recursion). As far as I can see, the recursive descent algorithm works on all LL(k) grammars and possibly more, whereas an LL parser works on all LL(k) grammars. A recursive descent parser is clearly much simpler than an LL parser to implement, however (just as an LL one is simply than an LR one). So my question is, what are the advantages/problems one might encounter when using either of the algorithms? Why might one ever pick LL over recursive descent, given that it works on the same set of grammars and is trickier to implement? Hopefully this question makes some amount of sense. Sorry if it doesn't - I blame my the fact that this entire subject is almost entirely new to me.

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  • Recursive move utility on Unix?

    - by Thomas Vander Stichele
    Sometimes I have two trees that used to have the same content, but have grown out of sync (because I moved disks around or whatever). A good example is a tree where I mirror upstream packages from Fedora. I want to merge those two trees again by moving all of the files from tree1 into tree2. Usually I do this with: rsync -arv tree1/* tree2 Then delete tree1. However, this takes an awful lot of time and disk space, and it would be much easier to be able to do: mv -r tree1/* tree2 In other words, a recursive move. It would be faster because first of all it would not even copy, just move the inodes, and second I wouldn't need a delete at the end. Does this exist ? As a test case, consider the following sequence of commands: $ mkdir -p a/b $ touch a/b/c1 $ rsync -arv a/ a2 sending incremental file list created directory ./ b/ b/c1 b/c2 sent 173 bytes received 57 bytes 460.00 bytes/sec total size is 0 speedup is 0.00 $ touch a/b/c2 What command would now have the effect of moving a/b/c2 to a2/b/c2 and then deleting the a subtree (since everything in it is already in the destination tree) ?

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  • php run function on all images from one dir in recursive mode (noob)

    - by Steve
    hey guyz i have a function $result = create_watermark( 'input_file_name' ,'output_file_name'); i have dir called /images n have 500 images in it and all images are link images_(some_unknown_numbers).png (all png) now i want run them thru function in loop and want out put like /markedimage/images_1.png images_2.png images_3.png i need help how can i run them in loop and how out put name can change want run script on Ubuntu so we can use shell too if any body want check function it is here http://paste2.org/p/789149 plz provide me code because i m newbie thanks in advance

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  • a non recursive approach to the problem of generating combinations at fault

    - by mark
    Hi, I wanted a non recursive approach to the problem of generating combination of certain set of characters or numbers. So, given a subset k of numbers n, generate all the possible combination n!/k!(n-k)! The recursive method would give a combination, given the previous one combination. A non recursive method would generate a combination of a given value of loop index i. I approached the problem with this code: Tested with n = 4 and k = 3, and it works, but if I change k to a number 3 it does not work. Is it due to the fact that (n-k)! in case of n = 4 and k = 3 is 1. and if k 3 it will be more than 1? Thanks. int facto(int x); int len,fact,rem=0,pos=0; int str[7]; int avail[7]; str[0] = 1; str[1] = 2; str[2] = 3; str[3] = 4; str[4] = 5; str[5] = 6; str[6] = 7; int tot=facto(n) / facto(n-k) / facto(k); for (int i=0;i<tot;i++) { avail[0]=1; avail[1]=2; avail[2]=3; avail[3]=4; avail[4]=5; avail[5]=6; avail[6]=7; rem = facto(i+1)-1; cout<<rem+1<<". "; for(int j=len;j>0;j--) { int div = facto(j); pos = rem / div; rem = rem % div; cout<<avail[pos]<<" "; avail[pos]=avail[j]; } cout<<endl; } int facto(int x) { int fact=1; while(x0) fact*=x--; return fact; }

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  • Java Generics Type Safety warning with recursive Hashmap

    - by GC
    Hi, I'm using a recursive tree of hashmaps, specifically Hashmap map where Object is a reference to another Hashmap and so on. This will be passed around a recursive algorithm: foo(String filename, Hashmap<String, Object> map) { //some stuff here for (Entry<String, Object> entry : map.entrySet()) { //type warning that must be suppressed foo(entry.getKey(), (HashMap<String, Object>)entry.getValue()); } } I know for sure Object is of type Hashmap<String, Object> but am irritated that I have to suppress the warning using @SuppressWarnings("unchecked"). I'll be satisfied with a solution that does either a assert(/*entry.getValue() is of type HashMap<String, Object>*/) or throws an exception when it isn't. I went down the Generics route for compile type safety and if I suppress the warning then it defeats the purpose. Thank you for your comments, ksb

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  • Tail-recursive implementation of take-while

    - by Giorgio
    I am trying to write a tail-recursive implementation of the function take-while in Scheme (but this exercise can be done in another language as well). My first attempt was (define (take-while p xs) (if (or (null? xs) (not (p (car xs)))) '() (cons (car xs) (take-while p (cdr xs))))) which works correctly but is not tail-recursive. My next attempt was (define (take-while-tr p xs) (let loop ((acc '()) (ys xs)) (if (or (null? ys) (not (p (car ys)))) (reverse acc) (loop (cons (car ys) acc) (cdr ys))))) which is tail recursive but needs a call to reverse as a last step in order to return the result list in the proper order. I cannot come up with a solution that is tail-recursive, does not use reverse, only uses lists as data structure (using a functional data structure like a Haskell's sequence which allows to append elements is not an option), has complexity linear in the size of the prefix, or at least does not have quadratic complexity (thanks to delnan for pointing this out). Is there an alternative solution satisfying all the properties above? My intuition tells me that it is impossible to accumulate the prefix of a list in a tail-recursive fashion while maintaining the original order between the elements (i.e. without the need of using reverse to adjust the result) but I am not able to prove this. Note The solution using reverse satisfies conditions 1, 3, 4.

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  • Right recursive grammar or left recursive?

    - by user2485710
    I have little to no knowledge of what I'm about to ask, so I would like a suggestion based on the level of skills required to implemented a parser for the given grammar ( since I'm a beginner in this kind of formal approach to parsers and languages ). Just by going back of a couple of years, this situation reminds me a little of Pascal grammar vs C/C++ grammar, this left vs right stuff. But I'm not going to do any of that, my purpose is to implement a simple parser for a markup language for documents like Markdown. So considering that I'm starting with a markup language in mind, I want to keep things simple, which is the easiest one to handle between this 2 options and why . Another kind of grammar could be an easier option for me ? If yes which one do you suggest ?

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  • scheme recursive lambda

    - by Mike
    Is there a way to have a recursive lambda expression in scheme without relying an external identifier? I know you can have (define fact (lambda (n) (if (= n 0) 1 (fact (- n 1)))) but it would be nice if fact wasn't hard coded in the lambda expression, it seems improper.

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  • What is a RECURSIVE Function in PHP?

    - by Imran
    Can anyone please explain a recursive function to me in PHP (without using Fibonacci) in layman language and using examples? i was looking at an example but the Fibonacci totally lost me! Thank you in advance ;-) Also how often do you use them in web development?

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  • lua recursive repl on error?

    - by anon
    In many scheme/lisp dialects, when an error occurs, a "recursive repl" is popped up ... one can execute scheme/lisp code at the frame where the error occured, and go up/down the stack. Is it possible to do something similar to this in lua? Thanks!

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  • SQL SERVER – Quiz and Video – Introduction to Hierarchical Query using a Recursive CTE

    - by pinaldave
    This blog post is inspired from SQL Queries Joes 2 Pros: SQL Query Techniques For Microsoft SQL Server 2008 – SQL Exam Prep Series 70-433 – Volume 2.[Amazon] | [Flipkart] | [Kindle] | [IndiaPlaza] This is follow up blog post of my earlier blog post on the same subject - SQL SERVER – Introduction to Hierarchical Query using a Recursive CTE – A Primer. In the article we discussed various basics terminology of the CTE. The article further covers following important concepts of common table expression. What is a Common Table Expression (CTE) Building a Recursive CTE Identify the Anchor and Recursive Query Add the Anchor and Recursive query to a CTE Add an expression to track hierarchical level Add a self-referencing INNER JOIN statement Above six are the most important concepts related to CTE and SQL Server.  There are many more things one has to learn but without beginners fundamentals one can’t learn the advanced  concepts. Let us have small quiz and check how many of you get the fundamentals right. Quiz 1) You have an employee table with the following data. EmpID FirstName LastName MgrID 1 David Kennson 11 2 Eric Bender 11 3 Lisa Kendall 4 4 David Lonning 11 5 John Marshbank 4 6 James Newton 3 7 Sally Smith NULL You need to write a recursive CTE that shows the EmpID, FirstName, LastName, MgrID, and employee level. The CEO should be listed at Level 1. All people who work for the CEO will be listed at Level 2. All of the people who work for those people will be listed at Level 3. Which CTE code will achieve this result? WITH EmpList AS (SELECT Boss.EmpID, Boss.FName, Boss.LName, Boss.MgrID, 1 AS Lvl FROM Employee AS Boss WHERE Boss.MgrID IS NULL UNION ALL SELECT E.EmpID, E.FirstName, E.LastName, E.MgrID, EmpList.Lvl + 1 FROM Employee AS E INNER JOIN EmpList ON E.MgrID = EmpList.EmpID) SELECT * FROM EmpList WITH EmpListAS (SELECT EmpID, FirstName, LastName, MgrID, 1 as Lvl FROM Employee WHERE MgrID IS NULL UNION ALL SELECT EmpID, FirstName, LastName, MgrID, 2 as Lvl ) SELECT * FROM BossList WITH EmpList AS (SELECT EmpID, FirstName, LastName, MgrID, 1 as Lvl FROM Employee WHERE MgrID is NOT NULL UNION SELECT EmpID, FirstName, LastName, MgrID, BossList.Lvl + 1 FROM Employee INNER JOIN EmpList BossList ON Employee.MgrID = BossList.EmpID) SELECT * FROM EmpList 2) You have a table named Employee. The EmployeeID of each employee’s manager is in the ManagerID column. You need to write a recursive query that produces a list of employees and their manager. The query must also include the employee’s level in the hierarchy. You write the following code segment: WITH EmployeeList (EmployeeID, FullName, ManagerName, Level) AS ( –PICK ANSWER CODE HERE ) SELECT EmployeeID, FullName, ” AS [ManagerID], 1 AS [Level] FROM Employee WHERE ManagerID IS NULL UNION ALL SELECT emp.EmployeeID, emp.FullName mgr.FullName, 1 + 1 AS [Level] FROM Employee emp JOIN Employee mgr ON emp.ManagerID = mgr.EmployeeId SELECT EmployeeID, FullName, ” AS [ManagerID], 1 AS [Level] FROM Employee WHERE ManagerID IS NULL UNION ALL SELECT emp.EmployeeID, emp.FullName, mgr.FullName, mgr.Level + 1 FROM EmployeeList mgr JOIN Employee emp ON emp.ManagerID = mgr.EmployeeId Now make sure that you write down all the answers on the piece of paper. Watch following video and read earlier article over here. If you want to change the answer you still have chance. Solution 1) 1 2) 2 Now compare let us check the answers and compare your answers to following answers. I am very confident you will get them correct. Available at USA: Amazon India: Flipkart | IndiaPlaza Volume: 1, 2, 3, 4, 5 Please leave your feedback in the comment area for the quiz and video. Did you know all the answers of the quiz? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Type checking and recursive types (Writing the Y combinator in Haskell/Ocaml)

    - by beta
    When explaining the Y combinator in the context of Haskell, it's usually noted that the straight-forward implementation won't type-check in Haskell because of its recursive type. For example, from Rosettacode [1]: The obvious definition of the Y combinator in Haskell canot be used because it contains an infinite recursive type (a = a -> b). Defining a data type (Mu) allows this recursion to be broken. newtype Mu a = Roll { unroll :: Mu a -> a } fix :: (a -> a) -> a fix = \f -> (\x -> f (unroll x x)) $ Roll (\x -> f (unroll x x)) And indeed, the “obvious” definition does not type check: ?> let fix f g = (\x -> \a -> f (x x) a) (\x -> \a -> f (x x) a) g <interactive>:10:33: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 Expected type: t2 -> t0 -> t1 Actual type: (t2 -> t0 -> t1) -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a <interactive>:10:57: Occurs check: cannot construct the infinite type: t2 = t2 -> t0 -> t1 In the first argument of `x', namely `x' In the first argument of `f', namely `(x x)' In the expression: f (x x) a (0.01 secs, 1033328 bytes) The same limitation exists in Ocaml: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; Error: This expression has type 'a -> 'b but an expression was expected of type 'a The type variable 'a occurs inside 'a -> 'b However, in Ocaml, one can allow recursive types by passing in the -rectypes switch: -rectypes Allow arbitrary recursive types during type-checking. By default, only recursive types where the recursion goes through an object type are supported. By using -rectypes, everything works: utop # let fix f g = (fun x a -> f (x x) a) (fun x a -> f (x x) a) g;; val fix : (('a -> 'b) -> 'a -> 'b) -> 'a -> 'b = <fun> utop # let fact_improver partial n = if n = 0 then 1 else n*partial (n-1);; val fact_improver : (int -> int) -> int -> int = <fun> utop # (fix fact_improver) 5;; - : int = 120 Being curious about type systems and type inference, this raises some questions I'm still not able to answer. First, how does the type checker come up with the type t2 = t2 -> t0 -> t1? Having come up with that type, I guess the problem is that the type (t2) refers to itself on the right side? Second, and perhaps most interesting, what is the reason for the Haskell/Ocaml type systems to disallow this? I guess there is a good reason since Ocaml also will not allow it by default even if it can deal with recursive types if given the -rectypes switch. If these are really big topics, I'd appreciate pointers to relevant literature. [1] http://rosettacode.org/wiki/Y_combinator#Haskell

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  • Resume recursive scp transfer (with rsync?)

    - by vgm64
    I was transferring several thousand files each ~1MB via scp and my connection was broken after the first 2k files or so. I wanted to know if there was a way to resume the recursive transfer w/o starting over. Something like $ scp -r [email protected]:/datafiles/ ./ ... Happy Transfer ... ... BREAK! ... $ rsync -P [email protected]:/datafiles/ ./ ... Continue transf... The problem is I can't seem to get the syntax correct if it is possible. Can anyone shed some light on if/how it can be done? PS. If you specify the slash after "datafiles" in the rsync line, does that transfer the directory or its contents? I saw conflicting comments when I googled.

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  • Recursive CTE Problem

    - by Chris
    Hi, I am trying to use a recursive CTE in SQL Server to build up a predicate formula from a table containing the underlying tree structure. For example, my table looks like: -------------------------- Id Operator/Val ParentId -------------------------- 1. 'OR' NULL 2. 'AND' 1 3. 'AND' 1 4. '' 2 5. 'a' 4 6. 'alpha' 4 : : : -------------------------- which represents ((a alpha) AND (b beta)) OR ((c gamma) AND (a < delta)). ParentId is a reference to the Id in the same table of the parent node. I want to write a query which will build up this string from the table. Is it possible? Thanks

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  • SQL server recursive query error.The maximum recursion 100 has been exhausted before statement completion

    - by ienax_ridens
    I have a recursive query that returns an error when I run it; in other databases (with more data) I have not the problem. In my case this query returns 2 colums (ID_PARENT and ID_CHILD) doing a recursion because my tree can have more than one level, bit I wanna have only "direct" parent. NOTE: I tried to put OPTION (MAXRECURSION 0) at the end of the query, but with no luck. The following query is only a part of the entire query, I tried to put OPTION only at the end of the "big query" having a continous running query, but no errors displayed. Error have in SQL Server: "The statement terminated.The maximum recursion 100 has been exhausted before statement completion" The query is the following: WITH q AS (SELECT ID_ITEM, ID_ITEM AS ID_ITEM_ANCESTOR FROM ITEMS_TABLE i JOIN ITEMS_TYPES_TABLE itt ON itt.ID_ITEM_TYPE = i.ID_ITEM_TYPE UNION ALL SELECT i.ID_ITEM, q.ID_ITEM_ANCESTOR FROM q JOIN ITEMS_TABLE i ON i.ID_ITEM_PADRE = q.ID_ITEM JOIN ITEMS_TYPES_TABLE itt ON itt.ID_ITEM_TYPE = i.ID_ITEM_TYPE) SELECT ID_ITEM AS ID_CHILD, ID_ITEM_ANCESTOR AS ID_PARENT FROM q I need a suggestion to re-write this query to avoid the error of recursion and see the data, that are few.

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  • PHP DOMXml XPath of recursive Xpointer

    - by user256007
    My xml document reflects an Object. as referential Recursion is possible in objects and arrays. I need to reflect that in reproduced XML Structure too. Currently I am using Unique IDs to identify each node separately and a node like <recursion refer="IDREF"> and specifying the ID of the referenced Element. But in This way I need My Own Custom XPath resolver cause I want to let the users go deeper into the recursive node through the Identifying IDREF (Hope I am able to make you understand). So is there any better/liteweight solution ?? might be XPointer or XLink (I am not sure). Any help ??

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  • Recursive query question - break rows into columns?

    - by Stew
    I have a table "Families", like so FamilyID PersonID Relationship ----------------------------------------------- F001 P001 Son F001 P002 Daughter F001 P003 Father F001 P004 Mother F002 P005 Daughter F002 P006 Mother F003 P007 Son F003 P008 Mother and I need output like FamilyID PersonID Father Mother ------------------------------------------------- F001 P001 P003 P004 F001 P002 P003 P004 F001 P003 F001 P004 F002 P005 P006 F002 P006 F003 P007 P008 F003 P008 In which the PersonID of the Father and Mother for a given PersonID are listed (if applicable) in separate columns. I know this must be a relatively trivial query to write (and therefore to find instructions for), but I can't seem to come up with the right search terms. Searching "SQL recursive queries" has gotten me closest, but I can't quite translate those methods to what I'm trying to do here. I'm trying to learn, so multiple methods are welcome, as is vocabulary I should read up on. Thanks!

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  • Unix tree convert to recursive php array

    - by Fordnox
    I have a response from remote server like this: /home/computer/Downloads |-- /home/computer/Downloads/Apple | `-- /home/computer/Downloads/Apple/Pad |-- /home/computer/Downloads/Empty_Folder `-- /home/computer/Downloads/Subfolder |-- /home/computer/Downloads/Subfolder/Empty `-- /home/computer/Downloads/Subfolder/SubSubFolder `-- /home/computer/Downloads/Subfolder/SubSubFolder/Test this is the output for command [email protected]:$ tree -df --noreport -L 5 /home/computer/Downloads/ I would like to parse this string to recursive php array or object, something like this. I would show only part of result to get the idea. array( 'title' => '/home/computer/Downloads', 'children' => array( 0 => array( 'title' => '/home/computer/Downloads/Apple', 'children' => array( ... ) ) ); Response from server can change according to scanned directory. Can someone help me write this function. Please note that this is response from remote server and php functions can not scan any remote dir.

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  • Recursive function for a binary search in C++

    - by boomsnack
    Create a recursive function for the binary search. This function accepts a sorted array and a give item being search for and returns the index of the item if this give item in the array or returns -1 if this give item is not in the array. Moreover, write a test program to test your function. Sorry for the bad english but my teacher can not write it or speak it very well. This is for a final project and determines whether I graduate or not I went to the tutor and he did not know how to do it either. Any help is greatly appreicated.

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  • Good grammar for date data type for recursive descent parser LL(1)

    - by Totophil
    I'm building a custom expression parser and evaluator for production enviroment to provide a limited DSL to the users. The parser itself as the DSL, need to be simple. The parser is going to be built in an exotic language that doesn't support dynamic expression parsing nor has any parser generator tools available. My decision is to go for recursive descent approach with LL(1) grammar, so that even programmers with no previous experience in evaluating expression could quickly learn how the code works. It has to handle mixed expressions made up of several data types: decimals, percentages, strings and dates. And dates in the format of dd/mm/yyyy are easy to confuse with a string of devision ops. Is where a good solution to this problem? My own solution that is aimed at keeping the parser simple involves prefixing dates with a special symbol, let's say apostrophe: <date> ::= <apostr><digit><digit>/<digit><digit>/<digit><digit><digit><digit> <apostr> ::= ' <digit> ::= '0'..'9'

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