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• Recursion in assembly?

  - by Davis

  I'm trying to get a better grasp of assembly, and I am a little confused about how to recursively call functions when I have to deal with registers, popping/pushing, etc. I am embedding x86 assembly in C++. Here I am trying to make a method which given an array of integers will build a linked list containing these integers in the order they appear in the array. I am doing this by calling a recursive function: insertElem (struct elem *head, struct elem *newElem, int data) -head: head of the list -data: the number that will be inserted at the end of a list -newElem: points to the location in memory where I will store the new element (data field) My problem is that I keep overwriting the registers instead of a typical linked list. For example, if I give it an array {2,3,1,8,3,9} my linked-list will return the first element (head) and only the last element, because the elements keep overwriting each other after head is no longer null. So here my linked list looks something like: 2--9 instead of 2--3--1--8--3--9 I feel like I don't have a grasp on how to organize and handle the registers. newElem is in EBX and just keeps getting rewritten. Thanks in advance!

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• looping problem while appending data to existing text file

  - by Manu

  try { stmt = conn.createStatement(); stmt1 = conn.createStatement(); stmt2 = conn.createStatement(); rs = stmt.executeQuery("select cust from trip1"); rs1 = stmt1.executeQuery("select cust from trip2"); rs2 = stmt2.executeQuery("select cust from trip3"); File f = new File(strFileGenLoc); OutputStream os = (OutputStream)new FileOutputStream(f,true); String encoding = "UTF8"; OutputStreamWriter osw = new OutputStreamWriter(os, encoding); BufferedWriter bw = new BufferedWriter(osw); } while ( rs.next() ) { while(rs1.next()){ while(rs2.next()){ bw.write(rs.getString(1)==null? "":rs.getString(1)); bw.write("\t"); bw.write(rs1.getString(1)==null? "":rs1.getString(1)); bw.write("\t"); bw.write(rs2.getString(1)==null? "":rs2.getString(1)); bw.write("\t"); bw.newLine(); } } } Above code working fine. My problem is 1. "rs" resultset contains one record in the table 2. "rs1" resultset contains 5 record in the table 3. "rs2" resultset contains 5 record in the table "rs" data is getting recursive. while writing to the same text file , the output i am getting like 1 2 3 1 12 21 1 23 25 1 10 5 1 8 54 but i need output like below 1 2 3 12 21 23 25 10 5 8 54 What things i need to change in my code.. Please advice

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• Haskell Cons Operator (:)

  - by Carson Myers

  I am really new to Haskell (Actually I saw "Real World Haskell" from O'Reilly and thought "hmm, I think I'll learn functional programming" yesterday) and I am wondering: I can use the construct operator to add an item to the beginning of a list: 1 : [2,3] [1,2,3] I tried making an example data type I found in the book and then playing with it: --in a file data BillingInfo = CreditCard Int String String | CashOnDelivery | Invoice Int deriving (Show) --in ghci $ let order_list = [Invoice 2345] $ order_list [Invoice 2345] $ let order_list = CashOnDelivery : order_list $ order_list [CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, CashOnDelivery, ...- etc... it just repeats forever, is this because it uses lazy evaluation? -- EDIT -- okay, so it is being pounded into my head that let order_list = CashOnDelivery:order_list doesn't add CashOnDelivery to the original order_list and then set the result to order_list, but instead is recursive and creates an infinite list, forever adding CashOnDelivery to the beginning of itself. Of course now I remember that Haskell is a functional language and I can't change the value of the original order_list, so what should I do for a simple "tack this on to the end (or beginning, whatever) of this list?" Make a function which takes a list and BillingInfo as arguments, and then return a list? -- EDIT 2 -- well, based on all the answers I'm getting and the lack of being able to pass an object by reference and mutate variables (such as I'm used to)... I think that I have just asked this question prematurely and that I really need to delve further into the functional paradigm before I can expect to really understand the answers to my questions... I guess what i was looking for was how to write a function or something, taking a list and an item, and returning a list under the same name so the function could be called more than once, without changing the name every time (as if it was actually a program which would add actual orders to an order list, and the user wouldn't have to think of a new name for the list each time, but rather append an item to the same list).

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• PHP elseif statement not executed even though initial if statement is false

  - by DarwinIcesurfer

  I am writing a recursive function to print out the differences between 2 multildimensional php arrays. The purpose of this code is to see the difference between jpeg headers to deteremine how adobe bridge cs3 is saving rating information within the jpg file. When I am single-stepping through the code using my eclipse - zend debugger ide, it appears that even though the initial if statement is false (ie both values are arrays), the subsequent elseif statements are never executed. The function is attached below. function array_diff_multi($array1,$array2,$level){ $keys = array_keys($array1); foreach($keys as $key) { $value1 = $array1[$key]; if(array_key_exists($key,$array2) ){ $value2 = $array2[$key]; // Check if they are both arrays, if so recursion is needed if (is_array($value1) && is_array($value2)){ array_diff_multi($value1,$value2,$level . "[ " . $key . " ]"); } // the values aren't both arrays *** THE CODE IN THE ELSEIF BELOW IS NOT EXECUTED *** elseif(is_array($value1) != is_array($value2)){ print "" . $level . $key ."=" . $value1 . "as array, compared to ". $value2 .""; } // the values don't match elseif($value1 != $value2){ print "" . $level . $key ."=" . $value1 ." != " . $value2 .""; } else; } else{ print "" . $level. $key . "does not exist in array2"; } } }

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• caching previous return values of procedures in scheme

  - by Brock

  In Chapter 16 of "The Seasoned Schemer", the authors define a recursive procedure "depth", which returns 'pizza nested in n lists, e.g (depth 3) is (((pizza))). They then improve it as "depthM", which caches its return values using set! in the lists Ns and Rs, which together form a lookup-table, so you don't have to recurse all the way down if you reach a return value you've seen before. E.g. If I've already computed (depthM 8), when I later compute (depthM 9), I just lookup the return value of (depthM 8) and cons it onto null, instead of recursing all the way down to (depthM 0). But then they move the Ns and Rs inside the procedure, and initialize them to null with "let". Why doesn't this completely defeat the point of caching the return values? From a bit of experimentation, it appears that the Ns and Rs are being reinitialized on every call to "depthM". Am I misunderstanding their point? I guess my question is really this: Is there a way in Scheme to have lexically-scoped variables preserve their values in between calls to a procedure, like you can do in Perl 5.10 with "state" variables?

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• Aggregate path counts using HierarchyID

  - by austincav

  Business problem - understand process fallout using analytics data. Here is what we have done so far: Build a dictionary table with every possible process step Find each process "start" Find the last step for each start Join dictionary table to last step to find path to final step In the final report output we end up with a list of paths for each start to each final step: User Fallout Step HierarchyID.ToString() A 1/1/1 B 1/1/1/1/1 C 1/1/1/1 D 1/1/1 E 1/1 What this means is that five users (A-E) started the process. Assume only User B finished, the other four did not. Since this is a simple example (without branching) we want the output to look as follows: Step Unique Users 1 5 2 5 3 4 4 2 5 1 The easiest solution I could think of is to take each hierarchyID.ToString(), parse that out into a set of subpaths, JOIN back to the dictionary table, and output using GROUP BY. Given the volume of data, I'd like to use the built-in HierarchyID functions, e.g. IsAncestorOf. Any ideas or thoughts how I could write this? Maybe a recursive CTE?

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• How to get the size of a binary tree ?

  - by Andrei Ciobanu

  I have a very simple binary tree structure, something like: struct nmbintree_s { unsigned int size; int (*cmp)(const void *e1, const void *e2); void (*destructor)(void *data); nmbintree_node *root; }; struct nmbintree_node_s { void *data; struct nmbintree_node_s *right; struct nmbintree_node_s *left; }; Sometimes i need to extract a 'tree' from another and i need to get the size to the 'extracted tree' in order to update the size of the initial 'tree' . I was thinking on two approaches: 1) Using a recursive function, something like: unsigned int nmbintree_size(struct nmbintree_node* node) { if (node==NULL) { return(0); } return( nmbintree_size(node->left) + nmbintree_size(node->right) + 1 ); } 2) A preorder / inorder / postorder traversal done in an iterative way (using stack / queue) + counting the nodes. What approach do you think is more 'memory failure proof' / performant ? Any other suggestions / tips ? NOTE: I am probably going to use this implementation in the future for small projects of mine. So I don't want to unexpectedly fail :).

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• What does this structure actually do?

  - by LGTrader

  I found this structure code in a Julia Set example from a book on CUDA. I'm a newbie C programmer and cannot get my head around what it's doing, nor have I found the right thing to read on the web to clear it up. Here's the structure: struct cuComplex { float r; float i; cuComplex( float a, float b ) : r(a), i(b) {} float magnitude2( void ) { return r * r + i * i; } cuComplex operator*(const cuComplex& a) { return cuComplex(r*a.r - i*a.i, i*a.r + r*a.i); } cuComplex operator+(const cuComplex& a) { return cuComplex(r+a.r, i+a.i); } }; and it's called very simply like this: cuComplex c(-0.8, 0.156); cuComplex a(jx, jy); int i = 0; for (i=0; i<200; i++) { a = a * a + c; if (a.magnitude2() > 1000) return 0; } return 1; So, the code did what? Defined something of structure type 'cuComplex' giving the real and imaginary parts of a number. (-0.8 & 0.156) What is getting returned? (Or placed in the structure?) How do I work through the logic of the operator stuff in the struct to understand what is actually calculated and held there? I think that it's probably doing recursive calls back into the stucture float magnitude2 (void) { return return r * r + i * i; } probably calls the '*' operator for r and again for i, and then the results of those two operations call the '+' operator? Is this correct and what gets returned at each step? Just plain confused. Thanks!

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• How to accurately resize nested elements with ems and font-size percentage?

  - by moonDogDog

  I have a carousel with textboxes for each image, and my client (who knows nothing about HTML) edits the textboxes using a WYSIWYG text editor. The resulting output is akin to your worst nightmares; something like: <div class="carousel-text-container"> <span style="font-size:18pt;"> <span style="font-weight:bold;"> Lorem <span style="font-size:15pt:">Dolor</span> </span> Ipsum <span style="font-size:19pt;"><span>&nbsp;<span>Sit</span>Amet</span> </span> </div> This site has to be displayed at 3 different sizes to accomodate smaller monitors, so I have been using CSS media queries to resize the site. Now I am having trouble resizing the text inside the textbox correctly. I have tried using jQuery.css to get the font size of each element in px, and then convert it to em. Then, by setting a font-size:x% sort of declaration on .carousel-text-container, I hoped that that would resize everything properly. Unfortunately, there seems to be a recursive nature with how font-size is applied in ems. That is, .example is not resized properly in the following because its parent is also influencing it <span style="font-size:2em;"> Something <span class="example" style="font-size:1.5em;">Else</span> </span> How can I resize everything reliably and precisely such I can achieve a true percentage of my original font size, margin, padding, line-height, etc. for all the children of .carousel-text-container?

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• Add leading zeros to this javascript countdown script?

  - by eddjedi

  I am using the following countdown script which works great, but I can't figure out how to add leading zeros to the numbers (eg so it displays 09 instead of 9.) Can anybody help me out please? Here's the current script: function countDown(id, end, cur){ this.container = document.getElementById(id); this.endDate = new Date(end); this.curDate = new Date(cur); var context = this; var formatResults = function(day, hour, minute, second){ var displayString = [ '<div class="stat statBig">',day,'</div>', '<div class="stat statBig">',hour,'</div>', '<div class="stat statBig">',minute,'</div>', '<div class="stat statBig">',second,'</div>' ]; return displayString.join(""); } var update = function(){ context.curDate.setSeconds(context.curDate.getSeconds()+1); var timediff = (context.endDate-context.curDate)/1000; // Check if timer expired: if (timediff<0){ return context.container.innerHTML = formatResults(0,0,0,0); } var oneMinute=60; //minute unit in seconds var oneHour=60*60; //hour unit in seconds var oneDay=60*60*24; //day unit in seconds var dayfield=Math.floor(timediff/oneDay); var hourfield=Math.floor((timediff-dayfield*oneDay)/oneHour); var minutefield=Math.floor((timediff-dayfield*oneDay-hourfield*oneHour)/oneMinute); var secondfield=Math.floor((timediff-dayfield*oneDay-hourfield*oneHour-minutefield*oneMinute)); context.container.innerHTML = formatResults(dayfield, hourfield, minutefield, secondfield); // Call recursively setTimeout(update, 1000); }; // Call the recursive loop update(); }

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• Creating a three level ASP.NET menu with SiteMap, how do i do it?

  - by user270399

  I want to create a three level menu, I have got a recursive function today that works with three levels. But the thing is how do i output the third lever? Using two repeaters i have managed to get a hold of the first two levels through the ChildNodes property. But that only gives me the second level. What if a want the third level? Example code below. How do i get the third level? :) <asp:Repeater ID="FirstLevel" DataSourceID="SiteMapDataSource" runat="server" EnableViewState="false"> <ItemTemplate> <li class="top"> <a href='/About/<%#Eval("Title")%>.aspx' class="top_link"><span class="down"><%#Eval("Title")%></span><!--[if gte IE 7]><!--></a><!--<![endif]--> <asp:Repeater runat="server" ID="SecondLevel" DataSource='<%#((SiteMapNode)Container.DataItem).ChildNodes%>'> <HeaderTemplate><!--[if lte IE 6]><table><tr><td><![endif]--><ul class="sub"></HeaderTemplate> <ItemTemplate> <li> <a href='<%#((string)Eval("Url")).Replace("~", "")%>' style="text-align: left;"><%#Eval("Title")%></a> Third repeater here? </li> </ItemTemplate> <FooterTemplate></ul><!--[if lte IE 6]></td></tr></table></a><![endif]--></FooterTemplate> </asp:Repeater> </li> </ItemTemplate> </asp:Repeater>

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• How to transform a production to LL(1) grammar for a list separated by a semicolon?

  - by Subb

  Hi, I'm reading this introductory book on parsing (which is pretty good btw) and one of the exercice is to "build a parser for your favorite language." Since I don't want to die today, I thought I could do a parser for something relatively simple, ie a simplified CSS. Note: This book teach you how to right a LL(1) parser using the recursive-descent algorithm. So, as a sub-exercice, I am building the grammar from what I know of CSS. But I'm stuck on a production that I can't transform in LL(1) : //EBNF block = "{", declaration, {";", declaration}, [";"], "}" //BNF <block> =:: "{" <declaration> "}" <declaration> =:: <single-declaration> <opt-end> | <single-declaration> ";" <declaration> <opt-end> =:: "" | ";" This describe a CSS block. Valid block can have the form : { property : value } { property : value; } { property : value; property : value } { property : value; property : value; } ... The problem is with the optional ";" at the end, because it overlap with the starting character of {";", declaration}, so when my parser meet a semicolon in this context, it doesn't know what to do. The book talk about this problem, but in its example, the semicolon is obligatory, so the rule can be modified like this : block = "{", declaration, ";", {declaration, ";"}, "}" So, Is it possible to achieve what I'm trying to do using a LL(1) parser?

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• C++. How to define template parameter of type T for class A when class T needs a type A template parameter?

  - by jaybny

  Executor class has template of type P and it takes a P object in constructor. Algo class has a template E and also has a static variable of type E. Processor class has template T and a collection of Ts. Question how can I define Executor< Processor<Algo> > and Algo<Executor> ? Is this possible? I see no way to defining this, its kind of an "infinite recursive template argument" See code. template <class T> class Processor { map<string,T> ts; void Process(string str, int i) { ts[str].Do(i); } } template <class P> class Executor { Proc &p; Executor(P &p) : Proc(p) {} void Foo(string str, int i) { p.Process(str,i); } Execute(string str) { } } template <class E> class Algo { static E e; void Do(int i) {} void Foo() { e.Execute("xxx"); } } main () { typedef Processor<Algo> PALGO; // invalid typedef Executor<PALGO> EPALGO; typedef Algo<EPALGO> AEPALGO; Executor<PALGO> executor(PALGO()); AEPALGO::E = executor; }

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• Scheme: Mysterious void in pattern match.

  - by Schemer

  Hi. I am writing a function called annotate that uses match-lambda -- often with recursive calls to annotate. Here is one of the pattern matches: (`(lambda (,<param1> . ,<params>) ,<stmts>) `(CLOSURE ENV (,<param1> . ,<params>) (lambda (ENV) ,(map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))))) However, when this pattern is matched this is what returns: '(CLOSURE ENV (x) (lambda (ENV) ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y)))))) #<void>) Specifically I can't figure out where "void" is coming from. In fact, if I include the line: ,(displayln (map annotate (map (lambda (x) (append `(,<param1> . ,<params>) (list x))) `(,<stmts>)))) it prints: ((CLOSURE ENV (x y) (lambda (ENV) ((+ x y))))) notably without "void". If someone could tell me what the problem is it would be greatly appreciated. Thanks.

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• Best Functional Approach

  - by dbyrne

  I have some mutable scala code that I am trying to rewrite in a more functional style. It is a fairly intricate piece of code, so I am trying to refactor it in pieces. My first thought was this: def iterate(count:Int,d:MyComplexType) = { //Generate next value n //Process n causing some side effects return iterate(count - 1, n) } This didn't seem functional at all to me, since I still have side effects mixed throughout my code. My second thought was this: def generateStream(d:MyComplexType):Stream[MyComplexType] = { //Generate next value n return Stream.cons(n, generateStream(n)) } for (n <- generateStream(initialValue).take(2000000)) { //process n causing some side effects } This seemed like a better solution to me, because at least I've isolated my functional value-generation code from the mutable value-processing code. However, this is much less memory efficient because I am generating a large list that I don't really need to store. This leaves me with 3 choices: Write a tail-recursive function, bite the bullet and refactor the value-processing code Use a lazy list. This is not a memory sensitive app (although it is performance sensitive) Come up with a new approach. I guess what I really want is a lazily evaluated sequence where I can discard the values after I've processed them. Any suggestions?

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• Best implementation of Java Queue?

  - by Georges Oates Larsen

  I am working (In java) on a recursive image processing algorithm that recursively traverses the pixels of the image, outward from a center point. Unfortunately... That causes stack overflows, so I have decided to switch to a Queue-based algorithm. Now, this is all fine and dandy -- But considering the fact that its queue will be analyzing THOUSANDS of pixels in a very short amount of time, while constantly popping and pushing, WITHOUT maintaining a predictable state (It could be anywhere between length 100, and 20000); The queue implementation needs to have significantly fast popping and pushing abilities. A linked list seems attractive due to its ability to push elements unto its self without rearranging anything else in the list, but in order for it to be fast enough, it would need easy access to both its head, AND its tail (or second-to-last node if it were not doubly-linked). Sadly, though I cannot find any information related to the underlying implementation of linked lists in Java, so it's hard to say if a linked list is really the way to go... This brings me to my question... What would be the best implementation of the Queue interface in Java for what I intend to do? (I do not wish to edit or even access anything other than the head and tail of the queue -- I do not wish to do any sort of rearranging, or anything. On the flip side, I DO intend to do a lot of pushing and popping, and the queue will be changing size quite a bit, so preallocating would be inefficient)

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• Communication between lexer and parser

  - by FredOverflow

  Every time I write a simple lexer and parser, I stumble upon the same question: how should the lexer and the parser communicate? I see four different approaches: The lexer eagerly converts the entire input string into a vector of tokens. Once this is done, the vector is fed to the parser which converts it into a tree. This is by far the simplest solution to implement, but since all tokens are stored in memory, it wastes a lot of space. Each time the lexer finds a token, it invokes a function on the parser, passing the current token. In my experience, this only works if the parser can naturally be implemented as a state machine like LALR parsers. By contrast, I don't think it would work at all for recursive descent parsers. Each time the parser needs a token, it asks the lexer for the next one. This is very easy to implement in C# due to the yield keyword, but quite hard in C++ which doesn't have it. The lexer and parser communicate through an asynchronous queue. This is commonly known under the title "producer/consumer", and it should simplify the communication between the lexer and the parser a lot. Does it also outperform the other solutions on multicores? Or is lexing too trivial? Is my analysis sound? Are there other approaches I haven't thought of? What is used in real-world compilers? It would be really cool if compiler writers like Eric Lippert could shed some light on this issue.

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• How to write a simple Lexer/Parser with antlr 2.7?

  - by Burkhard

  Hello, I have a complex grammar (in antlr 2.7) which I need to extend. Having never used antlr before, I wanted to write a very simple Lexer and Parser first. I found a very good explanation for antlr3 and tried to adapt it: header{ #include <iostream> using namespace std; } options { language="Cpp"; } class P2 extends Parser; /* This will be the entry point of our parser. */ eval : additionExp ; /* Addition and subtraction have the lowest precedence. */ additionExp : multiplyExp ( "+" multiplyExp | "-" multiplyExp )* ; /* Multiplication and addition have a higher precedence. */ multiplyExp : atomExp ( "*" atomExp | "/" atomExp )* ; /* An expression atom is the smallest part of an expression: a number. Or when we encounter parenthesis, we're making a recursive call back to the rule 'additionExp'. As you can see, an 'atomExp' has the highest precedence. */ atomExp : Number | "(" additionExp ")" ; /* A number: can be an integer value, or a decimal value */ number : ("0".."9")+ ("." ("0".."9")+)? ; /* We're going to ignore all white space characters */ protected ws : (" " | "\t" | "\r" | "\n") { newline(); } ; It does generate four files without errors: P2.cpp, P2.hpp, P2TokenTypes.hpp and P2TokenTypes.txt. But now what? How do I create a working programm with that? I tried to add these files to a VS2005-WinConsole-Project but it does not compile: p2.cpp(277) : fatal error C1010: unexpected end of file while looking for precompiled header. Did you forget to add '#include "stdafx.h"' to your source?

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• TortoiseSVN Error: "OPTIONS of 'https://...' could not connect to server (...)"

  - by Zack Peterson

  I'm trying to setup a new computer to synchronize with my SVN repository that's hosted with cvsdude.com. I get this error: Here's what I did (these have worked in the past): Downloaded and installed TortoiseSVN Created a new folder C:\aspwebsite Right-clicked, chose SVN Checkout... Entered the following information, clicked OK: URL of repository: https://<reponame>-svn.cvsdude.com/aspwebsite Checkout directory: C:\aspwebsite Checkout depth: Fully recursive Omit externals: Unchecked Revision: HEAD revision Got TortoiseSVN error: OPTIONS of 'https://<reponame>-svn.cvsdude.com/aspwebsite': could not connect to server (https://<reponame>-svn.cvsdude.com) Rather than getting the error, TortoiseSVN should have asked for my username and password and then downloaded about 90MB. Why can't I checkout from my Subversion repository? Kent Fredric wrote: Either their security certificate has expired, or their hosting is broken/down. Contact CVSDude and ask them whats up. It could also be a timeout, because for me their site is exhaustively slow.. It errors after only a couple seconds. I don't think it's a timeout. Matt wrote: Try visiting https://[redacted]-svn.cvsdude.com/aspwebsite and see what happens. If you can visit it in your browser, you ought to be able to get the files in your SVN client and we can work from there. If it fails, then there's your answer. I can access the site in a web browser.

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• How to handle build rule with unknown targets in OMake when target list generator is built

  - by Michael E

  I have a project which uses OMake for its build system, and I am trying to handle a rather tough corner case. I have some definition files and a tool which can take these definition files and create GraphViz files. There are two problems, though: Each definition file can produce multiple graphs, and the list of graphs it can produce is encoded in the file. My dump tool does have a -list option which lists all the graphs a definition file will produce. This dump tool is built in the source tree. I want this list available in the OMakefile so I can use other rules to convert the DOT files to SVG, and have a phony target depend on all the SVGs (goal: a single build command which builds SVG descriptions of all my graphs). If I only had the first problem, it would be easy - I would run the tool to build a list, and then use that list to build a target which invokes the dumper to output the GraphViz files. However, I am rather stuck on forcing the dump tool to be built before it is needed. If this were make, I would just run make recursively to build the dump tool. OMake does not allow recursive invocation, however, and the build function is only usable from osh. Any suggestions for a good solution to this problem?

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• Implement a threading to prevent UI block on a bug in an async function

  - by Marcx

  I think I ran up againt a bug in an async function... Precisely the getDirectoryListingAsync() of the File class... This method is supposted to return an object containing the lists of files in a specified folder. I found that calling this method on a direcory with a lot of files (in my tests more than 20k files), after few seconds there is a block on the UI until the process is completed... I think that this method is separated in two main block: 1) get the list of files 2) create the array with the details of the files The point 1 seems to be async (for a few second the ui is responsive), then when the process pass from point 1 to point 2 the block of the UI occurs until the complete event is dispathed... Here's some (simple) code: private function checkFiles(dir:File):void { if (dir.exists) { dir.addEventListener( FileListEvent.DIRECTORY_LISTING, listaImmaginiLocale); dir.getDirectoryListingAsync(); // after this point, for the firsts seconds the UI respond well (point 1), // few seconds later (point 2) the UI is frozen } } private function listaImmaginiLocale( event:FileListEvent ):void { // from this point on the UI is responsive again... } Actually in my projects there are some function that perform an heavy cpu usage and to prevent the UI block I implemented a simple function that after some iteration will wait giving time to UI to be refreshed. private var maxIteration:int = 150000; private function sampleFunct(offset:int = 0) :void { if (offset < maxIteration) { // do something // call the recursive function using a timeout.. // if the offset in multiple by 1000 the function will wait 15 millisec, // otherwise it will be called immediately // 1000 is a random number for the pourpose of this example, but I usually change the // value based on how much heavy is the function itself... setTimeout(function():void{aaa(++offset);}, (offset%1000?15:0)); } } Using this method I got a good responsive UI without afflicting performance... I'd like to implement it into the getDirectoryListingAsync method but I don't know if it's possibile how can I do it where is the file to edit or extend.. Any suggestion???

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• Subversion update misses new directories

  - by Mike Q

  Hi all, Periodically we have trouble with SVN when doing updates. Very occasionally when someone adds a new directory doing an update through Tortoise doesn't work. If we do a "Fully Recursive" update using "Update from revision..." option then it picks it up fine. I'm poked around and seen this question which is virtually identical but with no answer. I've found the item on the SVN website, referenced by that post, that talks about an issue in 1.6.0 which is now fixed. However my SVN version is 1.6.9 and Tortoise is 1.6.7 so I wouldn't expect to have this problem any more. This only seems to occur with new directories, never seen it for individual files. We may have had older versions of Tortoise at one point (can't remember which tho) so maybe some issue has been introduced into our repo that an upgrade doesn't solve. We have the workaround but it wastes a few minutes of head-scratching after failed builds to figure it out and people who haven't come across this problem before really struggle until they ask someone else. Anyone know if this is a known bug and any permanent solutions? Thanks.

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• breadth-first traversal of directory tree is not lazy

  - by user855443

  I try to traverse the diretory tree. A naive depth-first traversal seems not to produce the data in a lazy fashion and runs out of memory. I next tried a breadth first approach, which shows the same problem - it uses all the memory available and then crashes. the code i have is: getFilePathBreadtFirst :: FilePath -> IO [FilePath] getFilePathBreadtFirst fp = do fileinfo <- getInfo fp res :: [FilePath] <- if isReadableDirectory fileinfo then do children <- getChildren fp lower <- mapM getFilePathBreadtFirst children return (children ++ concat lower) return (children ++ concat () else return [fp] -- should only return the files? return res getChildren :: FilePath -> IO [FilePath] getChildren path = do names <- getUsefulContents path let namesfull = map (path </>) names return namesfull testBF fn = do -- crashes for /home/frank, does not go to swap fps <- getFilePathBreadtFirst fn putStrLn $ unlines fps I think all the code is either linear or tail recursive, and I would expect that the listing of filenames starts immediately, but in fact it does not. Where is the error in my code and my thinking? where have I lost lazy evaluation?

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• Pascals Triangle by recursion

  - by Olpers

  Note : My Class Teacher gave me this question as an assignment... I am not asked to do it but please tell me how to do it with recursion Binomial coefficients can be calculated using Pascal's triangle: 1 n = 0 1 1 1 2 1 1 3 3 1 1 4 6 4 1 n = 4 Each new level of the triangle has 1's on the ends; the interior numbers are the sums of the two numbers above them. Task: Write a program that includes a recursive function to produce a list of binomial coefficients for the power n using the Pascal's triangle technique. For example, Input = 2 Output = 1 2 1 Input = 4 Output = 1 4 6 4 1 done this So Far but tell me how to do this with recursion... #include<stdio.h> int main() { int length,i,j,k; //Accepting length from user printf("Enter the length of pascal's triangle : "); scanf("%d",&length); //Printing the pascal's triangle for(i=1;i<=length;i++) { for(j=1;j<=length-i;j++) printf(" "); for(k=1;k<i;k++) printf("%d",k); for(k=i;k>=1;k--) printf("%d",k); printf("\n"); } return 0; }

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• Tree iterator, can you optimize this any further?

  - by Ron

  As a follow up to my original question about a small piece of this code I decided to ask a follow up to see if you can do better then what we came up with so far. The code below iterates over a binary tree (left/right = child/next ). I do believe there is room for one less conditional in here (the down boolean). The fastest answer wins! The cnt statement can be multiple statements so lets make sure this appears only once The child() and next() member functions are about 30x as slow as the hasChild() and hasNext() operations. Keep it iterative <-- dropped this requirement as the recursive solution presented was faster. This is C++ code visit order of the nodes must stay as they are in the example below. ( hit parents first then the children then the 'next' nodes). BaseNodePtr is a boost::shared_ptr as thus assignments are slow, avoid any temporary BaseNodePtr variables. Currently this code takes 5897ms to visit 62200000 nodes in a test tree, calling this function 200,000 times. void processTree (BaseNodePtr current, unsigned int & cnt ) { bool down = true; while ( true ) { if ( down ) { while (true) { cnt++; // this can/will be multiple statesments if (!current->hasChild()) break; current = current->child(); } } if ( current->hasNext() ) { down = true; current = current->next(); } else { down = false; current = current->parent(); if (!current) return; // done. } } }

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