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  • dynamic programming: speeding up this function

    - by aristotaly
    i have this program //h is our N static int g=0; int fun(int h){ if(h<=0){ g++; return g; } return g+fun(h-1)+fun(h-4); } is it possible to speed it up using dynamic programming i fugured out this function runs in O(2^n) it means that i suppose to reduce this time but the trouble is that i don get the idea of dinamic programming even a leading hint or a useful link to a resource will do it is a work assingment i do not ask for the solution :) just asking for the right direction

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  • StringBuilder/StringBuffer vs. "+" Operator

    - by matt.seil
    I'm reading "Better, Faster, Lighter Java" (by Bruce Tate and Justin Gehtland) and am familiar with the readability requirements in agile type teams, such as what Robert Martin discusses in his clean coding books. On the team I'm on now, I've been told explicitly not to use the "+" operator because it creates extra (and unnecessary) string objects during runtime. But this article: http://www.ibm.com/developerworks/java/library/j-jtp01274.html Written back in '04 talks about how object allocation is about 10 machine instructions. (essentially free) It also talks about how the GC also helps to reduce costs in this environment. What is the actual performance tradeoffs between using "+," "StringBuilder," or "StringBuffer?" (In my case it is StringBuffer only as we are limited to Java 1.4.2.) StringBuffer to me results in ugly, less readable code, as a couple of examples in Tate's book demonstrates. And StringBuffer is thread-synchronized which seems to have its own costs that outweigh the "danger" in using the "+" operator. Thoughts/Opinions?

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  • Resizing Tab Bar Controller Views (iPhone dev)

    - by damiandawber
    Hello, I have an application set up where the window contains a tab bar controller and one of the tabs loads a NIB called 'ShowCaseView.xib': this file is owned by a custom ShowcaseViewController class. In the ShowcaseViewcontroller class I have added a UIScrollView object, like so: imageScrollView = [[UIScrollView alloc] initWithFrame:[[self view] bounds]]; [[self view] addSubview:imageScrollView]; The issue I am having is that this UIScrollView object extends beneath my tab bar controller. So I have had to reduce its insets manually: #define TAB_BAR_HEIGHT 48 . . UIEdgeInsets edgeInsets = UIEdgeInsetsMake(0, 0, TAB_BAR_HEIGHT, 0); [imageScrollView setScrollIndicatorInsets:edgeInsets]; So, Is it common to have to manually deduct the tab bar height from a view (whether this be by reducing the size of subviews or the View NIB in inspector)? Is there a way that I can tell a NIB's view loaded from a tab bar to resize itself automatically to NOT sit behind the tab bar? Cheers

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  • .NET Deployment of Interface/Classes for Command Pattern Question

    - by Jonno
    In theory I would like to produce 2 projects: 1) Asp.net (Sever A) 2) DAL running (Server B) I would like to utilise command objects to comunicate with the DAL. ASP.net instantiates a command class e.g. CmdGetAllUsers which impliments IMyCommand interface and sends it to the DAL (using ASMX or WCF). My question is: Would the class definition of CmdGetAllUsers need to exist on the DAL server? Or would having the interface definition be enough? My goal is to reduce the need to redeploy the DAL code, and have it as a fairly simple pass-through layer. Many thanks for your time.

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  • DNS resolution problems; dig SERVFAIL error

    - by JustinP
    I'm setting up a couple of dedicated servers, and having problems setting up my nameservers properly. One of these is a LEMP server (LAMP with nginx in place of Apache), and the other will function solely as an email server, running exim/dovecot/ASSP antispam (no Apache). The LEMP server is CentOS 5.5, with no control panel, while the email server is CentOS 5.5 as well, with cPanel/WHM. So, I've had problems getting DNS set up properly. I have two domains, each one pointing to one of these servers. The nameservers are registered correctly with the domain registrar, and the nameserver IPs are entered correctly as well. I've spoken to tech support at the registrar and they confirm that everything is set up on their end. Not knowing much about DNS, I googled nameservers and DNS until I nearly went blind, and spent hours messing with the configuration. Eventually, I got the LEMP server's DNS working properly (no cPanel). Pleased with this triumph, I'm trying to mimic that configuration and repeat the process with the email server, and it's just not happening. The nameserver starts and stops, but the domain doesn't resolve. Things I have tried Going through standard procedures to set up DNS in WHM Clearing all DNS information, uninstalling BIND, then reinstalling all of that and again going through WHM procedures for setting up DNS Clearing all DNS information, and setting up BIND via shell (completely outside of cPanel) by using my config and zone files from the LEMP server as a template named runs just fine, but nothing is resolving. When I "dig any example.com" I get a SERVFAIL message. Nslookups return no information. Here are my config and zone files. named.conf controls { inet 127.0.0.1 allow { localhost; } keys { coretext-key; }; }; options { listen-on port 53 { any; }; listen-on-v6 port 53 { ::1; }; directory "/var/named"; dump-file "/var/named/data/cache_dump.db"; statistics-file "/var/named/data/named_stats.txt"; memstatistics-file "/var/named/data/named_mem_stats.txt"; // Those options should be used carefully because they disable port // randomization // query-source port 53; // query-source-v6 port 53; allow-query { any; }; allow-query-cache { any; }; }; logging { channel default_debug { file "data/named.run"; severity dynamic; }; }; view "localhost_resolver" { match-clients { 127.0.0.0/24; }; match-destinations { localhost; }; recursion yes; //zone "." IN { // type hint; // file "/var/named/named.ca"; //}; include "/etc/named.rfc1912.zones"; }; view "internal" { /* This view will contain zones you want to serve only to "internal" clients that connect via your directly attached LAN interfaces - "localnets" . */ match-clients { localnets; }; match-destinations { localnets; }; recursion yes; zone "." IN { type hint; file "/var/named/named.ca"; }; // include "/var/named/named.rfc1912.zones"; // you should not serve your rfc1912 names to non-localhost clients. // These are your "authoritative" internal zones, and would probably // also be included in the "localhost_resolver" view above : zone "example.com" { type master; file "data/db.example.com"; }; zone "3.2.1.in-addr.arpa" { type master; file "data/db.1.2.3"; }; }; view "external" { /* This view will contain zones you want to serve only to "external" clients * that have addresses that are not on your directly attached LAN interface subnets: */ match-clients { any; }; match-destinations { any; }; recursion no; // you'd probably want to deny recursion to external clients, so you don't // end up providing free DNS service to all takers allow-query-cache { none; }; // Disable lookups for any cached data and root hints // all views must contain the root hints zone: //include "/etc/named.rfc1912.zones"; zone "." IN { type hint; file "/var/named/named.ca"; }; zone "example.com" { type master; file "data/db.example.com"; }; zone "3.2.1.in-addr.arpa" { type master; file "data/db.1.2.3"; }; }; include "/etc/rndc.key"; db.example.com $TTL 1D ; ; Zone file for example.com ; ; Mandatory minimum for a working domain ; @ IN SOA ns1.example.com. contact.example.com. ( 2011042905 ; serial 8H ; refresh 2H ; retry 4W ; expire 1D ; default_ttl ) NS ns1.example.com. NS ns2.example.com. ns1 A 1.2.3.4 ns2 A 1.2.3.5 example.com. A 1.2.3.4 localhost A 127.0.0.1 www CNAME example.com. mail CNAME example.com. ; db.1.2.3 $TTL 1D $ORIGIN 3.2.1.in-addr.arpa. @ IN SOA ns1.example.com contact.example.com. ( 2011042908 ; 8H ; 2H ; 4W ; 1D ; ) NS ns1.example.com. NS ns2.example.com. 4 PTR hostname.example.com. 5 PTR hostname.example.com. ; Also of note: both of these servers are managed. Tech support is very responsive, and largely useless. Hours go by with them asking me questions to narrow down what could be wrong, then they pass the ticket to the tech on the next shift, who ignores everything that's happened already and spend his whole shift asking all the same questions the last guy asked. So, in summary: *Nameservers, with IPs, are correctly registered with domain registrar *named is configured and running *...and must not be configured correctly, because nothing resolves. Any help would be great. I changed domains and IPs in the files to generics, but let me know if you need to know the domain in question. Thanks! UPDATE I found that I didn't have 127.0.0.1 in /etc/resolv.conf, so I added it, along with my two public IPs that I have named listening on. resolv.conf search www.example.com example.com nameserver 127.0.0.1 nameserver 7.8.9.10 ;Was in here by default, authoritative nameserver of hosting company nameserver 1.2.3.4 ;Public IP #1 nameserver 1.2.3.5 ;Public IP #2 Now when I DIG example.com from the host, it resolves. If I try to DIG from my other server (in the same datacenter), or from the internet, it times out or I get SERVFAIL.

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  • PHP APC - Why is loading cached array op codes slow?

    - by Aaron Kreider
    I'm using APC to reduce my loading time for my PHP files. My files load very fast, except for one file where I define more than 100 arrays. This 270 kb file takes 200 ms to load. The rest of the files are full of objects, methods, and functions. I'm wondering: does OP code caching not work as well for arrays? My APC cache should be big enough to handle all of my classes. Currently 40% of my cache is free. My hit rate is 99%. apc.shm_size=32 M apc.max_file_size = 1M apc.shm_segments= 1 APC 3.1.6 I'm using PHP 5.2, Apache 2, and Windows Vista.

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  • AES acceleration for Java

    - by chris_l
    I want to encrypt/decrypt lots of small (2-10kB) pieces of data. The performance is ok for now: On a Core2Duo, I get about 90 MBytes/s AES256 (when using 2 threads). But I may need to improve that in the future - or at least reduce the impact on the CPU. Is it possible to use dedicated AES encryption hardware with Java (using JCE, or maybe a different API)? Would Java take advantage of special CPU features (SSE5?!), if I get a better CPU? Or are there faster JCE providers? (I tried SunJCE and BouncyCastle - no big difference.) Other possiblilities?

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  • How does one modify the thread scheduling behavior when using Threading Building Blocks (TBB)?

    - by J Teller
    Does anyone know how to modify the thread scheduling (specifically affinity) when using TBB? Doing a high level analysis on a simple parallel-for application, it seems like TBB is specifying the underlying threads' affinity in a way that reduces performance. Specifically, the cores I'm running on have hyper-threading enabled, and it looks like TBB is affinitizing threads to the same core even if there is a different core left completely unloaded. FWIW, I realize it's likely that TBB is doing the "right thing" and that changing the threads' affinity will only reduce performance. I'd just like to experiment with it to see if that's really the case.

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  • String.fromCharCode & CharacterSets

    - by jAndy
    Hi Folks, I recently tried to mirror some input within input(text) fields. Using String.fromCharCode(event.which) for instance, translates all 'standard' characters correctly. Well it translates them all to uppercase, but that you can easily catch by looking up the shift key aswell. My Problem is, it can't translate characters like dots, commas, questionmarks etc. First guess was that I have to define a character encoding set, but that does not seem to help. Maybe it'm completly off? Kind Regards --Andy

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  • Google App Engine Database Index

    - by fjsj
    I need to store a undirected graph in a Google App Engine database. For optimization purposes, I am thinking to use database indexes. Using Google App Engine, is there any way to define the columns of a database table to create its index? I will need some optimization, since my app uses this stored undirected graph on a content-based filtering for item recommendation. Also, the recommender algorithm updates the weights of some graph's edges. If it is not possible to use database indexes, please suggest another method to reduce query time for the graph table. I believe my algorithm does more data retrieval operations from graph table than write operations. PS: I am using Python.

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  • Optimizing a fluid grid layout

    - by user1815176
    I recently just added a grid layout, but I can't figure out how to make my links work. The grid that I used is the 1140 one at http://cssgrid.net/. I studied the source code of that website, and tried to make my page like theirs, but when I put everything in it made mine worse, and the grid didn't even work. This is how my website is supposed to look http://spencedesign.netau.net/singaporehome.html and this is how it does http://spencedesign.netau.net/home.html And when you reduce the size, it doesn't look like it's supposed to. When you minimize it I want the pictures(links) to be two per row, then one per row depending on how small the page is. I also want the quote to turn into different rows when it is too small for it. But I can't figure out how to make the page look normal regularly let alone make it look good with a smaller browser. Thanks!

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  • LearnBoost's Socket.IO-Node why onClientMessage not work

    - by KingPin
    Hi, all, I tried to put the module "LearnBoost's Socket.IO-Node", all works, except event 'onClientMessage' Tell, in what there can be a problem, thanks! ...sorry for my english io.listen(server, { onClientConnect: function(client){ client.send(json({ buffer: buffer })); client.broadcast(json({ announcement: client.sessionId + ' connected' })); }, onClientDisconnect: function(client){ client.broadcast(json({ announcement: client.sessionId + ' disconnected' })); }, onClientMessage: function(message, client){ var msg = { mess: [client.sessionId, message] }; buffer.push(msg); if (buffer.length > 15) { buffer.shift(); } client.broadcast(json(msg)); }

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  • Before the lablel for each of the menu item, there is space with the some color, i want to remove th

    - by anandhinaveen
    Hello, I am using richfaces dropDownMenu component which contains a set of rich menuItems. When the menu items are displayed, a extra space is displayed before the lablel for each of the menu item. But I have a requirement of not displaying the space before the labels and to change the color. I used the css to reduce the space: .rich-menu-item-icon img { width: 0px; } .rich-menu-group-icon img { width: 0px; } but, i need to change the color in that place.

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  • foreign key constraints on primary key columns - issues ?

    - by zzzeek
    What are the pros/cons from a performance/indexing/data management perspective of creating a one-to-one relationship between tables using the primary key on the child as foreign key, versus a pure surrogate primary key on the child? The first approach seems to reduce redundancy and nicely constrains the one-to-one implicitly, while the second approach seems to be favored by DBAs, even though it creates a second index: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key references parent(id), data varchar(50) ) pure surrogate key: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key, parent_id integer unique references parent(id), data varchar(50) ) the platforms of interest here are Postgresql, Microsoft SQL Server.

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  • How to create Web services and link it to Smart device Application?

    - by Crimsonland
    I am a fresh graduate and hired to develop Smart Device Application.They use Data logic Memoir with windows CE 5.0. Even though i have novice skills in programming in vb.net,I just finish my project and applications for Data logic memoir wherein the data has been save to text file or SQL compact server database in the Handheld Device and use Active Sync Connection to pass Data into H/PC to Desktop P.C and Vice Versa.I just shift now to C#.net and start learning it and i just successfully transpose my Smart Device Project from VB to C#. But now i want to Start Projects linking The device to server using Web services but i don't have any idea how to begin?

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  • Uploadify and Image Compression

    - by Ilya Biryukov
    Hi, I am using Uploadify on one of my client's web sites to allow them to upload a large amount of pictures at once to their photo gallery. I am seeing issues lately. They seem to upload large photographs (3 MB and above). I am wondering, is it possible to compress (reduce their size) on the client side, instead of doing it on the server (just like facebook does it). I know I could easily do it on the server, but I am working on another project right now, where I am expecting a large flow of photo uploads. It would require significant amount of CPU time to process them all. So I thought, I'd ask about the client side processing. Thanks.

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  • Script Speed vs Memory Usage

    - by Doug Neiner
    I am working on an image generation script in PHP and have gotten it working two ways. One way is slow but uses a limited amount of memory, the second is much faster, but uses 6x the memory . There is no leakage in either script (as far as I can tell). In a limited benchmark, here is how they performed: -------------------------------------------- METHOD | TOTAL TIME | PEAK MEMORY | IMAGES -------------------------------------------- One | 65.626 | 540,036 | 200 Two | 20.207 | 3,269,600 | 200 -------------------------------------------- And here is the average of the previous numbers (if you don't want to do your own math): -------------------------------------------- METHOD | TOTAL TIME | PEAK MEMORY | IMAGES -------------------------------------------- One | 0.328 | 540,036 | 1 Two | 0.101 | 3,269,600 | 1 -------------------------------------------- Which method should I use and why? I anticipate this being used by a high volume of users, with each user making 10-20 requests to this script during a normal visit. I am leaning toward the faster method because though it uses more memory, it is for a 1/3 of the time and would reduce the number of concurrent requests.

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  • Java M4A atom tagging free space issue

    - by Brett
    Hey, I've been trying to be able to read and write iTunes style M4A atoms and while I've successfully done the reading part, I've come to a bit of a halt in regards to the free space atoms. I figured that I should be able edit and shift the padding around to accommodate writing an atom with more data than it originally had. I've been stuck on this for about a day now, and I've been trying to figure out how to determine the closest free space atom with enough size to accommodate the new data. so far I have: private freeAtom acquireFreeSpaceAtom( long position ) { long atomStart = Long.MAX_VALUE; freeAtom atom = null; for( freeAtom a : freeSpace ) { if( Math.abs( position - atomStart ) > Math.abs( position - a.getAtomStart() ) ) atomStart = ( atom = a ).getAtomStart(); } return atom; } That code only takes into account the closest free space atom and completely disregards the fact that it should be greater than or equal to a certain size, but I can't quite figure out how I should check for both closeness and size efficiently.

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  • Combine and compress script files in asp.net mvc

    - by victor_foster
    I am working in Visual Studio 2008, IIS7 and using asp.net MVC. I would like to know the best way to combine all of my Javascript files into one file to reduce the number of HTTP requests to the server. I have seen many articles on this subject but I'm not sure which one I should look at first (many of them are over a year old). Here are the things I would like to do: Combine my Javascript and css files Safely compress my Javascript files when I publish, but keep them uncompressed while I am debugging Cache my Css and Javascript files but allow them to refreshed with a hard refresh when they are updated without having to rename them.

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  • Toshiba Laptop Problem - Black Screen on Startup [using Win Vista]

    - by BubblySue
    Hi guys, can anyone help me on my problem? I only see black screen after the startup.. It just shows the logo and the status bar upon start, then it goes black screen with moveable cursor. I tried alt+ctrl+del, but it doesn't work. I pressed shift 5 times and it makes a sound. I already removed battery and restarted it, but still the same. I can go to safe mode and scanned thru there. Still, desktop won't show up. Don't know what else to check? Been searching the net for solutions. Please help? :(

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  • What Windows message is fired for mouse-up with modifier keys?

    - by Greg
    My WndProc isn't seeing mouse-up notifications when I click with a modifier key (shift or control) pressed. I see them without the modifier key, and I see mouse-down notifications with the modifier keys. I'm using the Windows Forms NativeWindow wrapper to get Windows messages from the WndProc() method. I've tried tracking the notifications I do get, and I the only clue I see is WM_CAPTURECHANGED. I've tried calling SetCapture when I receive the WM_LBUTTONDOWN message, but it doesn't help. Without modifier (skipping paint, timer and NCHITTEST messages): WM_LBUTTONDOWN WM_SETCURSOR WM_MOUSEMOVE WM_SETCURSOR WM_LBUTTONUP With modifier (skipping paint, timer and NCHITTEST messages): WM_KEYDOWN WM_PARENTNOTIFY WM_MOUSEACTIVATE WM_MOUSEACTIVATE WM_SETCURSOR WM_LBUTTONDOWN WM_SETCURSOR (repeats) WM_KEYDOWN (repeats) WM_KEYUP If I hold the mouse button down for a long time, I can usually get a WM_LBUTTONUP notification, but it should be possible to make it more responsive.. What am I missing? Thanks.

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  • Avoiding dog-piling or thundering herd in a memcached expiration scenario

    - by Quintin Par
    I have the result of a query that is very expensive. It is the join of several tables and a map reduce job. This is cached in memcached for 15 minutes. Once the cache expires the queries are obviously run and the cache warmed again. But at the point of expiration the thundering herd problem issue can happen. One way to fix this problem, that I do right now is to run a scheduled task that kicks in the 14th minute. But somehow this looks very sub optimal to me. Another approach I like is nginx’s proxy_cache_use_stale updating; mechanism. The webserver/machine continues to deliver stale cache while a thread kicks in the moment expiration happens and updates the cache. Has someone applied this to memcached scenario though I understand this is a client side strategy? If it benefits, I use Django.

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  • How can I Query only __key__ on a Google Appengine PolyModel child?

    - by Gabriel
    So the situation is: I want to optimize my code some for doing counting of records. So I have a parent Model class Base, a PolyModel class Entry, and a child class of Entry Article: How would I query Article.key so I can reduce the query load but only get the Article count. My first thought was to use: q = db.GqlQuery("SELECT __key__ from Article where base = :1", i_base) but it turns out GqlQuery doesn't like that because articles are actually stored in a table called Entry. Would it be possible to Query the class attribute? something like: q = db.GqlQuery("select __key__ from Entry where base = :1 and :2 in class", i_base, 'Article') neither of which work. Turns out the answer is even easier. But I am going to finish this question because I looked everywhere for this. q = db.GqlQuery("select __key__ from Entry where base = :1 and class = :2", i_base, 'Article')

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  • Self-Configuring Classes W/ Command Line Args: Pattern or Anti-Pattern?

    - by dsimcha
    I've got a program where a lot of classes have really complicated configuration requirements. I've adopted the pattern of decentralizing the configuration and allowing each class to take and parse the command line/configuration file arguments in its c'tor and do whatever it needs with them. (These are very coarse-grained classes that are only instantiated a few times, so there is absolutely no performance issue here.) This avoids having to do shotgun surgery to plumb new options I add through all the levels they need to be passed through. It also avoids having to specify each configuration option in multiple places (where it's parsed and where it's used). What are some advantages/disadvantages of this style of programming? It seems to reduce separation of concerns in that every class is now doing configuration stuff, and to make programs less self-documenting because what parameters a class takes becomes less explicit. OTOH, it seems to increase encapsulation in that it makes each class more self-contained because no other part of the program needs to know exactly what configuration parameters a class might need.

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  • Perl passing argument into eval

    - by ehretf
    I'm facing an issue using eval function. Indeed I have some function name inside a SQL database, my goal is to execute those functions within perl (after retrieve in SQL). Here is what I'm doing, considering that $RssSource-{$k}{Proceed} contains "&test" as a string retrieved from SQL: my $str2 = "ABCD"; eval "$RssSource->{$k}{Proceed}";warn if $@; sub test { my $arg = shift; print "fct TEST -> ", $row, "\n"; } This is working correctly and display: fct TEST -> However I would like to be able to pass $str2 as an argument to $RssSource-{$k}{Proceed} but I don't know how, every syntax I tried return an error: eval "$RssSource->{$k}{Proceed}$str2" eval "$RssSource->{$k}{Proceed}($str2)" eval "$RssSource->{$k}{Proceed}"$str2 eval "$RssSource->{$k}{Proceed}"($str2) May someone tell me how to properly pass an argument to the evaluated function? Thanks a lot for your help Regards. Florent

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