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  • Add code to html pages automatically

    - by piede
    I need to add some code to the of several html contained in a folder on my desktop. How can i do that? I am using a prototyping tool (Axure) on Mac and I want to add some html meta tags to the generated pages. These pages can be overwritten every time I generate the prototype. What I need is a sort of script that I can launch after re-generating the prototype, to reinsert the code. There is something for windows but it doesn't work on Mac: http://joshuamorse.com/2009/01/14/axure-protonotes-an-alternative-to-protoshare/ thanks

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  • Staticly linked libraries not running code inside to setup static variables.

    - by MJD
    In a c++ project I am working on, I have a simple c++ file that needs to run some code at the beginning of the progam execution. This file is linked into a static library, which is then linked into the main program. I have similar code in other files running fine, that looks something like: bool ____nonexistant_value = executeAction(); However, it does not work inside this file unless I make use of a function implemented in this file. It does work if the library is compilied as a shared library. I'd prefer to link this statically as the library is only a convience as the file is in a different directory.

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  • Statically linked libraries not running code inside to setup static variables.

    - by MJD
    In a c++ project I am working on, I have a simple c++ file that needs to run some code at the beginning of the program execution. This file is linked into a static library, which is then linked into the main program. I have similar code in other files running fine, that looks something like: bool ____nonexistent_value = executeAction(); However, it does not work inside this file unless I make use of a function implemented in this file. It does work if the library is compiled as a shared library. I'd prefer to link this statically as the library is only a convenience as the file is in a different directory.

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  • Given an XML which contains a representation of a graph, how to apply it DFS algorithm? [on hold]

    - by winston smith
    Given the followin XML which is a directed graph: <?xml version="1.0" encoding="iso-8859-1" ?> <!DOCTYPE graph PUBLIC "-//FC//DTD red//EN" "../dtd/graph.dtd"> <graph direct="1"> <vertex label="V0"/> <vertex label="V1"/> <vertex label="V2"/> <vertex label="V3"/> <vertex label="V4"/> <vertex label="V5"/> <edge source="V0" target="V1" weight="1"/> <edge source="V0" target="V4" weight="1"/> <edge source="V5" target="V2" weight="1"/> <edge source="V5" target="V4" weight="1"/> <edge source="V1" target="V2" weight="1"/> <edge source="V1" target="V3" weight="1"/> <edge source="V1" target="V4" weight="1"/> <edge source="V2" target="V3" weight="1"/> </graph> With this classes i parsed the graph and give it an adjacency list representation: import java.io.IOException; import java.util.HashSet; import java.util.LinkedList; import java.util.Collection; import java.util.Iterator; import java.util.logging.Level; import java.util.logging.Logger; import practica3.util.Disc; public class ParsingXML { public static void main(String[] args) { try { // TODO code application logic here Collection<Vertex> sources = new HashSet<Vertex>(); LinkedList<String> lines = Disc.readFile("xml/directed.xml"); for (String lin : lines) { int i = Disc.find(lin, "source=\""); String data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } Vertex v = new Vertex(); v.setName(data); v.setAdy(new HashSet<Vertex>()); sources.add(v); } } Iterator it = sources.iterator(); while (it.hasNext()) { Vertex ver = (Vertex) it.next(); Collection<Vertex> adyacencias = ver.getAdy(); LinkedList<String> ls = Disc.readFile("xml/graphs.xml"); for (String lin : ls) { int i = Disc.find(lin, "target=\""); String data = ""; if (lin.contains("source=\""+ver.getName())) { Vertex v = new Vertex(); if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setName(data); } i = Disc.find(lin, "weight=\""); data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setWeight(Integer.parseInt(data)); } if (v.getName() != null) { adyacencias.add(v); } } } } for (Vertex vert : sources) { System.out.println(vert); System.out.println("adyacencias: " + vert.getAdy()); } } catch (IOException ex) { Logger.getLogger(ParsingXML.class.getName()).log(Level.SEVERE, null, ex); } } } This is another class: import java.util.Collection; import java.util.Objects; public class Vertex { private String name; private int weight; private Collection ady; public Collection getAdy() { return ady; } public void setAdy(Collection adyacencias) { this.ady = adyacencias; } public String getName() { return name; } public void setName(String nombre) { this.name = nombre; } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } @Override public int hashCode() { int hash = 7; hash = 43 * hash + Objects.hashCode(this.name); hash = 43 * hash + this.weight; return hash; } @Override public boolean equals(Object obj) { if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final Vertex other = (Vertex) obj; if (!Objects.equals(this.name, other.name)) { return false; } if (this.weight != other.weight) { return false; } return true; } @Override public String toString() { return "Vertice{" + "name=" + name + ", weight=" + weight + '}'; } } And finally: /** * * @author user */ /* -*-jde-*- */ /* <Disc.java> Contains the main argument*/ import java.io.*; import java.util.LinkedList; /** * Lectura y escritura de archivos en listas de cadenas * Ideal para el uso de las clases para gráficas. * * @author Peralta Santa Anna Victor Miguel * @since Julio 2011 */ public class Disc { /** * Metodo para lectura de un archivo * * @param fileName archivo que se va a leer * @return El archivo en representacion de lista de cadenas */ public static LinkedList<String> readFile(String fileName) throws IOException { BufferedReader file = new BufferedReader(new FileReader(fileName)); LinkedList<String> textlist = new LinkedList<String>(); while (file.ready()) { textlist.add(file.readLine().trim()); } file.close(); /* for(String linea:textlist){ if(linea.contains("source")){ //String generado = linea.replaceAll("<\\w+\\s+\"", ""); //System.out.println(generado); } }*/ return textlist; }//readFile public static int find(String linea,String palabra){ int i,j; boolean found = false; for(i=0,j=0;i<linea.length();i++){ if(linea.charAt(i)==palabra.charAt(j)){ j++; if(j==palabra.length()){ found = true; return i; } }else{ continue; } } if(!found){ i= -1; } return i; } /** * Metodo para la escritura de un archivo * * @param fileName archivo que se va a escribir * @param tofile la lista de cadenas que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String fileName, LinkedList<String> tofile, boolean append) throws IOException { FileWriter file = new FileWriter(fileName, append); for (int i = 0; i < tofile.size(); i++) { file.write(tofile.get(i) + "\n"); } file.close(); }//writeFile /** * Metodo para escritura de un archivo * @param msg archivo que se va a escribir * @param tofile la cadena que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String msg, String tofile, boolean append) throws IOException { FileWriter file = new FileWriter(msg, append); file.write(tofile); file.close(); }//writeFile }// I'm stuck on what can be the best way to given an adjacency list representation of the graph how to apply it Depth-first search algorithm. Any idea of how to aproach to complete the task?

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  • nginx+django serving static files

    - by avalore
    I have followed instruction for setting up django with nginx from the django wiki (https://code.djangoproject.com/wiki/DjangoAndNginx) and have nginx setup as follows (a few name changes to fit my setup). user nginx nginx; worker_processes 2; error_log /var/log/nginx/error_log info; events { worker_connections 1024; use epoll; } http { include /etc/nginx/mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] ' '"$request" $status $bytes_sent ' '"$http_referer" "$http_user_agent" ' '"$gzip_ratio"'; client_header_timeout 10m; client_body_timeout 10m; send_timeout 10m; connection_pool_size 256; client_header_buffer_size 1k; large_client_header_buffers 4 2k; request_pool_size 4k; gzip on; gzip_min_length 1100; gzip_buffers 4 8k; gzip_types text/plain; output_buffers 1 32k; postpone_output 1460; sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 75 20; ignore_invalid_headers on; index index.html; server { listen 80; server_name localhost; location /static/ { root /srv/static/; } location ~* ^.+\.(jpg|jpeg|gif|png|ico|css|zip|tgz|gz|rar|bz2|doc|xls|exe|pdf|ppt|txt|tar|mid|midi|wav|bmp|rtf|js|mov) { access_log off; expires 30d; } location / { # host and port to fastcgi server fastcgi_pass 127.0.0.1:8080; fastcgi_param PATH_INFO $fastcgi_script_name; fastcgi_param REQUEST_METHOD $request_method; fastcgi_param QUERY_STRING $query_string; fastcgi_param CONTENT_TYPE $content_type; fastcgi_param CONTENT_LENGTH $content_length; fastcgi_pass_header Authorization; fastcgi_intercept_errors off; fastcgi_param REMOTE_ADDR $remote_addr; } access_log /var/log/nginx/localhost.access_log main; error_log /var/log/nginx/localhost.error_log; } } Static files aren't being served (nginx 404). If I look in the access log it seems nginx is looking in /etc/nginx/html/static... rather than /srv/static/ as specified in the config. I've no clue why it's doing this, any help would be hugely appreciated.

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  • A Simple Approach For Presenting With Code Samples

    - by Jesse Taber
    Originally posted on: http://geekswithblogs.net/GruffCode/archive/2013/07/31/a-simple-approach-for-presenting-with-code-samples.aspxI’ve been getting ready for a presentation and have been struggling a bit with the best way to show and execute code samples. I don’t present often (hardly ever), but when I do I like the presentation to have a lot of succinct and executable code snippets to help illustrate the points that I’m making. Depending on what the presentation is about, I might just want to build an entire sample application that I would run during the presentation. In other cases, however, building a full-blown application might not really be the best way to present the code. The presentation I’m working on now is for an open source utility library for dealing with dates and times. I could have probably cooked up a sample app for accepting date and time input and then contrived ways in which it could put the library through its paces, but I had trouble coming up with one app that would illustrate all of the various features of the library that I wanted to highlight. I finally decided that what I really needed was an approach that met the following criteria: Simple: I didn’t want the user interface or overall architecture of a sample application to serve as a distraction from the demonstration of the syntax of the library that the presentation is about. I want to be able to present small bits of code that are focused on accomplishing a single task. Several of these examples will look similar, and that’s OK. I want each sample to “stand on its own” and not rely much on external classes or methods (other than the library that is being presented, of course). “Debuggable” (not really a word, I know): I want to be able to easily run the sample with the debugger attached in Visual Studio should I want to step through any bits of code and show what certain values might be at run time. As far as I know this rules out something like LinqPad, though using LinqPad to present code samples like this is actually a very interesting idea that I might explore another time. Flexible and Selectable: I’m going to have lots of code samples to show, and I want to be able to just package them all up into a single project or module and have an easy way to just run the sample that I want on-demand. Since I’m presenting on a .NET framework library, one of the simplest ways in which I could execute some code samples would be to just create a Console application and use Console.WriteLine to output the pertinent info at run time. This gives me a “no frills” harness from which to run my code samples, and I just hit ‘F5’ to run it with the debugger. This satisfies numbers 1 and 2 from my list of criteria above, but item 3 is a little harder. By default, just running a console application is going to execute the ‘main’ method, and then terminate the program after all code is executed. If I want to have several different code samples and run them one at a time, it would be cumbersome to keep swapping the code I want in and out of the ‘main’ method of the console application. What I really want is an easy way to keep the console app running throughout the whole presentation and just have it run the samples I want when I want. I could setup a simple Windows Forms or WPF desktop application with buttons for the different samples, but then I’m getting away from my first criteria of keeping things as simple as possible. Infinite Loops To The Rescue I found a way to have a simple console application satisfy all three of my requirements above, and it involves using an infinite loop and some Console.ReadLine calls that will give the user an opportunity to break out and exit the program. (All programs that need to run until they are closed explicitly (or crash!) likely use similar constructs behind the scenes. Create a new Windows Forms project, look in the ‘Program.cs’ that gets generated, and then check out the docs for the Application.Run method that it calls.). Here’s how the main method might look: 1: static void Main(string[] args) 2: { 3: do 4: { 5: Console.Write("Enter command or 'exit' to quit: > "); 6: var command = Console.ReadLine(); 7: if ((command ?? string.Empty).Equals("exit", StringComparison.OrdinalIgnoreCase)) 8: { 9: Console.WriteLine("Quitting."); 10: break; 11: } 12: 13: } while (true); 14: } The idea here is the app prompts me for the command I want to run, or I can type in ‘exit’ to break out of the loop and let the application close. The only trick now is to create a set of commands that map to each of the code samples that I’m going to want to run. Each sample is already encapsulated in a single public method in a separate class, so I could just write a big switch statement or create a hashtable/dictionary that maps command text to an Action that will invoke the proper method, but why re-invent the wheel? CLAP For Your Own Presentation I’ve blogged about the CLAP library before, and it turns out that it’s a great fit for satisfying criteria #3 from my list above. CLAP lets you decorate methods in a class with an attribute and then easily invoke those methods from within a console application. CLAP was designed to take the arguments passed into the console app from the command line and parse them to determine which method to run and what arguments to pass to that method, but there’s no reason you can’t re-purpose it to accept command input from within the infinite loop defined above and invoke the corresponding method. Here’s how you might define a couple of different methods to contain two different code samples that you want to run during your presentation: 1: public static class CodeSamples 2: { 3: [Verb(Aliases="one")] 4: public static void SampleOne() 5: { 6: Console.WriteLine("This is sample 1"); 7: } 8:   9: [Verb(Aliases="two")] 10: public static void SampleTwo() 11: { 12: Console.WriteLine("This is sample 2"); 13: } 14: } A couple of things to note about the sample above: I’m using static methods. You don’t actually need to use static methods with CLAP, but the syntax ends up being a bit simpler and static methods happen to lend themselves well to the “one self-contained method per code sample” approach that I want to use. The methods are decorated with a ‘Verb’ attribute. This tells CLAP that they are eligible targets for commands. The “Aliases” argument lets me give them short and easy-to-remember aliases that can be used to invoke them. By default, CLAP just uses the full method name as the command name, but with aliases you can simply the usage a bit. I’m not using any parameters. CLAP’s main feature is its ability to parse out arguments from a command line invocation of a console application and automatically pass them in as parameters to the target methods. My code samples don’t need parameters ,and honestly having them would complicate giving the presentation, so this is a good thing. You could use this same approach to invoke methods with parameters, but you’d have a couple of things to figure out. When you invoke a .NET application from the command line, Windows will parse the arguments and pass them in as a string array (called ‘args’ in the boilerplate console project Program.cs). The parsing that gets done here is smart enough to deal with things like treating strings in double quotes as one argument, and you’d have to re-create that within your infinite loop if you wanted to use parameters. I plan on either submitting a pull request to CLAP to add this capability or maybe just making a small utility class/extension method to do it and posting that here in the future. So I now have a simple class with static methods to contain my code samples, and an infinite loop in my ‘main’ method that can accept text commands. Wiring this all up together is pretty easy: 1: static void Main(string[] args) 2: { 3: do 4: { 5: try 6: { 7: Console.Write("Enter command or 'exit' to quit: > "); 8: var command = Console.ReadLine(); 9: if ((command ?? string.Empty).Equals("exit", StringComparison.OrdinalIgnoreCase)) 10: { 11: Console.WriteLine("Quitting."); 12: break; 13: } 14:   15: Parser.Run<CodeSamples>(new[] { command }); 16: Console.WriteLine("---------------------------------------------------------"); 17: } 18: catch (Exception ex) 19: { 20: Console.Error.WriteLine("Error: " + ex.Message); 21: } 22:   23: } while (true); 24: } Note that I’m now passing the ‘CodeSamples’ class into the CLAP ‘Parser.Run’ as a type argument. This tells CLAP to inspect that class for methods that might be able to handle the commands passed in. I’m also throwing in a little “----“ style line separator and some basic error handling (because I happen to know that some of the samples are going to throw exceptions for demonstration purposes) and I’m good to go. Now during my presentation I can just have the console application running the whole time with the debugger attached and just type in the alias of the code sample method that I want to run when I want to run it.

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  • .NET Code Evolution

    - by Alois Kraus
    Originally posted on: http://geekswithblogs.net/akraus1/archive/2013/07/24/153504.aspxAt my day job I do look at a lot of code written by other people. Most of the code is quite good and some is even a masterpiece. And there is also code which makes you think WTF… oh it was written by me. Hm not so bad after all. There are many excuses reasons for bad code. Most often it is time pressure followed by not enough ambition (who cares) or insufficient training. Normally I do care about code quality quite a lot which makes me a (perceived) slow worker who does write many tests and refines the code quite a lot because of the design deficiencies. Most of the deficiencies I do find by putting my design under stress while checking for invariants. It does also help a lot to step into the code with a debugger (sometimes also Windbg). I do this much more often when my tests are red. That way I do get a much better understanding what my code really does and not what I think it should be doing. This time I do want to show you how code can evolve over the years with different .NET Framework versions. Once there was  time where .NET 1.1 was new and many C++ programmers did switch over to get rid of not initialized pointers and memory leaks. There were also nice new data structures available such as the Hashtable which is fast lookup table with O(1) time complexity. All was good and much code was written since then. At 2005 a new version of the .NET Framework did arrive which did bring many new things like generics and new data structures. The “old” fashioned way of Hashtable were coming to an end and everyone used the new Dictionary<xx,xx> type instead which was type safe and faster because the object to type conversion (aka boxing) was no longer necessary. I think 95% of all Hashtables and dictionaries use string as key. Often it is convenient to ignore casing to make it easy to look up values which the user did enter. An often followed route is to convert the string to upper case before putting it into the Hashtable. Hashtable Table = new Hashtable(); void Add(string key, string value) { Table.Add(key.ToUpper(), value); } This is valid and working code but it has problems. First we can pass to the Hashtable a custom IEqualityComparer to do the string matching case insensitive. Second we can switch over to the now also old Dictionary type to become a little faster and we can keep the the original keys (not upper cased) in the dictionary. Dictionary<string, string> DictTable = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase); void AddDict(string key, string value) { DictTable.Add(key, value); } Many people do not user the other ctors of Dictionary because they do shy away from the overhead of writing their own comparer. They do not know that .NET has for strings already predefined comparers at hand which you can directly use. Today in the many core area we do use threads all over the place. Sometimes things break in subtle ways but most of the time it is sufficient to place a lock around the offender. Threading has become so mainstream that it may sound weird that in the year 2000 some guy got a huge incentive for the idea to reduce the time to process calibration data from 12 hours to 6 hours by using two threads on a dual core machine. Threading does make it easy to become faster at the expense of correctness. Correct and scalable multithreading can be arbitrarily hard to achieve depending on the problem you are trying to solve. Lets suppose we want to process millions of items with two threads and count the processed items processed by all threads. A typical beginners code might look like this: int Counter; void IJustLearnedToUseThreads() { var t1 = new Thread(ThreadWorkMethod); t1.Start(); var t2 = new Thread(ThreadWorkMethod); t2.Start(); t1.Join(); t2.Join(); if (Counter != 2 * Increments) throw new Exception("Hmm " + Counter + " != " + 2 * Increments); } const int Increments = 10 * 1000 * 1000; void ThreadWorkMethod() { for (int i = 0; i < Increments; i++) { Counter++; } } It does throw an exception with the message e.g. “Hmm 10.222.287 != 20.000.000” and does never finish. The code does fail because the assumption that Counter++ is an atomic operation is wrong. The ++ operator is just a shortcut for Counter = Counter + 1 This does involve reading the counter from a memory location into the CPU, incrementing value on the CPU and writing the new value back to the memory location. When we do look at the generated assembly code we will see only inc dword ptr [ecx+10h] which is only one instruction. Yes it is one instruction but it is not atomic. All modern CPUs have several layers of caches (L1,L2,L3) which try to hide the fact how slow actual main memory accesses are. Since cache is just another word for redundant copy it can happen that one CPU does read a value from main memory into the cache, modifies it and write it back to the main memory. The problem is that at least the L1 cache is not shared between CPUs so it can happen that one CPU does make changes to values which did change in meantime in the main memory. From the exception you can see we did increment the value 20 million times but half of the changes were lost because we did overwrite the already changed value from the other thread. This is a very common case and people do learn to protect their  data with proper locking.   void Intermediate() { var time = Stopwatch.StartNew(); Action acc = ThreadWorkMethod_Intermediate; var ar1 = acc.BeginInvoke(null, null); var ar2 = acc.BeginInvoke(null, null); ar1.AsyncWaitHandle.WaitOne(); ar2.AsyncWaitHandle.WaitOne(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Intermediate did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Intermediate() { for (int i = 0; i < Increments; i++) { lock (this) { Counter++; } } } This is better and does use the .NET Threadpool to get rid of manual thread management. It does give the expected result but it can result in deadlocks because you do lock on this. This is in general a bad idea since it can lead to deadlocks when other threads use your class instance as lock object. It is therefore recommended to create a private object as lock object to ensure that nobody else can lock your lock object. When you read more about threading you will read about lock free algorithms. They are nice and can improve performance quite a lot but you need to pay close attention to the CLR memory model. It does make quite weak guarantees in general but it can still work because your CPU architecture does give you more invariants than the CLR memory model. For a simple counter there is an easy lock free alternative present with the Interlocked class in .NET. As a general rule you should not try to write lock free algos since most likely you will fail to get it right on all CPU architectures. void Experienced() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Experienced); t1.Wait(); t2.Wait(); if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Experienced did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Experienced() { for (int i = 0; i < Increments; i++) { Interlocked.Increment(ref Counter); } } Since time does move forward we do not use threads explicitly anymore but the much nicer Task abstraction which was introduced with .NET 4 at 2010. It is educational to look at the generated assembly code. The Interlocked.Increment method must be called which does wondrous things right? Lets see: lock inc dword ptr [eax] The first thing to note that there is no method call at all. Why? Because the JIT compiler does know very well about CPU intrinsic functions. Atomic operations which do lock the memory bus to prevent other processors to read stale values are such things. Second: This is the same increment call prefixed with a lock instruction. The only reason for the existence of the Interlocked class is that the JIT compiler can compile it to the matching CPU intrinsic functions which can not only increment by one but can also do an add, exchange and a combined compare and exchange operation. But be warned that the correct usage of its methods can be tricky. If you try to be clever and look a the generated IL code and try to reason about its efficiency you will fail. Only the generated machine code counts. Is this the best code we can write? Perhaps. It is nice and clean. But can we make it any faster? Lets see how good we are doing currently. Level Time in s IJustLearnedToUseThreads Flawed Code Intermediate 1,5 (lock) Experienced 0,3 (Interlocked.Increment) Master 0,1 (1,0 for int[2]) That lock free thing is really a nice thing. But if you read more about CPU cache, cache coherency, false sharing you can do even better. int[] Counters = new int[12]; // Cache line size is 64 bytes on my machine with an 8 way associative cache try for yourself e.g. 64 on more modern CPUs void Master() { var time = Stopwatch.StartNew(); Task t1 = Task.Factory.StartNew(ThreadWorkMethod_Master, 0); Task t2 = Task.Factory.StartNew(ThreadWorkMethod_Master, Counters.Length - 1); t1.Wait(); t2.Wait(); Counter = Counters[0] + Counters[Counters.Length - 1]; if (Counter != 2 * Increments) throw new Exception(String.Format("Hmm {0:N0} != {1:N0}", Counter, 2 * Increments)); Console.WriteLine("Master did take: {0:F1}s", time.Elapsed.TotalSeconds); } void ThreadWorkMethod_Master(object number) { int index = (int) number; for (int i = 0; i < Increments; i++) { Counters[index]++; } } The key insight here is to use for each core its own value. But if you simply use simply an integer array of two items, one for each core and add the items at the end you will be much slower than the lock free version (factor 3). Each CPU core has its own cache line size which is something in the range of 16-256 bytes. When you do access a value from one location the CPU does not only fetch one value from main memory but a complete cache line (e.g. 16 bytes). This means that you do not pay for the next 15 bytes when you access them. This can lead to dramatic performance improvements and non obvious code which is faster although it does have many more memory reads than another algorithm. So what have we done here? We have started with correct code but it was lacking knowledge how to use the .NET Base Class Libraries optimally. Then we did try to get fancy and used threads for the first time and failed. Our next try was better but it still had non obvious issues (lock object exposed to the outside). Knowledge has increased further and we have found a lock free version of our counter which is a nice and clean way which is a perfectly valid solution. The last example is only here to show you how you can get most out of threading by paying close attention to your used data structures and CPU cache coherency. Although we are working in a virtual execution environment in a high level language with automatic memory management it does pay off to know the details down to the assembly level. Only if you continue to learn and to dig deeper you can come up with solutions no one else was even considering. I have studied particle physics which does help at the digging deeper part. Have you ever tried to solve Quantum Chromodynamics equations? Compared to that the rest must be easy ;-). Although I am no longer working in the Science field I take pride in discovering non obvious things. This can be a very hard to find bug or a new way to restructure data to make something 10 times faster. Now I need to get some sleep ….

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  • Is this a good code (came across while reading code of a colleague)

    - by eriks
    // file a.hpp class a; typedef boost::shared_ptr<a> aPtr class a{ public: static aPtr CreateImp(); virtual void Foo() = 0 ; .... }; //file aImp.hpp class aImp : public a{ virtual void Foo(); }; //file aImp.cpp aPtr a::CreateImp() { return aPtr(new aImp()); } void aImp::Foo(){} The client must use CreateImp to get ptr to 'a', and can't use 'a' other ways. What do you think about this implementation? what do you think about this king of implementation?

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  • Static libraries, dynamic libraries, DLLs, entry points, headers ... how to get out of this alive?

    - by tunnuz
    Hello, I recently had to program C++ under Windows for an University project, and I'm pretty confused about static and dynamic libraries system, what the compiler needs, what the linker needs, how to build a library ... is there any good document about this out there? I'm pretty confused about the *nix library system as well (so, dylibs, the ar tool, how to compile them ...), can you point a review document about the current library techniques on the various architectures? Note: due to my poor knowledge this message could contain wrong concepts, feel free to edit it. Thank you Feel free to add more reference, I will add them to the summary. References Since most of you posted *nix or Windows specific references I will summarize here the best ones, I will mark as accepted answer the Wikipedia one, because is a good start point (and has references inside too) to get introduced to this stuff. Program Library Howto (Unix) Dynamic-Link Libraries (from MSDN) (Windows) DLL Information (StackOverflow) (Windows) Programming in C (Unix) An Overview of Compiling and Linking (Windows)

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  • Jquery validation does not stop execution of "code behind" code of asp.net button

    - by shahk26
    Hi, I have a asp.net button which has click event which basically adds data into datbase. I also have a radiobuttonlist(i.e Approve / Decline) and a textbox. If user selects decline, the textbox becomes visible. I want to run validation that when user clicks on submit button, if the decline is selected then the textbox can not blank. I have used jquery validation for that. when I click button, the message apppears next to textbox that the field is required but it does not stop the execution of code behind. i.e.It adds data into database. Here is my code. <script type="text/javascript" language="javascript"> $(function() { $('#declinediv').hide(); //////// var $radBtn = $("table.rblist input:radio"); $radBtn.click(function() { var $radChecked = $(':radio:checked'); var value = $radChecked.val(); if (value == 'Decline' || value == 'Approve') { if (value == 'Decline') $('#declinediv').show(); else $('#declinediv').hide(); } else { $('#declinediv').hide(); } }); ////////////////////////// $("#aspnetForm").validate({ rules: { <%=txtdeclinereason.UniqueID %>: { minlength: 2, required: true } }, messages: { <%=txtdeclinereason.UniqueID %>:{ required: "* Required Field *", minlength: "* Please enter atleast 2 characters *" } }, onsubmit: true }); ////////////////////////////////// $('#btnsubmit').click(function(evt){ var isValid = $("#aspnetForm").valid(); if (!isValid) { evt.preventDefault(); } }); }); function myredirect(v, m, f) { window.location.href = v; } </script> <table style="border: 1px black solid; text-align: center; vertical-align: middle" width="100%"> <tr> <td> <asp:RadioButtonList ID="rbtnlstapprover" runat="server" RepeatDirection="Horizontal" CssClass="rblist" DataTextField="username" DataValueField="emailaddress"> <asp:ListItem Text="Approve" Value="Approve" /> <asp:ListItem Text="Decline" Value="Decline" /> </asp:RadioButtonList> <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="rbtnlstapprover" Text="*" ErrorMessage="Please select atleast one Approver" ValidationGroup="approvalgroup" Display="Dynamic" /> </td> </tr> <tr> <td> <div id="declinediv"> <asp:TextBox ID="txtdeclinereason" runat="server" TextMode="MultiLine" Columns="80" Rows="5" /> </div> </td> </tr> <tr> <td> <asp:Button ID="btnsubmit" runat="server" Text="Submit" CssClass="RegularButton" CausesValidation="true" ValidationGroup="approvalgroup" OnClick="btnsubmit_Click" /> </td> </tr> </table> How do I stop the execution of code behind? Thanks for your help.

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  • .NET interview, code structure and the design

    - by j_lewis
    I have been given the below .NET question in an interview. I don’t know why I got low marks. Unfortunately I did not get a feedback. Question: The file hockey.csv contains the results from the Hockey Premier League. The columns ‘For’ and ‘Against’ contain the total number of goals scored for and against each team in that season (so Alabama scored 79 goals against opponents, and had 36 goals scored against them). Write a program to print the name of the team with the smallest difference in ‘for’ and ‘against’ goals. the structure of the hockey.csv looks like this (it is a valid csv file, but I just copied the values here to get an idea) Team - For - Against Alabama 79 36 Washinton 67 30 Indiana 87 45 Newcastle 74 52 Florida 53 37 New York 46 47 Sunderland 29 51 Lova 41 64 Nevada 33 63 Boston 30 64 Nevada 33 63 Boston 30 64 Solution: class Program { static void Main(string[] args) { string path = @"C:\Users\<valid csv path>"; var resultEvaluator = new ResultEvaluator(string.Format(@"{0}\{1}",path, "hockey.csv")); var team = resultEvaluator.GetTeamSmallestDifferenceForAgainst(); Console.WriteLine( string.Format("Smallest difference in ‘For’ and ‘Against’ goals > TEAM: {0}, GOALS DIF: {1}", team.Name, team.Difference )); Console.ReadLine(); } } public interface IResultEvaluator { Team GetTeamSmallestDifferenceForAgainst(); } public class ResultEvaluator : IResultEvaluator { private static DataTable leagueDataTable; private readonly string filePath; private readonly ICsvExtractor csvExtractor; public ResultEvaluator(string filePath){ this.filePath = filePath; csvExtractor = new CsvExtractor(); } private DataTable LeagueDataTable{ get { if (leagueDataTable == null) { leagueDataTable = csvExtractor.GetDataTable(filePath); } return leagueDataTable; } } public Team GetTeamSmallestDifferenceForAgainst() { var teams = GetTeams(); var lowestTeam = teams.OrderBy(p => p.Difference).First(); return lowestTeam; } private IEnumerable<Team> GetTeams() { IList<Team> list = new List<Team>(); foreach (DataRow row in LeagueDataTable.Rows) { var name = row["Team"].ToString(); var @for = int.Parse(row["For"].ToString()); var against = int.Parse(row["Against"].ToString()); var team = new Team(name, against, @for); list.Add(team); } return list; } } public interface ICsvExtractor { DataTable GetDataTable(string csvFilePath); } public class CsvExtractor : ICsvExtractor { public DataTable GetDataTable(string csvFilePath) { var lines = File.ReadAllLines(csvFilePath); string[] fields; fields = lines[0].Split(new[] { ',' }); int columns = fields.GetLength(0); var dt = new DataTable(); //always assume 1st row is the column name. for (int i = 0; i < columns; i++) { dt.Columns.Add(fields[i].ToLower(), typeof(string)); } DataRow row; for (int i = 1; i < lines.GetLength(0); i++) { fields = lines[i].Split(new char[] { ',' }); row = dt.NewRow(); for (int f = 0; f < columns; f++) row[f] = fields[f]; dt.Rows.Add(row); } return dt; } } public class Team { public Team(string name, int against, int @for) { Name = name; Against = against; For = @for; } public string Name { get; private set; } public int Against { get; private set; } public int For { get; private set; } public int Difference { get { return (For - Against); } } } Output: Smallest difference in for' andagainst' goals TEAM: Boston, GOALS DIF: -34 Can someone please review my code and see anything obviously wrong here? They were only interested in the structure/design of the code and whether the program produces the correct result (i.e lowest difference). Much appreciated. "P.S - Please correct me if the ".net-interview" tag is not the right tag to use"

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  • WordPress front page (homepage) fails to redirect when static front page is set.

    - by Keyslinger
    I have configured WordPress to display a static front page as described here: http://codex.wordpress.org/Settings_Reading_SubPanel#Reading_Settings When save changes and try to visit my front page, my browser displays the following error: "The page isn't redirecting properly. Firefox has detected that the server is redirecting the request for this address in a way that will never complete." Disabling cookies does not remedy the situation. I'm using the theme, Constructor (http://wordpress.org/extend/themes/constructor), which I suspect may be contributing to the problem. How can I make WordPress properly display my front page?

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  • PHP: How to access array values returned by a static function?

    - by Prashant
    I am running following code, getAccount() is a static function, $ac_info = AccountClass::getAccount($ac_code); print_r($ac_info); and getting following output AccountClass Object ( [account_code] => [email protected] [username] => XYZ [email] => [first_name] => [last_name] => [company_name] => [id] => [email protected] [balance_in_cents] => 0 [created_at] => 1271333048 [state] => active ) But I want to access the value of "account_code" shown above, how to access it, and AccountClass Object what is this, this is array or what? I am not getting it properly. Please explain what is AccountClass Object and how to access value of properties account_code, first_name inside this array. Thanks

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  • Is an ArrayList automatically declared static in Java, if it is an instance variable?

    - by Alex
    I'm trying to do something like this: private class aClass { private ArrayList<String> idProd; aClass(ArrayList<String> prd) { this.idProd=new ArrayList<String>(prd); } public ArrayList<String> getIdProd() { return this.idProd; } } So if I have multiple instances of ArrayLIst<String> (st1 ,st2 ,st3) and I want to make new objects of aClass: { aClass obj1,obj2,obj3; obj1=new aClass(st1); obj2=new aClass(st2); obj3=new aClass(st3); } Will all of the aClass objects return st3 if I access the method getIdProd() for each of them(obj1..obj3)? Is an ArrayList as an instance variable automatically declared static?

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  • Question about ASP.NET MVC and static data (ie. images, scripts, etc)

    - by Pure.Krome
    Hi folks, If i have a request for a resource in my ASP.NET MVC1 (or 2) web app for a static resource, say ... an image or a javascript file or a css file ... does the .NET framework try and see if the request matches the route list ... and eventually can't find a controller for it? eg. Resource: /Content/Images/Foo.png Does this request go through my route list .. fails to match any controllers / actions to this request and then .. i donno ... attempt that path directly?

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  • How should I make up for the lack of static initializers in PHP?

    - by kahoon
    I'm thinking about putting every class into a separate file and doing the static initialization outside of the class definition. The problem with this is the fact that the initialization will happen before the said class is actually needed (it will happen when the file which contains the class is included for the first time). It's a problem, because it may happen that the class won't be used at all, hence the initialization is unnecessary. And I think the practice of including the used files not in the beginning of your code is simply a dirty technique. If anybody has a viable solution to this problem, I would greatly appreciate it.

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  • Code Golf: 1x1 black pixel

    - by Joey Adams
    Recently, I used my favorite image editor to make a 1x1 black pixel (which can come in handy when you want to draw solid boxes in HTML cheaply). Even though I made it a monochrome PNG, it came out to be 120 bytes! I mean, that's kind of steep. 120 bytes. For one pixel. I then converted it to a GIF, which dropped the size down to 43 bytes. Much better, but still... Challenge The shortest image file or program that is or generates a 1x1 black pixel. A submission may be: An image file that represents a 1x1 black pixel. The format chosen must be able to represent larger images than 1x1, and cannot be ad-hoc (that is, it can't be an image format you just made up for code golf). Image files will be ranked by byte count. A program that generates such an image file. Programs will be ranked by character count, as usual in code golf. As long as an answer falls into one of these two categories, anything is fair game.

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  • Code Golf: Leibniz formula for Pi

    - by Greg Beech
    I recently posted one of my favourite interview whiteboard coding questions in "What's your more controversial programming opinion", which is to write a function that computes Pi using the Leibniz formula. It can be approached in a number of different ways, and the exit condition takes a bit of thought, so I thought it might make an interesting code golf question. Shortest code wins! Given that Pi can be estimated using the function 4 * (1 - 1/3 + 1/5 - 1/7 + ...) with more terms giving greater accuracy, write a function that calculates Pi to within 0.00001. Edit: 3 Jan 2008 As suggested in the comments I changed the exit condition to be within 0.00001 as that's what I really meant (an accuracy 5 decimal places is much harder due to rounding and so I wouldn't want to ask that in an interview, whereas within 0.00001 is an easier to understand and implement exit condition). Also, to answer the comments, I guess my intention was that the solution should compute the number of iterations, or check when it had done enough, but there's nothing to prevent you from pre-computing the number of iterations and using that number. I really asked the question out of interest to see what people would come up with.

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  • Programming language shootout: code most like pseudocode for Dijkstra's Algorithm

    - by Casebash
    Okay, so this question here asked which language is most like executable pseudocode, so why not find out by actually writing some code! Here we have a competition where I will award a 100 point bounty (I know its not much, but I am poor after the recalc) to the code which most resembles this pseudocode. I've read through this a few times so I'm pretty sure that this pseudocode below is correct and about as unambiguous as pseudocode can be. Personally, I'm going to have a go in Python and probably Haskell as well, but I'm just learning the later so my attempt will probably be pretty poor. Note: Obviously to implement anything looking like this you'll have to define quite a few library functions. define DirectedGraph G with: Vertices as V, Edges as E define Vertex A, Z declare each e in E as having properties: Boolean fixed with: initial=false Real minSoFar with: initial=0 for A else infinity define PriorityQueue pq with: objects=V initial=A priority v=v.minSoFar create triggers for v in V: when v.minSoFar event reduced then pq.addOrUpdate v when v.fixed event becomesTrue then pq.remove v Repeat until Z.fixed==True: define Vertex U=pq.pop() U.fixed=True for Edge E adjacentTo U with other Vertex V: V.minSoFar=U.minSoFar+length(E) if reducesValue return Z.name, Z.minSoFar

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  • Code Golf: Tic Tac Toe

    - by Aistina
    Post your shortest code, by character count, to check if a player has won, and if so, which. Assume you have an integer array in a variable b (board), which holds the Tic Tac Toe board, and the moves of the players where: 0 = nothing set 1 = player 1 (X) 2 = player 2 (O) So, given the array b = [ 1, 2, 1, 0, 1, 2, 1, 0, 2 ] would represent the board X|O|X -+-+- |X|O -+-+- X| |O For that situation, your code should output 1 to indicate player 1 has won. If no-one has won you can output 0 or false. My own (Ruby) solution will be up soon. Edit: Sorry, forgot to mark it as community wiki. You can assume the input is well formed and does not have to be error checked. Update: Please post your solution in the form of a function. Most people have done this already, but some haven't, which isn't entirely fair. The board is supplied to your function as the parameter. The result should be returned by the function. The function can have a name of your choosing.

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  • Code Golf: Connect 4

    - by Matthieu M.
    If you don't know the Connect 4 game, follow the link :) I used to play it a lot when I was a child. At least until my little sister got bored with me winning... Anyway I was reading the Code Golf: Tic Tac Toe the other day and I thought that solving the Tic Tac Toe problem was simpler than solving the Connect 4... and wondered how much this would reflect on the number of characters a solution would yield. I thus propose a similar challenge: Find the winner The grid is given under the form of a string meant to passed as a parameter to a function. The goal of the code golf is to write the body of the function, the parameter will be b, of string type The image in the wikipedia article leads to the following representation: "....... ..RY... ..YYYR. ..RRYY. ..RYRY. .YRRRYR" (6 rows of 7 elements) but is obviously incomplete (Yellow has not won yet) There is a winner in the grid passed, no need to do error checking Remember that it might not be exactly 4 The expected output is the letter representing the winner (either R or Y) I expect perl mongers to produce the most unreadable script (along with Ook and whitespace, of course), but I am most interested in reading innovative solutions. I must admit the magic square solution for Tic Tac Toe was my personal fav and I wonder if there is a way to build a similar one with this. Well, happy Easter weekend :) Now I just have a few days to come up with a solution of my own!

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  • .NET/C#: How to remove/minimize code clutter while 'triggering' Events

    - by eibhrum
    Hi, I just wanna find out if there's a way I could minimize code clutter in my application. I have written code/s similar to this: private void btnNext_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) { btnNext.Opacity = 1; } private void btnNext_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) { btnNext.Opacity = 0.5; } private void btnShowAll_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) { btnShowAll.Opacity = 1; } private void btnShowAll_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) { btnShowAll.Opacity = 0.5; } private void btnPrev_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) { btnPrev.Opacity = 1; } private void btnPrev_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) { btnPrev.Opacity = 0.5; } private void btnSearch_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) { btnSearch.Opacity = 1; } private void btnSearch_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) { btnSearch.Opacity = 0.5; } private void btnSearchStore_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) { btnSearchStore.Opacity = 1; } private void btnSearchStore_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) { btnSearchStore.Opacity = 0.5; } private void btnCloseSearch_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) { btnCloseSearch.Opacity = 1; } private void btnCloseSearch_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) { btnCloseSearch.Opacity = 0.5; } private void btnHome_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e) { btnHome.Opacity = 1; } private void btnHome_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e) { btnHome.Opacity = 0.5; } and so on and so forth... Do I need to create a 'function' that will run initially? Or do I have to create another class just so I can 'organize' them? Any suggestions?

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  • How to deal with recursive dependencies between static libraries using the binutils linker?

    - by Jack Lloyd
    I'm porting an existing system from Windows to Linux. The build is structured with multiple static libraries. I ran into a linking error where a symbol (defined in libA) could not be found in an object from libB. The linker line looked like g++ test_obj.o -lA -lB -o test The problem of course being that by the time the linker finds it needs the symbol from libA, it has already passed it by, and does not rescan, so it simply errors out even though the symbol is there for the taking. My initial idea was of course to simply swap the link (to -lB -lA) so that libA is scanned afterwards, and any symbols missing from libB that are in libA are picked up. But then I find there is actually a recursive dependency between libA and libB! I'm assuming the Visual C++ linker handles this in some way (does it rescan by default?). Ways of dealing with this I've considered: Use shared objects. Unfortunately this is undesirable from the perspective of requiring PIC compliation (this is performance sensitive code and losing %ebx to hold the GOT would really hurt), and shared objects aren't needed. Build one mega ar of all of the objects, avoiding the problem. Restructure the code to avoid the recursive dependency (which is obviously the Right Thing to do, but I'm trying to do this port with minimal changes). Do you have other ideas to deal with this? Is there some way I can convince the binutils linker to perform rescans of libraries it has already looked at when it is missing a symbol?

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  • Should I store generated code in source control

    - by Ron Harlev
    This is a debate I'm taking a part in. I would like to get more opinions and points of view. We have some classes that are generated in build time to handle DB operations (in This specific case, with SubSonic, but I don't think it is very important for the question). The generation is set as a pre-build step in Visual Studio. So every time a developer (or the official build process) runs a build, these classes are generated, and then compiled into the project. Now some people are claiming, that having these classes saved in source control could cause confusion, in case the code you get, doesn't match what would have been generated in your own environment. I would like to have a way to trace back the history of the code, even if it is usually treated as a black box. Any arguments or counter arguments? UPDATE: I asked this question since I really believed there is one definitive answer. Looking at all the responses, I could say with high level of certainty, that there is no such answer. The decision should be made based on more than one parameter. Reading the answers below could provide a very good guideline to the types of questions you should be asking yourself when having to decide on this issue. I won't select an accepted answer at this point for the reasons mentioned above.

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  • Organizing code, logical layout of segmented files

    - by David H
    I have known enough about programming to get me in trouble for about 10 years now. I have no formal education, though I've read many books on the subject for various languages. The language I am primarily focused on now would be php, atleast for the scale of things I am doing now. I have used some OOP classes for a while, but never took the dive into understanding principals behind the scenes. I am still not at the level I would like to be expression-wise...however my recent reading into a book titled The OOP Thought Process has me wanting to advance my programming skills. With motivation from the new concepts, I have started with a new project that I've coded some re-usable classes that deal with user auth, user profiles, database interfacing, and some other stuff I use regularly on most projects. Now having split my typical garbled spaghetti bowl mess of code into somewhat organized files, I've come into some problems when it comes to making sure files are all included when they need to be, and how to logically divide the scripts up into classes, aswell as how segmented I should be making each class. I guess I have rambled on enough about much of nothing, but what I am really asking for is advise from people, or suggested reading that focuses not on specific functions and formats of code, but the logical layout of projects that are larger than just a hobby project. I want to learn how to do things proper, and while I am still learning in some areas, this is something that I have no clue about other than just being creative, and trial/error. Mostly error. Thanks for any replies. This place is great.

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