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  • Scalaz: request for use case

    - by oxbow_lakes
    This question isn't meant as flame-bait! As it might be apparent, I've been looking at Scalaz recently. I'm trying to understand why I need some of the functionality that the library provides. Here's something: import scalaz._ import Scalaz._ type NEL[A] = NonEmptyList[A] val NEL = NonEmptyList I put some println statements in my functions to see what was going on (aside: what would I have done if I was trying to avoid side effects like that?). My functions are: val f: NEL[Int] => String = (l: NEL[Int]) => {println("f: " + l); l.toString |+| "X" } val g: NEL[String] => BigInt = (l: NEL[String]) => {println("g: " + l); BigInt(l.map(_.length).sum) } Then I combine them via a cokleisli and pass in a NEL[Int] val k = cokleisli(f) =>= cokleisli(g) println("RES: " + k( NEL(1, 2, 3) )) What does this print? f: NonEmptyList(1, 2, 3) f: NonEmptyList(2, 3) f: NonEmptyList(3) g: NonEmptyList(NonEmptyList(1, 2, 3)X, NonEmptyList(2, 3)X, NonEmptyList(3)X) RES: 57 The RES value is the character count of the (String) elements in the final NEL. Two things occur to me: How could I have known that my NEL was going to be reduced in this manner from the method signatures involved? (I wasn't expecting the result at all) What is the point of this? Can a reasonably simple and easy-to-follow use case be distilled for me? This question is a thinly-veiled plea for some lovely person like retronym to explain how this powerful library actually works.

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  • Query on Booleans in Lambda Calculus

    - by darkie15
    Hi All, I have following query on lambda calculus which am not able to understand: Here is the lambda calculus representation for the AND operator: lambda(m).lambda(n).lambda (a).lambda (b). m(n a b) b Can anyone help me in understanding this representation? Regards, darkie

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  • Genetic Algorithms applied to Curve Fitting

    - by devoured elysium
    Let's imagine I have an unknown function that I want to approximate via Genetic Algorithms. For this case, I'll assume it is y = 2x. I'd have a DNA composed of 5 elements, one y for each x, from x = 0 to x = 4, in which, after a lot of trials and computation and I'd arrive near something of the form: best_adn = [ 0, 2, 4, 6, 8 ] Keep in mind I don't know beforehand if it is a linear function, a polynomial or something way more ugly, Also, my goal is not to infer from the best_adn what is the type of function, I just want those points, so I can use them later. This was just an example problem. In my case, instead of having only 5 points in the DNA, I have something like 50 or 100. What is the best approach with GA to find the best set of points? Generating a population of 100, discard the worse 20% Recombine the remaining 80%? How? Cutting them at a random point and then putting together the first part of ADN of the father with the second part of ADN of the mother? Mutation, how should I define in this kind of problem mutation? Is it worth using Elitism? Any other simple idea worth using around? Thanks

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  • Python equivalent of IDL's stop and .reset

    - by Jamie
    Hi there, I'm relatively new to python but have a bit of experience using IDL. I was wondering if anyone knows if there are equivalent commands in python for IDL's stop and .reset commands. If I'm running some IDL script I wrote that I put a stop command in, essentially what it does is stop the script there and give me access to the command line in the middle of the script. So I have access to all the functions and variables that I defined before the stop command, which I find really useful for debugging. The .reset command I find extremely useful too. What it does is reset the the IDL environment (clears all variables, functions, etc.). It's as if I closed that session and opened a new one, but without having to exit and restart IDL. I find that if I'm trying to debug a script I wrote it's useful sometimes to start from scratch and not have to reset IDL (or python now). It would be useful also in python to be able to un-import any modules I had previously imported. Any help with these issues would be greatly appreciated. Cheers Related Python Drop into REPL Is it possible to go into ipython from code?

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  • C# bluetooth file send.

    - by cheesebunz
    i'm new to bluetooth development and i found the 32netfeet . Right now i'm able to search for bluetooth devices nearby and connect to them but how do i send a file e.g SendTest.txt? I tried buttonclick event using the OBEX but i don't understand this is my example code: using InTheHand.Net; using InTheHand.Net.Sockets; using InTheHand.Net.Bluetooth; namespace BluetoothIntheHand { public partial class Form2 : Form { private Guid service = BluetoothService.DialupNetworking; private BluetoothClient bluetoothClient; public Form2() { InitializeComponent(); } private void btnSearch_Click(object sender, EventArgs e) { BluetoothRadio.PrimaryRadio.Mode = RadioMode.Discoverable; BluetoothRadio myRadio = BluetoothRadio.PrimaryRadio; lblSearch.Text = "" + myRadio.LocalAddress.ToString(); bluetoothClient = new BluetoothClient(); Cursor.Current = Cursors.WaitCursor; BluetoothDeviceInfo[] bluetoothDeviceInfo = { }; bluetoothDeviceInfo = bluetoothClient.DiscoverDevices(10); comboBox1.DataSource = bluetoothDeviceInfo; comboBox1.DisplayMember = "DeviceName"; comboBox1.ValueMember = "DeviceAddress"; comboBox1.Focus(); Cursor.Current = Cursors.Default; } private void btnConnect_Click(object sender, EventArgs e) { if (comboBox1.SelectedValue != null) { try { bluetoothClient.Connect(new BluetoothEndPoint((BluetoothAddress)comboBox1.SelectedValue, service)); MessageBox.Show("Connected"); } catch (Exception ex) { MessageBox.Show(ex.Message); } } } private void btnSend_Click(object sender, EventArgs e) { bluetoothClient.Connect(new BluetoothEndPoint((BluetoothAddress)comboBox1.SelectedValue, service)); String addr = "112233445566"; Uri uri = new Uri("obex://"+@"SendTest.txt"); ObexWebRequest req= new ObexWebRequest(uri); ObexWebResponse rsp; } I found the guide but don't really knw hw to convert to C# ' The host part of the URI is the device address, e.g. IrDAAddress.ToString(), ' and the file part is the OBEX object name. Dim addr As String = "112233445566" Dim uri As New Uri("obex://" & addr & "/HelloWorld2.txt") Dim req As New ObexWebRequest(uri) Using content As Stream = req.GetRequestStream() ' Using a StreamWriter to write text to the stream... Using wtr As New StreamWriter(content) wtr.WriteLine("Hello World GetRequestStream") wtr.WriteLine("Hello World GetRequestStream 2") wtr.Flush() ' Set the Length header value req.ContentLength = content.Length End Using ' In this case closing the StreamWriter also closed the Stream, but ... End Using Dim rsp As ObexWebResponse = CType(req.GetResponse(),ObexWebResponse) Console.WriteLine("Response Code: {0} (0x{0:X})", rsp.StatusCode)

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  • Visual Studio T4 vs CodeSmith

    - by Jake
    I've been using CodeSmith for the past 2 years and love what it does for me. However, I also know about T4 which is built in to Visual Studio and can do some pretty cool stuff too. Based on conversations with friends T4 in VS2010 T4 is going to be even better. So the question is: do I keep riding the CodeSmith bus or is it time to start converting all of my templates to T4?

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  • What's the simplest way to call Http GET url using Delphi?

    - by Mohammed Nasman
    There's a web services I want to call in my application, I can use it with importing the WSDL or by just use "HTTP GET" with the URL and parameters, so I prefer the later because it's simple thing. I know I can use indy idhttp.get, to do the job, but this is very simple thing and I don't want to add complex indy code to my application. UPDATE: sorry if I was not clear, I meant by "not to add complex indy code", that I don't want add indy components for just this simple task, and prefer more lighter way for that.

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  • Where did the "Polymorphism" word come from?

    - by Alon
    I've always wondered where did the word "Polymorphism" word come from. I know what is polymorphism and I use it of course, but I just don't understand why this technique called polymorphism. Note that I'm not a native English speaker, and I will thank you if you'll use simple English in your answers. Thank you.

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  • Do you guys recommend any business magazine? [closed]

    - by kunjaan
    I want to get a birds eye view of the computing industry, read about company profiles, management decisions, new upcoming software companies, learn more about our industry and about the business aspect of my profession. Do you guys read recommend any good business magazines for me to increase my business acumen?

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  • how to stop generating code on a particular button?

    - by coure06
    I am trying to create an input button for my own use in my web-application thats using jquery framework. But when I see the html code in browser, the framework is generating some wrapper code around that input, how to prevent that code to be not generated? my code: <input type="button" value="off" class="toggle-btn" id="toggle-btn1" /> Generated output: <div data-theme="c" class="ui-btn ui-btn-corner-all ui-shadow ui-btn-up-c"> <span class="ui-btn-inner ui-btn-corner-all"> <span class="ui-btn-text">off</span> </span> <input type="button" id="toggle-btn1" class="toggle-btn ui-btn-hidden" value="off"> </div>

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  • Using HTMLAgility Pack to Extract Links

    - by Soham
    Hi Folks, Consider this simplest piece of code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using HtmlAgilityPack; namespace WebScraper { class Program { static void Main(string[] args) { HtmlDocument doc = new HtmlDocument(); doc.LoadHtml("http://www.google.com"); foreach (HtmlNode link in doc.DocumentNode.SelectNodes("//a[@href]")) { } } } } This effectively doesnt do anything at all, and is copied/inspired from various other StackOverflow questions like this. When compiling this, there is a runtime error which says "Object reference not set to an instance of an object." highlighting the foreach line. I can't understand, why the environment has become irritable to this humble,innocent and useless piece of code. I would also like to know, does HTMLAgilityPack accept HTML classes as nodes?

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  • Web serivce time out errors in delphi

    - by JD
    Hi, I have a client application that makes SOAP requests. I have set the timeout to 20 minutes. However, sometimes I see the timeout error occurring after 10 seconds. I have the following in code: RIO.HTTPWebNode.ReceiveTimeout := 1200000 Do I need to set the ConnectTimeout and SendTimeOut? Currently they are set to the default values of 0. What difference would setting these make? I am using Delphi 2007. Looking further at the error message I see I get "The operation timed out....". So should I be setting my ReceiveTimeOut to zero since I really do not want any timeout at all?

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  • picturebox image randomisation C#

    - by cheesebunz
    Hi everyone, i am working on a puzzle slider program and trying to randomize images inside of pictureboxes. I did some research on the internet can't find any examples i could work on. These are my code: Random r = new Random(); PictureBox[] picBox = new PictureBox[9]; picBox[0] = new PictureBox(); picBox[1] = new PictureBox(); picBox[2] = new PictureBox(); picBox[3] = new PictureBox(); picBox[4] = new PictureBox(); picBox[5] = new PictureBox(); picBox[6] = new PictureBox(); picBox[7] = new PictureBox(); picBox[8] = new PictureBox(); i have bitmap array too: Bitmap[] pictures = new Bitmap[9]; pictures[0] = new Bitmap(@"1.1Bright.jpg"); pictures[1] = new Bitmap(@"1.2Bright.jpg"); pictures[2] = new Bitmap(@"1.3Bright.jpg"); pictures[3] = new Bitmap(@"2.1Bright.jpg"); pictures[4] = new Bitmap(@"2.2Bright.jpg"); pictures[5] = new Bitmap(@"2.3Bright.jpg"); pictures[6] = new Bitmap(@"3.1Bright.jpg"); pictures[7] = new Bitmap(@"3.2Bright.jpg"); pictures[8] = new Bitmap(@"3.3Dark.jpg"); i tried a few ways but i don't know how to set random pictures[] into the picBox[]: for(int i=0; i<=8;i++) { picBox[i].Image= pictures[r.Next(0,9)]; } the problem here is that some pictureboxes e.g picBox[1] and picBox[6] are repeated pictures. How do i make them non repeats? Examples are greatly appreciated thanks.

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  • Generic Data Structure Description Language

    - by Jon Purdy
    I am wondering whether there exists any declarative language for arbitrarily describing the format and semantics of a data structure, that can be compiled to a specific implementation of that structure in any of a set of target languages. That is, something like a generic data definition language but geared toward describing arbitrary data structures such as vectors, lists, trees, etc., and the semantics of operations on those structures. I ask because I had an idea for a feasible implementation of this concept, and I'm just wondering whether it's worth it, and, consequently, whether it's been done before. Another, slightly more abstract question: is there any real difference between the normative specification of a data structure (what it does) and its implementation (how it does it)?

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  • When is calculating or variable-reading faster?

    - by Andreas Hornig
    hi, to be honest, I don't really know what the "small green men" in my cpu and compiler do, so I sometimes would like to know :). Currently I would like to know what's faster, so that I can design my code in a more efficient way. So for example I want to calclate something at different points in my sourcecode, when will it be faster to calculate it once and store it in a variable that's read and used for the next points it's needed and when is it faster to calculate it everytime? I think it's depending on how "complex" and "long" the calculation is and how fast then cache is, where variables are stored, but I don't have any clue what's faster :). Thanks for any reply to my tiny but important question! Andreas PS: perhaps it's important to know that I code in JAVA, but it's more a genral question.

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  • Why not allow mutation of the this binding?

    - by gnucom
    Hi Everyone, I'm building a interpreter/compiler for a school project (well now its turning into a hobby project) and an instructor warned me not to allow mutation of the 'this' binding (he said it was gross and made a huge deal about it) but I never learned why this is so... dangerous or bad. I'm very curious about why this is so bad. I figured this sort of feature could be useful in some way or another. I'm wondering if anyone familiar with building languages can tell me what sort of problems mutation on the 'this' binding can cause, and if they know of any cool or useful tricks that one could do if it actually was allowed. Do any languages that you're aware of allow mutation of 'this'? Thanks,

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  • Phone Application For .Net

    - by Terry
    Hello guys, As a .net developer main c#, I want to know what would be the best approach for me to develop Phone application that runs on major phones. Just to let you know Iphone is out of the question because of the costs that are involved, not ready to buy Mac book. I want something I can develop within Windows operating system, Android could have been the best option but it does not integrated well with .net. Any idea please ? Terry

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  • How do I test OpenCL on GPU when logged in remotely on Mac?

    - by Christopher Bruns
    My OpenCL program can find the GPU device when I am logged in at the console, but not when I am logged in remotely with ssh. Further, if I run the program as root in the ssh session, the program can find the GPU. The computer is a Snow Leopard Mac with a GeForce 9400 GPU. If I run the program (see below) from the console or as root, the output is as follows (notice the "GeForce 9400" line): 2 devices found Device #0 name = GeForce 9400 Device #1 name = Intel(R) Core(TM)2 Duo CPU P8700 @ 2.53GHz but if it is just me, over ssh, there is no GeForce 9400 entry: 1 devices found Device #0 name = Intel(R) Core(TM)2 Duo CPU P8700 @ 2.53GHz I would like to test my code on the GPU without having to be root. Is that possible? Simplified GPU finding program below: #include <stdio.h> #include <OpenCL/opencl.h> int main(int argc, char** argv) { char dname[500]; size_t namesize; cl_device_id devices[10]; cl_uint num_devices; int d; clGetDeviceIDs(0, CL_DEVICE_TYPE_ALL, 10, devices, &num_devices); printf("%d devices found\n", num_devices); for (d = 0; d < num_devices; ++d) { clGetDeviceInfo(devices[d], CL_DEVICE_NAME, 500, dname, &namesize); printf("Device #%d name = %s\n", d, dname); } return 0; } EDIT: I found essentially the same question being asked on nvidia's forums. Unfortunately, the only answer was of the form "this is the wrong forum".

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  • Web Sockets: Browser won't receive the message, complains about it not starting with 0x00 (byte)

    - by giggsey
    Here is my code: import java.net.*; import java.io.*; import java.util.*; import org.jibble.pircbot.*; public class WebSocket { public static int port = 12345; public static ArrayList<WebSocketClient> clients = new ArrayList<WebSocketClient>(); public static ArrayList<Boolean> handshakes = new ArrayList<Boolean>(); public static ArrayList<String> nicknames = new ArrayList<String>(); public static ArrayList<String> channels = new ArrayList<String>(); public static int indexNum; public static void main(String args[]) { try { ServerSocket ss = new ServerSocket(WebSocket.port); WebSocket.console("Created socket on port " + WebSocket.port); while (true) { Socket s = ss.accept(); WebSocket.console("New Client connecting..."); WebSocket.handshakes.add(WebSocket.indexNum,false); WebSocket.nicknames.add(WebSocket.indexNum,""); WebSocket.channels.add(WebSocket.indexNum,""); WebSocketClient p = new WebSocketClient(s,WebSocket.indexNum); Thread t = new Thread( p); WebSocket.clients.add(WebSocket.indexNum,p); indexNum++; t.start(); } } catch (Exception e) { WebSocket.console("ERROR - " + e.toString()); } } public static void console(String msg) { Date date = new Date(); System.out.println("[" + date.toString() + "] " + msg); } } class WebSocketClient implements Runnable { private Socket s; private int iAm; private String socket_res = ""; private String socket_host = ""; private String socket_origin = ""; protected String nick = ""; protected String ircChan = ""; WebSocketClient(Socket socket, int mynum) { s = socket; iAm = mynum; } public void run() { String client = s.getInetAddress().toString(); WebSocket.console("Connection from " + client); IRCclient irc = new IRCclient(iAm); Thread t = new Thread( irc ); try { Scanner in = new Scanner(s.getInputStream()); PrintWriter out = new PrintWriter(s.getOutputStream(),true); while (true) { if (! in.hasNextLine()) continue; String input = in.nextLine().trim(); if (input.isEmpty()) continue; // Lets work out what's wrong with our input if (input.length() > 3 && input.charAt(0) == 65533) { input = input.substring(2); } WebSocket.console("< " + input); // Lets work out if they authenticate... if (WebSocket.handshakes.get(iAm) == false) { checkForHandShake(input); continue; } // Lets check for NICK: if (input.length() > 6 && input.substring(0,6).equals("NICK: ")) { nick = input.substring(6); Random generator = new Random(); int rand = generator.nextInt(); WebSocket.console("I am known as " + nick); WebSocket.nicknames.set(iAm, "bo-" + nick + rand); } if (input.length() > 9 && input.substring(0,9).equals("CHANNEL: ")) { ircChan = "bo-" + input.substring(9); WebSocket.console("We will be joining " + ircChan); WebSocket.channels.set(iAm, ircChan); } if (! ircChan.isEmpty() && ! nick.isEmpty() && irc.started == false) { irc.chan = ircChan; irc.nick = WebSocket.nicknames.get(iAm); t.start(); continue; } else { irc.msg(input); } } } catch (Exception e) { WebSocket.console(e.toString()); e.printStackTrace(); } t.stop(); WebSocket.channels.remove(iAm); WebSocket.clients.remove(iAm); WebSocket.handshakes.remove(iAm); WebSocket.nicknames.remove(iAm); WebSocket.console("Closing connection from " + client); } private void checkForHandShake(String input) { // Check for HTML5 Socket getHeaders(input); if (! socket_res.isEmpty() && ! socket_host.isEmpty() && ! socket_origin.isEmpty()) { send("HTTP/1.1 101 Web Socket Protocol Handshake\r\n" + "Upgrade: WebSocket\r\n" + "Connection: Upgrade\r\n" + "WebSocket-Origin: " + socket_origin + "\r\n" + "WebSocket-Location: ws://" + socket_host + "/\r\n\r\n",false); WebSocket.handshakes.set(iAm,true); } return; } private void getHeaders(String input) { if (input.length() >= 8 && input.substring(0,8).equals("Origin: ")) { socket_origin = input.substring(8); return; } if (input.length() >= 6 && input.substring(0,6).equals("Host: ")) { socket_host = input.substring(6); return; } if (input.length() >= 7 && input.substring(0,7).equals("Cookie:")) { socket_res = "."; } /*input = input.substring(4); socket_res = input.substring(0,input.indexOf(" HTTP")); input = input.substring(input.indexOf("Host:") + 6); socket_host = input.substring(0,input.indexOf("\r\n")); input = input.substring(input.indexOf("Origin:") + 8); socket_origin = input.substring(0,input.indexOf("\r\n"));*/ return; } protected void send(String msg, boolean newline) { byte c0 = 0x00; byte c255 = (byte) 0xff; try { PrintWriter out = new PrintWriter(s.getOutputStream(),true); WebSocket.console("> " + msg); if (newline == true) msg = msg + "\n"; out.print(msg + c255); out.flush(); } catch (Exception e) { WebSocket.console(e.toString()); } } protected void send(String msg) { try { WebSocket.console(">> " + msg); byte[] message = msg.getBytes(); byte[] newmsg = new byte[message.length + 2]; newmsg[0] = (byte)0x00; for (int i = 1; i <= message.length; i++) { newmsg[i] = message[i - 1]; } newmsg[message.length + 1] = (byte)0xff; // This prints correctly..., apparently... System.out.println(Arrays.toString(newmsg)); OutputStream socketOutputStream = s.getOutputStream(); socketOutputStream.write(newmsg); } catch (Exception e) { WebSocket.console(e.toString()); } } protected void send(String msg, boolean one, boolean two) { try { WebSocket.console(">> " + msg); byte[] message = msg.getBytes(); byte[] newmsg = new byte[message.length+1]; for (int i = 0; i < message.length; i++) { newmsg[i] = message[i]; } newmsg[message.length] = (byte)0xff; // This prints correctly..., apparently... System.out.println(Arrays.toString(newmsg)); OutputStream socketOutputStream = s.getOutputStream(); socketOutputStream.write(newmsg); } catch (Exception e) { e.printStackTrace(); } } } class IRCclient implements Runnable { protected String nick; protected String chan; protected int iAm; boolean started = false; IRCUser irc; IRCclient(int me) { iAm = me; irc = new IRCUser(iAm); } public void run() { WebSocket.console("Connecting to IRC..."); started = true; irc.setNick(nick); irc.setVerbose(false); irc.connectToIRC(chan); } void msg(String input) { irc.sendMessage("#" + chan, input); } } class IRCUser extends PircBot { int iAm; IRCUser(int me) { iAm = me; } public void setNick(String nick) { this.setName(nick); } public void connectToIRC(String chan) { try { this.connect("irc.appliedirc.com"); this.joinChannel("#" + chan); } catch (Exception e) { WebSocket.console(e.toString()); } } public void onMessage(String channel, String sender,String login, String hostname, String message) { // Lets send this message to me WebSocket.clients.get(iAm).send(message); } } Whenever I try to send the message to the browser (via Web Sockets), it complains that it doesn't start with 0x00 (which is a byte). Any ideas? Edit 19/02 - Added the entire code. I know it's real messy and not neat, but I want to get it functioning first. Spend last two days trying to fix.

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