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  • Make All Types Constant by Default in C++

    - by Jon Purdy
    What is the simplest and least obtrusive way to indicate to the compiler, whether by means of compiler options, #defines, typedefs, or templates, that every time I say T, I really mean T const? I would prefer not to make use of an external preprocessor. Since I don't use the mutable keyword, that would be acceptable to repurpose to indicate mutable state. Potential (suboptimal) solutions so far: // I presume redefinition of keywords is implementation-defined or illegal. #define int int const #define ptr * const int i(0); int ptr j(&i); typedef int const Int; typedef int const* const Intp; Int i(0); Intp j(&i); template<class T> struct C { typedef T const type; typedef T const* const ptr; }; C<int>::type i(0); C<int>::ptr j(&i);

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  • Interpreted languages: The higher-level the faster?

    - by immersion
    I have designed around 5 experimental languages and interpreters for them so far, for education, as a hobby and for fun. One thing I noticed: The assembly-like language featuring only subroutines and conditional jumps as structures was much slower than the high-level language featuring if, while and so on. I developed them both simultaneously and both were interpreted languages. I wrote the interpreters in C++ and I tried to optimize the code-execution part to be as fast as possible. My hypothesis: In almost all cases, performance of interpreted languages rises with their level (high/low). Am I basically right with this? (If not, why?)

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  • Testing for a closed socket

    - by Robert S. Barnes
    I'm trying to test for a closed socket that has been gracefully closed by the peer without incurring the latency hit of a double send to induce a SIGPIPE. One of the assumptions here is that the socket if closed was gracefully closed by the peer immediately after it's last write / send. Actual errors like a premature close are dealt with else where in the code. If the socket is still open, there will be 0 or more bytes data which I don't actually want to pull out of the socket buffer yet. I was thinking that I could call int ret = recv(sockfd, buf, 1, MSG_DONTWAIT | MSG_PEEK); to determine if the socket is still connected. If it's connected but there's no data in the buffer I'll get a return of -1 with errno == EAGAIN and return the sockfd for reuse. If it's been gracefully closed by the peer I'll get ret == 0 and open a new connection. I've tested this and it seems to work. However, I suspect there is a small window between when I recv the last bit of my data and when the peer FIN arrives in which I could get a false-positive EAGAIN from my test recv. Is this going to bite me, or is there a better way of doing this?

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  • Javascript - Wait for function to return

    - by LoadData
    So, I am working on a project which requires me to call upon a function to get data from an external source. The issue I am having, I call upon the function - However the code after the function call is continuing before the function has returned a value. Here is the function - function getData() { var myVar; var xmlLoc = $.get("http://ec.urbentom.co.uk/StudentAppData.xml", function(data) { $xml = $(data); myVar = $xml; console.log(myVar); console.log(String($xml)); localStorage.setItem("Data", $xml); console.log(String(localStorage.getItem("Data"))); return myVar; }); return myVar; console.log("Does this continue"); } And here is where it is called upon - $(document).on("pageshow","#Information",function() { $xml = $(getData()); //Here is the function call console.log($xml); //However, it will instantly go to this line before 'getData' has returned a value. $xml.find('AllData').each(function() { $(this).find('item').each(function() { if ($(this).find('Category').text()=="Facilities") { console.log($(this).find('Title').text()); //Do stuff here } else if ($(this).find('Category').text()=="Contacts" || $(this).find('Category').text()=="Information") { console.log($(this).find('Title').text()); //Do stuff here too } }); $('#informationList').html(output).listview().listview("refresh"); console.log("Finished"); }); }); Right now, I'm unsure of why it is not working. My guess is that it is because I am calling a function within a function. Does anyone have any ideas on how this issue can be fixed?

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  • Custom collision

    - by bali182
    I was recently assigned to create a siple game using the Corona SDK. The main pillar of the game would be a simple event: the user should put a ball in a basket, and I should be able to handle this event. Here is a picture for better understanding: I successfully managed to create the collision shape for the basket, but i have trouble with the collision of the inside of this basket. My first thought was the following: create a new shape size and position it to fit the "belly" of this basket add it to the physics-world, and listen to the collision. With hybrid drawing it looks like this: But there is a problem: if i add this shape to the physics, it wouldn't let the ball fall into the, basket, it will handle this shape as a solid object as well. So my question is: How could I get this custom object to collide, without blocking the ball to fall through it? I have read a lots of forum post with similar questions but none of them got a proper answer. There must be a way to do this in an elegant way. And one note: Please don't suggest checking the collision manually, with rectangle intersection, because in this simple case it would work, but later I may need to change the shape of the basket, and then it will be useless!

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  • Dividing a list in specific number of sublists

    - by Surya
    I want to divide a list in "a specific number of" sublists. That is, for example if I have a list List(34, 11, 23, 1, 9, 83, 5) and the number of sublists expected is 3 then I want List(List(34, 11), List(23, 1), List(9, 83, 5)). How do I go about doing this? I tried grouped but it doesn't seem to be doing what I want. PS: This is not a homework question. Kindly give a direct solution instead of some vague suggestions.

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  • Socket send recv functions

    - by viswanathan
    I have created a socket using the following lines of code. Now i change the value of the socket i get like this m_Socket++; Even now the send recv socket functions succeeds without throwing SOCKET_ERROR. I expect that it must throw error. Am i doing something wrong. struct sockaddr_in ServerSock; // Socket address structure to bind the Port Number to listen to char *localIP ; SOCKET SocServer; //To Set up the sockaddr structure ServerSock.sin_family = AF_INET; ServerSock.sin_addr.s_addr = INADDR_ANY; ServerSock.sin_port = htons(pLantronics->m_wRIPortNo); // To Create a socket for listening on wPortNumber if(( SocServer = socket( AF_INET, SOCK_STREAM, 0 )) == INVALID_SOCKET ) { return FALSE; } //To bind the socket with wPortNumber if(bind(SocServer,(sockaddr*)&ServerSock,sizeof(ServerSock))!=0) { return FALSE; } // To Listen for the connection on wPortNumber if(listen(SocServer,SOMAXCONN)!=0) { return FALSE; } // Structure to get the IP Address of the connecting Entity sockaddr_in insock; int insocklen=sizeof(insock); //To accept the Incoming connection on the wPortNumber pLantronics->m_Socket=accept(SocServer,(struct sockaddr*)&insock,&insocklen); if(pLantronics->m_Socket == INVALID_SOCKET) { shutdown(SocServer, 2 ); closesocket(SocServer ); return FALSE; } // To make socket non-blocking DWORD dwNonBlocking = 1; if(ioctlsocket( pLantronics->m_Socket, FIONBIO, &dwNonBlocking )) { shutdown(pLantronics->m_Socket, 2); closesocket(pLantronics->m_Socket); return FALSE; } pLantronics->m_sModemName = inet_ntoa(insock.sin_addr); Now i do m_Socket++;//change to some other number ideally expecting send recv to fail. Even now the send recv socket functions succeeds without throwing SOCKET_ERROR. I expect that it must throw error. Am i doing something wrong.

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  • Is it possible to draw simultaneously on a panel?

    - by swift
    I have to develop a whiteboard application in which both the local user and the remote user should be able to draw simultaneously, is this possible? If possible then any logic? I have already developed a code but in which i am not able to do this, when the remote user starts drawing the shape which i am drawing is being replaced by his shape and co-ordinates. This problem is only when both draw simultaneously. any idea guys?

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  • twisted .loseConnection does not immediately lose connection?

    - by Claudiu
    I have a server with a few clients connected to it. When CTRL+C is hit (that is, reactor starts shutting down), I want to close all my connections, wait until they are cleanly closed, and then stop. I do this by going through the connected clients' transports and calling .loseConnection(). On the ones that are connected locally, they immediately disconnect. However, on one that is connected through the internet, the connection is not immediately lost. Communication stops - and closing the client program no longer even tells the server that the connection has died, although it does before calling .loseConnection() - but the connection is not deemed 'lost' until a few minutes later after I send a few heartbeat requests from the server. I understand that if a connection dies, there's no way for the server to know unless it tries to send some data. But if I specifically ask for a connection to be closed, why does it not just close/disconnect immediately? Am I calling the wrong function?

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  • how to send text to a process in a shell script?

    - by Martin
    So I have a Linux program that runs in a while(true) loop, which waits for user input, process it and print result to stdout. I want to write a shell script that open this program, feed it lines from a txt file, one line at a time and save the program output for each line to a file. So I want to know if there is any command for: - open a program - send text to a process - receive output from that program Many thanks.

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  • How to get at TCP RTT on Windows (Linux TCP_INFO) as an user

    - by FredAlkin
    I am porting a streaming TCP app from Linux to Windows. The app streams real-time audio data using a preexisting TCP protocol (so switching to UDP isn't an option). Further, I wish to avoid being "part of the problem" and requiring Administrator rights. The Linux code uses getsockopt(... ,SOL_TCP, TCP_INFO, ..) to get the RTT (round trip time) information from the TCP connection. The application level uses this to throttle the amount of data sent over the connection (apparently to balance quality with latency). Is there an equivalent to TCP_INFO on WIndows? (google tells me that Win2K and later supports "TCP Timestamps" which would provide this information, but I've yet to find a way to get at it. Thanks in advance.

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  • Having trouble getting GET variables from url.

    - by mchl
    Hey everyone, I'm having trouble with this algorithm to extract the get variables from a url and print them each on a new line like: x=y z=hello etc. but instead it prints a seemingly random section of the url with no newlines to the file. There must be a logic error of some kind but i just can't spot it. for(i_m=0;i_m<len_m;i_m++) { if(var_m[i_m]=='&') { fwrite(var_m+offset_m, 1, amp_m, echo_out); fputc('\n',echo_out); offset_m+=amp_m; amp_m=0; } amp_m++; } any help appreciated.

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  • Why can I not have two SocketServers bound to two different ports in the same application?

    - by uriDium
    I am using .Net 3.5 and Windows XP not sure if any more information is needed. I have an application that creates a socket, binds to a port and starts listening. A client comes and connects and then disconnects no problem. It can then reconnect no problem. If I have to sockets each listening on a different (e.g. 50 000 and 55 000) then it will accept the connection but it will not allow a reconnect. I will post source code if needed but I am assuming that it is just something simple that I am not catching.

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  • How to delete Drawn Line in java?

    - by Jeyjey
    Hello Folks, well this is my code: import javax.swing.; import javax.; import java.awt.; import java.awt.Color; import java.awt.Graphics.; import java.awt.event.*; import javax.swing.UIManager; public class SimpleGUI extends JFrame{ public SimpleGUI(){ this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ; } public void go(){ Drawpanel = new Mypanel(); JFrame frame = new JFrame("Chasing Line"); frame.getContentPane().add(BorderLayout.CENTER, Drawpanel); frame.setSize(300,300); frame.setVisible(true); Drawpanel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() { public void mouseMoved(java.awt.event.MouseEvent evt) { DrawpanelMouseMoved(evt); } }); } public void DrawpanelMouseMoved(java.awt.event.MouseEvent evt) { xpos=evt.getX(); ypos=evt.getY(); System.out.println("Coordinates : X :"+ xpos+"Y: "+ypos); Drawpanel.paintImage(xpos,ypos); } class Mypanel extends JPanel{ public void paintImage(int xpost,int ypost){ Graphics d = getGraphics(); d.setColor(Color.black); d.drawLine(xpost, 0, xpost, this.getHeight()); d.setColor(Color.red); d.drawLine(0, ypost, this.getWidth(),ypost); this.validate(); } } // end the inner class public static void main(String[] args){ try { UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); } catch(Exception e) { System.err.println("Look and feel not set"); } SimpleGUI win = new SimpleGUI(); win.go(); } Mypanel Drawpanel; private int xpos=0; private int ypos=0; } // close SimpleGUI class The problem is how can i delete the old lines?, i mea,make only the current x and y lines appear on the screen, make the intersection between both lines "follow" the mouse pointer. thanks for any reply.

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  • F# - Function with no arguments?

    - by Rubys
    When thinking in a functional mindset, given that functions are supposed to be pure, one can conclude any function with no arguments is basically just a value. However, reallity gets in the way, and with different inputs, I might not need a certain function, and if that function is computationally expensive, I'd like to not evaluate it if it's not needed. I found a workaround, using let func _ = ... and calling it with func 1 or whatever, but that feels very non-idiomatic and confusing to the reader. This boils down to one question: In F#, Is there a proper way to declare a function with zero arguments, without having it evaluated on declaration?

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