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  • How can I use functools.partial on multiple methods on an object, and freeze parameters out of order

    - by Joseph Garvin
    I find functools.partial to be extremely useful, but I would like to be able to freeze arguments out of order (the argument you want to freeze is not always the first one) and I'd like to be able to apply it to several methods on a class at once, to make a proxy object that has the same methods as the underlying object except with some of its methods parameter being frozen (think of it as generalizing partial to apply to classes). I've managed to scrap together a version of functools.partial called 'bind' that lets me specify parameters out of order by passing them by keyword argument. That part works: >>> def foo(x, y): ... print x, y ... >>> bar = bind(foo, y=3) >>> bar(2) 2 3 But my proxy class does not work, and I'm not sure why: >>> class Foo(object): ... def bar(self, x, y): ... print x, y ... >>> a = Foo() >>> b = PureProxy(a, bar=bind(Foo.bar, y=3)) >>> b.bar(2) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: bar() takes exactly 3 arguments (2 given) I'm probably doing this all sorts of wrong because I'm just going by what I've pieced together from random documentation, blogs, and running dir() on all the pieces. Suggestions both on how to make this work and better ways to implement it would be appreciated ;) One detail I'm unsure about is how this should all interact with descriptors. Code follows. from types import MethodType class PureProxy(object): def __init__(self, underlying, **substitutions): self.underlying = underlying for name in substitutions: subst_attr = substitutions[name] if hasattr(subst_attr, "underlying"): setattr(self, name, MethodType(subst_attr, self, PureProxy)) def __getattribute__(self, name): return getattr(object.__getattribute__(self, "underlying"), name) def bind(f, *args, **kwargs): """ Lets you freeze arguments of a function be certain values. Unlike functools.partial, you can freeze arguments by name, which has the bonus of letting you freeze them out of order. args will be treated just like partial, but kwargs will properly take into account if you are specifying a regular argument by name. """ argspec = inspect.getargspec(f) argdict = copy(kwargs) if hasattr(f, "im_func"): f = f.im_func args_idx = 0 for arg in argspec.args: if args_idx >= len(args): break argdict[arg] = args[args_idx] args_idx += 1 num_plugged = args_idx def new_func(*inner_args, **inner_kwargs): args_idx = 0 for arg in argspec.args[num_plugged:]: if arg in argdict: continue if args_idx >= len(inner_args): # We can't raise an error here because some remaining arguments # may have been passed in by keyword. break argdict[arg] = inner_args[args_idx] args_idx += 1 f(**dict(argdict, **inner_kwargs)) new_func.underlying = f return new_func

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  • Java: Is clone() really ever used? What about defensive copying in getters/setters?

    - by GreenieMeanie
    Do people practically ever use defensive getters/setters? To me, 99% of the time you intend for the object you set in another object to be a copy of the same object reference, and you intend for changes you make to it to also be made in the object it was set in. If you setDate(Date dt) and modify dt later, who cares? Unless I want some basic immutable data bean that just has primitives and maybe something simple like a Date, I never use it. As far as clone, there are issues as to how deep or shallow the copy is, so it seems kind of "dangerous" to know what is going to come out when you clone an Object. I think I have only used clone() once or twice, and that was to copy the current state of the object because another thread (ie another HTTP request accessing the same object in Session) could be modifying it. Edit - A comment I made below is more the question: But then again, you DID change the Date, so it's kind of your own fault, hence whole discussion of term "defensive". If it is all application code under your own control among a small to medium group of developers, will just documenting your classes suffice as an alternative to making object copies? Or is this not necessary, since you should always assume something ISN'T copied when calling a setter/getter?

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  • How to File Transfer client to Server?

    - by Phsika
    i try to recieve a file from server but give me error on server.Start() ERROR : In a manner not permitted by the access permissions to access a socket was attempted to How can i solve it? private void btn_Recieve_Click(object sender, EventArgs e) { TcpListener server = null; // Set the TcpListener on port 13000. Int32 port = 13000; IPAddress localAddr = IPAddress.Parse("192.168.1.201"); // TcpListener server = new TcpListener(port); server = new TcpListener(localAddr, port); // Start listening for client requests. server.Start(); // Buffer for reading data Byte[] bytes = new Byte[277577]; String data; data = null; // Perform a blocking call to accept requests. // You could also user server.AcceptSocket() here. TcpClient client = server.AcceptTcpClient(); NetworkStream stream = client.GetStream(); int i; i = stream.Read(bytes, 0, 277577); BinaryWriter writer = new BinaryWriter(File.Open("GoodLuckToMe.jpg", FileMode.Create)); writer.Write(bytes); writer.Close(); client.Close(); }

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  • Python: Cannot concatenate str and NoneType objects

    - by Chase Higgins
    sql = """ INSERT INTO [SCHOOLINFO] VALUES( '""" + self.accountNo + """', '""" + self.altName + """', '""" + self.address1 + """', '""" + self.address2 + """', '""" + self.city + """', '""" + self.state + """', '""" + self.zipCode + """', '""" + self.phone1 + """', '""" + self.phone2 + """', '""" + self.fax + """', '""" + self.contactName + """', '""" + self.contactEmail + """', '""" + self.prize_id + """', '""" + self.shipping + """', '""" + self.chairTempPass + """', '""" + self.studentCount + """' ) """; I have the following code and Python keeps throwing the error that it cannon concatenate strings and nonetype objects. The thing is I have verified every variable here is in fact a string and is not null. I have been stuck on this for quite some time today, and any help would be greatly appreciated.

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  • How to handle Socket Exception ideally?

    - by cbz
    Hi, I'm using socket for chat application and I get SocketException unexpectedly. How this exception should ideally be handled? I'm currently simply reconnecting socket. How to make sure my socket is live on application level? I'm aware of method setKeepAlive

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  • List of Lua derived VMs and Languages

    - by Shane Holloway
    Is there a compendium of virtual machines and languages derived or inspired by Lua? By derived, I mean usage beyond embedding and extending with modules. I'm wanting to research the Lua technology tree, and am looking for our combined knowledge of what already exists. Current List: Bright - A C-like Lua Derivative http://bluedino.net/luapix/Bright.pdf Agena - An Algol68/SQL like Lua Derivative http://agena.sourceforge.net/ LuaJIT - A (very impressive) JIT for Lua http://luajit.org MetaLua - An ML-style language extension http://metalua.luaforge.net/

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  • Why does this Object wonk out & get deleted ?

    - by brainydexter
    Stepping through the debugger, the BBox object is okay at the entry of the function, but as soon as it enters the function, the vfptr object points to 0xccccc. I don't get it. What is causing this ? Why is there a virtual table reference in there when the object is not derived from other class. (Though, it resides in GameObject from which my Player class inherits and I retrieve the BBox from within player. But, why does the BBox have the reference ? Shouldn't it be player who should be maintained in that reference ?) For 1; some code for reference: A. I retrieve the bounding box from player. This returns a bounding box as expected. I then send its address to GetGridCells. const BoundingBox& l_Bbox = l_pPlayer-GetBoundingBox(); boost::unordered_set < Cell*, CellPHash & l_GridCells = GetGridCells ( &l_Bbox ); B. This is where a_pBoundingBox goes crazy and gets that garbage value. boost::unordered_set< Cell*, CellPHash CollisionMgr::GetGridCells(const BoundingBox *a_pBoundingBox) { I think the following code is also pertinent, so I'm sticking this in here anyways: const BoundingBox& Player::GetBoundingBox(void) { return BoundingBox( &GetBoundingSphere() ); } const BoundingSphere& Player::GetBoundingSphere(void) { BoundingSphere& l_BSphere = m_pGeomMesh-m_BoundingSphere; l_BSphere.m_Center = GetPosition(); return l_BSphere; } // BoundingBox Constructor BoundingBox(const BoundingSphere* a_pBoundingSphere); Can anyone please give me some idea as to why this is happening? Also, if you want me to post more code, please do let me know. Thanks!

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  • How to counter the "one true language" perspective?

    - by Rob Wells
    How do you work with someone when they haven't been able to see that there is a range of other languages out there beyond "The One True Path"? I mean someone who hasn't realised that the modern software professional has a range of tools in his toolbox. The person whose knee jerk reaction is, for example, "We must do this is C++!" "Everything must be done in C++!" What's the best approach to open people up to the fact that "not everything is a nail"? How may I introduce them to having a well-equipped toolbox, selecting the best tool for the job at hand?

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  • packet mmap send packet format

    - by SeregASM
    I want to improve packet transmitting performance. Before that I used raw sockets and now I study packet_mmap. I have packets(frames) which I already captured from kernel module from another PC, put to current PC and now I want to retransmit them to local interface with following forwarding. I have got example of packet_mmap, integrated it to my project, but I send fd_socket = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); memset(&my_addr, 0, sizeof(struct sockaddr_ll)); my_addr.sll_family = PF_PACKET; my_addr.sll_protocol = htons(ETH_P_ALL); strcpy(str_devname, "eth0"); strncpy(s_ifr.ifr_name, str_devname, sizeof(s_ifr.ifr_name)); ec = ioctl(fd_socket, SIOCGIFINDEX, &s_ifr); i_ifindex = s_ifr.ifr_ifindex; memset(&my_addr, 0, sizeof(struct sockaddr_ll)); my_addr.sll_family = AF_PACKET; my_addr.sll_protocol = ETH_P_ALL; my_addr.sll_ifindex = i_ifindex; bind(fd_socket, (struct sockaddr *) &my_addr, sizeof(struct sockaddr_ll) s_packet_req.tp_block_size = c_buffer_sz; s_packet_req.tp_frame_size = c_buffer_sz; s_packet_req.tp_block_nr = c_buffer_nb; s_packet_req.tp_frame_nr = c_buffer_nb; size = s_packet_req.tp_block_size * s_packet_req.tp_block_nr; if (setsockopt(fd_socket, SOL_PACKET, PACKET_TX_RING, (char *) &s_packet_req, sizeof(s_packet_req)) < 0) { perror("setsockopt: PACKET_TX_RING"); return; } if (c_sndbuf_sz) { printf("send buff size = %d\n", c_sndbuf_sz); if (setsockopt(fd_socket, SOL_SOCKET, SO_SNDBUF, &c_sndbuf_sz, sizeof(c_sndbuf_sz)) < 0){ perror("getsockopt: SO_SNDBUF"); exit(1); } } data_offset = TPACKET_HDRLEN - sizeof(struct sockaddr_ll); printf("data offset = %d bytes\n", data_offset); ps_header_start = (tpacket_hdr *) mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_socket, 0); if (ps_header_start == (void*) -1) { perror("mmap"); exit(1); } Then I fill data ps_header = ((struct tpacket_hdr *) ((char *) ps_header_start + (c_buffer_sz * i_index))); if (!ps_header) { perror("ps_header") ; return NULL; } data = ((char*) ps_header) + data_offset; switch ((volatile uint32_t) ps_header->tp_status) { case TP_STATUS_AVAILABLE: printf("TP_STATUS_AVAILABLE, index=%d\n",i_index) ; memcpy(data, packet_data, size); pthread_mutex_lock(&index_locker) ; i_index++; pthread_mutex_unlock(&index_locker) ; if (i_index >= c_buffer_nb) { i_index = 0; first_loop = 0; } /* update packet len */ ps_header->tp_len = size; /* set header flag to USER (trigs xmit)*/ ps_header->tp_status = TP_STATUS_SEND_REQUEST; then I send ec_send = sendto(fd_socket, NULL, 0, 0, (struct sockaddr *) ps_sockaddr, sizeof(struct sockaddr_ll)); I have got no errors, ec_send=not null size of sended data. But there are no data routed to destination host. So, I ask - what data I should pass to ring buffer, now I include headers ip,tcp, should I include MAC header? - May be I have to set additional flags to route my packets.

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  • F# exercise help - Beginner

    - by bobjink
    I hope you can help me with these exercises I have been stuck with. I am not in particular looking for the answers. Tips that help me solve them myself are just as good :) 1. Write a function implode : char list - string so that implode s returns the characters concatenated into a string: let implode (cArray:char list) = List.foldBack (+) 0 cArray;; Error. I am thinking that i need to cast every char to strings before I do the above. I bet however, that there is a much simpler and better solution. 2. Write a function palindrome : string - bool, so that palindrome s returns true if the string s is a palindrome let isIdentical cArray1 cArray2 = (cArray1 = cArray2);; let palinDrome (word:string) = isIdentical(word.ToCharArray(), Array.rev(word.ToCharArray()));; I get the value: val palinDrome : string - (char [] * char [] - bool), which is not what I want. 3. Write a function combinePair : int list - int list so that combinePair xs returns the list with elements from xs combined into pairs. If xs contains an odd number of elements, then the last element is thrown away: I have no idea for this one.

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  • How to determine if an application is using the GPU

    - by Andrew
    I'm looking for a way to determine how to know whether an application is using the GPU with Objective-C. I want to be able to determine if any applications currently running on the system have work going on on the GPU (ie: a reason why the latest MacBook Pros would switch to the discrete graphics over the Intel HD graphics). I've tried getting the information by crossing the list of active windows with the list of windows that have their backing location stored in video memory using Quartz Window Services, but all that does is return the Dock application and I have other applications open that I know are using the GPU (Photoshop CS5, Interface Builder), that and the Dock doesn't require the 330m.

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  • Inform me when site (server) is online again

    - by dede
    When I ping one site it returns "Request timed out". I want to make little program that will inform me (sound beep or something like that) when this server is online again. No matter in which language. I think it should be very simple script with a several lines of code. So how to write it?

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  • Consuming Web Services in Netbeans

    - by Seven
    Hi. I've setup a project in Netbeans 6.5 with some web services that I've created myself and some web services that I've imported from WSDL files. I've setup a couple of desktop application through Netbeans in order to consume these web services. I'm not too sure where to go from here. I have the GUI setup but not sure how to reference the web services so they can be consumed. I was wondering would anybody be able to guide me through this process or point me in the direction of a relevant tutorial. I'd also like to learn how to consume a web service through a JSP (also created in Netbeans) if possible. Thanks.

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  • UI Controls layer on top of operating system.

    - by Mason Blier
    I'm kind of curious about what layer writing a UI platform to the level of Win32 or the X Windowing System would fall in the grand scheme of an operating system. What layers below do they primarily make use of, is it heavily based on direct communication with the graphics card driver (I can't imagine going though a rendering pipeline like OpenGL for this), or is there a graphical platform as part of the operating system which extracts this out a little more. I'm also interested in the creation of shells and the like, and I"m particularly curious as to how people go about creating alternative shells for windows, what do people look for when figuring out what methods to call or what to hook into, etc? I guess I'm fairly lost at these concepts and finding it difficult to find documentation on them. I was initially excited to have taken Operating Systems in college but it was all low level resource management stuff. Thanks all, Mason

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  • Function overloading by return type?

    - by dsimcha
    Why don't more mainstream statically typed languages support function/method overloading by return type? I can't think of any that do. It seems no less useful or reasonable than supporting overload by parameter type. How come it's so much less popular?

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  • Using different languages in one project

    - by Tarbal
    I recently heard about the use of several different languages in a (big) project, I also read about famous services such as Twitter using Rails as frontend, mixed with some other languages, and Scala I think it was as backend. Is this common practice? Who does that? I'm sure there are disadvantages to this. I think that you will have problems with the different interpreters/compilers and seamlessly connecting the different languages. Is this true? Why is this actually done? For performance?

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  • Odd performance with C# Asynchronous server socket

    - by The.Anti.9
    I'm working on a web server in C# and I have it running on Asynchronous socket calls. The weird thing is that for some reason, when you start loading pages, the 3rd request is where the browser won't connect. It just keeps saying "Connecting..." and doesn't ever stop. If I hit stop. and then refresh, it will load again, but if I try another time after that it does the thing where it doesn't load again. And it continues in that cycle. I'm not really sure what is making it do that. The code is kind of hacked together from a couple of examples and some old code I had. Any miscellaneous tips would be helpful as well. Heres my little Listener class that handles everything (pastied here. thought it might be easier to read this way) using System; using System.Collections.Generic; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; namespace irek.Server { public class Listener { private int port; private Socket server; private Byte[] data = new Byte[2048]; static ManualResetEvent allDone = new ManualResetEvent(false); public Listener(int _port) { port = _port; } public void Run() { server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iep = new IPEndPoint(IPAddress.Any, port); server.Bind(iep); Console.WriteLine("Server Initialized."); server.Listen(5); Console.WriteLine("Listening..."); while (true) { allDone.Reset(); server.BeginAccept(new AsyncCallback(AcceptCon), server); allDone.WaitOne(); } } private void AcceptCon(IAsyncResult iar) { allDone.Set(); Socket s = (Socket)iar.AsyncState; Socket s2 = s.EndAccept(iar); SocketStateObject state = new SocketStateObject(); state.workSocket = s2; s2.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); } private void Read(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; Socket s = state.workSocket; int read = s.EndReceive(iar); if (read > 0) { state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, read)); if (s.Available > 0) { s.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); return; } } if (state.sb.Length > 1) { string requestString = state.sb.ToString(); // HANDLE REQUEST HERE // Temporary response string resp = "<h1>It Works!</h1>"; string head = "HTTP/1.1 200 OK\r\nContent-Type: text/html;\r\nServer: irek\r\nContent-Length:"+resp.Length+"\r\n\r\n"; byte[] answer = Encoding.ASCII.GetBytes(head+resp); // end temp. state.workSocket.BeginSend(answer, 0, answer.Length, SocketFlags.None, new AsyncCallback(Send), state.workSocket); } } catch (Exception) { return; } } private void Send(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; int sent = state.workSocket.EndSend(iar); state.workSocket.Shutdown(SocketShutdown.Both); state.workSocket.Close(); } catch (Exception) { } return; } } } And my SocketStateObject: public class SocketStateObject { public Socket workSocket = null; public const int BUFFER_SIZE = 1024; public byte[] buffer = new byte[BUFFER_SIZE]; public StringBuilder sb = new StringBuilder(); }

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  • Explaining persistent data structures in simple terms

    - by Jason Baker
    I'm working on a library for Python that implements some persistent data structures (mainly as a learning exercise). However, I'm beginning to learn that explaining persistent data structures to people unfamiliar with them can be difficult. Can someone help me think of an easy (or at least the least complicated) way to describe persistent data structures to them? I've had a couple of people tell me that the documentation that I have is somewhat confusing. (And before anyone asks, no I don't mean persistent data structures as in persisted to the file system. Google persistent data structures if you're unclear on this.)

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  • Best way to store sales tax information

    - by Seph
    When designing a stock management database system (sales / purchases) what would be the best way to store the various taxes and other such amounts? A few of the fields that could be saved are: Unit price excluding tax Unit price including tax Tax per item Total excluding tax (rounded to 2 decimals) Total including tax (rounded to 2 decimals) Total tax (rounded to 2 decimals) Currently the most reasonable solution so far is storing down (roughly) item, quantity, total excluding tax (rounded) and the total tax (rounded). Can anyone suggest some better way of storing this details for a generic system? Also, given the system needs to be robust, what should be done if there were multiple tax values (eg: state and city) which might need to be separated, in this case a separate table would be in order, but would it be considered excessive to just have a rowID and some taxID mapping to a totalTax column?

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  • Known "Z notation" applications ?

    - by Amadeus45
    I was just remembering back my university classes and was wondering to know if anyone out here even used the "Z notation" in a professional environment. I honestly must say that it was the single most boring class that I have ever attended in my life. Maybe because of the teacher, but at the time we really all thought it was a big waste of time. I might have been wrong, which is why I'd like to hear you about it. If you are using it or some derived language (Z++), I'd just like to know how is it useful for you. Just curious to know some commonly-known applications of Z or your application. For those who are not familiar : http://staff.washington.edu/jon/z/z-examples.html

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  • How do I write to a file and print to a terminal cuncurrently in Unix?

    - by bias
    I have a little bash function to log my Macports outputs to a file (since installs often spew little tidbits that are easy to lose in terminal noise), then I just cat the file to the terminal: function porti { command sudo port install $@ >> $1.log 2>&1; cat $1.log } Is there a way to do this concurrently? I don't care about it being in Bash, that's just how I started it. BTW I pass $@ to install but only $1 for the file name so that I can do something like: porti git-gore +bash_completion and only get the file git-core.log however someone else might prefer to include variants in the file name ...

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  • n++ vs n=n+1. Which one is faster

    - by piemesons
    Somebody asked me Is n++ faster than n=n+1? My answer:-- ++ is a unary operator in C which(n++) takes only one machine instruction to execute while n=n+1 takes more than one machine instructions to execute. Anyone correct me if I am wrong, but in Assembler it take something like this: n++: inc n n = n + 1; mov ax n add ax 1 mov n ax its not exactli this, but it's near it.but in most cases a good compiler will change n = n + 1 to ++n.So A good compiler will generate same code for both and hence the same time to execute.

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