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  • Prove that the set of regular languages is a proper subset of the set of the context-free languages

    - by David Relihan
    I was brushing up (not homework)on some computation-theory and came accross this problem: How can you prove that the set of regular languages is a proper subset of the set of the context-free languages. Now I know a language is regular iff it is accepted by a finite automaton. And I know a language is context-free iff it is accepted by a pushdown automaton. But I'm not sure of what solution is.

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  • How to manually set an authenticated user in Spring Security / SpringMVC

    - by David Parks
    After a new user submits a 'New account' form, I want to manually log that user in so they don't have to login on the subsequent page. The normal form login page going through the spring security interceptor works just fine. In the new-account-form controller I am creating a UsernamePasswordAuthenticationToken and setting it in the SecurityContext manually: SecurityContextHolder.getContext().setAuthentication(authentication); On that same page I later check that the user is logged in with: SecurityContextHolder.getContext().getAuthentication().getAuthorities(); This returns the authorities I set earlier in the authentication. All is well. But when this same code is called on the very next page I load, the authentication token is just UserAnonymous. I'm not clear why it did not keep the authentication I set on the previous request. Any thoughts? Could it have to do with session ID's not being set up correctly? Is there something that is possibly overwriting my authentication somehow? Perhaps I just need another step to save the authentication? Or is there something I need to do to declare the authentication across the whole session rather than a single request somehow? Just looking for some thoughts that might help me see what's happening here.

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  • Observer Design Pattern - multiple event types

    - by David
    I'm currently implementing the Observer design pattern and using it to handle adding items to the session, create error logs and write messages out to the user giving feedback on their actions (e.g. You've just logged out!). I began with a single method on the subject called addEvent() but as I added more Observers I found that the parameters required to detail all the information I needed for each listener began to grow. I now have 3 methods called addMessage(), addStorage() and addLog(). These add data into an events array that has a key related to the event type (e.g. log, message, storage) but I'm starting to feel that now the subject needs to know too much about the listeners that are attached. My alternative thought is to go back to addEvent() and pass an event type (e.g. USER_LOGOUT) along with the data associated and each Observer maintains it's own list of event handles it is looking for (possibly in a switch statement), but this feels cumbersome. Also, I'd need to check that sufficient data had also been passed along with the event type. What is the correct way of doing this? Please let me know if I can explain any parts of this further. I hope you can help and see the problem I'm battling with.

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  • User input in Perl with IO::Socket

    - by David
    I am trying to make a perl program which allows a user to input the host and the port number of a foreign host to connect to using IO::Socket. It allows me to run the program and input a host and a port but it never connects and says "Could not connect to [host] at c:\users\USER\Documents\code\perl\sql.pl line 18, line 2." What am i doing wrong with this code shown below? And also, how can i have input validation on my host, which can either be a host name or an ip address? Thanks a bunch! Code Below use IO::Socket print "Host to connect to: "; chomp ($host = <STDIN>); print "Port to connect with: "; chomp ($port = <STDIN>); while(($port > 65535) || ($port <= 0)){ print "Port to connect with [Port > 0 < 65535] : "; chomp ($port = <STDIN>); } print "\nConnecting to host $host on port $port\n"; $socket = new IO::Socket::INET ( LocalHost => '$host', LocalPort => '$port', Proto => 'tcp', Listen => 5, Reuse => 1 ); die "Could not connect to $host";

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  • Architecture for database analytics

    - by David Cournapeau
    Hi, We have an architecture where we provide each customer Business Intelligence-like services for their website (internet merchant). Now, I need to analyze those data internally (for algorithmic improvement, performance tracking, etc...) and those are potentially quite heavy: we have up to millions of rows / customer / day, and I may want to know how many queries we had in the last month, weekly compared, etc... that is the order of billions entries if not more. The way it is currently done is quite standard: daily scripts which scan the databases, and generate big CSV files. I don't like this solutions for several reasons: as typical with those kinds of scripts, they fall into the write-once and never-touched-again category tracking things in "real-time" is necessary (we have separate toolset to query the last few hours ATM). this is slow and non-"agile" Although I have some experience in dealing with huge datasets for scientific usage, I am a complete beginner as far as traditional RDBM go. It seems that using column-oriented database for analytics could be a solution (the analytics don't need most of the data we have in the app database), but I would like to know what other options are available for this kind of issues.

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  • Session-timeout configuration doesn't work?

    - by David
    In web.xml I have this <session-config> <session-timeout>2</session-timeout> </session-config> <listener> <listener-class>myapplication.SessionListener</listener-class> In the SessionListener.java I have public void sessionDestroyed (HttpSessionEvent event){ System.out.println("Visitor Removed!!"); } But it seems System.out.println("Visitor Removed!!") has never been executed. I am new to Tombat6 and JSp. Any suggestion please?

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  • C++ Passing `this` into method by reference

    - by David
    I have a class constructor that expects a reference to another class object to be passed in as an argument. I understand that references are preferable to pointers when no pointer arithmetic will be performed or when a null value will not exist. This is the header declaration of the constructor: class MixerLine { private: MIXERLINE _mixerLine; public: MixerLine(const MixerDevice& const parentMixer, DWORD destinationIndex); ~MixerLine(); } This is the code that calls the constructor (MixerDevice.cpp): void MixerDevice::enumerateLines() { DWORD numLines = getDestinationCount(); for(DWORD i=0;i<numLines;i++) { MixerLine mixerLine( this, i ); // other code here removed } } Compilation of MixerDevice.cpp fails with this error: Error 3 error C2664: 'MixerLine::MixerLine(const MixerDevice &,DWORD)' : cannot convert parameter 1 from 'MixerDevice *const ' to 'const MixerDevice &' But I thought pointer values could be assigned to pointers, e.g. Foo* foo = new Foo(); Foo& bar = foo;

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  • Specializating a template function that takes a universal reference parameter

    - by David Stone
    How do I specialize a template function that takes a universal reference parameter? foo.hpp: template<typename T> void foo(T && t) // universal reference parameter foo.cpp template<> void foo<Class>(Class && class) { // do something complicated } Here, Class is no longer a deduced type and thus is Class exactly; it cannot possibly be Class &, so reference collapsing rules will not help me here. I could perhaps create another specialization that takes a Class & parameter (I'm not sure), but that implies duplicating all of the code contained within foo for every possible combination of rvalue / lvalue references for all parameters, which is what universal references are supposed to avoid. Is there some way to accomplish this? To be more specific about my problem in case there is a better way to solve it: I have a program that can connect to multiple game servers, and each server, for the most part, calls everything by the same name. However, they have slightly different versions for a few things. There are a few different categories that these things can be: a move, an item, etc. I have written a generic sort of "move string to move enum" set of functions for internal code to call, and my server interface code has similar functions. However, some servers have their own internal ID that they communicate with, some use strings, and some use both in different situations. Now what I want to do is make this a little more generic. I want to be able to call something like ServerNamespace::server_cast<Destination>(source). This would allow me to cast from a Move to a std::string or ServerMoveID. Internally, I may need to make a copy (or move from) because some servers require that I keep a history of messages sent. Universal references seem to be the obvious solution to this problem. The header file I'm thinking of right now would expose simply this: namespace ServerNamespace { template<typename Destination, typename Source> Destination server_cast(Source && source); } And the implementation file would define all legal conversions as template specializations.

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  • How to set a filter for an estimated maximum price

    - by David
    I cannot figure out how to set an estimated maximum price for a collection of records. What I want to avoid is to simply use SQL MAX, because maybe there are records with exorbitant prices. For example, in the "computers-hardware" category of OLX (http://www.olx.com/computers-hardware-cat-240) the filter for maximum price is estimately set to $1400, but sorting by price, the first items are above $10000 Maybe they calculated the average and then estimated some maximum price... what do you think? And what about the stepping? How would you calculate it?

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  • Installed Android on Mac, cannot find SDK

    - by David Matuszek
    Using Mac OS X 10.6.2, Eclipse SDK 3.5.2. I installed the Android plugin, following the instructions at: http://developer.android.com/sdk/eclipse-adt.html In the next section (step #3) it says: For the SDK Location in the main panel, click Browse... and locate your downloaded SDK directory. I cannot find such a directory. When I try some other directory, it says the directory has no 'tools' folder, so I've searched for a 'tools' folder, but none of those found (of 15 or 20) appear to be Android. Where is this directory??? --Dave [email protected]

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  • Getting true video Height/Width from ASF videos

    - by David
    I am trying to convert an ASF video with FFMPEG using an interface called mediahandler. The issue is, the metadata on the ASF video appears to be corrupt. It states that the video is 640x240, and 4:3 aspect ratio. The aspect ratio is correct, but obviously the resolution is not. This causes the converter to incorrectly scale the video, because it uses the resolution to determine the original aspect ratio. I am able to get the aspect ratio metadata, but I'm not sure this solves the issue, because I would think that if the resolution could be incorrect, then so could the aspect ratio metadata. So, is there any way to get the actual height/width? It appears that players like VLC have no issue with this. How do I do such a thing w/ FFMPEG?

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  • GetAcceptExSockaddrs returns garbage! Does anyone know why?

    - by David
    Hello, I'm trying to write a quick/dirty echoserver in Delphi, but I notice that GetAcceptExSockaddrs seems to be writing to only the first 4 bytes of the structure I pass it. USES SysUtils; TYPE BOOL = LongBool; DWORD = Cardinal; LPDWORD = ^DWORD; short = SmallInt; ushort = Word; uint16 = Word; uint = Cardinal; ulong = Cardinal; SOCKET = uint; PVOID = Pointer; _HANDLE = DWORD; _in_addr = packed record s_addr : ulong; end; _sockaddr_in = packed record sin_family : short; sin_port : uint16; sin_addr : _in_addr; sin_zero : array[0..7] of Char; end; P_sockaddr_in = ^_sockaddr_in; _Overlapped = packed record Internal : Int64; Offset : Int64; hEvent : _HANDLE; end; LP_Overlapped = ^_Overlapped; IMPORTS function _AcceptEx (sListenSocket, sAcceptSocket : SOCKET; lpOutputBuffer : PVOID; dwReceiveDataLength, dwLocalAddressLength, dwRemoteAddressLength : DWORD; lpdwBytesReceived : LPDWORD; lpOverlapped : LP_OVERLAPPED) : BOOL; stdcall; external MSWinsock name 'AcceptEx'; procedure _GetAcceptExSockaddrs (lpOutputBuffer : PVOID; dwReceiveDataLength, dwLocalAddressLength, dwRemoteAddressLength : DWORD; LocalSockaddr : P_Sockaddr_in; LocalSockaddrLength : LPINT; RemoteSockaddr : P_Sockaddr_in; RemoteSockaddrLength : LPINT); stdcall; external MSWinsock name 'GetAcceptExSockaddrs'; CONST BufDataSize = 8192; BufAddrSize = SizeOf (_sockaddr_in) + 16; VAR ListenSock, AcceptSock : SOCKET; Addr, LocalAddr, RemoteAddr : _sockaddr_in; LocalAddrSize, RemoteAddrSize : INT; Buf : array[1..BufDataSize + BufAddrSize * 2] of Byte; BytesReceived : DWORD; Ov : _Overlapped; BEGIN //WSAStartup, create listen socket, bind to port 1066 on any interface, listen //Create event for overlapped (autoreset, initally not signalled) //Create accept socket if _AcceptEx (ListenSock, AcceptSock, @Buf, BufDataSize, BufAddrSize, BufAddrSize, @BytesReceived, @Ov) then WinCheck ('SetEvent', _SetEvent (Ov.hEvent)) else if GetLastError <> ERROR_IO_PENDING then WinCheck ('AcceptEx', GetLastError); {do WaitForMultipleObjects} _GetAcceptExSockaddrs (@Buf, BufDataSize, BufAddrSize, BufAddrSize, @LocalAddr, @LocalAddrSize, @RemoteAddr, @RemoteAddrSize); So if I run this, connect to it with Telnet (on same computer, connecting to localhost) and then type a key, WaitForMultipleObjects will unblock and GetAcceptExSockaddrs will run. But the result is garbage! RemoteAddr.sin_family = -13894 RemoteAddr.sin_port = 64 and the rest is zeroes. What gives? Thanks in advance!

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  • PostgreSQL: Why does this simple query not use the index?

    - by David
    I have a table t with a column c, which is an int and has a btree index on it. Why does the following query not utilize this index? explain select c from t group by c; The result I get is: HashAggregate (cost=1005817.55..1005817.71 rows=16 width=4) -> Seq Scan on t (cost=0.00..946059.84 rows=23903084 width=4) My understanding of indexes is limited, but I thought such queries were the purpose of indexes.

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  • Module Adminhtml blocks not loading

    - by David Tay
    I was working on a Magento module and it was working fine. At some point, I was trying to enable WYSIWYG in an edit form 'content' field and suddenly, my adminhtml grid and edit blocks stopped being generated. On my system are TinyMCE and Fontis FCKEditor WYSIWYG editors extensions. I'm not sure what I did wrong but my adminhtml blocks will no longer generate. Here's a dump of all the blocks from my module's adminhtml layout: array(17) { [0]=> string(4) "root" [1]=> string(4) "head" [2]=> string(13) "head.calendar" [3]=> string(14) "global_notices" [4]=> string(6) "header" [5]=> string(4) "menu" [6]=> string(11) "breadcrumbs" [7]=> string(7) "formkey" [8]=> string(12) "js_translate" [9]=> string(4) "left" [10]=> string(7) "content" [11]=> string(8) "messages" [12]=> string(2) "js" [13]=> string(6) "footer" [14]=> string(8) "profiler" [15]=> string(15) "before_body_end" [16]=> string(7) "wysiwyg" } As you can see, the last item is "wysiwyg" but on the layout output of other magento modules, there are more blocks. For example, on MathieuF's calendar extension, these are all the layout blocks: array(26) { [0]=> string(4) "root" [1]=> string(4) "head" [2]=> string(13) "head.calendar" [3]=> string(14) "global_notices" [4]=> string(6) "header" [5]=> string(4) "menu" [6]=> string(11) "breadcrumbs" [7]=> string(7) "formkey" [8]=> string(12) "js_translate" [9]=> string(4) "left" [10]=> string(7) "content" [11]=> string(8) "messages" [12]=> string(2) "js" [13]=> string(6) "footer" [14]=> string(8) "profiler" [15]=> string(15) "before_body_end" [16]=> string(7) "wysiwyg" [17]=> string(27) "adminhtml_event.grid.child0" [18]=> string(12) "ANONYMOUS_19" [19]=> string(27) "adminhtml_event.grid.child1" [20]=> string(12) "ANONYMOUS_21" [21]=> string(27) "adminhtml_event.grid.child2" [22]=> string(20) "adminhtml_event.grid" [23]=> string(12) "ANONYMOUS_24" [24]=> string(19) "ANONYMOUS_17.child1" [25]=> string(14) "content.child0" } Does anyone have any idea what's wrong? I've already tried Alan Storm's Layout and Config Viewers and cannot find any clues as to what I did wrong. Any help would be greatly appreciated.

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  • Memory management technique for Objective-C iVars/properties

    - by David Rea
    Is the following code doing anything unnecessary? @interface MyClass { NSArray *myArray; } -(void)replaceArray:(NSArray *)newArray; @implementation MyClass -(void)replaceArray:(NSArray *)newArray { if( myArray ) { [myArray release]; myArray = nil; } myArray = [[NSArray alloc] initWithArray: newArray]; } @end What if I made the following changes: 1) Made myArray a property: @property (nonatomic, retain) NSArray myArray; 2) Changed the assignment to: self.myArray = [NSArray arrayWithArray: newArray]; Would that allow me to remove the conditional?

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  • iPhone Application: force landscape mode, strange behaviour...?

    - by David Lawson
    This is a method I use to switch display views, based on a string passed (for example you could pass MainMenuViewController to switch views to a new instance of that class): - (void)displayView:(NSString *)newView { NSLog(@"%@", newView); [[currentView view] removeFromSuperview]; [currentView release]; UIViewController *newView = [[NSClassFromString(newView) alloc] init]; [[newView view] setFrame:CGRectMake(0, 0, 320, 460)]; [self setCurrentView:newView]; [[self view] addSubview:[currentView view]]; } I have my application forced into landscape view (.plist and -shouldRotate), but if you look in the code: [[newView view] setFrame:CGRectMake(0, 0, 320, 460)]; I have to set the frame of the newView to a portrait frame for the view to be displayed correctly - otherwise, for example, a button on the new view can only be pressed in certain parts of the screen (rectangle up the top), unresponsive anywhere else. Even though in all my NIB files they are set to landscape.

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  • Facebook Like Button (<fb:like>) Height Always 80px

    - by David
    Why is the height of my Facebook Like button (technically the iframe that gets generated) always getting set to 80px? Example page is here: http://www.davidkasper.net/test.html I am using the javascript sdk and have had it work on other pages but for some reason the height will not change dynamically on this one! I can even do something like <fb:like style="height:40px"> and that will indeed set the visible height, but the iframe will still be 80px, whereas I can see it changing in the demo at http://developers.facebook.com/docs/reference/plugins/like

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  • How to retrieve XML attribute for custom control

    - by David
    I've created a combo box control with a edittext and spinner. I'm trying to let the android:prompt attribute be passed onto the spinner, which means I need to catch it in the constructor which passes my the AttributeSet and set it on the spinner. I can't figure out how to get the value of the prompt. I'm trying, int[] ra = { android.R.attr.prompt }; TypedArray ta = context.getTheme().obtainStyledAttributes(ra); int id = ta.getResourceId(0, 0); I get back 0, which means it didn't find the attribute. I also did a ta.count() which returned 0. So I'm not getting anything back. My XML simply defines an android:prompt value. Thanks

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  • How do I deliver mail for wildcard addresses to a particular user/alias/program?

    - by David M
    I need to configure sendmail so that mail delivered for wildcard addresses is accepted for delivery and then delivered to a user, alias, or directly to a script. I can rewrite the envelope/headers any number of ways, but I don't know how to accept the wildcard address when it's provided in RCPT TO: Everything I've tried so far winds up with a 550 user unknown error. So here's a specific example: I want to be able to handle any address that consists of a series of digits followed by a dot followed by a word, then pipe that to a script. If the headers get rewritten, that's OK, but I need the envelope to contain the actual Delivered-To address. Here's the sort of SMTP session I need: 220 blah.foo.com ESMTP server ready; Thu, 22 Apr 2010 20:41:08 -0700 (PDT) HELO blort.foo.com 250 blah.foo.com Hello blort.foo.com [10.1.2.3], pleased to meet you MAIL FROM: <[email protected]> 250 2.1.0 <[email protected]>... Sender ok RCPT TO: <[email protected]> 250 2.1.5 <[email protected]>... Recipient ok I tried some stuff with regex maps, but I never got past 550 user unknown.

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