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• Generating easy-to-remember random identifiers

  - by Carl Seleborg

  Hi all, As all developers do, we constantly deal with some kind of identifiers as part of our daily work. Most of the time, it's about bugs or support tickets. Our software, upon detecting a bug, creates a package that has a name formatted from a timestamp and a version number, which is a cheap way of creating reasonably unique identifiers to avoid mixing packages up. Example: "Bug Report 20101214 174856 6.4b2". My brain just isn't that good at remembering numbers. What I would love to have is a simple way of generating alpha-numeric identifiers that are easy to remember. Examples would be "azil3", "ulmops", "fel2way", etc. I just made these up, but they are much easier to recognize when you see many of them at once. I know of algorithms that perform trigram analysis on text (say you feed them a whole book in German) and that can generate strings that look and feel like German words. This requires lots of data, though, and makes it slightly less suitable for embedding in an application just for this purpose. Do you know of anything else? Thanks! Carl

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• 1k of Program Space, 64 bytes of RAM. Is 1 wire communication possible?

  - by Earlz

  (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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• Strange Matlab error: "??? Subscript indices must either be real positive integers or logicals"

  - by Roee Adler

  I have a function func that returns a vector a. I usually plot a and then perform further analysis on it. I have a certain scenario when once I try to plot a, I get a "??? Subscript indices must either be real positive integers or logicals" error. Take a look at the following piece of code to see the vector's behavior: K>> a a = 5.7047 6.3529 6.4826 5.5750 4.1488 5.8343 5.3157 5.4454 K>> plot(a) ??? Subscript indices must either be real positive integers or logicals. K>> for i=1:length(a); b(i) = a(i); end; K>> b b = 5.7047 6.3529 6.4826 5.5750 4.1488 5.8343 5.3157 5.4454 K>> plot(b) ??? Subscript indices must either be real positive integers or logicals. The scenario where this happens is when I call function func from within another function (call it outer_func), and return the result directly as outer_func's result. When debugging inside outer_func, I can plot a properly, but outside the scope of outer_func, its result has the above behavior. What can cause this? Where do I start from?

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• Advanced All In One .NET Framework

  - by alfredo dobrekk

  Hi, i m starting a new project that would basically take input from user and save them to database among about 30 screens, and i would like to find a framework that will allow the maximum number of these features out of the box : .net c#. windows form. unit testing continuous integration screens with lists, combo boxes, text boxes, add, delete, save, cancel that are easy to update when you add a property to your classes or a field to your database. auto completion on controls to help user find its way use of an orm like nhibernate easy multithreading and display of wait screens for user easy undo redo tabbed child windows search forms ability to grant access to some functionnalities according to user profiles mvp/mvvm or whatever design patterns either some code generation from database to c# classe or generation of database schema from c# classes some kind of database versioning / upgrade to easily update database when i release patches to application once in production automatic control resizing code metrics analysis some code generator i can use against my entities that would generate some rough form i can rearrange after code documentation generator ... Any ideas ? I know its lot but i really would like to use existing code to build upon so i can focus on business rules. Could splitting the requirements on 3 or 4 existing open source framework be possible ? Do u have any suggestion to add to the list before starting ? What open source tools would u use to achieve these ?

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• Qt and variadic functions

  - by Noah Roberts

  OK, before lecturing me on the use of C-style variadic functions in C++...everything else has turned out to require nothing short of rewriting the Qt MOC. What I'd like to know is whether or not you can have a "slot" in a Qt object that takes an arbitrary amount/type of arguments. The thing is that I really want to be able to generate Qt objects that have slots of an arbitrary signature. Since the MOC is incompatible with standard preprocessing and with templates, it's not possible to do so with either direct approach. I just came up with another idea: struct funky_base : QObject { Q_OBJECT funky_base(QObject * o = 0); public slots: virtual void the_slot(...) = 0; }; If this is possible then, because you can make a template that is a subclass of a QObject derived object so long as you don't declare new Qt stuff in it, I should be able to implement a derived templated type that takes the ... stuff and turns it into the appropriate, expected types. If it is, how would I connect to it? Would this work? connect(x, SIGNAL(someSignal(int)), y, SLOT(the_slot(...))); If nobody's tried anything this insane and doesn't know off hand, yes I'll eventually try it myself...but I am hoping someone already has existing knowledge I can tap before possibly wasting my time on it.

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• Generic dataset handling library

  - by Pep.

  Hello, I want to build a generic Perl module for handling and analysing biomedical character separated datasets and which can, most certain, be used on any kind of datasets that contain a mixture of categorical (A,B,C,..) and continuous (1.2,3,881..) and identifier (XXX1,XXX2...). The plan is to have people initialize the module and then use some arguments to point to the data file(s), the place were the analysis reports should be placed and the structure of the data. By structure of data I mean which variable is in which place and its name/type. And this is where I need some enlightenment. I am baffled how to do this in a clean way. Obviously, having people create a simple schema file, be it XML or some other format would be the cleanest but maybe not all people enjoy doing something like this. The solutions I can think of are: Create a configuration file in XML or similar and with a prespecified format. Pass the information during initialization of the module. Use the first row of the data as headers and try to guess types (ouch) Surely there must be a "canonical" way of doing this that is also usable and efficient. Thanks p.

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• How can I compare market data feed sources for quality and latency improvement?

  - by yves Baumes

  I am in the very first stages of implementing a tool to compare 2 market data feed sources in order to prove the quality of new developed sources to my boss ( meaning there are no regressions, no missed updates, or wrong ), and to prove latencies improvement. So the tool I need must be able to check updates differences as well as to tell which source is the best (in term of latency). Concrectly, reference source could be Reuters while the other one is a Feed handler we develop internally. People warned me that updates might not arrive in the same order as Reuters implementation could differs totally from ours. Therefore a simple algorithm based on the fact that updates could arrive in the same order is likely not to work. My very first idea would be to use fingerprint to compare feed sources, as Shazaam application does to find the title of the tube you are submitting. Google told me it is based on FFT. And I was wondering if signal processing theory could behaves well with market access applications. I wanted to know your own experience in that field, is that possible to develop a quite accurate algorithm to meet the needs? What was your own idea? What do you think about fingerprint based comparison?

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• How can I superimpose modified loess lines on a ggplot2 qplot?

  - by briandk

  Background Right now, I'm creating a multiple-predictor linear model and generating diagnostic plots to assess regression assumptions. (It's for a multiple regression analysis stats class that I'm loving at the moment :-) My textbook (Cohen, Cohen, West, and Aiken 2003) recommends plotting each predictor against the residuals to make sure that: The residuals don't systematically covary with the predictor The residuals are homoscedastic with respect to each predictor in the model On point (2), my textbook has this to say: Some statistical packages allow the analyst to plot lowess fit lines at the mean of the residuals (0-line), 1 standard deviation above the mean, and 1 standard deviation below the mean of the residuals....In the present case {their example}, the two lines {mean + 1sd and mean - 1sd} remain roughly parallel to the lowess {0} line, consistent with the interpretation that the variance of the residuals does not change as a function of X. (p. 131) How can I modify loess lines? I know how to generate a scatterplot with a "0-line,": # First, I'll make a simple linear model and get its diagnostic stats library(ggplot2) data(cars) mod <- fortify(lm(speed ~ dist, data = cars)) attach(mod) str(mod) # Now I want to make sure the residuals are homoscedastic qplot (x = dist, y = .resid, data = mod) + geom_smooth(se = FALSE) # "se = FALSE" Removes the standard error bands But does anyone know how I can use ggplot2 and qplot to generate plots where the 0-line, "mean + 1sd" AND "mean - 1sd" lines would be superimposed? Is that a weird/complex question to be asking?

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• WPF, notify a child in the element tree about an event in a parent

  - by jester

  I am developing a WPF app and I want an event in a parent to be notified to several of its children in the element tree, so that each of them can take an action accordingly. I know that a custom RoutedEvent can be used to signal in the other direction from a child to one of its ancestors by bubbling the event upwards, so that any of the ancestor elements can handle the event. What I want is the children to be notified about an event in the parent and they handle them appropriately. What is the best strategy to achieve this? EDIT: Clarifying the comments : Say I have a parent UserControl. It has a TabControl and its contents are several nested child UserControls. Now consider a scenario where I want the TabControl.SelectionChanged() event to cause some changes in each of the child UserControl. How to achieve this? (The contents of each tab is a UserControl which themselves may contain another few levels of children UserControls. I want the UserControl in the bottom level to know about the SelectionChanged() event and respond accordingly).

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• Catching / blocking SIGINT during system call

  - by danben

  I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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• C# Accepting sockets in async fasion - best practices

  - by psulek

  What is the best way to accept new sockets in async way. First way: while (!abort && listener.Server.IsBound) { acceptedSocketEvent.Reset(); listener.BeginAcceptSocket(AcceptConnection, null); bool signaled = false; do { signaled = acceptedSocketEvent.WaitOne(1000, false); } while (!signaled && !abort && listener.Server.IsBound); } where AcceptConnection should be: private void AcceptConnection(IAsyncResult ar) { // Signal the main thread to continue. acceptedSocketEvent.Set(); Socket socket = listener.EndAcceptSocket(ar); // continue to receive data and so on... .... } or Second way: listener.BeginAcceptSocket(AcceptConnection, null); while (!abort && listener.Server.IsBound) { Thread.Sleep(500); } and AcceptConnection will be: private void AcceptConnection(IAsyncResult ar) { Socket socket = listener.EndAcceptSocket(ar); // begin accepting next socket listener.BeginAcceptSocket(AcceptConnection, null); // continue to receive data and so on... .... } What is your prefered way and why?

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• Deterministic and non uniform long string generation from seed

  - by Limonup

  I had this weird idea for an encryption that I wanted to try out, it may be bad, and it may have done before, but I'm just doing it for fun. The short version of the question is: Is it possible to generate a long, deterministic and non-uniformly distributed string/sequence of numbers from a small seed? Long(er) version: I was thinking to encrypt a text by changing encoding. The new encoding would be generated via Huffman algorithm. To work well, the Huffman algorithm would need a fairly long text with non uniform distribution. Then characters can have different bit-lengths which would be the primary strength of this encryption. The problem is that its impractical to enter in/remember a long text each time you want to decrypt the text. So I was wondering if it was possible to generate a text from password seed? It doesn't matter what the text is, as long as it has non uniform distribution of characters and that the exact same sequence can be recreated each time you give it the same seed. Preferably, are there any functions/extensions in Python that can do this? EDIT: To expand on the "strength" of varying bit length: if I have a string "test", ASCII values 116, 101, 115, 116, which gives bit values of 1110100 1100101 1110011 1110100 Then, say my Huffman algorithm generates encoding like t = 101 e = 1100111 s = 10001 The final string is 101 1100111 10001 101, if we encode this back to ASCII, we get 1011100 1111000 1101000, which is 3 entirely different characters. Obviously its impossible to perform any kind of frequency analysis or something like that on this.

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• How to compare two variables from a java class in jess and execute a rule?

  - by user3417084

  I'm beginner in Jess. I'm trying to compare two variables from a Java class in Jess and trying to execute a rule. I have imported cTNumber and measuredCurrent (both are integer)form a java class called CurrentSignal. Similarly imported vTNumberand measuredVoltage form a java class DERSignal. Now I want to make a rule such that if cTNumber is equal to vTNumber then multiply measuredCurrent and measuredVoltage (Both are double) for calculating power. I'm trying in this way.... (import signals.*) (deftemplate CurrentSignal (declare (from-class CurrentSignal))) (deftemplate DERSignal (declare (from-class DERSignal))) (defglobal ?*CTnumber* = 0) (defglobal ?*VTnumber* = 0) (defglobal ?*VTnumberDER* = 0) (defglobal ?*measuredCurrent* = 0) (defglobal ?*measuredVoltage* = 0) (defglobal ?*measuredVoltageDER* = 0) (defrule Get-CT-Number (CurrentSignal (cTNumber ?m)) (CurrentSignal (measuredCurrent ?c)) => (bind ?*measuredCurrent* ?c) (printout t "Measured Current : " ?*measuredCurrent*" Amps"crlf) (bind ?*CTnumber* ?m) (printout t ?*CTnumber* crlf) ) (defrule Get-DER-Number (DERSignal (vTNumber ?o)) (DERSignal (measuredVoltage ?V)) => (bind ?*measuredVoltageDER* ?V) (printout t "Measured Voltage : " ?*measuredVoltageDER* " V" crlf) (bind ?*VTnumberDER* ?o) (printout t ?*VTnumberDER* crlf) ) (defrule Power-Calculation-DER-signal "Power calculation of DER Bay" (test (= ?*CTnumber* ?*VTnumberDER* )) => (printout t "Total Generation : " (* ?*measuredCurrent* ?*measuredVoltageDER*) crlf) ) But the Total Generation is showing 0. But I tried calculating in Java and it's showing a number. Can anyone please help me to solve this problem. Thank you.

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• html body inside if condition

  - by gautam

  Hi, i have two different bodies for different conditions. can i do like this.... <% if(yes) %> <body onload="JavaScript:timedRefresh(120000);"> <% } else { %> <body> <% } %> Please help me... Thanks in advance.. I want to compare my title in if condition how can i do??? currently i am doing like this: <head> <title> <tiles:getAsString name="title"/> </title> </head> <% if(%><tiles:getAsString name="title"/><%.equals("Trade Confirmation Analysis Screen")) %> <body onload="JavaScript:timedRefresh(120000);"> <%else { %> <body> <% } %> Its giving me error..Unable to compile class for JSP:

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• writing into csv file

  - by arin

  I recived alarms in a form of text as the following NE=JKHGDUWJ3 Alarm=Data Center STALZ AC Failure Occurrence=2012/4/3 22:18:19 GMT+02:00 Clearance=Details=Cabinet No.=0, Subrack No.=40, Slot No.=0, Port No.=5, Board Type=EDS, Site No.=49, Site Type=HSJYG500 GSM, Site Name=Google1 . I need to fill it in csv file so later I can perform some analysis I came up with this namespace AlarmSaver { public partial class Form1 : Form { string filesName = "c:\\alarms.csv"; public Form1() { InitializeComponent(); } private void buttonSave_Click(object sender, EventArgs e) { if (!File.Exists(filesName)) { string header = "NE,Alarm,Occurrence,Clearance,Details"; File.AppendAllText(filesName,header+Environment.NewLine); } StringBuilder sb = new StringBuilder(); string line = textBoxAlarm.Text; int index = line.IndexOf(" "); while (index > 0) { string token = line.Substring(0, index).Trim(); line = line.Remove(0, index + 2); string[] values = token.Split('='); if (values.Length ==2) { sb.Append(values[1] + ","); } else { if (values.Length % 2 == 0) { string v = token.Remove(0, values[0].Length + 1).Replace(',', ';'); sb.Append(v + ","); } else { sb.Append("********" + ","); string v = token.Remove(0, values[0].Length + 1 + values[1].Length + 1).Replace(',', ';'); sb.Append(v + ","); } } index = line.IndexOf(" "); } File.AppendAllText(filesName, sb.ToString() + Environment.NewLine); } } } the results are as I want except when I reach the part of Details=Cabinet No.=0, Subrack No.=40, Slot No.=0, Port No.=5, Board Type=KDL, Site No.=49, Site Type=JDKJH99 GSM, Site Name=Google1 . I couldnt split them into seperate fields. as the results showing is as I want to split the details I want each element in details to be in a column to be somthin like its realy annoying :-) please help , thank you in advance

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• Weird Qt SSL issue -- error "No Error" shows up, nothing else, and if I ignore it, everything works

  - by houbysoft

  The issue is as follows : in my Qt app, I have a QWebView, which I use to load a HTTPS page. Everything worked fine on my development machine, so I'm now trying to get it to run on a test machine. I ran the app, but the page didn't load (the QWebView was blank). After much debugging, I found the problem is that an SSL error shows up, and the sslErrors() signal is fired. Here is my sslErrors() handling code: void blah::sslErrors(QNetworkReply *reply, const QList<QSslError> &errors) { foreach(QSslError error, errors) { qDebug() << error.errorString() << endl; } reply->ignoreSslErrors(); } The only thing the above code prints is: "No error" So there's no error, but unless I call reply->ignoreSslErrors(), the page doesn't load (on the test machine, on my developer computer no error is reported). Huh? Is this a bug? Is it safe to ignore the error, if I make sure it's of the type "No error"?

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• Raw types and subtyping

  - by Dmitrii

  We have generic class SomeClass<T>{ } We can write the line: SomeClass s= new SomeClass<String>(); It's ok, because raw type is supertype for generic type. But SomeClass<String> s= new SomeClass(); is correct to. Why is it correct? I thought that type erasure was before type checking, but it's wrong. From Hacker's Guide to Javac When the Java compiler is invoked with default compile policy it performs the following passes: parse: Reads a set of *.java source files and maps the resulting token sequence into AST-Nodes. enter: Enters symbols for the definitions into the symbol table. process annotations: If Requested, processes annotations found in the specified compilation units. attribute: Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. flow: Performs data ow analysis on the trees from the previous step. This includes checks for assignments and reachability. desugar: Rewrites the AST and translates away some syntactic sugar. generate: Generates Source Files or Class Files. Generic is syntax sugar, hence type erasure invoked at 6 pass, after type checking, which invoked at 4 pass. I'm confused.

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• Which to use, XMP or RDF?

  - by zotty

  What's the difference between RDF and XMP? From what I can tell, XMP is derived from RDF... so what does it offer that RDF doesn't? My particular situation is this: I've got some images which need tagging with details of how an experiment was performed, and what sort of data analysis has been performed on the images. A colleague of mine is pushing for XMP, but he's thinking of the images as photos - they're not really, they're just bits of data. From what I've seen (mainly by opening images in notepad++) the XMP data looks very similar to RDF - even so far as using RDF in the tag names (e.g. <rdf:Seq>). I'd like this data to be usable by other people who use similar instruments for similar experiments, so creating a mini standard (schema?) seems like the way to go. Apologies for the lack of fundemental understanding - I'm a Doctor, not a programmer! If it makes any difference, the language of choice will be C#. Edit for more information: First off, thanks for the excellent replies - thinking of XMP as a vocabulary for RDF makes things a lot clearer. The sort of data I'll be storing wont be avaliable in any of the pre-defined sets. It'll detail experimental set ups, locations and results. I think using RDF is the way to go.

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• Avoiding a fork()/SIGCHLD race condition

  - by larry

  Please consider the following fork()/SIGCHLD pseudo-code. // main program excerpt for (;;) { if ( is_time_to_make_babies ) { pid = fork(); if (pid == -1) { /* fail */ } else if (pid == 0) { /* child stuff */ print "child started" exit } else { /* parent stuff */ print "parent forked new child ", pid children.add(pid); } } } // SIGCHLD handler sigchld_handler(signo) { while ( (pid = wait(status, WNOHANG)) > 0 ) { print "parent caught SIGCHLD from ", pid children.remove(pid); } } In the above example there's a race-condition. It's possible for "/* child stuff */" to finish before "/* parent stuff */" starts which can result in a child's pid being added to the list of children after it's exited, and never being removed. When the time comes for the app to close down, the parent will wait endlessly for the already-finished child to finish. One solution I can think of to counter this is to have two lists: started_children and finished_children. I'd add to started_children in the same place I'm adding to children now. But in the signal handler, instead of removing from children I'd add to finished_children. When the app closes down, the parent can simply wait until the difference between started_children and finished_children is zero. Another possible solution I can think of is using shared-memory, e.g. share the parent's list of children and let the children .add and .remove themselves? But I don't know too much about this. EDIT: Another possible solution, which was the first thing that came to mind, is to simply add a sleep(1) at the start of /* child stuff */ but that smells funny to me, which is why I left it out. I'm also not even sure it's a 100% fix. So, how would you correct this race-condition? And if there's a well-established recommended pattern for this, please let me know! Thanks.

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• CLLocationManager class method not calling in iPodTouch

  - by Siddharth

  HI all, I was using a sample code which uses CLLocationManager class to determine the current location of user. when i run this app on iPad i am getting the correct location but when i run the same app on iPod Touch i am getting a blank label i.e nothing is displayed on the label .although wi-fi signal strength is good in both iPod and iPad.The code looks like... - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{ int degrees = newLocation.coordinate.latitude; double decimal = fabs(newLocation.coordinate.latitude - degrees); int minutes = decimal * 60; double seconds = decimal * 3600 - minutes * 60; NSString *lat = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; latLabel.text = lat; [latLocationArray addObject:lat]; degrees = newLocation.coordinate.longitude; decimal = fabs(newLocation.coordinate.longitude - degrees); minutes = decimal * 60; seconds = decimal * 3600 - minutes * 60; NSString *longt = [NSString stringWithFormat:@"%d° %d' %1.4f\"", degrees, minutes, seconds]; longLabel.text = longt; [longLocationArray addObject:longt]; }

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• Implementing eval and load functions inside a scripting engine with Flex and Bison.

  - by Simone Margaritelli

  Hy guys, i'm developing a scripting engine with flex and bison and now i'm implementing the eval and load functions for this language. Just to give you an example, the syntax is like : import std.*; load( "some_script.hy" ); eval( "foo = 123;" ); println( foo ); So, in my lexer i've implemented the function : void hyb_parse_string( const char *str ){ extern int yyparse(void); YY_BUFFER_STATE prev, next; /* * Save current buffer. */ prev = YY_CURRENT_BUFFER; /* * yy_scan_string will call yy_switch_to_buffer. */ next = yy_scan_string( str ); /* * Do actual parsing (yyparse calls yylex). */ yyparse(); /* * Restore previous buffer. */ yy_switch_to_buffer(prev); } But it does not seem to work. Well, it does but when the string (loaded from a file or directly evaluated) is finished, i get a sigsegv : Program received signal SIGSEGV, Segmentation fault. 0xb7f2b801 in yylex () at src/lexer.cpp:1658 1658 if ( YY_CURRENT_BUFFER_LVALUE->yy_buffer_status == YY_BUFFER_NEW ) As you may notice, the sigsegv is generated by the flex/bison code, not mine ... any hints, or at least any example on how to implement those kind of functions? PS: I've succesfully implemented the include directive, but i need eval and load to work not at parsing time but execution time (kind of PHP's include/require directives).

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• Are functional programming languages good for practical tasks?

  - by Clueless

  It seems to me from my experimenting with Haskell, Erlang and Scheme that functional programming languages are a fantastic way to answer scientific questions. For example, taking a small set of data and performing some extensive analysis on it to return a significant answer. It's great for working through some tough Project Euler questions or trying out the Google Code Jam in an original way. At the same time it seems that by their very nature, they are more suited to finding analytical solutions than actually performing practical tasks. I noticed this most strongly in Haskell, where everything is evaluated lazily and your whole program boils down to one giant analytical solution for some given data that you either hard-code into the program or tack on messily through Haskell's limited IO capabilities. Basically, the tasks I would call 'practical' such as Aceept a request, find and process requested data, and return it formatted as needed seem to translate much more directly into procedural languages. The most luck I have had finding a functional language that works like this is Factor, which I would liken to a reverse-polish-notation version of Python. So I am just curious whether I have missed something in these languages or I am just way off the ball in how I ask this question. Does anyone have examples of functional languages that are great at performing practical tasks or practical tasks that are best performed by functional languages?

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• How to start writing out an existing AudioQueue in response to an event?

  - by Halle

  Hello, I am writing a class that opens an AudioQueue and analyzes its characteristics, and then under certain conditions can begin or end writing out a file from that AudioQueue that is already instantiated. This is my code (entirely based on SpeakHere) that opens the AudioQueue without writing anything out to tmp: void AQRecorder::StartListen() { int i, bufferByteSize; UInt32 size; try { SetupAudioFormat(kAudioFormatLinearPCM); XThrowIfError(AudioQueueNewInput(&mRecordFormat, MyInputBufferHandler, this, NULL, NULL, 0, &mQueue), "AudioQueueNewInput failed"); mRecordPacket = 0; size = sizeof(mRecordFormat); XThrowIfError(AudioQueueGetProperty(mQueue, kAudioQueueProperty_StreamDescription, &mRecordFormat, &size), "couldn't get queue's format"); bufferByteSize = ComputeRecordBufferSize(&mRecordFormat, kBufferDurationSeconds); for (i = 0; i < kNumberRecordBuffers; ++i) { XThrowIfError(AudioQueueAllocateBuffer(mQueue, bufferByteSize, &mBuffers[i]), "AudioQueueAllocateBuffer failed"); XThrowIfError(AudioQueueEnqueueBuffer(mQueue, mBuffers[i], 0, NULL), "AudioQueueEnqueueBuffer failed"); } mIsRunning = true; XThrowIfError(AudioQueueStart(mQueue, NULL), "AudioQueueStart failed"); } catch (CAXException &e) { char buf[256]; fprintf(stderr, "Error: %s (%s)\n", e.mOperation, e.FormatError(buf)); } catch (...) { fprintf(stderr, "An unknown error occurred\n"); } } But I'm a little unclear on how to write a function that will tell this queue "from now until the stop signal, start writing out this queue to tmp as a file". I understand how to tell an AudioQueue to write out as a file at the time that it's created, how to set files format, etc, but not how to tell it to start and stop midstream. Much appreciative of any pointers, thanks.

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• How do I get started designing and implementing a script interface for my .NET application?

  - by Peter Mortensen

  How do I get started designing and implementing a script interface for my .NET application? There is VSTA (the .NET equivalent of VBA for COM), but as far as I understand I would have to pay a license fee for every installation of my application. It is an open source application so this will not work. There is also e.g. the embedding of interpreters (IronPython?), but I don't understand how this would allow exposing an "object model" (see below) to external (or internal) scripts. What is the scripting interface story in .NET? Is it somehow trivial in .NET to do this? Background: I have once designed and implemented a fairly involved script interface for a Macintosh application for acquisition and analysis of data from a mass spectrometer (Mac OS, System 7) and later a COM interface for a Windows application. Both were designed with an "object model" and classes (that can have properties). These are overloaded words, but in a scripting interface context object model is essentially a containment hiarchy of objects of specific classes. Classes have properties and lists of contained objects. E.g. like in the COM interfaces exposed in Microsoft Office applications, where the application object can be used to add to its list of documents (with the side effect of creating the GUI representation of a document). External scripts can create new objects in a container and navigate through the content of the hiarchy at any given time. In the Macintosh case scripts could be written in e.g. AppleScript or Frontier. On the Macintosh the implementation of a scripting interface was very complicated. Support for it in Metroworks' C++ class library (the name escapes me right now) made it much simpler.

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• MYSQL not running on Ubuntu OS - Error 2002.

  - by mgj

  Hi, I am a novice to mysql DB. I am trying to run the MYSQL Server on Ubuntu 10.04. Through Synaptic Package Manager I am have installed the mysql version: mysql-client-5.1 I wonder that how was the database password set for the mysql-client software that I installed through the above way.It would be nice if you could enlighten me on this. When I tried running this database, I encountered the error given below: mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) mohnish@mohnish-laptop:/var/lib$ I referred to a similar question posted by another user. I didn't find a solution through the proposed answers. For instance when I tried the solutions posted for the similar question I got the following: mohnish@mohnish-laptop:/var/lib$ service start mysqld start: unrecognized service mohnish@mohnish-laptop:/var/lib$ ps -u mysql ERROR: User name does not exist. ********* simple selection ********* ********* selection by list ********* -A all processes -C by command name -N negate selection -G by real group ID (supports names) -a all w/ tty except session leaders -U by real user ID (supports names) -d all except session leaders -g by session OR by effective group name -e all processes -p by process ID T all processes on this terminal -s processes in the sessions given a all w/ tty, including other users -t by tty g OBSOLETE -- DO NOT USE -u by effective user ID (supports names) r only running processes U processes for specified users x processes w/o controlling ttys t by tty *********** output format ********** *********** long options *********** -o,o user-defined -f full --Group --User --pid --cols --ppid -j,j job control s signal --group --user --sid --rows --info -O,O preloaded -o v virtual memory --cumulative --format --deselect -l,l long u user-oriented --sort --tty --forest --version -F extra full X registers --heading --no-heading --context ********* misc options ********* -V,V show version L list format codes f ASCII art forest -m,m,-L,-T,H threads S children in sum -y change -l format -M,Z security data c true command name -c scheduling class -w,w wide output n numeric WCHAN,UID -H process hierarchy mohnish@mohnish-laptop:/var/lib$ which mysql /usr/bin/mysql mohnish@mohnish-laptop:/var/lib$ mysql ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) I even tried referring to http://forums.mysql.com/read.php?11,27769,84713#msg-84713 but couldn't find anything useful. Please let me know how I could tackle this error. Thank you very much..

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