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• Java Prepared Statement arguments!

  - by Epitaph

  I am planning to replace repeatedly executed Statement objects with PreparedStatement objects to improve performance. I am using arguments like the MySQL function now(), and string variables. Most of the PreparedStatement queries I have seen contained constant values (like 10, and strings like "New York") as arguments used for the "?" in the queries. How would I go about using functions like now(), and variables as arguments? Is it necessary to use the "?"s in the queries instead of actual values? I am quite confounded.

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• What useful GDB scripts have you used/written?

  - by nik

  People use gdb on and off for debugging, of course there are lots of other debugging tools across the varied OSes, with and without GUI and, maybe other fancy IDE features. I would like to know what useful gdb scripts you have written and liked. While, I do not mean a dump of commands in a something.gdb file that you source to pull out a bunch of data, if that made your day, go ahead and talk about it. Lets think conditional processing, control loops and functions written for more elegant and refined programming to debug and, maybe even for whitebox testing Things get interesting when you start debugging remote systems (say, over a serial/ethernet interface) And, what if the target is a multi-processor (and, multithreaded) system Let me put a simple case as an example... Say, A script that traversed serially over entries to locate a bad entry in a large hash-table that is implemented on an embedded platform. That helped me debug a broken hash-table once.

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• How to link a SQlite Extension Source File into Xcode for iPhone?

  - by crunchyt

  I use a statically linked library for Sqlite in an iPhone Xcode project. I am now trying to include a .C extension to Sqlite in this project. However, I am having trouble making the Sqlite in the build SEE the extension. The statically linked Sqlite library works fine. Also the .C extension works on my desktop, and builds fine as a statically linked library in Xcode. However, the custom functions it defines are missing when called. For example, I load the extension as so with no errors. SELECT load_extension('extension_name.so'); But when I try to call a function defined in the extension, I get this message DB Error: 1 "no such function: custom_function" Does anyone know much about linking a Sqlite extension into an Xcode project?

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• jquery dynatree class methods

  - by Jj Zhang

  I'm a new user of dynatree plugin. When I read the documentation, I found the list of tree and node class member functions, such as tree.getRoot(), node.countChildren(). However, when I tried to use them, it complained that no such methods were found. Here is a sample code I am testing with: var tree = ("#test").dynatree(treeData); var rootNode = tree.getRoot(); //not working var rootNode2 = ("#test").dynatree("getRoot"); //this works var numChildren = rootNode2.countChildren(); //not working Help please. Thanks. -JJ

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• Setting data source for reports in Crystal Reports 2008 Java (performance)

  - by Daniel

  Hi, we have Crystal Reports 2008 on the server, and use the Java SDK to display reports and convert them to PDF. Since the server hat its own database, we have to set the data source on the DatabaseController to make CR connect to this database. We do it like specified in the docs, and tried the functions in CRJavaHelper, but for a reason unknown to me setting the connection string takes 300ms to 1500ms. What is the fastest way to tell Crystal which datasource to use in its reports? I already saw a JNDI name somewhere, but i don't believe CR actually does a JNDI lookup to find an existing datasource, doesn't it?

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• what is duck typing?

  - by ashish yadav

  I recently read an article about duck-typing.It said about calling functions of different classes using object of any class. Is it true?And how will the compiler do it on runtime? I apologize if i am not clear.But it really fascinates me , if we could do it dynamically. So if u people got any idea.I am all ears. thank you!! how will the function be accessed by object of any other class. that violates the basic principle of OOP.and that too dynamically during runtime. And is this feature possible in case of OOP languages?

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• Where do I find a good explanation of Javascript-ese

  - by tzenes

  I realize that title may require explanation. The language I first learned was C, and it shows in all my programs... even those not written in C. For example, when I first learned F# I wrote my F# programs like C programs. It wasn't until someone explained the pipe operator and mapping with anonymous functions that I started to understand the F#-ese, how to write F# like a F# programmer and not a C programmer. Now I've written a little javascript, mostly basic stuff using jquery, but I was hoping there was a good resource where I could learn to write javascript programs like a javascript programmer.

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• Prototyping Object in Javascript breaks jQuery?

  - by blesh

  I have added a simple .js to my page that has some pretty mundane common-task sort of functions added to the Object and Array prototypes. Through trial and error I've figured out that adding any function to Object.prototype, no matter it's name or what it does causes javascript errors in jQuery: The culprit? Object.prototype.foo = function() { /*do nothing and break jQuery*/ }; The error I'm getting line 1056 of jquery-1.3.2.js, in the attr:function { } declaration: /*Object doesn't support this property or method*/ name = name.replace(/-([a-z])/ig, function(all, letter) { return letter.toUpperCase(); }); Apparently G.replace is undefined. While it's obvious that there's something I'm just not wrapping my head around with prototyping, I'm failing miserably to figure out what it is. To be clear, I'm not looking for a workaround, I have that handled... what I'm looking for is an answer to 'Why?'. Why does adding a function to Object.prototype break this bit of code?

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• Break nested loop in Django views.py with a function

  - by knuckfubuck

  I have a nested loop that I would like to break out of. After searching this site it seems the best practice is to put the nested loop into a function and use return to break out of it. Is it acceptable to have functions inside the views.py file that are not a view? What is the best practice for the location of this function? Here's the example code from inside my views.py @login_required def save_bookmark(request): if request.method == 'POST': form = BookmarkSaveForm(request.POST) if form.is_valid(): bookmark_list = Bookmark.objects.all() for bookmark in bookmark_list: for link in bookmark.link_set.all(): if link.url == form.cleaned_data['url']: # Do something. break else: # Do something else. else: form = BookmarkSaveForm() return render_to_response('save_bookmark_form.html', {'form': form})

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• Knowledge base web app -- need a demo mode

  - by Smandoli

  I was contracted to build an on-line knowledge base that searches and cross-references many thousands of replacement parts for a niche industry. My client furnishes this app to his customers on a subscription basis. It uses MySQL and PHP and it works great. I want to deploy it in "demo mode" to sell my skills. I want the user to see the functions, but I have to guard the data for my client. My first idea was to obfuscate the results. That's at cross-purposes with showing how well it searches. I'm considering a limit on how many searches you can perform, but that's awkward too as someone could visit every day and get more answers than we would prefer. Other posts I've found are about letting people interact with an app, but without the challenge of protecting a big knowledge base. Can you suggest an approach? (Note, I put the tag obfuscation, but not sure it applies because java code obfuscation seems to be unrelated.)

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• Graphviz DOT arrange Nodes in circles, layout too "compact"

  - by Ivo Wetzel

  I'm halfway there please see the edit OK here's my problem, I'm generating a graph of a python module, including all the files with their functions/methods/classes. I want to arrange it so, that nodes gather in circles around their parent nodes, currently everything is on one gargantuan horizontal row, which makes the thing 50k pixels wide and also let's the svg converter fail(only renders about the half of the graph). I went trough the docs(http://www.graphviz.org/doc/info/attrs.html) but couldn't find anything that seems to do the trick. So the question is: Is there a simple way to do this or do I have to layout the whole thing by myself? :/ EDIT: Thanks to Andrews comment I've got the right layout, the only problem now is that it's a bit to "compact"... so the question now is, how to fix this?

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• jQuery selective hover

  - by Vitor

  Hello everyone, I'm trying to do a simple task with jQuery: I have a list of words which, when hovered, should fadeIn its corresponding image. For example: <a href="#" class="yellow">Yellow</a> <a href="#" class="blue">Blue</a> <a href="#" class="green">Green</a> <img src="yellow.jpg" class="yellow"> <img src="blue.jpg" class="blue"> <img src="green.jpg" class="green"> I'm currently doing it this way for each link/image: $('a.yellow').hover( function () { $('img.yellow').fadeIn('fast'); }, function () { $('img.yellow').fadeOut('fast'); }); The method above works fine, but as I'm still learning, I guess there's a better way to do that instead of repeating functions. Can anyone give me some light here? How can I improve this code?

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• Data Structure Behind Amazon S3s Keys (Filtering Data Structure)

  - by dimo414

  I'd like to implement a data structure similar to the lookup functionality of Amazon S3. For those of you who don't know what I'm taking about, Amazon S3 stores all files at the root, but allows you to look up groups of files by common prefixes in their names, therefore replicating the power of a directory tree without the complexity of it. The catch is, both lookup and filter operations are O(1) (or close enough that even on very large buckets - S3's disk equivalents - both operations might as well be O(1))). So in short, I'm looking for a data structure that functions like a hash map, with the added benefit of efficient (at the very least not O(n)) filtering. The best I can come up with is extending HashMap so that it also contains a (sorted) list of contents, and doing a binary search for the range that matches the prefix, and returning that set. This seems slow to me, but I can't think of any other way to do it. Does anyone know either how Amazon does it, or a better way to implement this data structure?

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• Python 3: timestamp to datetime: where does this additional hour come from?

  - by Beau Martínez

  I'm using the following functions: # The epoch used in the datetime API. EPOCH = datetime.datetime.fromtimestamp(0) def timedelta_to_seconds(delta): seconds = (delta.microseconds * 1e6) + delta.seconds + (delta.days * 86400) seconds = abs(seconds) return seconds def datetime_to_timestamp(date, epoch=EPOCH): # Ensure we deal with `datetime`s. date = datetime.datetime.fromordinal(date.toordinal()) epoch = datetime.datetime.fromordinal(epoch.toordinal()) timedelta = date - epoch timestamp = timedelta_to_seconds(timedelta) return timestamp def timestamp_to_datetime(timestamp, epoch=EPOCH): # Ensure we deal with a `datetime`. epoch = datetime.datetime.fromordinal(epoch.toordinal()) epoch_difference = timedelta_to_seconds(epoch - EPOCH) adjusted_timestamp = timestamp - epoch_difference date = datetime.datetime.fromtimestamp(adjusted_timestamp) return date And using them with the passed code: twenty = datetime.datetime(2010, 4, 4) print(twenty) print(datetime_to_timestamp(twenty)) print(timestamp_to_datetime(datetime_to_timestamp(twenty))) And getting the following results: 2010-04-04 00:00:00 1270339200.0 2010-04-04 01:00:00 For some reason, I'm getting an additional hour added in the last call, despite my code having, as far as I can see, no flaws. Where is this additional hour coming from?

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• NSNumberFormatter crashing iPhone SDK 4.0b2

  - by Ward

  Hey there, I've got an app that's been in the app store for a while and functions perfectly on OS 3.1 - 3.13. However, when tested on 4.0b2 I noticed that it crashes in the same place every time, but only on the device, never on the simulator. I'm using a 3GS to test. On loadView I initialize an NSNumberFormatter object which is declared and retained in the interface so I have access to it everywhere. In my method I call it several times to convert string values into nsnumbers to be stored in a mutable dictionary. Here's an example: [myDictionary setObject:[myStyleFormatter numberFromString:@"1"] forKey:@"hours"]; [myDictionary setObject:[myStyleFormatter numberFromString:@"30"] forKey:@"minutes"]; [myDictionary setObject:[myStyleFormatter numberFromString:@"10"] forKey:@"seconds"]; For some reason it crashes as soon as it tries to set hours. The error is "attempt to insert nil value (key: hours)" Have I been doing something wrong all along? Has the api changed for 4.0b2? Thanks, Howie

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• Sharing memory among YACC, Lex, and C files

  - by sczizzo

  I have a YACC (Bison) grammar, a Lex (Flex) tokenizer, and a C program among which I need to share a struct (or really any variable). Currently, I declare the actual object in the grammar file and extern it wherever I need it (which is to say, my C source file), usually using a pointer to manipulate it. I have a shared header (and implementation) file between the C file and the grammar file with functions useful for manipulating my data structure. This works, but it feels a little uncomfortable. Is there a better way to share memory between the grammar and program?

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• ruby on rails named scope implementation

  - by Engwan

  From the book Agile Web Development With Rails class Order < ActiveRecord::Base named_scope :last_n_days, lambda { |days| {:conditions => ['updated < ?' , days] } } named_scope :checks, :conditions => {:pay_type => :check} end The statement orders = Orders.checks.last_n_days(7) will result to only one query to the database. How does rails implement this? I'm new to Ruby and I'm wondering if there's a special construct that allows this to happen. To be able to chain methods like that, the functions generated by named_scope must be returning themselves or an object than can be scoped further. But how does Ruby know that it is the last function call and that it should query the database now? I ask this because the statement above actually queries the database and not just returns an SQL statement that results from chaining.

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• clear javascript console in Google Chrome

  - by Reigel

  Hi, I was wondering if I could clear up the console with some command.. console.log(), can print... is there a command to clear up console?.. I've tried to console.log(console); and got this functions below... assert: function assert() { [native code] } constructor: function Console() { [native code] } count: function count() { [native code] } debug: function debug() { [native code] } dir: function dir() { [native code] } dirxml: function dirxml() { [native code] } error: function error() { [native code] } group: function group() { [native code] } groupEnd: function groupEnd() { [native code] } info: function info() { [native code] } log: function log() { [native code] } markTimeline: function markTimeline() { [native code] } profile: function profile() { [native code] } profileEnd: function profileEnd() { [native code] } time: function time() { [native code] } timeEnd: function timeEnd() { [native code] } trace: function trace() { [native code] } warn: function warn() { [native code] } __proto__: Object [ I guess there's no way to clear up the console... but I wanted someone to say it to me... ]

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• MATLAB: dealing with java.lang.String

  - by Jason S

  I seem to be stuck in Kafka-land, with a java.lang.String that I can't seem to use in MATLAB functions: K>> name name = Jason K>> sprintf('%s', name) ??? Error using ==> sprintf Function is not defined for 'java.lang.String' inputs. K>> ['my name is ' name] ??? Error using ==> horzcat The following error occurred converting from char to opaque: Error using ==> horzcat Undefined function or method 'opaque' for input arguments of type 'char'. how can I get a java.lang.String to convert to a regular MATLAB character array?

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• Why won't the VisualVM Profiler profile my application?

  - by Luke

  I've created a simple 1 file java application that iterates through a loop, calls some functions, allocates some memory, adds some numbers, etc. I run that application via eclipse's Run As->Java Application. The running application shows up in Java VisualVM under Local. I double click on that application and go to the Profiler tab. The default settings are: Start profiling from classes: my.main.package.** Do not profile classes: java.*, javax.*, sun.*, sunw.*, com.sun.* I click on CPU. The CPU and Memory buttons gray out. Nothing happens. The Status says profiling inactive. When my application terminates the Status says application terminated. What am I doing wrong here? Are there some settings I need to tweak? Do I need to set a VM flag when I launch my application?

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• how to do this in shell

  - by user150674

  I have a very large file, named 'ColCheckMe', tab-delimited, that you are asked to process. You are told that each line in 'ColCheckMe' has 7 columns, and that the values in the 5th column are integers. Using shell functions indicate how you would verify that these conditions are satisfied in 'ColCheckMe' if In the same file, each value in column 1 is unique. How would I verify that? Also how to write a shell function that counts the number of occurrences of the word “SpecStr” in the file 'ColCheckMe' I tried the first part which checks for the valid number of field and checks the 5th field being integer field. nawk ' NF != 7 { printf("[%d] has invalid [%d] number of fields\n", FNR, NF) } $5 !~ /^[0-9]+$/ { printf("[%d] 5th field is invalid [%s]\n", FNR, $5) }' ColCheckMe now i wanna verify in the same file if the value in column 1 is unique. Also is there a way to write a shell function to count the occurrences of the world "SpecStr" in the file 'ColCheckMe' Thanks a lot

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• Why array size in llvm created by llvm's internal tools is not good enough for llvm?

  - by vava

  I'm getting strange error message from the following code: ArrayType * arrayType = ArrayType::get(Type::getInt32Ty(ctx), 0); stack = builder->CreateAlloca(arrayType, ConstantArray::get(arrayType, std::vector<Constant *>())); This code compiles fine but it gives me llvm::Value* getAISize(llvm::LLVMContext&, llvm::Value*): Assertion `Amt-getType() == Type::getInt32Ty(Context) && "Malloc/Allocation array size is not a 32-bit integer!"' failed. during execution. What's interesting, is that I never said of what type array size should be, it was created somewhere inside helper functions. So I naturally see no good reason for assert to be there. But I must be doing something wrong anyway, can you help me spot the problem? Thanks in advance. PS. LLVM, as good as it is, lacking documentation tremendously.

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• Using LINQ to SQL with multiple databases

  - by Stuart Ferguson

  I am working on a new project and hoping to use LINQ to SQL for the data access but have come across the following issue. I need to have my application access 3 databases with similar but not the same table structure, for example Database1 and Database 2 has a table called tblCustomer with 2 columns CustomerKey and CustomerName Database2 has a table called tblCustomer with 3 columns CustomerKey, CustomerName and CustomerPostCode I am looking for a solution that will allow me a query all three databases without the need for 3 GetCustomerList functions as Database1 and Database2 could use the same function as are the same structure, with an override function for database 3 to bring back the additional field. Is there a way i can declare a base datacontext class to handle Database 1 and 2 with an inherited version for Database 3. Thanks In Advance Stuart Ferguson

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• JavaScript setTimeout setInterval within one function

  - by dagoof

  I think I might be overtired but I cannot for the life of me make sense of this, and I think it's due to a lack of knowledge of javascript var itv=function(){ return setInterval(function(){ sys.puts('interval'); }, 1000); } var tout=function(itv){ return setTimeout(function(){ sys.puts('timeout'); clearInterval(itv); }, 5500); } With these two functions I can call a=tout(itv()); and get a looping timer to run for 5.5 seconds and then exit, essentially. By my logic, this should work but it simply is not var dotime=function(){ return setTimeout(function(){ clearInterval(function(){ return setInterval(function(){ sys.puts("interval"); }, 1000); }); }, 5500); } any insight in this matter would be appreciated.

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• Daubechies-4 Transform in MATLAB

  - by Myx

  Hello: I have a 4x4 matrix which I wish to decompose into 4 frequency bands (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4 wavelet transform. As a result of the transform, each band should contain 2x2 coefficients. How can I do this in MATLAB? I know that MATLAB has dbaux and dbwavf functions. However, I'm not sure how to use them and I also don't have the wavelet toolbox. Any help is greatly appreciated. Thanks.

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