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  • Using C++, why can `throw` cause `terminate()`, and when are the stack variables to be freed?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • Combine Hibernate class with @Bindable for SwingBuilder without Griffon?

    - by Misha Koshelev
    Dear All: I have implemented a back-end for my application in Groovy/Gradle, and am now trying to implement a GUI. I am using Hibernate for my data storage (with HSQLDB) per http://groovy.codehaus.org/Using+Hibernate+with+Groovy (with Jasypt for encryption) and it is working quite well. I was wondering if there are any good tips for using @Bindable with, e.g., an @Entity class such as @Entity class Book { @Id @GeneratedValue(strategy = GenerationType.AUTO) public Long id @OneToMany(cascade=CascadeType.ALL) public Set<Author> authors public String title String toString() { "$title by ${authors.name.join(', ')}" } } or if I am: (i) asking for Griffon (ii) completely on the wrong track? Thank you! Misha

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  • Does Perl auto-vivify variables used as references in subroutine calls?

    - by FM
    I've declared 2010 to be the year of higher-order programming, so I'm learning Haskell. The introduction has a slick quick-sort demo, and I thought, "Hey, that's easy to do in Perl". It turned to be easier than I expected. Note that I don't have to worry about whether my partitions ($less and $more) are defined. Normally you can't use an undefined value as an array reference. use strict; use warnings; use List::MoreUtils qw(part); my @data = (5,6,7,4,2,9,10,9,5,1); my @sorted = qsort(@data); print "@sorted\n"; sub qsort { return unless @_; my $pivot = shift @_; my ($less, $more) = part { $_ < $pivot ? 0 : 1 } @_; # Works, even though $less and $more are sometimes undefined. return qsort(@$less), $pivot, qsort(@$more); } As best I can tell, Perl will auto-vivify a variable that you try to use as a reference -- but only if you are passing it to a subroutine. For example, my call to foo() works, but not the attempted print. use Data::Dumper qw(Dumper); sub foo { print "Running foo(@_)\n" } my ($x); print Dumper($x); # Fatal: Can't use an undefined value as an ARRAY reference. # print @$x, "\n"; # But this works. foo(@$x); # Auto-vivification: $x is now []. print Dumper($x); My questions: Am I understanding this behavior correctly? What is the explanation or reasoning behind why Perl does this? Is this behavior explained anywhere in the docs?

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  • Resolving type parameter values passed to ancester type using reflection

    - by Tom Tucker
    I've asked a similar question before, but this one is much more challenging. How do I find a value of a specific type parameter that is passed to an ancestor class or an interface implemented by one of its ancestor classes using reflection? I basically need to write a method that looks like this. // Return the value of the type parameter at the index passed to the parameterizedClass from the clazz. Object getParameterValue(Class<?> clazz, Class<?> parameterizedClass, int index) For the example below, getParameterValue(MyClass.class, Map.class, 1) would return String.class public class Foo<K, V> implements Map<K, V>{ } public class Bar<V> extends Foo<Integer, V> { } public class MyClass extends Bar<String> { } Thanks!

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  • Junit Parameterized tests together with Powermock - how!?

    - by Subtwo
    Hi! I've been trying to figure out how to run parameterized tests in Junit4 together with PowerMock. The problem is that to use PowerMock you need to decorate your test class with @RunWith(PowerMock.class) and to use parameterized tests you have to decorate with @RunWith(Parameterized.class) From what I can see they seem mutually excluded!? Is this true? Is there any way around this? I've tried to create a parameterized class within a class running with PowerMock; something like this: @RunWith(PowerMock.class) class MyTestClass { @RunWith(Parameterized.class) class ParamTestClass { // Yadayada } } But unfortunately this doesn't do much good... The ParamTestClass still doesn't run with PowerMock support (not that surprisingly maybe)... And I've kind of run out of ideas so any help is greatly appreciated!

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  • Can threads safely read variables set by VCL events?

    - by Tom1952
    Is it safe for a thread to READ a variable set by a Delphi VCL event? When a user clicks on a VCL TCheckbox, the main thread sets a boolean to the checkbox's Checked state. CheckboxState := CheckBox1.Checked; At any time, a thread reads that variable if CheckBoxState then ... It doesn't matter if the thread "misses" a change to the boolean, because the thread checks the variable in a loop as it does other things. So it will see the state change eventually... Is this safe? Or do I need special code? Is surrounding the read and write of the variable (in the thread and main thread respectively) with critical code calls necessary and sufficient? As I said, it doesn't matter if the thread gets the "wrong" value, but I keep thinking that there might be a low-level problem if one thread tries to read a variable while the main thread is in the middle of writing it, or vice versa. My question is similar to this one: http://stackoverflow.com/questions/1353096/cross-thread-reading-of-a-variable. (Also related to my previous question: http://stackoverflow.com/questions/2449183/using-entercriticalsection-in-thread-to-update-vcl-label)

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  • When defining a class as internal, do you define what would usually be public fields as internal?

    - by devoured elysium
    When defining a class as internal, do you define what would usually be public fields as internal? Or do you leave them as public? I have a set of classes with public/private methods that I have decided to set as internal. Now, should I change the class' modifier to internal and let the rest of the methods/properties as they are (public/private) or switch them to (internal/private)? I don't see a big point in changing it to internal, and if by some reason later I want to set them back to public it's going to give a lot of work to have to put them back to public again. Any other thoughts on this?

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  • R ggplot barplot; Fill based on two separate variables

    - by user1476968
    A picture says more than a thousand words. As you can see, my fill is based on the variable variable. Within each bar there is however multiple data entities (black borders) since the discrete variable complexity make them unique. What I am trying to find is something that makes each section of the bar more distinguishable than the current look. Preferable would be if it was something like shading. Here's an example (not the same dataset, since the original was imported): dat <- read.table(text = "Complexity Method Sens Spec MMC 1 L Alpha 50 20 10 2 M Alpha 40 30 80 3 H Alpha 10 10 5 4 L Beta 70 50 60 5 M Beta 49 10 80 6 H Beta 90 17 48 7 L Gamma 19 5 93 8 M Gamma 18 39 4 9 H Gamma 10 84 74", sep = "", header=T) library(ggplot2) library(reshape) short.m <- melt(dat) ggplot(short.m, aes(x=Method, y= value/100 , fill=variable)) + geom_bar(stat="identity",position="dodge", colour="black") + coord_flip()

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  • How can I get jsonp to play nice with my class?

    - by George Edison
    This whole jsonp thing is quite confusing... Here is what I want to do: I have a class DataRetriever The class has a method GetData GetData makes a jsonp request with the following code: var new_tag = document.createElement('script'); new_tag.type = 'text/javascript'; new_tag.src = 'http://somesite.com/somemethod?somedata'; // Add the element var bodyRef = document.getElementsByTagName("body").item(0); bodyRef.appendChild(new_tag); Now, the jsonp data from the server somesite.com can call a function in my code with the data. The problem is, how does the data get delivered to the instance of DataRetriever that requested it? I'm really stuck here.

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  • Why isn't DBIx::Class::Schema::Loader creating my classes?

    - by Robert Wohlfarth
    I am trying to generate static schemas using DBIx::Class in Perl. The command shown below outputs a Schema.pm and no other files. Any idea what I'm doing wrong, or how to to debug this? U:\wohlfarj\Software\PARS>perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:.\lib -e "make_schema_at('PARS::Schema',{debug=>1},['dbi:ODBC:PARS','user','password',{AutoCommit=>0}])" Dumping manual schema for PARS::Schema to directory .\lib ... Schema dump completed. I'm using Strawberry Perl on Windows XP. The database is SQL Server 2000, accessed through an ODBC connection. I can successfully run queries using plain old DBI with the same ODBC connection.

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  • Does `throw` cause stack variables (full types) to be freed from memory in C++?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • Lua metatable Objects cannot be purge from memory?

    - by Prometheus3k
    Hi there, I'm using a proprietary platform that reported memory usage in realtime on screen. I decided to use a Class.lua I found on http://lua-users.org/wiki/SimpleLuaClasses However, I noticed memory issues when purging object created by this using a simple Account class. Specifically, I would start with say 146k of memory used, create 1000 objects of a class that just holds an integer instance variable and store each object into a table. The memory used is now 300k I would then exit, iterating through the table and setting each element in the table to nil. But would never get back the 146k, usually after this I am left using 210k or something similar. If I run the load sequence again during the same session, it does not exceed 300k so it is not a memory leak. I have tried creating 1000 integers in a table and setting these to nil, which does give me back 146k. In addition I've tried a simpler class file (Account2.lua) that doesn't rely on a class.lua. This still incurs memory fragmentation but not as much as the one that uses Class.lua Can anybody explain what is going on here? How can I purge these objects and get back the memory? here is the code --------Class.lua------ -- class.lua -- Compatible with Lua 5.1 (not 5.0). --http://lua-users.org/wiki/SimpleLuaClasses function class(base,ctor) local c = {} -- a new class instance if not ctor and type(base) == 'function' then ctor = base base = nil elseif type(base) == 'table' then -- our new class is a shallow copy of the base class! for i,v in pairs(base) do c[i] = v end c._base = base end -- the class will be the metatable for all its objects, -- and they will look up their methods in it. c.__index = c -- expose a ctor which can be called by () local mt = {} mt.__call = function(class_tbl,...) local obj = {} setmetatable(obj,c) if ctor then ctor(obj,...) else -- make sure that any stuff from the base class is initialized! if base and base.init then base.init(obj,...) end end return obj end c.init = ctor c.instanceOf = function(self,klass) local m = getmetatable(self) while m do if m == klass then return true end m = m._base end return false end setmetatable(c,mt) return c end --------Account.lua------ --Import Class template require 'class' local classname = "Account" --Declare class Constructor Account = class(function(acc,balance) --Instance variables declared here. if(balance ~= nil)then acc.balance = balance else --default value acc.balance = 2097 end acc.classname = classname end) --------Account2.lua------ local account2 = {} account2.classname = "unnamed" account2.balance = 2097 -----------Constructor 1 do local metatable = { __index = account2; } function Account2() return setmetatable({}, metatable); end end --------Main.lua------ require 'Account' require 'Account2' MAX_OBJ = 5000; test_value = 1000; Obj_Table = {}; MODE_ACC0 = 0 --integers MODE_ACC1 = 1 --Account MODE_ACC2 = 2 --Account2 TEST_MODE = MODE_ACC0; Lua_mem = ""; print("##1) collectgarbage('count'): " .. collectgarbage('count')); function Load() for i=1, MAX_OBJ do if(TEST_MODE == MODE_ACC0 )then table.insert(Obj_Table, test_value); elseif(TEST_MODE == MODE_ACC1 )then table.insert(Obj_Table, Account(test_value)); --Account.lua elseif(TEST_MODE == MODE_ACC2 )then table.insert(Obj_Table, Account2()); --Account2.lua Obj_Table[i].balance = test_value; end end print("##2) collectgarbage('count'): " .. collectgarbage('count')); end function Purge() --metatable purge if(TEST_MODE ~= MODE_ACC0)then --purge stage 0: print("set each elements metatable to nil") for i=1, MAX_OBJ do setmetatable(Obj_Table[i], nil); end end --purge stage 1: print("set table element to nil") for i=1, MAX_OBJ do Obj_Table[i] = nil; end --purge stage 2: print("start table.remove..."); for i=1, MAX_OBJ do table.remove(Obj_Table, i); end print("...end table.remove"); --purge stage 3: print("create new object_table {}"); Obj_Table= {}; --purge stage 4: print("collectgarbage('collect')"); collectgarbage('collect'); print("##3) collectgarbage('count'): " .. collectgarbage('count')); end --Loop callback function OnUpdate() collectgarbage('collect'); Lua_mem = collectgarbage('count'); end ------------------- --NOTE: --On start of game runs Load(), another runs Purge() --Update I've updated the code with suggestions from comments below, and will post my findings later today.

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  • Inheriting the main method

    - by Eric
    I want to define a base class that defines a main method that instantiates the class, and runs a method. There are a couple of problems though. Here is the base class: public abstract class Strategy { abstract void execute(SoccerRobot robot); public static void main(String args) { Strategy s = new /*Not sure what to put here*/(); s.execute(new SoccerRobot()) } } And here is an example derived class: public class UselessStrategy { void execute(SoccerRobot robot) { System.out.println("I'm useless") } } It defines a simple execute method, which should be called in a main method upon usage as a the main application. However, in order to do so, I need to instantiate the derived class from within the base class's main method. Which doesn't seem to be possible. I'd rather not have to repeat the main method for every derived class, as it feels somewhat unnessary. Is there a right way of doing this?

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  • What is a class outlet and where is it?

    - by chrish
    I am trying to learn iPhone development and someone passed along the website www.appsamuck.com. On Day 1, the tutorial instructs the developer We need to reference the label in our code so we can update the label * In the document window "File's Owner" * Click: Tools->Idenity Inspector * In the inspector click the + under "Class Outlets" * Change myOutlet1 to "countdownLabel" * Change id to UILabel * Click enter to make sure they commit I really don't want to get hung up on this, but I can't find "Class Outlets" either when creating a new project from scratch or opening the zipped source code project. Is this just a difference in versions of Interface Builder? Where did it go?

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  • Password test in 1st Tab.m to load a loginView gives class error?

    - by Michael Robinson
    I have a name and password in NSUserDefaults for login. I have this in my 1stTab View.m class to test for presence and load a login/signup loginView.xib modally if there is no password or name stored in the app. Here is the pulling of the defaults: -(void)refreshFields { NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; usernameLabel.text = [defaults objectForKey:kUsernameKey]; passwordLabel.text = [defaults objectForKey:kPasswordKey]; { Here is the Test: - (void)viewDidAppear:(BOOL)animated { [self refreshFields]; [super viewDidAppear:animated]; if ([usernameLabel.text length] == 0 || [passwordLabel.text length] == 0) { LoginViewController * vc = [[[LoginViewController alloc] initWithNibName:@"LoginView" bundle:nil] autorelease]; [self presentModalViewController:vc animated: false]; } else { [[self tableView ]reloadData]; } } Thanks in advance, I'm getting this error in the console: * Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[ setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key usernameLabel.'

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  • Can we you the attached properties in C# class library?

    - by Manas Agarwal
    Hi I have implemented the Observer Pattern with lazy load. The class that requests the data from the database is a singleton class. Now I am able to load the data from one database (located in one datacenter) very easily. But I need to get the data from other data centers too and display on the same UI. I can somehow pass the address of second data center and fetch the data from there also. But once I will get the data from second data center, it will be added to earlier list only. So later it will be thought for me to distinguish between the data. So I thought of attaching a property with the result set, so that while displaying the output I can show the data for both the data centers separately but on the same UI. I thought of attached property as an option where I can attach the data center name with the list of the data obtained. How is it possible to do in C#? Thanks Manas

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  • Does `throw` cause stack variables to be freed from memory in C++?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • Should class IOException in Java have been an unchecked RuntimeException?

    - by Derek Mahar
    Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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