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  • How important is managing memory in Objective-C?

    - by Alex Mcp
    Background: I'm (jumping on the bandwagon and) starting learning about iPhone/iPad development and Objective-C. I have a great background in web development and most of my programming is done in javascript (no libraries), Ruby, and PHP. Question: I'm learning about allocating and releasing memory in Objective-C, and I see it as quite a tricky task to layer on top of actually getting the farking thing to run. I'm trying to get a sense of applications that are out there and what will happen with a poorly memory-managed program. A) Are apps usually released with no memory leaks? Is this a feasible goal, or do people more realistically just excise the worst offenders and that's ok? B) If I make an NSString for a title of a view, let's say, and forget to deallocate it it, does this really only become a problem if I recreate that string repeatedly? I imagine what I'm doing is creating an overhead of the memory needed to store that string, so it's probably quite piddling (a few bytes?) However if I have a rapidly looping cycle in a game that 'leaks' an int every cycle or something, that would overflow the app quite quickly. Are these assumptions correct? Sorry if this isn't up the community-wiki alley, I'm just trying to get a handle on how to think about memory and how careful I'll need to be. Any anecdotes or App Store-submitted app experiences would be awesome to hear as well.

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  • Simple way to decrease values without making a new attribute?

    - by Jam
    I'm making a program where you're firing a 'blaster', and I have 5 ammo. I'm blasting an alien who has 5 health. At the end I instantiate the player and make him blast 6 times to check that the program works correctly. But the way I've done it makes it so that the amount won't decrease. Is there an easy fix to this, or do I just have to make a new attribute for ammo and health? Here's what I have: class Player(object): """ A player in a shooter game. """ def blast(self, enemy, ammo=5): if ammo>=1: ammo-=1 print "You have blasted the alien." print "You have", ammo, "ammunition left." enemy.die(5) else: print "You are out of ammunition!" class Alien(object): """ An alien in a shooter game. """ def die(self, health=5): if health>=1: health-=1 print "The alien is wounded. He now has", health, "health left." elif health==0: health-=1 print "The alien gasps and says, 'Oh, this is it. This is the big one. \n" \ "Yes, it's getting dark now. Tell my 1.6 million larvae that I loved them... \n" \ "Good-bye, cruel universe.'" else: print "The alien's corpse sits up momentarily and says, 'No need to blast me, I'm dead already!" # main print "\t\tDeath of an Alien\n" hero = Player() invader = Alien() hero.blast(invader) hero.blast(invader) hero.blast(invader) hero.blast(invader) hero.blast(invader) hero.blast(invader) raw_input("\n\nPress the enter key to exit.")

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  • magento getCollection() can we put where condition?

    - by jarus
    hello , i am working on a magento project and i need to get the value according to country wise like select address where country ="Nepal" can we send the where condition in getCollection() function $collection = Mage::getModel('relocator/location')-getCollection(); any help will be appreciated

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  • Why isn't my operator overloading working properly?

    - by Mithrax
    I have the following Polynomial class I'm working on: #include <iostream> using namespace std; class Polynomial { //define private member functions private: int coef[100]; // array of coefficients // coef[0] would hold all coefficients of x^0 // coef[1] would hold all x^1 // coef[n] = x^n ... int deg; // degree of polynomial (0 for the zero polynomial) //define public member functions public: Polynomial::Polynomial() //default constructor { for ( int i = 0; i < 100; i++ ) { coef[i] = 0; } } void set ( int a , int b ) //setter function { //coef = new Polynomial[b+1]; coef[b] = a; deg = degree(); } int degree() { int d = 0; for ( int i = 0; i < 100; i++ ) if ( coef[i] != 0 ) d = i; return d; } void print() { for ( int i = 99; i >= 0; i-- ) { if ( coef[i] != 0 ) { cout << coef[i] << "x^" << i << " "; } } } // use Horner's method to compute and return the polynomial evaluated at x int evaluate ( int x ) { int p = 0; for ( int i = deg; i >= 0; i-- ) p = coef[i] + ( x * p ); return p; } // differentiate this polynomial and return it Polynomial differentiate() { if ( deg == 0 ) { Polynomial t; t.set ( 0, 0 ); return t; } Polynomial deriv;// = new Polynomial ( 0, deg - 1 ); deriv.deg = deg - 1; for ( int i = 0; i < deg; i++ ) deriv.coef[i] = ( i + 1 ) * coef[i + 1]; return deriv; } Polynomial Polynomial::operator + ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] += b.coef[i]; c.deg = c.degree(); return c; } Polynomial Polynomial::operator += ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] += b.coef[i]; c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator -= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator *= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) for ( int j = 0; j <= b.deg; j++ ) c.coef[i+j] += ( a.coef[i] * b.coef[j] ); c.deg = c.degree(); for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } Polynomial Polynomial::operator - ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); return c; } Polynomial Polynomial::operator * ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) for ( int j = 0; j <= b.deg; j++ ) c.coef[i+j] += ( a.coef[i] * b.coef[j] ); c.deg = c.degree(); return c; } }; int main() { Polynomial a, b, c, d; a.set ( 7, 4 ); //7x^4 a.set ( 1, 2 ); //x^2 b.set ( 6, 3 ); //6x^3 b.set ( -3, 2 ); //-3x^2 c = a - b; // (7x^4 + x^2) - (6x^3 - 3x^2) a -= b; c.print(); cout << "\n"; a.print(); cout << "\n"; c = a * b; // (7x^4 + x^2) * (6x^3 - 3x^2) c.print(); cout << "\n"; d = c.differentiate().differentiate(); d.print(); cout << "\n"; cout << c.evaluate ( 2 ); //substitue x with 2 cin.get(); } Now, I have the "-" operator overloaded and it works fine: Polynomial Polynomial::operator - ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); return c; } However, I'm having difficulty with my "-=" operator: Polynomial Polynomial::operator -= ( Polynomial b ) { Polynomial a = *this; //a is the poly on the L.H.S Polynomial c; for ( int i = 0; i <= a.deg; i++ ) c.coef[i] += a.coef[i]; for ( int i = 0; i <= b.deg; i++ ) c.coef[i] -= b.coef[i]; c.deg = c.degree(); // overwrite value of 'a' with the newly computed 'c' before returning 'a' for ( int i = 0; i < 100; i++) a.coef[i] = c.coef[i]; a.deg = a.degree(); return a; } I just slightly modified my "-" operator method to overwrite the value in 'a' and return 'a', and just use the 'c' polynomial as a temp. I've put in some debug print statement and I confirm that at the time of computation, both: c = a - b; and a -= b; are computed to the same value. However, when I go to print them, their results are different: Polynomial a, b; a.set ( 7, 4 ); //7x^4 a.set ( 1, 2 ); //x^2 b.set ( 6, 3 ); //6x^3 b.set ( -3, 2 ); //-3x^2 c = a - b; // (7x^4 + x^2) - (6x^3 - 3x^2) a -= b; c.print(); cout << "\n"; a.print(); cout << "\n"; Result: 7x^4 -6x^3 4x^2 7x^4 1x^2 Why is my c = a - b and a -= b giving me different results when I go to print them?

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  • [python]: path between two nodes

    - by www.yegorov-p.ru
    I'm using networkx to work with graphs. I have pretty large graph (it's near 200 nodes in it) and I try to find all possible paths between two nodes. But, as I understand, networkx can find only shortest path. How can I get not just shortest path, but all possible paths?

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  • PDCurses TUI C++ Win32 console app - Access violation reading location

    - by Bach
    I have downloaded pdcurses source and was able to successfully include curses.h in my project, linked the pre-compiled library and all good. After few hours of trying out the library, I saw the tuidemo.c in the demos folder, compiled it into an executable and brilliant! exactly what I needed for my project. Now the problem is that it's a C code, and I am working on a C++ project in VS c++ 2008. The files I need are tui.c and tui.h How can I include that C file in my C++ code? I saw few suggestions here but the compiler was not too happy with 100's of warnings and errors. How can I go on including/using that TUI pdcurses includes!? Thanks EDIT: I added extern "C" statement, so my test looks like this now, but I'm getting some other type of error #include <stdio.h> #include <stdlib.h> using namespace std; extern "C" { #include <tui.h> } void sub0(void) { //do nothing } void sub1(void) { //do nothing } int main (int argc, char * const argv[]) { menu MainMenu[] = { { "Asub", sub0, "Go inside first submenu" }, { "Bsub", sub1, "Go inside second submenu" }, { "", (FUNC)0, "" } /* always add this as the last item! */ }; startmenu(MainMenu, "TUI - 'textual user interface' demonstration program"); return 0; } Although it is compiling successfully, it is throwing an Error at runtime, which suggests a bad pointer: 0xC0000005: Access violation reading location 0x021c52f9 at line startmenu(MainMenu, "TUI - 'textual user interface' demonstration program"); Not sure where to go from here. thanks again.

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  • Itertools group by functionality

    - by Nil
    I want to group by on dict key >>> x [{'a': 10, 'b': 90}, {'a': 20}, {'a': 30}, {'a': 10}] >>> [(name, list(group)) for name, group in groupby(x, lambda p:p['a'])] [(10, [{'a': 10, 'b': 90}]), (20, [{'a': 20}]), (30, [{'a': 30}]), (10, [{'a': 10}])] This must group on key 10 :(

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  • Adding values to a C# array

    - by Ross
    Probably a really simple one this - I'm starting out with C# and need to add values to an array, for example: int[] terms; for(int runs = 0; runs < 400; runs++) { terms[] = value; } For those who have used PHP, here's what I'm trying to do in C#: $arr = array(); for ($i = 0; $i < 10; $i++) { $arr[] = $i; } Thanks, Ross

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  • PROLOG all different

    - by inspectorG4dget
    Hello SO, I have a very weird problem with PROLOG. I have used it before, but it's been a while and I'm rusty. I have a list of variables and I need to ensure that none of them are the same. I have tried: use_module(library(bounds)). all_different(A, B, C, D, 6, 8). However, when I try this, I get an error saying that all_different/6 is undefined. How can I go about solving this issue? Is there any library function that I can call directly for this? I am VERY stuck and would greatly appreciate any help. Thanks in advance.

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  • Intro to GPU programming

    - by Adam Davis
    Everyone has this huge massively parallelized supercomputer on their desktop in the form of a graphics card GPU. What is the "hello world" equivalent of the GPU community? What do I do, where do I go, to get started programming the GPU for the major GPU vendors? -Adam

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  • What are basic programs like, recursion, Fibonacci, small trick programs?

    - by Mike
    This question may seem daft (I'm a new to 'programming' and should probably stop if this is the type of question I'm required to ask)... What are: "basic programs like, recursion, fibonacci, factorial, string manipulation, small trick programs"? I've recently read Coding Horror - the non programmer and followed the links to Kegel and How to get hired. Then I delved through some similar questions here (hence the block quote) and I realised that as a fully fledged non-programmer I probably wouldn't know if I knew recursion (or any of the others) because I wouldn't know what it looked like, or why it was used, and what the results would look like after it was used. I suppose I'm trying to get a picture of "the basics". What the principles are and why we learn them - where they'll be used and what result/s your looking for. If they'll be used as an interview question during my first interview sometime in 2020 I would like to look less ignorant than those 199 out of 200 who just don't know the how, or the why, of programming. As always...I'll get my coat. Thanks Mike

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  • Listview with copy-paste

    - by Zubirg
    Hi, Is there an easy way of adding copy-paste for a listview, or should I just switch to DataGridView instead? My application is kinda like an address book, it contains emails, numbers etc where copy paste would be useful.

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  • Proper way in Python to raise errors while setting variables

    - by ensnare
    What is the proper way to do error-checking in a class? Raising exceptions? Setting an instance variable dictionary "errors" that contains all the errors and returning it? Is it bad to print errors from a class? Do I have to return False if I'm raising an exception? Just want to make sure that I'm doing things right. Below is some sample code: @property def password(self): return self._password @password.setter def password(self,password): # Check that password has been completed try: # Check that password has a length of 6 characters if (len(password) < 6): raise NameError('Your password must be greater \ than 6 characters') except NameError: print 'Please choose a password' return False except TypeError: print 'Please choose a password' return False #Set the password self._password = password #Encrypt the password password_md5 = md5.new() password_md5.update(password) self._password_md5 = password_md5.hexdigest()

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  • python: variable not getting defined after several conditionals

    - by Protean
    For some reason this program is saying that 'switch' is not defined. What is going on? #PYTHON 3.1.1 class mysrt: def __init__(self): self.DATA = open('ORDER.txt', 'r') self.collect = 0 cache1 = str(self.DATA.readlines()) cache2 = [] for i in range(len(cache1)): if cache1[i] == '*': if self.collect == 0: self.collect = 1 elif self.collect == 1: self.collect = 0 elif self.collect == 1: cache2.append(cache1[i]) self.ORDER = cache2 self.ARRAY = [] self.GLOBALi = 0 self.GLOBALmax = range(len(self.ORDER)) self.GLOBALc = [] self.GLOBALl = [] def sorter(self, array): CACHE_LIST_1 = [] CACHE_LIST_2 = [] i = 0 for ORDERi in range(len(self.ORDER)): for ARRAYi in range(len(array)): CACHE = array[ARRAYi] if CACHE[self.GLOBALi] == self.ORDER[ORDERi]: CACHE_LIST_1.append(CACHE) else: CACHE_LIST_2.append(CACHE) for i in range(len(CACHE_LIST_1)): if CACHE_LIST_1[0] == CACHE_LIST_1[i] or range(len(CACHE_LIST_1)) == 1: switch = 1 print ('1') else: switch = 0 print ('0') break if switch == 1: self.GLOBALl += CACHE_LIST_1 + self.GLOBALc self.GLOBALi = 0 self.GLOBALc = [] else: self.GLOBALi += 1 self.GLOBALc += CACHE_LIST_2 mysrt.sorter(CACHE) return (self.GLOBALl) #GLOBALi =0 # if range(len(self.GLOBALc)) =! range(len(self.ARRAY)) array = ['ape', 'cow','dog','bat'] ORDER_FILE = [] mysort = mysrt() print (mysort.sorter(array))

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  • How do you handle key down events on Android? I am having issues making it work.

    - by user279112
    For an Android program, I am having trouble handling key down and key up events, and the problem I am having with them can almost certainly be generalized to any sort of user input event. I am using Lunar Lander as one of my main learning devices as I make my first meaningful program, and I noticed that it was using onKeyDown as an overridden method to receive key down events, and it would call one of their more original methods doKeyDown. But when I tried to implement a very small version of my own onKeyDown overide and the actual handler that it calls, it didn't work. I would probably copy and paste my implementations of those two methods, but that doesn't seem to be the problem. You see, I ran the debugger and noticed that they were not getting called - at all. The same goes for my implementations of onKeyUp and the handler that it calls. Something is a little weird here, and when I tried to look at the Android documentation for it, that didn't help at all. I thought that if you had an overide for onKeyDown, then when a key was pressed during execution of the program, onKeyDown would be called as soon as reasonably possible. End of story. But apparently there's something more to it. Apparently you have to do something else somewhere - possibly in the XML when defining the layout or something - to make it work. But I do not know what, and I could not find what in their documentation. What's the secret to this? Thanks!

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  • Java: how to use 3rd-party library?

    - by HH
    $ cat MultiTest.java import com.*; // CODE $ javac Code.java MultiTest.java:1: package com does not exist import com.*; ^ Google Collections Com-dir in the dir where the MultiTest.java -file is located.

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  • Proper way to set class variables

    - by ensnare
    I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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  • Problems with Routing URLs using CGI and Bottle.py

    - by Risingson
    I've been having difficulty getting anything more than a simple index / to return correctly using bottle.py in a CGI environment. When I try to return /hello I get a 404 response. However, if I request /index.py/hello import bottle from bottle import route @route('/') def index(): return 'Index' @route('/hello') def hello(): return 'Hello' if __name__ == '__main__': from wsgiref.handlers import CGIHandler CGIHandler().run(bottle.default_app()) And here is my .htaccess file DirectoryIndex index.py <ifmodule mod_rewrite.c=""> RewriteEngine on RewriteBase / RewriteCond %{REQUEST_FILENAME} !-f RewriteRule ^(.*)$ /index.py/$1 [L] </ifmodule> I copied much of the code from here as I'm using DH and it seemed relevant: http://blog.coderonfire.com/2010/02/running-bottle-python-micro-framework.html Thanks for helping.

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  • Store value of os.system or os.popen

    - by chrissygormley
    Hello, I want to grep the error's out of a log file and save the value as an error. When I use: errors = os.system("cat log.txt | grep 'ERROR' | wc -l") I get the return code that the command worked or not. When I use: errors = os.popen("cat log.txt | grep 'ERROR' | wc -l") I get what the command is trying to do. When I run this in the command line I get 3 as thats how many errors there are. Can anyone suggest another way? Thanks

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  • Android Custom View Constructor

    - by Mitch
    I'm learning about using Custom Views from the following: http://developer.android.com/guide/topics/ui/custom-components.html#modifying The description says: Class Initialization As always, the super is called first. Furthermore, this is not a default constructor, but a parameterized one. The EditText is created with these parameters when it is inflated from an XML layout file, thus, our constructor needs to both take them and pass them to the superclass constructor as well. Is there a better description? I've been trying to figure out what the constructor(s) should look like and I've come up with 4 possible choices (see example at end of post). I'm not sure what these 4 choices do (or don't do), why I should implement them, or what the parameters mean. Is there a description of these? Thanks. Mitch public MyCustomView() { super(); } public MyCustomView(Context context) { super(context); } public MyCustomView(Context context, AttributeSet attrs) { super(context, attrs); } public MyCustomView(Context context, AttributeSet attrs, Map params) { super(context, attrs, params); }

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  • newbie question -- how does one override show for a newtype?

    - by gatoatigrado
    I want to override the default integer constructors in Haskell so they produce strings (mostly for curiosity, but temporarily to make a nice input alternative for LaTeX's \frac{}{} inconvenience). I wanted to be able to use the language itself, instead of a special parser, but I guess that's probably not going to work out... module Main where import Prelude hiding ((+)) newtype A = A Int deriving (Eq, Show, Num) default (A) (+) :: A -> (A -> String) (A a) + (A b) = (show a) ++ " + " ++ (show b) main2 = 3+4 main :: IO () main = putStrLn main2 The problem with the above is that the + function only works for (A, A) instead of (A, String), etc. If one simply leaves out the pattern match "(A a)" and writes "a" instead, then the show() function prepends "A " so "3" becomes "A 3" instead of just "3". I want to override Show for A, but it seems to be quite a headache...

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  • mpicc hangs when called from makefile; runs fine as single command

    - by user2518579
    i'm trying to compile WRF (doubt that's relevant) and am having a problem where mpicc will hang when run w/ the compile script. icc and mpif90 have no issues. the compile script is executed w/ #!/bin/csh -f just to be verbose, here's an example. i run the script and get here make[3]: Entering directory `/home/jason/wrf/wrf3.5/external/RSL_LITE' mpicc -DMPI2_SUPPORT -DMPI2_THREAD_SUPPORT -DFSEEKO64_OK -w -O3 -DDM_PARALLEL -DMAX_HISTORY=25 -DNMM_CORE=0 -c rsl_bcast.c and hang. so then i run that line by itself jason@server:~/wrf/wrf3.5$ cd /home/jason/wrf/wrf3.5/external/RSL_LITE jason@server:wrf3.5/external/RSL_LITE$ mpicc -DMPI2_SUPPORT -DMPI2_THREAD_SUPPORT -DFSEEKO64_OK -w -O3 -DDM_PARALLEL -DMAX_HISTORY=25 -DNMM_CORE=0 -c rsl_bcast.c jason@server:wrf3.5/external/RSL_LITE$ compiles instantly. starting the compile script again does the exact same thing but on the next file. i have no idea what to do, and this is basically impossible to google for.

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  • Single-player pong game

    - by Jam
    I am just starting out learning pygame and livewires, and I'm trying to make a single-player pong game, where you just hit the ball, and it bounces around until it passes your paddle (located on the left side of the screen and controlled by the mouse), which makes you lose. However, I keep getting the error: "Cannot have more than on Screen object", which I can find no references to online really, and I can't make sense of it. I want to eventually make the game more complicated, but I need to make it work first. Help please! Here's the code so far: from livewires import games games.init(screen_width=640, screen_height=480, fps=50) class Paddle(games.Sprite): image=games.load_image("paddle.bmp") def __init__(self): super(Paddle, self).__init__(image=Paddle.image, y=games.mouse.y, left=0) self.score=games.Text(value=0, size=25, top=5, right=games.screen.width-10) games.screen.add(self.score) def update(self): self.y=games.mouse.y self.check_collide() def check_collide(self): for ball in self.overlapping_sprites: self.score.value+=1 self.score.right=games.screen.width-10 ball.handle_collide() class Ball(games.Sprite): image=games.load_image("ball.bmp") speed=1 def __init__(self, x, y=90): super(Ball, self).__init__(image=Ball.image, x=x, y=y, dx=Ball.speed, dy=Ball.speed) def update(self): if self.left<0: self.end_game() self.destroy() def handle_collide(self): if self.right>games.screen.width: self.dx=-self.dx if self.bottom>games.screen.height or self.top<0: self.dy=-self.dy def ball_destroy(self): self.destroy() def main(): background_image=games.load_image("background.bmp", transparent=False) games.screen.background=background_image the_ball=Ball() games.screen.add(the_ball) the_paddle=Paddle() games.screen.add(the_paddle) games.mouse.is_visible=False games.screen.event_grab=True games.screen.mainloop() main()

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