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  • Stop overlooking minor details

    - by Mark Lubin
    Compared to most people on this site I am admittedly a novice. I wanted to get some advice from the pros on how to avoid making stupid errors in your code. Is there anyone else who had the problem when they were first starting out of missing some detail that causes big problems? Are there any habits or behaviors that helped you over come this.

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  • sending address of a variable declared on the stack?

    - by kobac
    I have a doubt concerning declaring variables, their scope, and if their address could be sent to other functions even if they are declared on the stack? class A{ AA a; void f1(){ B b; aa.f2(&b); } }; class AA{ B* mb; f2(B* b){ mb = b; //... } }; Afterwards, I use my AA::mb pointer in the code. So things I would like to know are following. When the program exits A::f1() function, b variable since declared as a local variable and placed on the stack, can't be used anymore afterwards. What happens with the validity of the AA::mb pointer? It contains the address of the local variable which could not be available anymore, so the pointer isn't valid anymore? If B class is a std::<vector>, and AA::mb is not a pointer anymore to that vector, but a vector collection itself for example. I would like to avoid copying all of it's contents in AA::f2() to a member AA::mb in line mb = b. Which solution would you recommend since I can't assign a pointer to it, because it'll be destroyed when the program exits AA::f2()

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  • Java queue and multi-dimension array

    - by javaLearner.java
    First of all, this is my code (just started learning java): Queue<String> qe = new LinkedList<String>(); qe.add("b"); qe.add("a"); qe.add("c"); qe.add("d"); qe.add("e"); My question: Is it possible to add element to the queue with two values, like: qe.add("a","1"); // where 1 is integer So, that I know element "a" have value 1. If I want to add a number let say "2" to element a, I will have like a = 3. If this cant be done, what else in java classes that can handle this? I tried to use multi-dimention array, but its kinda hard to do the queue, like pop, push etc. (Maybe I am wrong) How to call specific element in the queue? Like, call element a, to check its value. [Note] Please don't give me links that ask me to read java docs. I was reading, and I still dont get it. The reason why I ask here is because, I know I can find the answer faster and easier.

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  • Java: ListA.addAll(ListB) fires NullPointerException?

    - by HH
    The err part is Capitalized in the code, it also comes in foreaching. Because of the abstract list, it cannot be initialized, declaration is in a static field. The lists have the same type. import java.util.*; public class Test { public static final List<String> highPrio = Arrays.asList("*","/"); public static List<String> ops; public static void main(String[] args) { //ERROR HERE, why do it throw nullPointer? ops.addAll(highPrio); for(String s : ops) { System.out.println(s); } } }

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  • C++ - Efficient way to iterate over the contents of a vector?

    - by Francisco P.
    Hello, everyone! I am implementing a text-based version of Scrabble for a college project. I have a vector containing around 400K strings (my dictionary), and, at some point in every turn, I'm going to have to check if any word in the dictionary can be formed with the pieces in the player's hand. My only solution to this is iterating through the string, one by one, and using a sub-routine I have to check if the string in question can be formed from the player's pieces. I'll implement a quickfail checking if the user has any vowels, but it'll still be woefully inefficient. Any suggestions? Thanks for your time!

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  • What things can I teach a group of children about programming in one day?

    - by Rich Bradshaw
    I'm running a day for 30 kids aged 11-18 about computer game programming. They have all opted to do it, but they have no experience at all of programming. My main aim is for them to learn a few things: programming is hard/challenging programming is something they can learn to do being a computer games programmer != playing games all day a little more insight into how games actually work I'd thought of splitting them into two groups, of younger/less experience and older/more experience, then doing slightly different things. I'd considered showing them Scratch, Game Maker, before showing them the basics of Python and getting them to write a simple text based game (perhaps something like, computer picks a random number, you have to guess it in as few guesses as possible, computer says higher/lower for each guess). Does anyone have any ideas of things to do/show them/ways to teach them?

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  • Binding a collection to Listbox

    - by Blub
    Hi, I basically started today with WPF, and I'm astounded by how difficult it is to do binding. I have an array of Textboxes, in an ObservableCollection, and just want to bind that in my Listbox, so that they arrange themselves vertically. I have fiddled around with this for 3 already, can you help? I'm working in a Wpf "UserControl", not a window as so many tutorials seem to rely on.

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  • using MySQL without installing server

    - by Meko
    Is there any way to use MySQL without install? I am making an desctop application using Visual studio and C# that uses MySQL.I will use this program on another computer.if this computer has no MySQL installation my program will also work? Can I move my data base with my application?

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  • change values in a list - python

    - by ariel
    I have this code: a=[['a','b','c'],['a','f','c'],['a','c','d']] for x in a: for y in x: if 'a' in x: x.replace('a','*')` but the result is: a=[['a','b','c'],['a','f','c'],['a','c','d']] and bot a=[['b','c'],['f','c'],['c','d']] What should I do so the changes will last?

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  • what is the regular expression for this

    - by bn
    I want to parse this (adv) much (thanks) I want to eliminate the words and the bracket (adv) but not (thanks) the condition is: inside bracket, and word length inside bracket is 1-5 characters I am using preg_match in PHP Thank You

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  • Worst aspect of Python for a newbie

    - by schickb
    I'm wondering specifically what experienced programmers thought when they started developing in Python. I'm sure the answer depends on your background, but my own personal answer is the conversion of basically anything in the language to a True/False value in boolean contexts. Resulting in "oddities" like: if x: not meaning the same thing as: if x == True: I understand why, but it bugs me, and I certainly had to think about it a bit when I first ran into it.

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  • C++ - Error: expected unqualified-id before ‘using’

    - by Francisco P.
    Hello, everyone. I am having some trouble on a project I'm working on. Here's the header file for the calor class: #ifndef _CALOR_ #define _CALOR_ #include "gradiente.h" using namespace std; class Calor : public Gradiente { public: Calor(); Calor(int a); ~Calor(); int getTemp(); int getMinTemp(); void setTemp(int a); void setMinTemp(int a); void mostraSensor(); }; #endif When I try to compile it: calor.h|6|error: expected unqualified-id before ‘using’| Why does this happen? I've been searching online and learned this error occurs mostly due to corrupted included files. Makes no sense to me, though. This class inherits from gradiente: #ifndef _GRADIENTE_ #define _GRADIENTE_ #include "sensor.h" using namespace std; class Gradiente : public Sensor { protected: int vActual, vMin; public: Gradiente(); ~Gradiente(); } #endif Which in turn inherits from sensor #ifndef _SENSOR_ #define _SENSOR_ #include <iostream> #include <fstream> #include <string> #include "definicoes.h" using namespace std; class Sensor { protected: int tipo; int IDsensor; bool estadoAlerta; bool estadoActivo; static int numSensores; public: Sensor(/*PARAMETROS*/); Sensor(ifstream &); ~Sensor(); int getIDsensor(); bool getEstadoAlerta(); bool getEstadoActivo(); void setEstadoAlerta(int a); void setEstadoActivo(int a); virtual void guardaSensor(ofstream &); virtual void mostraSensor(); // FUNÇÃO COMUM /* virtual int funcaoComum() = 0; virtual int funcaoComum(){return 0;};*/ }; #endif For completeness' sake, here's definicoes.h #ifndef _DEFINICOES_ #define _DEFINICOES_ const unsigned int SENSOR_MOVIMENTO = 0; const unsigned int SENSOR_SOM = 1; const unsigned int SENSOR_PRESSAO = 2; const unsigned int SENSOR_CALOR = 3; const unsigned int SENSOR_CONTACTO = 4; const unsigned int MIN_MOVIMENTO = 10; const unsigned int MIN_SOM = 10; const unsigned int MIN_PRESSAO = 10; const unsigned int MIN_CALOR = 35; #endif Any help'd be much appreciated. Thank you for your time. Thanks for your time!

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  • Does the OS make a significant difference for Ruby Development ?

    - by Bragaadeesh
    Hi, I have been working in Java for the past 4 years and I am currently switching over to Ruby. I am so excited about it and I feel good to finally get a hands on experience on a scripting language first time. The task assigned to me is to first pick a OS of my choice and setup a Ruby in it and study for 2 weeks. I have been developing applications in windows and Linux is not my cup of tea. Some part of me wants to try out Linux but I want to first convince myself whether OS really matters for Ruby development. If Linux does matter, which distribution can I start looking at? Please advise.

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  • C++: Trouble with dependent types in templates

    - by Rosarch
    I'm having trouble with templates and dependent types: namespace Utils { void PrintLine(const string& line, int tabLevel = 0); string getTabs(int tabLevel); template<class result_t, class Predicate> set<result_t> findAll_if(typename set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred) // warning C4346 { set<result_t> result; return findAll_if_rec(begin, end, pred, result); } } namespace detail { template<class result_t, class Predicate> set<result_t> findAll_if_rec(set<result_t>::iterator begin, set<result_t>::iterator end, Predicate pred, set<result_t> result) { typename set<result_t>::iterator nextResultElem = find_if(begin, end, pred); if (nextResultElem == end) { return result; } result.add(*nextResultElem); return findAll_if_rec(++nextResultElem, end, pred, result); } } Compiler complaints, from the location noted above: warning C4346: 'std::set<result_t>::iterator' : dependent name is not a type. prefix with 'typename' to indicate a type error C2061: syntax error : identifier 'iterator' What am I doing wrong?

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  • How to use the php fopen() correctly

    - by Jacksta
    I am learning php, trying to use the fopen() function. The php file I am coding is in this directory /domains/xxxxx.com.au/public_html/phpfile.php What path do I specify for the file to be opened, the example I am looking at is based on a server on a pc where this is the file path $filename = "c:/newfile.txt"; not an online server.

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  • How to enumerate returned rows in SQL?

    - by SilentGhost
    I was wondering if it would be possible to enumerate returned rows. Not according to any column content but just yielding a sequential integer index. E.g. select ?, count(*) as usercount from users group by age would return something along the lines: 1 12 2 78 3 4 4 42

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  • linked list problem (with insert)

    - by JohnWong
    The problem appears with the insert function that I wrote. 3 conditions must work, I tested b/w 1 and 2, b/w 2 and 3 and as last element, they worked. But b/w 3 and 4, it did not work. It only display up to the new added record, and did not show the fourth element. Efficiency is not my concern here (not yet). Please guide me through this debug process. Thank you very much. #include<iostream> #include<string> using namespace std; struct List // we create a structure called List { string name; string tele; List *nextAddr; }; void populate(List *); void display(List *); void insert(List *); int main() { const int MAXINPUT = 3; char ans; List * data, * current, * point; // create two pointers data = new List; current = data; for (int i = 0; i < (MAXINPUT - 1); i++) { populate(current); current->nextAddr = new List; current = current->nextAddr; } // last record we want to do it sepeartely populate(current); current->nextAddr = NULL; cout << "The current list consists of the following data records: " << endl; display(data); // now ask whether user wants to insert new record or not cout << "Do you want to add a new record (Y/N)?"; cin >> ans; if (ans == 'Y' || ans == 'y') { /* To insert b/w first and second, use point as parameter between second and third uses point->nextAddr between third and fourth uses point->nextAddr->nextAddr and insert as last element, uses current instead */ point = data; insert(()); display(data); } return 0; } void populate(List *data) { cout << "Enter a name: "; cin >> data->name; cout << "Enter a phone number: "; cin >> data->tele; return; } void display(List *content) { while (content != NULL) { cout << content->name << " " << content->tele; content = content->nextAddr; cout << endl; // we skip to next line } return; } void insert(List *last) { List * temp = last->nextAddr; //save the next address to temp last->nextAddr = new List; // now modify the address pointed to new allocation last = last->nextAddr; populate(last); last->nextAddr = temp; // now link all three together, eg 1-NEW-2 return; }

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  • C++ - Efficient container for large amounts of searchable data?

    - by Francisco P.
    Hello, everybody! I am implementing a text-based version of Scrabble for a College project. My dictionary is quite large, weighing in at around 400.000 words (std::string). Searching for a valid word will suck, big time, in terms of efficiency if I go for a vector<string> ( O(n) ). Are there any good alternatives? Keep in mind, I'm enrolled in freshman year. Nothing TOO complex! Thanks for your time! Francisco

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  • Zsh: how to see all buffers?

    - by HH
    You can push things to buffer with ^Q and pop them with ESC-g. Alt+x vi-set-buffer changes buffer somehow. How can I see all the buffers? They are probably some files to look at.

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  • Several modules in a package importing one common module

    - by morpheous
    I am writing a python package. I am using the concept of plugins - where each plugin is a specialization of a Worker class. Each plugin is written as a module (script?) and spawned in a separate process. Because of the base commonality between the plugins (e.g. all extend a base class 'Worker'), The plugin module generally looks like this: import commonfuncs def do_work(data): # do customised work for the plugin print 'child1 does work with %s' % data In C/C++, we have include guards, which prevent a header from being included more than once. Do I need something like that in Python, and if yes, how may I make sure that commonfuncs is not 'included' more than once?

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