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  • creating a vector with references to some of the elements of another vector

    - by memC
    hi, I have stored instances of class A in a std:vector, vec_A as vec_A.push_back(A(i)). The code is shown below. Now, I want to store references some of the instances of class A (in vec_A) in another vector or another array. For example, if the A.getNumber() returns 4, 7, 2 , I want to put a reference to that instance of A in another vector, say std:vector<A*> filtered_A or an array. Can someone sow me how to do this?? Thanks! class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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  • How to improve the speed of a loop containing a sqlalchemy query statement as conditional

    - by LtPinback
    This loop checks if a record is in the sqlite database and builds a list of dictionaries for those records that are missing and then executes a multiple insert statement with the list. This works but it is very slow (at least i think it is slow) as it takes 5 minutes to loop over 3500 queries. I am a complete newbie in python, sqlite and sqlalchemy so I wonder if there is a faster way of doing this. list_dict = [] session = Session() for data in data_list: if session.query(Class_object).filter(Class_object.column_name_01 == data[2]).filter(Class_object.column_name_00 == an_id).count() == 0: list_dict.append({'column_name_00':a_id, 'column_name_01':data[2]}) conn = engine.connect() conn.execute(prices.insert(),list_dict) conn.close() session.close() edit: I moved session = Session() outside the loop. Did not make a difference.

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  • C#:Saving image to folder

    - by Meko
    HI. I know this is simple question but when I use FirstPersonTestImage.Save(IIdComboBox.Text + "-" + i + ".jpg"); it works and saves file to folder where is the .exe file . But I want to save it to specific folder like /photo/IO-66/ and tryed to use String StudentPath = PhotoPath + IGroupNoComboBox.Text + "/" + IIdComboBox.Text + "/" + IIdComboBox.Text + "-" + i + ".jpg"; FirstPersonTestImage.Save(StudentPath); BUt it gives An unhandled exception of type 'System.Runtime.InteropServices.ExternalException' occurred in System.Drawing.dll How can I solve this problem? Is is about folder path ? or using "/" ? EDIT Here My code for creating and checking existing or not folder if (!System.IO.Directory.Exists(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim())) { Directory.CreateDirectory(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim()); } if (!System.IO.Directory.Exists(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim()+ "/" + IIdComboBox.Text.ToString().Trim() + "/")) { Directory.CreateDirectory(PhotoPath + "/" + IGroupNoComboBox.Text.ToString().Trim()+"/" + IIdComboBox.Text.ToString().Trim() + "/"); }

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  • Replacing emty csv column values with a zero

    - by homerjay
    Hey, So I'm dealing with a csv file that has missing values. What I want my script to is: #!/usr/bin/python import csv import sys #1. Place each record of a file in a list. #2. Iterate thru each element of the list and get its length. #3. If the length is less than one replace with value x. reader = csv.reader(open(sys.argv[1], "rb")) for row in reader: for x in row[:]: if len(x)< 1: x = 0 print x print row Here is an example of data, I trying it on, ideally it should work on any column lenghth Before: actnum,col2,col4 xxxxx , , xxxxx , 845 , xxxxx , ,545 After actnum,col2,col4 xxxxx , 0 , 0 xxxxx , 845, 0 xxxxx , 0 ,545 Any guidance would be appreciated

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  • Java: how to initialize String[]?

    - by Heoa
    Error % javac StringTest.java StringTest.java:4: variable errorSoon might not have been initialized errorSoon[0] = "Error, why?"; Code public class StringTest { public static void main(String[] args) { String[] errorSoon; errorSoon[0] = "Error, why?"; } }

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  • Hash Tables - Java

    - by Antony
    Am about to do a homework, and i need to store quite a lot of information (Dictionary) in a data structure of my choice. I heard people in my classroom saying hash-tables are the way to go. How come?

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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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  • command line arg?

    - by kaushik
    This is a module named XYZ. def func(x) ..... ..... if __name__=="__main__": print func(sys.argv[1]) Now I have imported this module in another code and want to use the func. How can i use it? import XYZ After this, where to give the argument, and syntax on how to call it, please?

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  • What is/are the Scala way(s) to implement this Java "byte[] to Hex" class

    - by nicerobot
    I'm specifically interested in Scala (2.8) techniques for building strings with formats as well as interesting ways to make such a capability easily accessible where it's useful (lists of bytes, String, ...?).. public class Hex { public static String valueOf (final byte buf[]) { if (null == buf) { return null; } final StringBuilder sb = new StringBuilder(buf.length * 2); for (final byte b : buf) { sb.append(String.format("%02X", b & 0xff)); } return sb.toString(); } public static String valueOf (final Byteable o) { return valueOf(o.toByteArray()); } } This is only a learning exercise (so the utility and implementation of the Java isn't a concern.) Thanks

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  • Type signature "Maybe a" doesn't like "Just [Event]"

    - by sisif
    I'm still learning Haskell and need help with the type inference please! Using packages SDL and Yampa I get the following type signature from FRP.Yampa.reactimate: (Bool -> IO (DTime, Maybe a)) and I want to use it for: myInput :: Bool -> IO (DTime, Maybe [SDL.Event]) myInput isBlocking = do event <- SDL.pollEvent return (1, Just [event]) ... reactimate myInit myInput myOutput mySF but it says Couldn't match expected type `()' against inferred type `[SDL.Event]' Expected type: IO (DTime, Maybe ()) Inferred type: IO (DTime, Maybe [SDL.Event]) In the second argument of `reactimate', namely `input' In the expression: reactimate initialize input output process I thought Maybe a allows me to use anything, even a SDL.Event list? Why is it expecting Maybe () when the type signature is actually Maybe a? Why does it want an empty tuple, or a function taking no arguments, or what is () supposed to be?

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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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  • 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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  • How can I add file locations to a database after they are uploaded using a Perl CGI script?

    - by Paul K
    I have a CGI program I have written using Perl. One of its functions is to upload pics to the server. All of it is working well, including adding all kinds of info to a MySQL db. My question is: How can I get the uploaded pic files location and names added to the db? I would rather that instead of changing the script to actually upload the pics to the db. I have heard horror stories of uploading binary files to databases. Since I am new to all of this, I am at a loss. Have tried doing some research and web searches for 3 weeks now with no luck. Any suggestions or answers would be greatly appreciated. I would really hate to have to manually add all the locations/names to the db. I am using: a Perl CGI script, MySQL db, Linux server and the files are being uploaded to the server. I AM NOT looking to add the actual files to the db. Just their location(s).

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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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  • 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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  • 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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  • Ruby getting the diagonal elements in a 2d Array

    - by Calm Storm
    Hi, I was trying some problems with my 2D ruby array and my LOC reduces a lot when I do array slicing. So for example, require "test/unit" class LibraryTest < Test::Unit::TestCase def test_box array = [[1,2,3,4],[3,4,5,6], [5,6,7,8], [2,3,4,5]] puts array[1][2..3] # 5, 6 puts array[1..2][1] # 5, 6, 7, 8 end end I want to know if there is a way to get a diagonal slice? Lets say I want to start at [0,0] and want a diagonal slice of 3. Then I would get elements from [0,0], [1,1], [2,2] and I will get an array like [1,4,7] for example above. Is there any magic one-liner ruby code that can achieve this? 3.times do {some magic stuff?}

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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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  • 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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