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  • Where to put constant strings in C++: static class members or anonymous namespaces

    - by stone
    I need to define some constant strings that will be used only by one class. It looks like I have three options: Embed the strings directly into locations where they are used. Define them as private static constant members of the class: //A.h class A { private: static const std::string f1; static const std::string f2; static const std::string f3; }; //A.cpp const std::string f1 = "filename1"; const std::string f2 = "filename2"; const std::string f3 = "filename3"; //strings are used in this file Define them in an anonymous namespace in the cpp file: //A.cpp namespace { const std::string f1 = "filename1"; const std::string f2 = "filename2"; const std::string f3 = "filename3"; } //strings are used in this file Given these options, which one would you recommend and why? Thanks.

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  • Mysqld Crashes immediately on running on Windows 7...?

    - by Cyril Gupta
    I am trying to run MySql 5.1 on Windows 7 Home Premium 64 bit. I have downloaded the MSI installer from the MYSql website and installed it. The installation is successful, but the service does not start. If I try to run MySql manually using the mysqld executable, it crashes immediately on running (error: mysqld.exe has stopped working). Earlier mysql was running on the machine, but I had some problem with it (wasn't executing big queries) and installed it again which somehow broke the program. I had installed it to work as a service which started giving me this isse, and now it won't work even if I don't install it as a service. I have tried removing the mysql folder and re-installing. Is there somewhere else where Mysql saves configuration info or other data? Has anyone else found this problem and solved it? How can I find out why the process is failing to run?

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  • What's the best way to migrate a Django DB from SQLite to MySQL?

    - by Inshim
    I need to migrate my db from sqlite to mysql, and the various tools/scripts out there are too many for me to easily spot the safest and most elegant solution. This seemed to me nice http://djangosnippets.org/snippets/14/ but appears to be 3 years since getting an update which is worrying.. Can you recommend a solution that is known to be reliable with Django 1.1.1 ?

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  • How do I replace values within a data frame with a string in R?

    - by Arturito
    short version: How do I replace values within a data frame with a string found within another data frame? longer version: I'm a biologist working with many species of bees. I have a data set with many thousands of bees. Each row has a unique bee ID # along with all the relevant info about that specimen (data of capture, GPS location, etc). The species information for each bee has not been entered because it takes a long time to ID them. When IDing, I end up with boxes of hundred of bees, all of the same species. I enter these into a separate data frame. I am trying to write code that will update the original data file with species information (family, genus, species, sex, etc) as I ID the bees. Currently, in the original data file, the species info is blank and is interpreted as NA within R. I want to have R find all unique bee ID #'s and fill in the species info, but I am having trouble figuring out how to replace the NA values with a string (e.g. "Andrenidae") Here is a simple example of what I am trying to do: rawData<-data.frame(beeID=c(1:20),family=rep(NA,20)) speciesInfo<-data.frame(beeID=seq(1,20,3),family=rep("Andrenidae",7)) rawData[rawData$beeID == 4,"family"] <- speciesInfo[speciesInfo$beeID == 4,"family"] So, I am replacing things as I want, but with a number rather than the family name (a string). What I would eventually like to do is write a little loop to add in all the species info, e.g.: for (i in speciesInfo$beeID){ rawData[rawData$beeID == i,"family"] <- speciesInfo[speciesInfo$beeID == i,"family"] } Thanks in advance for any advice! Cheers, Zak EDIT: I just noticed that the first two methods below add a new column each time, which would cause problems if I needed to add species info multiple times (which I typically do). For example: rawData<-data.frame(beeID=c(1:20),family=rep(NA,20)) Andrenidae<-data.frame(beeID=seq(1,20,3),family=rep("Andrenidae",7)) Halictidae<-data.frame(beeID=seq(1,20,3)+1,family=rep("Halictidae",7)) # using join library(plyr) rawData <- join(rawData, Andrenidae, by = "beeID", type = "left") rawData <- join(rawData, Halictidae, by = "beeID", type = "left") # using merge rawData <- merge(x=rawData,y=Andrenidae,by='beeID',all.x=T,all.y=F) rawData <- merge(x=rawData,y=Halictidae,by='beeID',all.x=T,all.y=F) Is there a way to either collapse the columns so that I have one, unified data frame? Or a way to update the rawData rather than adding a new column each time? Thanks in advance!

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  • How can you tell MYSQL to TRIM the X number of characters, beginning from the Back?

    - by Tim
    How do I write the following in MYSQL? SELECT SUBSTRING(value - (1 TRAILING CHARACTER)) FROM table; Basically substring(value, 2) trims the first letters. But I need to trim the last letters. I can't use substring(value, -4, 3) because I don't know the length of the value. Here's another example: SELECT * FROM table WHERE SUBSTRING(value - (4 TRAILING CHARACTER)) in (SELECT SUBSTRING(value - (1 TRAILING CHARACTER)) FROM table);

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  • Idiomatic way to read .env variables in Ansible?

    - by Arms
    I'm provisioning a Vagrant box with Ansible, and using Benno Joy's MySQL role to setup MySQL (including creating a database and users.) The database name and credentials are stored in a .env file in the project's root. What would be the idiomatic way to use these variables when provisioning MySQL? Should I write a custom script that generates a YAML file from my .env, and then use the include_vars module? Or is there a simpler way?

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  • /data/tmp on database server?

    - by Mellon
    I am on a Linux ubuntu machine with MySQL installed. My teacher gave out an assignment which mentioned "copy cars.dat to /data/tmp on the MySQL database server" without any explanations, I do not know what is the "/data/tmp on database server" means exactly? Basically after that I need to execute SQL statement like LOAD DATA INFILE '/data/tmp/cars.dat' INTO TABLE cars So, what does copy cars.dat to /data/tmp on the database server means as there is no /data/tmp directory even? Personally, I checked /etc/mysql/my.cnf file, inside which there are definitions of : ... basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp ... Does it mean to copy cars.dat to the tmpdir which is just /tmp under root directory??

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  • What is faster in MySQL? WHERE sub request = 0 or IN list

    - by Nicolas Manzini
    Hello I was wondering what is better in MySQL. I have a SELECT querry that exclude every entry associated to a banned userID currently I have a subquerry clause in the WHERE statement that goes like AND (SELECT COUNT(*) FROM TheBlackListTable WHERE userID = userList.ID AND blackListedID = :userID2 ) = 0 Which will accept every userID not present in the TheBlackListTable Would it be faster to retrieve first all Banned ID in a previous request and replace the previous clause by AND creatorID NOT IN listOfBannedID Thank you!

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  • import a text file into a temporary table using 'Load data infile' inside a stored procedure- MySQL

    - by Pankaj
    I need to import a text file into a temporary table and from that select portions of it to insert in different tables. I wanted to use 'LOAD DATA INFILE'. Is there any way, i can use 'Load data infile' in a stored procedure. I am using mysql. LOAD DATA LOCAL INFILE 'C:\\MyData.txt' INTO TABLE tempprod fields terminated by ',' lines terminated by '\r\n'; SELECT * FROM product p;

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  • can use more than 1 column in MySQL Group BY?

    - by Am1rr3zA
    Hi, I want write these SQL Query: CREATE VIEW `uniaverage` AS select `averagegrade`.`mjr`,`averagegrade`.`lev` , avg(`averagegrade`.`average`) AS `uniAVG` from `averagegrade` group by `averagegrade`.`lev`, `averagegrade`.`mjr`; But MySQL Query Browser give this error: Operand Should Contain 1 column(s) I somewhere read can use group by on more than 1 column!!! How can I solve this error? or how can I change the Query to get the same result?

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  • compile time if && return string reference optimization

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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