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• Basic SQL Query, I am newbie

  - by user3530547

  I just started my database and query class on Monday. We met on Monday and just went over the syllabus, and on Wednesday the network at school was down so we couldn't even do the power point lecture. Right now I am working on my first homework assignment and I am almost finished but I am having trouble on one question. Here is is... Write a SELECT statement that returns one column from the Customers table named FullName that joins the LastName and FirstName columns. Format the columns with the last name, a comma, a space, and the first name like this: Doe, John Sort the result set by last name in ascending sequence. Return only the contacts whose last name begins with letters from M to Z. Here is what I have so far... USE md0577283 SELECT FirstName,LastName FROM Customers ORDER BY LastName,FirstName My question is how do I format is Lastname, FirstName like the professor wants and how do I only select names M-Z? If someone could point me in the right direction I would greatly appreciate it. Thank you. PS With all do respect, I didn't ask for the answer I asked for a nudge in the right direction so why the down vote guys?

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• Switching from php to python

  - by ts

  Hello I am trying to make a list of things which can be difficult/surprising to someone who is changing language from PHP to Python. so far i have rather short list: forget require / include, learn import (this was most difficult to me - to understand package - module - class - object hierarchy and its mapping to filesystem) you can't just upload file on server to have webpage (-mod_python, wsgi etc) learn the python way for use variable class names (new $class() vs import + getattr) / operator in python 2.x and all float-related horrors those were difficult to me, it takes few days before mind adapts a new paradigm after i found that there is few other areas which could be challenging for someone with (too) many years of php: everything is an object you have to live with exceptions array vs list, set, dictionary, tuple ... learn (effective) list comprehensions learn generators any other ideas / personal experiences ?

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• C++ template specialization

  - by user231536

  I have a class template <typename T> class C { static const int K=1; static ostream& print(ostream& os, const T& t) { return os << t;} }; I would like to specialize C for int. //specialization for int template <> C<int>{ static const int K=2; } I want the default print method that works for int to remain and just change the constant. For some specializations, I want to keep K=1 and change the print method because there is no << operator. How do I do this?

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• binary number comparison

  - by EquinoX

  If I have a 32 bit two's complement number and I want to know what is the easiest way to know of two numbers are equal... what would be the fastest bitwise operator to know this? I know xor'ing both numbers and check if the results are zero works well... any other one's? how about if a number is greater than 0?? I can check the 31'st bit to see if it's greater or equal to 0..but how about bgtz?

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• Quickest way to compute the number of shared elements between two vectors

  - by shn

  Suppose I have two vectors of the same size vector< pair<float, NodeDataID> > v1, v2; I want to compute how many elements from both v1 and v2 have the same NodeDataID. For example if v1 = {<3.7, 22>, <2.22, 64>, <1.9, 29>, <0.8, 7>}, and v2 = {<1.66, 7>, <0.03, 9>, <5.65, 64>, <4.9, 11>}, then I want to return 2 because there are two elements from v1 and v2 that share the same NodeDataIDs: 7 and 64. What is the quickest way to do that in C++ ? Just for information, note that the type NodeDataIDs is defined as I use boost as: typedef adjacency_list<setS, setS, undirectedS, NodeData, EdgeData> myGraph; typedef myGraph::vertex_descriptor NodeDataID; But it is not important since we can compare two NodeDataID using the operator == (that is, possible to do v1[i].second == v2[j].second)

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• C++ Reference of vector

  - by void

  Hello, class Refvect { public: vector<int> &refv; Refvect(int t, vector<int> &refv = vector<int>()) : refv(refv) { }; void operator()() { refv.clear(); } }; int main () { Refvect r(0); r(); } With Visual Studio 2010, this gives me an error : "vector iterators incompatible" at the execution, but I don't understand why (but I can insert elements in refv without any problem). The temporary object vector() lives as long as the reference, no?

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• Can't compile std::map sorting, why?

  - by Vincenzo

  This is my code: map<string, int> errs; struct Compare { bool operator() (map<string, int>::const_iterator l, map<string, int>::const_iterator r) { return ((*l).second < (*r).second); } } comp; sort(errs.begin(), errs.end(), comp); Can't compile. This is what I'm getting: no matching function for call to ‘sort(..’ Why so? Can anyone help? Thanks!

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• Double "!!" in Ruby [closed]

  - by Alex Maslakov

  Possible Duplicate: What does !! mean in ruby? Ruby, !! operator (a/k/a the double-bang) Sometimes I see a Ruby code like this def sent? !!@sent_at end It seems to be not logical. Is it necessary to use here double !? As far as I'm concerned, it might be just def sent? @sent_at end UPDATE: then what is the difference between these def sent? !!@sent_at end def sent? @sent_at.nil? end def sent? @sent_at == nil end

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• can function return 0 as reference

  - by helloWorld

  I have this snippet of the code Account& Company::findAccount(int id){ for(list<Account>::const_iterator i = listOfAccounts.begin(); i != listOfAccounts.end(); ++i){ if(i->nID == id){ return *i; } } return 0; } Is this right way to return 0 if I didn't find appropriate account? cause I receive an error: no match for 'operator!' in '!((Company*)this)->Company::findAccount(id)' I use it this way: if(!(findAccount(id))){ throw "hey"; } thanks in advance

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• name of class that manipulates the entities

  - by cyberguest

  hi, i have a general question regarding naming convention. if I separate the data and operations into two separate classes. one has the data elements (entity), the other class manipulates the entity class. what do we usually call that class that manipulates the entity class? (the entity I am referring to has nothing to do with any kind of entity framework) manager? controller? operator? manipulator? thanks in advance

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• How to check null element if it is integer array in Java?

  - by masato-san

  I'm quite new to Java and having an issue checking null element in integer array. I'm using Eclipse for editor and the line that checks null element is showing error: Line that complains: if(a[i] != null) { Error msg from Eclipse: The operator != is undefined for the argument type(s) int, null In PHP, this works without any problem but in Java it seems like I have to change the array type from integer to Object to make the line not complain (like below) Object[] a = new Object[3]; So my question is if I still want to declare as integer array and still want to check null, what is the syntax for it? Code: public void test() { int[] a = new int[3]; for(int i=0; i<a.length; i++) { if(a[i] != null) { //this line complains... System.out.println('null!'); } } }

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• Doubt regarding usage of array as a pointer in C

  - by Som

  For eg. I have an array of structs 'a' as below: struct mystruct{ int b int num; }; struct bigger_struct { struct my_struct a[10]; } struct bigger_struct *some_var; i know that the name of an array when used as a value implicitly refers to the address of the first element of the array.(Which is how the array subscript operator works at-least) Can i know do the other way around i.e if i do: some_var->a->b, it should be equivalent to some_var->a[0]->b, am i right? I have tested this and it seems to work , but is this semantically 100% correct?

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• question about copy constructor

  - by lego69

  I have this class: class A { private: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); ~A(); void foo() const; }; and I have function which contains this row: A *pa1 = new A(a2); can somebody please explain what exactly is going on, when I call A(a2) compiler calls copy constructor or constructor, thanks in advance

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• How to get it working in O(n)?

  - by evermean

  I came across an interview task/question that really got me thinking ... so here it goes: You have an array A[N] of N numbers. You have to compose an array Output[N] such that Output[i] will be equal to multiplication of all the elements of A[N] except A[i]. For example Output[0] will be multiplication of A[1] to A[N-1] and Output[1] will be multiplication of A[0] and from A[2] to A[N-1]. Solve it without division operator and in O(n). I really tried to come up with a solution but I always end up with a complexity of O(n^2). Perhaps the is anyone smarter than me who can tell me an algorithm that works in O(n) or at least give me a hint...

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• Implementing an iterator over binary tree using C++ 11

  - by user1459339

  I would like to create an iterator over the binary tree so as to be able to use range-based for loop. I understand I ought to implement the begin() and end() function first. Begin should probably point to the root. According to the specification, however, the end() functions returns "the element following the last valid element". Which element (node) is that? Would it not be illegal to point to some "invalid" place? The other thing is the operator++. What is the best way to return "next" element in tree? I just need some advice to begin with this programming.

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• casting a node to integer

  - by user1708762

  The code gives an error saying that "no operator matches these two operands" in the if comparison statement. I interpret,it should mean that "a node can't be converted/casted into an integer". But, the print statement prints an integer value for w[2] when used with %d format. Why is that happening? Isn't printf casting it? NODE *w=(NODE *)malloc(4*sizeof(NODE)); if(w[2]==0) printf("%d\n",w[2]); The structure of the node is- struct node{ int key; struct node *father; struct node *child[S]; int *ss; int current; };

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• Can typeid() be used to pass a function?

  - by Kerb_z

  I tried this and got the output as: void Please explain the following Code: #include <cstdio> #include <typeinfo> using namespace std ; void foo() { } int main(void) { printf("%s", typeid(foo()).name());// Please notice this line, is it same as typeid( ).name() ? return 0; } AFAIK: The typeid operator allows the type of an object to be determined at run time. So, does this sample code tell us that a function that returns void is of *type void*. I mean a function is a method and has no type. Correct?

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• Dynamic memory allocation with default values

  - by viswanathan

  class A { private: int m_nValue; public: A() { m_nValue = 0; } A(int nValue) { m_nValue = nValue); ~A() {} } Now in main if i call A a(2);// 2 will be assigned for m_nValue of object A. Now how do we do this if i want to define an array of objects. Also how do we do this if i dynamically create objects using operator new like A *pA; pA = new A[5];// while creating the object i want the parameterised constructor to be //called I hope the question is clear. Do let me know if more explanation is needed

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• partial string matching - R

  - by DonDyck

  I need to write a query in R to match partial string in column names. I am looking for something similar to LIKE operator in SQL. For e.g, if I know beginning, middle or end part of the string I would write the query in format: LIKE 'beginning%middle%' in SQL and it would return matching strings. In pmatch or grep it seems I can only specify 'beginning' , 'end' and not the order. Is there any similar function in R that I am looking for? For example, say I am looking in the vector: y<- c("I am looking for a dog", "looking for a new dog", "a dog", "I am just looking") Lets say I want to write a query which picks "looking for a new dog" and I know start of the string is "looking" and end of string is "dog". If I do a grep("dog",y) it will return 1,2,3. Is there any way I can specify beginning and end in grep?

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• use of const in c++ [closed]

  - by prp

  class X; class Y { public: Y(const X & x){cout<<"In Y"<<endl;} }; class X { public: operator Y()const{cout<<"In X"<<endl;} }; void fun(Y y) { cout<<"In fun"<<endl; } int main() { X x; fun(x); } can any one throw some light on this c++ program ...please i am new to c++

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• What does the & sign mean in PHP?

  - by jeffkee

  I was trying to find this answer on Google but I guess the symbol & works as some operator, or is just not generally a searchable term for any reason.. anyhow. I saw this code snippet while learning how to create wordpress plugins, so I just need to know what the & means when it precedes a variable that holds a class object. //Actions and Filters if (isset($dl_pluginSeries)) { //Actions add_action('wp_head', array(&$dl_pluginSeries, 'addHeaderCode'), 1); //Filters add_filter('the_content', array(&$dl_pluginSeries, 'addContent')); }

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• Script dies, I'm not sure why

  - by Webnet

  I'm trying to parse a 6,000 line 500 KB file into an array so I can import the data into our system. The problem is that the script stops executing somewhere between lines 3000-4000. There are no breaks in the code, we use it on other imports. Any ideas on why this might be happening and what I can do to prevent it? /** * Takes a seperated value string and makes it an array * @param $delimiter string The delimiter to be seperated by, usually a comma or tab * @param $string string The string to seperate * @return array The resulting array */ public function svToArray ($delimiter, $string) { $x = 0; $rowList = array(); $splitContent = preg_split("#\n+#", trim($string)); foreach ($splitContent as $key => $value) { $newData = preg_split("#".$delimiter."#", $value); if ($x == 0) { $headerValues = array_values($newData); } else { $tempRow = array(); foreach ($newData as $rowColumnKey => $rowColumnValue) { $tempRow[$headerValues[$rowColumnKey]] = $rowColumnValue; } $rowList[] = $tempRow; } $x++; } return $rowList; }

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• mySQL : using BETWEEN in table ?

  - by Meko

  I have a table that includes somestudent group name ,lesson time,day names like Schedule. I am using C# whit MYSql and I want to find which lesson is when user press button from table. I can find it like entering exact value like in table 08:30 or 10:25 , it finds. But I want to make that getting system time and checking that is it between 08:30 and 10:25 or 10:25 and 12:30 . Then I can sythat it is first lesson or it is second lesson . I have also table includes Table_Time column has 5 record like 08:20 , 10:25 , 12:20 so on. Could I use like : select Lesson_Time from mydb.clock where Lesson_Time between (current time)-30 AND (current time)+30 Or can I use between operator between two columns ? Like creating Lesson_Time_Start and Lesson_Time_End and compairing current time like Lesson_Start_Time

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• Get last row of many matrices (ASCII text files) and create a new matrix from these rows

  - by nofunsally

  I have over a thousand matrices (6 x 2000, ASCII files, comma delimited) that I generated from MATLAB. I want to get the last row of each matrix / text file and save them in a new matrix / text file. The text files have crazy names so when I load them I can name them whatever. Right now I would do this to achieve my goal: % A = load('crazyname.txt'); % B = load('crazynameagain.txt'); % C = load('crazynameyetagain.txt'); A = [5 5 5; 5 5 5; 1 1 1]; B = [5 5 5; 5 5 5; 2 2 2]; C = [5 5 5; 5 5 5; 3 3 3]; D(1,:)=A(end,:); D(2,:)=B(end,:); D(3,:)=C(end,:); I will create each command (e.g. load, building D step by step) in Excel by combining text cells to create a command. Is there a better way to do this? Could I load / assign the matrices with a name that would better suit them to be used in a for loop? Or is some other MATLAB command that would facilitate this? Thanks.

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• read integers from a file into a vector in C++

  - by user2922063

  I am trying to read an unknown number of double values stored on separate lines from a text file into a vector called rainfall. My code won't compile; I am getting the error no match for 'operator>>' in 'inputFile >> rainfall' for the while loop line. I understand how to read in from a file into an array, but we are required to use vectors for this project and I'm not getting it. I appreciate any tips you can give on my partial code below. vector<double> rainfall; // a vector to hold rainfall data // open file ifstream inputFile("/home/shared/data4.txt"); // test file open if (inputFile) { int count = 0; // count number of items in the file // read the elements in the file into a vector while ( inputFile >> rainfall ) { rainfall.push_back(count); ++count; } // close the file

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