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  • Two '==' equality operators in same 'if' condition are not working as intended.

    - by Manav MN
    I am trying to establish equality of three equal variables, but the following code is not printing the obvious true answer which it should print. Can someone explain, how the compiler is parsing the given if condition internally? #include<stdio.h> int main() { int i = 123, j = 123, k = 123; if ( i == j == k) printf("Equal\n"); else printf("NOT Equal\n"); return 0; } Output: manav@workstation:~$ gcc -Wall -pedantic calc.c calc.c: In function ‘main’: calc.c:5: warning: suggest parentheses around comparison in operand of ‘==’ manav@workstation:~$ ./a.out NOT Equal manav@workstation:~$ EDIT: Going by the answers given below, is the following statement okay to check above equality? if ( (i==j) == (j==k))

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  • VB.NET overloading array access?

    - by Wayne Werner
    Hi, Is it possible to overload the array/dict access operators in VB.net? For example, you can state something like: Dim mydict As New Hashtable() mydict.add("Cool guy", "Overloading is dangerous!") mydict("Cool guy") = "Overloading is cool!" And that works just fine. But what I would like to do is be able to say: mydict("Cool guy") = "3" and then have 3 automagically converted to the Integer 3. I mean, sure I can have a private member mydict.coolguy and have setCoolguy() and getCoolguy() methods, but I would prefer to be able to write it the former way if at all possible. Thanks

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  • Index, assignment and increment in one statement behaves differently in C++ and C#. Why?

    - by Ivan Zlatanov
    Why is this example of code behaving differently in c++ and C#. [C++ Example] int arr[2]; int index = 0; arr[index] = ++index; The result of which will be arr[1] = 1; [C# Example] int[] arr = new int[2]; int index = 0; arr[index] = ++index; The result of which will be arr[0] = 1; I find this very strange. Surely there must be some rationale for both languages to implement it differently? I wonder what would C++/CLI output?

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  • Linq like or other construction

    - by Yauhen Kavalenka
    I have DB oracle in my solution. I want to have some results in this query. Query example: select * from doctor where doctor.name like '%IVANOV_A%'; But if i do it at LINQ i cannot get any result. from p in repository.Doctor.Where(x => x.Name.ToLower().Containsname)) select p; Where 'name' is variable of string parameter. Web layout request next string: "Ivanov a" or "A Ivanov" But i suggest for user choose you pattetn for query. How i can to get "patient by name" if name consist of "First name" and "Last name" but user doesn't know your doctor's full name?

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  • MySQL: Which is faster — INSTR or LIKE?

    - by Grekker
    If your goal is to test if a string exists in a MySQL column (of type 'varchar', 'text', 'blob', etc) which of the following is faster / more efficient / better to use, and why? Or, is there some other method that tops either of these? INSTR( columnname, 'mystring' ) > 0 vs columnname LIKE '%mystring%'

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  • c++ how to ? function_x ( new object1 )

    - by ismail marmoush
    Hi i want to do the next instead of MyClass object; function_x (object); i want to function_x ( new object ); so what will be the structure of the MyClass to be able to do that .. if i just compiled it , it gives me a compile time error answer function_x (MyClass() ) New Edit thanks for the quick answers.. i did ask the wrong Question i should have asked how temporary variables created in C++ and the answer

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  • C++ brain teaser

    - by mxp
    I recently refactored code like this (MyClass to MyClassR). class SomeMember { long m_value; public: SomeMember() : m_value(0) {} SomeMember(int a) : m_value(a) {} SomeMember(int a, int b) : m_value(a+b) {} }; class MyClass { SomeMember m_first, m_second, m_third; public: MyClass(const bool isUp, const int x, const int y) { if (isUp) { m_first = SomeMember(x); m_second = SomeMember(y); m_third = SomeMember(x, y); } else { m_first = SomeMember(y); m_second = SomeMember(x); m_third = SomeMember(y, x); } } }; class MyClassR { SomeMember m_first, m_second, m_third; public: MyClassR(const bool isUp, const int x, const int y) : m_first(isUp ? x : y) , m_second(isUp ? y : x) , m_third(isUp ? x, y : y, x) { } }; What is the error, why does it compile (at least VC6 with warning level 3 doesn't complain) and what is the right way of doing it? I (assume) I already have all these answers but I think it's and interesting problem to share.

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  • Checking instance of non-class constrained type parameter for null in generic method

    - by casperOne
    I currently have a generic method where I want to do some validation on the parameters before working on them. Specifically, if the instance of the type parameter T is a reference type, I want to check to see if it's null and throw an ArgumentNullException if it's null. Something along the lines of: // This can be a method on a generic class, it does not matter. public void DoSomething<T>(T instance) { if (instance == null) throw new ArgumentNullException("instance"); Note, I do not wish to constrain my type parameter using the class constraint. I thought I could use Marc Gravell's answer on "How do I compare a generic type to its default value?", and use the EqualityComparer<T> class like so: static void DoSomething<T>(T instance) { if (EqualityComparer<T>.Default.Equals(instance, null)) throw new ArgumentNullException("instance"); But it gives a very ambiguous error on the call to Equals: Member 'object.Equals(object, object)' cannot be accessed with an instance reference; qualify it with a type name instead How can I check an instance of T against null when T is not constrained on being a value or reference type?

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  • Can I customize the indentation of ternary operators in emacs' cperl-mode?

    - by Ryan Thompson
    In emacs cperl-mode, ternary operators are not treated specially. If you break them over multiple lines, cperl-mode simply indents each line the same way it indents any continued statement, like this: $result = ($foo == $bar) ? 'result1' : ($foo == $baz) ? 'result2' : ($foo == $qux) ? 'result3' : ($foo == $quux) ? 'result4' : fail_result; This is not very readable. Is there some way that I can convince cperl-mode indent like this? $result = ($foo == $bar) ? 'result1' : ($foo == $baz) ? 'result2' : ($foo == $qux) ? 'result3' : ($foo == $quux) ? 'result4' : fail_result; By the way, code example from this question.

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  • printing using one '\n'

    - by Alex
    I am pretty sure all of you are familiar with the concept of the Big4, and I have several stuffs to do print in each of the constructor, assignment, destructor, and copy constructor. The restriction is this: I CAN'T use more than one newline (e.g., ƒn or std::endl) in any method I can have a method called print, so I am guessing print is where I will put that precious one and only '\n', my problem is that how can the method print which prints different things on each of the element I want to print in each of the Big4? Any idea? Maybe overloading the Big4?

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  • Using __str__ representation for printing objects in containers in Python

    - by BobDobbs
    I've noticed that when an instance with an overloaded str method is passed to the print() function as an argument, it prints as intended. However, when passing a container that contains one of those instances to print(), it uses the repr method instead. That is to say, print(x) displays the correct string representation of x, and print(x, y) works correctly, but print([x]) or print((x, y)) prints the repr representation instead. First off, why does this happen? Secondly, is there a way to correct that behavior of print() in this circumstance?

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  • Dynamic Like Statement in SQL

    - by Peter McElhinney
    Hey there! I've been racking my brain on how to do this for a while, and i know that some genius on this site will have the answer. Basically i'm trying to do this: SELECT column FROM table WHERE [table][column] LIKE string1 OR [table][column] LIKE string2 OR [table][column] LIKE string3... for a list of search strings stored in a column of a table. Obviously I can't do a like statement for each string by hand because i want the table to be dynamic. Any suggestions would be great. :D EDIT: I'm using MSSQL :(

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  • C++ arrays as parameters, subscript vs. pointer

    - by awshepard
    Alright, I'm guessing this is an easy question, so I'll take the knocks, but I'm not finding what I need on google or SO. I'd like to create an array in one place, and populate it inside a different function. I define a function: void someFunction(double results[]) { for (int i = 0; i<100; ++i) { for (int n = 0; n<16; ++n) //note this iteration limit { results[n] += i * n; } } } That's an approximation to what my code is doing, but regardless, shouldn't be running into any overflow or out of bounds issues or anything. I generate an array: double result[16]; for(int i = 0; i<16; i++) { result[i] = -1; } then I want to pass it to someFunction someFunction(result); When I set breakpoints and step through the code, upon entering someFunction, results is set to the same address as result, and the value there is -1.000000 as expected. However, when I start iterating through the loop, results[n] doesn't seem to resolve to *(results+n) or *(results+n*sizeof(double)), it just seems to resolve to *(results). What I end up with is that instead of populating my result array, I just get one value. What am I doing wrong?

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  • Are ternary operators not valid for linq-to-sql queries?

    - by KallDrexx
    I am trying to display a nullable date time in my JSON response. In my MVC Controller I am running the following query: var requests = (from r in _context.TestRequests where r.scheduled_time == null && r.TestRequestRuns.Count > 0 select new { id = r.id, name = r.name, start = DateAndTimeDisplayString(r.TestRequestRuns.First().start_dt), end = r.TestRequestRuns.First().end_dt.HasValue ? DateAndTimeDisplayString(r.TestRequestRuns.First().end_dt.Value) : string.Empty }); When I run requests.ToArray() I get the following exception: Could not translate expression ' Table(TestRequest) .Where(r => ((r.scheduled_time == null) AndAlso (r.TestRequestRuns.Count > 0))) .Select(r => new <>f__AnonymousType18`4(id = r.id, name = r.name, start = value(QAWebTools.Controllers.TestRequestsController). DateAndTimeDisplayString(r.TestRequestRuns.First().start_dt), end = IIF(r.TestRequestRuns.First().end_dt.HasValue, value(QAWebTools.Controllers.TestRequestsController). DateAndTimeDisplayString(r.TestRequestRuns.First().end_dt.Value), Invoke(value(System.Func`1[System.String])))))' into SQL and could not treat it as a local expression. If I comment out the end = line, everything seems to run correctly, so it doesn't seem to be the use of my local DateAndTimeDisplayString method, so the only thing I can think of is Linq to Sql doesn't like Ternary operators? I think I've used ternary operators before, but I can't remember if I did it in this code base or another code base (that uses EF4 instead of L2S). Is this true, or am I missing some other issue?

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  • MySQL searching using many 'like' operators: is there a better way?

    - by DrAgonmoray
    I have a page that gets all rows from a table in a database, then displays the rows in an HTML table. That works great, but now I want to implement a 'search' feature. There is a searchbox, and search-terms are separated by a space. I am going to make it search three fields for the search terms, 'make' 'model' and 'type.' These three fields are VARCHAR(30). Currently if I wanted to search using 3 terms (say 'cool' 'abc' and '123') my query would look something like this. SELECT * FROM table WHERE make LIKE '%cool%' OR make LIKE '%abc%' OR make LIKE '%123%' OR model LIKE '%cool%' OR model LIKE '%abc%' OR model LIKE '%123%' OR type LIKE '%cool%' OR type LIKE '%abc%' OR type LIKE '%123%' That looks really bad, and it will get even worse if there are more search terms or more fields to search. My question to you: is there a better way to search? If so, what?

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  • rails 3, active record: any way to tell how many unique values match a "x LIKE ?" query

    - by jpwynn
    I have a query to find all the phone numbers that match a partial expression such as "ends with 234" @matchingphones = Calls.find :all, :conditions => [ "(thephonenumber LIKE ?)", "%234"] The same phone number might be in the database several times, and so might be returned multiple times by this query if it matches. What I need is to know is UNIQUE phone numbers the query returns. For example if the database contains 000-111-1234 * 000-111-3333 000-111-2234 * 000-111-1234 * 000-111-4444 the existing query will return the 3 records marked with * (eg returns one phone number -1234 twice since it's in the database twice) what I need is a query that returns just once instance of each match, in this case 000-111-1234 * 000-111-2234 *

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  • Ternary operators and variable reassignment in PHP

    - by TomcatExodus
    I've perused the questions on ternary operators vs. if/else structures, and while I understand that under normal circumstances there is no performance loss/gain in using ternary operators over if/else structures, I've not seen any mention of this situation. Language specific to PHP (but any language agnostic details are welcome) does the interpreter reassign values in situations like this: $foo = 'bar' $foo = strlen($foo) > 3 ? substr($foo, 0, 3) : $foo; Since this would evaluate to $foo = $foo; is this inefficient, or does the interpreter simply overlook/discard this evaluation? On a side note, what about: !defined('SECURE') ? exit : null;

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  • Array of Structs Initialization....

    - by user69514
    Hi I am working on a program where I have to initialize a deck of cards. I am using a struct to represent a card. However I'm not filling it correctly as I get a bunch of zero's when I display the deck of cards. I believe my mistake is in this line but I'm not sure: struct card temp = {"Clubs", value, false}; The code: void initCards(){ int count = 0; int location = 0; const int hand = 12; //add hearts int value=2; while( count < hand ){ struct card temp = {"Hearts", value, false}; cards[location] = temp; value++; count++; } count = 0; //add diamonts value = 2; while( count < hand ){ struct card temp = {"Diamonds", value, false}; cards[count] = temp; value++; count++; } //add spades count = 0; value = 2; while( count < hand ){ struct card temp = {"Spades", value, false}; cards[count] = temp; value++; count++; } //add clubs count = 0; value = 2; while( count < hand ){ struct card temp = {"Clubs", value, false}; cards[count] = temp; value++; count++; } //print the deck for(int i=0; i<52; i++){ cout << cards[i].type << " " << cards[i].rank << endl; } }

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  • C++ arrays as parameters, EDIT: now includes variable scoping

    - by awshepard
    Alright, I'm guessing this is an easy question, so I'll take the knocks, but I'm not finding what I need on google or SO. I'd like to create an array in one place, and populate it inside a different function. I define a function: void someFunction(double results[]) { for (int i = 0; i<100; ++i) { for (int n = 0; n<16; ++n) //note this iteration limit { results[n] += i * n; } } } That's an approximation to what my code is doing, but regardless, shouldn't be running into any overflow or out of bounds issues or anything. I generate an array: double result[16]; for(int i = 0; i<16; i++) { result[i] = -1; } then I want to pass it to someFunction someFunction(result); When I set breakpoints and step through the code, upon entering someFunction, results is set to the same address as result, and the value there is -1.000000 as expected. However, when I start iterating through the loop, results[n] doesn't seem to resolve to *(results+n) or *(results+n*sizeof(double)), it just seems to resolve to *(results). What I end up with is that instead of populating my result array, I just get one value. What am I doing wrong? EDIT Oh fun, I have a typo: it wasn't void someFunction(double results[]). It was: void someFunction(double result[])... So perhaps this is turning into a scoping question. If my double result[16] array is defined in a main.cpp, and someFunction is defined in a Utils.h file that's included by the main.cpp, does the result variable in someFunction then wreak havoc on the result array in main?

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  • lua metatable __lt __le __eq forced boolean conversion of return value

    - by chris g.
    Overloading __eq, __lt, and __le in a metatable always converts the returning value to a boolean. Is there a way to access the actual return value? This would be used in the following little lua script to create an expression tree for an argument usage: print(_.a + _.b - _.c * _.d + _.a) -> prints "(((a+b)-(c*d))+a)" which is perfectly what I would like to have but it doesn't work for print(_.a == _.b) since the return value gets converted to a boolean ps: print should be replaced later with a function processing the expression tree -- snip from lua script -- function binop(op1,op2, event) if op1[event] then return op1[event](op1, op2) end if op2[event] then return op2[event](op1, op2) end return nil end function eq(op1, op2)return binop(op1,op2, "eq") end ... function div(op1, op2)return binop(op1,op2, "div") end function exprObj(tostr) expr = { eq = binExpr("=="), lt = binExpr("<"), le = binExpr("<="), add = binExpr("+"), sub=binExpr("-"), mul = binExpr("*"), div= binExpr("/") } setmetatable(expr, { __eq = eq, __lt = lt, __le = le, __add = add, __sub = sub, __mul = mul, __div = div, __tostring = tostr }) return expr end function binExpr(exprType) function binExprBind(lhs, rhs) return exprObj(function(op) return "(" .. tostring(lhs) .. exprType .. tostring(rhs) .. ")" end) end return binExprBind end function varExpr(obj, name) return exprObj(function() return name end) end _ = {} setmetatable(_, { __index = varExpr }) -- snap -- Modifing the lua vm IS an option, however it would be nice if I could use an official release

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