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  • How do I select a fixed number of rows for each group?

    - by Maiasaura
    Here is some example data in a mysql table a b distance 15 44 250 94 31 250 30 41 250 6 1 250 95 18 250 72 84 500 14 23 500 55 24 500 95 8 500 59 25 500 40 73 500 65 85 500 32 50 500 31 39 500 22 25 500 37 11 750 98 39 750 15 57 750 9 22 750 14 44 750 69 22 750 62 50 750 89 35 750 67 65 750 74 37 750 52 36 750 66 53 750 82 74 1000 79 22 1000 98 41 1000 How do I query this table such that I get 2 rows per distance selected at random? A successful query will produce something like a b distance 30 41 250 95 18 250 59 25 500 65 85 500 15 57 750 89 35 750 79 22 1000 98 41 1000

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  • Assign variable with variable in function

    - by freakazo
    Let's say we have def Foo(Bar=0,Song=0): print(Bar) print(Song) And I want to assign any one of the two parameters in the function with the variable sing and SongVal: Sing = Song SongVal = 2 So that it can be run like: Foo(Sing=SongVal) Where Sing would assign the Song parameter to the SongVal which is 2. The result should be printed like so: 0 2 So should I rewrite my function or is it possible to do it the way I want to? (With the code above you get an error saying Foo has no parameter Sing. Which I understand why, any way to overcome this without rewriting the function too much? Thanks in advance!

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  • Why is forwarding variadic parameters invalid?

    - by awesomeyi
    Consider the variadic function parameter: func foo(bar:Int...) -> () { } Here foo can accept multiple arguments, eg foo(5,4). I am curious about the type of Int... and its supported operations. For example, why is this invalid? func foo2(bar2:Int...) -> () { foo(bar2); } Gives a error: Could not find an overload for '_conversion' that accepts the supplied arguments Why is forwarding variadic parameters invalid? What is the "conversion" the compiler is complaining about?

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  • Should I make sure arguments aren't null before using them in a function.

    - by Nathan W
    The title may not really explain what I'm really trying to get at, couldn't really think of a way to describe what I mean. I was wondering if it is good practice to check the arguments that a function accepts for nulls or empty before using them. I have this function which just wraps some hash creation like so. Public Shared Function GenerateHash(ByVal FilePath As IO.FileInfo) As String If (FilePath Is Nothing) Then Throw New ArgumentNullException("FilePath") End If Dim _sha As New Security.Cryptography.MD5CryptoServiceProvider Dim _Hash = Convert.ToBase64String(_sha.ComputeHash(New IO.FileStream(FilePath.FullName, IO.FileMode.Open, IO.FileAccess.Read))) Return _Hash End Function As you can see I just takes a IO.Fileinfo as an argument, at the start of the function I am checking to make sure that it is not nothing. I'm wondering is this good practice or should I just let it get to the actual hasher and then throw the exception because it is null.? Thanks.

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  • c++ global operator not playing well with template class

    - by John
    ok, i found some similar posts on stackoverflow, but I couldn't find any that pertained to my exact situation and I was confused with some of the answers given. Ok, so here is my problem: I have a template matrix class as follows: template <typename T, size_t ROWS, size_t COLS> class Matrix { public: template<typename, size_t, size_t> friend class Matrix; Matrix( T init = T() ) : _matrix(ROWS, vector<T>(COLS, init)) { /*for( int i = 0; i < ROWS; i++ ) { _matrix[i] = new vector<T>( COLS, init ); }*/ } Matrix<T, ROWS, COLS> & operator+=( const T & value ) { for( vector<T>::size_type i = 0; i < this->_matrix.size(); i++ ) { for( vector<T>::size_type j = 0; j < this->_matrix[i].size(); j++ ) { this->_matrix[i][j] += value; } } return *this; } private: vector< vector<T> > _matrix; }; and I have the following global function template: template<typename T, size_t ROWS, size_t COLS> Matrix<T, ROWS, COLS> operator+( const Matrix<T, ROWS, COLS> & lhs, const Matrix<T, ROWS, COLS> & rhs ) { Matrix<T, ROWS, COLS> returnValue = lhs; return returnValue += lhs; } To me, this seems to be right. However, when I try to compile the code, I get the following error (thrown from the operator+ function): binary '+=' : no operator found which takes a right-hand operand of type 'const matrix::Matrix<T,ROWS,COLS>' (or there is no acceptable conversion) I can't figure out what to make of this. Any help if greatly appreciated!

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  • strcmp equivelant for integers (intcmp) in PHP

    - by Chase
    So we got this function in PHP strcmp(string $1,string $2) // returns -1,0, or 1; We Do not however, have an intcmp(); So i created one: function intcmp($a,$b) { if((int)$a == (int)$b)return 0; if((int)$a > (int)$b)return 1; if((int)$a < (int)$b)return -1; } This just feels dirty. What do you all think?

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  • Is a function kind of like a static method?

    - by lkm
    I'm a java programmer and am trying to understand the difference between a method (java methods) and a function (such as in c++). I used to think that they are the same, just different naming conventions for different programming languages. But now that I know they are not, I am having trouble understanding the difference. I know that a method relates to an instance of a class and has access to class data (member variables), while a function does not (?). So is a function kind of like a static method? See here for explanations I read which led me to think this.

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  • Stored procedure with output parameters vs. table-valued function?

    - by abatishchev
    Which approach is better to use if I need a member (sp or func) returning 2 parameters: CREATE PROCEDURE Test @in INT, @outID INT OUT, @amount DECIMAL OUT AS BEGIN ... END or CREATE FUNCTION Test ( @in INT ) RETURNS @ret TABLE (outID INT, amount DECIMAL) AS BEGIN ... END What are pros and cons of each approach considering that the result will passed to another stored procedure: EXEC Foobar @outID, @outAmount

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  • What's wrong with this function?

    - by ct2k7
    Hello, I'm using this function to determine whether my application should be online or offline: function online() { if ($online == "0") { if($_SESSION['exp_user']['userlevel'] != "1") { include("error/offline.php"); exit(); } } } However, with the data value set to 0 in the database, and $online does = '0', why is error/offline.php not included for those whoose user level is not 1? Thanks :)

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  • Why pass by const reference instead of by value?

    - by Maulrus
    From what I understand: when you pass by value, the function makes a local copy of the passed argument and uses that; when the function ends, it goes out of scope. When you pass by const reference, the function uses a reference to the passed argument that can't be modified. I don't understand, however, why one would choose one over the other, except in a situation where an argument needs to be modified and returned. If you had a void function where nothing is getting returned, why choose one over the other?

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  • C newbie malloc question

    - by roufamatic
    Why doesn't this print 5? void writeValue(int* value) { value = malloc(sizeof(int)); *value = 5; } int main(int argc, char * argv) { int* value = NULL; writeValue(value); printf("value = %d\n", *value); // error trying to access 0x00000000 } and how can I modify this so it would work while still using a pointer as an argument to writeValue?

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  • How to find the formula of best case and worst case of my algorithm?

    - by rachel7660
    I was given a task. Write an algorithm so that, the input of 2 lists of data, will have at least one in common. So, this is my algorithm: (I write the code in php) $arrayA = array('5', '6', '1', '2', '7'); $arrayB = array('9', '2', '1', '8', '3'); $arrayC = array(); foreach($arrayA as $val){ if(in_array($val, $arrayB)){ array_push($arrayC, $val); } } Thats my own algo, not sure if its a good one. So, based on my algorithm, how to find the formula of best case and worst case (big O)? Note: Please do let me know, if my algorithm is wrong. My goal is " input of 2 lists of data, will have at least one in common."

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  • JSP Problem ussing implicit object (session) in a function

    - by user234666
    Can the object of type HttpSession called session be accessed from a function? In a simple jsp page I have a function(see below) defined in the header of the page, and set to an onclick handle of for a button. When I press this button, I'll never see the second alert message. If I do something in the body of the page (like Session ID: <%= session.getId() % ) I have no trouble accessing it. What newbie mistake am I making? function doTest() { alert('Preforming test 122333232'); String sessionId = session.getId(); alert('After access'); if(sessionId == null) { alert('session id is null?'); } Thanks

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  • Passing a pointer to a function that doesn't match the requirements of the formal parameter

    - by Andreas Grech
    int valid (int x, int y) { return x + y; } int invalid (int x) { return x; } int func (int *f (int, int), int x, int y) { //f is a pointer to a function taking 2 ints and returning an int return f(x, y); } int main () { int val = func(valid, 1, 2), inval = func(invalid, 1, 2); // <- 'invalid' does not match the contract printf("Valid: %d\n", val); printf("Invalid: %d\n", inval); /* Output: * Valid: 3 * Invalid: 1 */ } At the line inval = func(invalid, 1, 2);, why am I not getting a compiler error? If func expects a pointer to a function taking 2 ints and I pass a pointer to a function that takes a single int, why isn't the compiler complaining? Also, since this is happening, what happens to the second parameter y in the invalid function?

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  • How can c let a function declaration with any parameter type ?

    - by kamil çakir
    it lets this function declaration print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i gives error in this situation 44 C:\Users.. previous implicit declaration of 'print' was here (print(size,table); call in main) void print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i

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  • If a Matlab function returns a variable number of values, how can I get all of them as a cellarray,

    - by kaleidomedallion
    I am writing a function to remove some values from a cellarray, like so: function left = remove(cells, item); left = cells{cellfun(@(i) ~isequal(item, i), cells)}; But when I run this, left has only the first value, as the call to cells{} with a logical array returns all of the matching cells as separate values. How do I group these separate return values into a single cellarray? Also, perhaps there is already a way to remove a given item from a cellarray? I could not find it in the documentation.

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  • how to interleaving lists

    - by user2829177
    I have two lists that could be not equal in lengths and I want to be able to interleave them. I want to be able to append the extra values in the longer list at the end of my interleaved list.I have this: a=xs b=ys minlength=[len(a),len(b)] extralist= list() interleave= list() for i in range((minval(minlength))): pair=a[i],b[i] interleave.append(pair) flat=flatten(interleave) c=a+b if len(b)>len(a): remainder=len(c)-len(a) for j in range(-remainder): extra=remainder[j] extralist.append(extra) if len(a)>len(b): remainder=len(c)-len(b) for j in range(-remainder): extra=remainder[j] final=flat+extralist return final but if I test it: >>> interleave([1,2,3], ["hi", "bye",True, False, 33]) [1, 'hi', 2, 'bye', 3, True] >>> The False and 33 don't appear. What is it that Im doing wrong?

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  • Passing an array as a function parameter in JavaScript

    - by Robert
    Hi all, i'd like to call a function using an array as a parameters: var x = [ 'p0', 'p1', 'p2' ]; call_me ( x[0], x[1], x[2] ); // i don't like it function call_me (param0, param1, param2 ) { // ... } Is there a better way of passing the contents of x into call_me()? Ps. I can't change the signature of call_me(), nor the way x is defined. Thanks in advance

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  • What are good uses for Python3's "Function Annotations"

    - by agscala
    Function Annotations: PEP-3107 I ran across a snippet of code demonstrating Python3's function annotations. The concept is simple but I can't think of why these were implemented in Python3 or any good uses for them. Perhaps SO can enlighten me? How it works: def foo(a: 'x', b: 5 + 6, c: list) -> max(2, 9): ... function body ... Everything following the colon after an argument is an 'annotation', and the information following the -> is an annotation for the function's return value. foo.func_annotations would return a dictionary: {'a': 'x', 'b': 11, 'c': list, 'return': 9} What's the significance of having this available?

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  • How do I send a javascript variable to a subsequent jquery function or set of braces?

    - by desbest
    How do I send a javascript variable to a subsequent jquery function? Here is my code. <script type="text/javascript"> $(function() { var name = $("#name"), email = $("#email"), password = $("#password"), itemid = $("#itemid"), tips = $(".validateTips"); function updateTips(t) { tips .text(t) .addClass('ui-state-highlight'); setTimeout(function() { tips.removeClass('ui-state-highlight', 1500); }, 500); } $("#dialog-form").dialog({ autoOpen: false, height: 320, width: 350, modal: true, /* buttons: { 'Change category': function() { alert("The itemid2 is "+itemid2); var bValid = true; $('#users tbody').append('<tr>' + '<td>' + name.val() + '</td>' + '<td>' + email.val() + '</td>' + '<td>' + password.val() + '</td>' + '<td>' + itemid.val() + '</td>' + '</tr>'); $(this).dialog('close'); }, Cancel: function() { $(this).dialog('close'); } }, */ close: function() { allFields.val('').removeClass('ui-state-error'); } }); $('.changecategory') .button() .click(function() { var categoryid = $(this).attr("categoryid"); var itemid = $(this).attr("itemid"); var itemid2 = $(this).attr("itemid"); var itemtitle = $(this).attr("itemtitle"); var parenttag = $(this).parent().get(0).tagName; var removediv = "itemid_" +itemid; alert("The itemid is "+itemid); $('#dialog-form').dialog('open'); }); }); </script> I'll break it down. The .changecategory section happens FIRST when an image on my page is clicked. $("#dialog-form").dialog({ is then called, and the variable item id is not passed to this function. How can I pass a variable from one function to another? Is that possible. Is there a way I can pass a variable to another jquery function without having to resort of setting a cookie with javascript and then using jquery to read it?

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  • How to call virtual function of an object in C++

    - by SoonDead
    I'm struggling with calling a virtual function in C++. I'm not experienced in C++, I mainly use C# and Java so I might have some delusions, but bear with me. I have to write a program where I have to avoid dynamic memory allocation if possible. I have made a class called List: template <class T> class List { public: T items[maxListLength]; int length; List() { length = 0; } T get(int i) const { if (i >= 0 && i < length) { return items[i]; } else { throw "Out of range!"; } }; // set the value of an already existing element void set(int i, T p) { if (i >= 0 && i < length) { items[i] = p; } else { throw "Out of range!"; } } // returns the index of the element int add(T p) { if (length >= maxListLength) { throw "Too many points!"; } items[length] = p; return length++; } // removes and returns the last element; T pop() { if (length > 0) { return items[--length]; } else { throw "There is no element to remove!"; } } }; It just makes an array of the given type, and manages the length of it. There is no need for dynamic memory allocation, I can just write: List<Object> objects; MyObject obj; objects.add(obj); MyObject inherits form Object. Object has a virtual function which is supposed to be overridden in MyObject: struct Object { virtual float method(const Input& input) { return 0.0f; } }; struct MyObject: public Object { virtual float method(const Input& input) { return 1.0f; } }; I get the elements as: objects.get(0).method(asdf); The problem is that even though the first element is a MyObject, the Object's method function is called. I'm guessing there is something wrong with storing the object in an array of Objects without dynamically allocating memory for the MyObject, but I'm not sure. Is there a way to call MyObject's method function? How? It's supposed to be a heterogeneous collection btw, so that's why the inheritance is there in the first place. If there is no way to call the MyObject's method function, then how should I make my list in the first place?

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  • Postgresql - Edit function signature

    - by drave
    POSTGRESQL 8.4.3 - i created a function with this signature CREATE OR REPLACE FUNCTION logcountforlasthour() RETURNS SETOF record AS realised i wanted to change it to this CREATE OR REPLACE FUNCTION logcountforlasthour() RETURNS TABLE(ip bigint, count bigint) record AS but when i apply that change in the query tool it isnt accepted or rather it is accepted, there is no syntax error, but the text of the function has not been changed. even if i run "DROP FUNCTION logcountforlasthour()" between edits the old syntax comes back if i edit the body of the function, thats fine, it changes but not the signature is there something i'm missing thanks

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  • Can I execute a "variable statements" within a function and without defines.

    - by René Nyffenegger
    I am facing a problem that I cannot see how it is solvable without #defines or incuring a performance impact although I am sure that someone can point me to a solution. I have an algorithm that sort of produces a (large) series of values. For simplicity's sake, in the following I pretend it's a for loop in a for loop, although in my code it's more complex than that. In the core of the loop I need to do calculations with the values being produced. Although the algorithm for the values stays the same, the calculations vary. So basically, what I have is: void normal() { // "Algorithm" producing numbers (x and y): for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { // Calculation with numbers being produced: if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } // end of calculation }} } So, the only part I need to change is if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } So, in order to solve that, I could construct an abstract base class: class inner_0 { public: virtual void call(int x, int y) = 0; }; and derive a "callable" class from it: class inner : public inner_0 { public: virtual void call(int x, int y) { if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } } }; I can then pass an instance of the class to the "algorithm" like so: void O(inner i) { for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { i.call(x,y); }} } // somewhere else.... inner I; O(I); In my case, I incur a performance hit because there is an indirect call via virtual function table. So I was thinking about a way around it. It's possible with two #defines: #define OUTER \ for (int x=0 ; x<1000 ; x++) { \ for (int y=0 ; y<1000 ; y++) { \ INNER \ }} // later... #define INNER \ if (x + y == 800 && y > 790) \ std::cout << x << ", " << y << std::endl; OUTER While this certainly works, I am not 100% happy with it because I don't necessarly like #defines. So, my question: is there a better way for what I want to achieve?

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