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  • Function template overloading: link error

    - by matt
    I'm trying to overload a "display" method as follows: template <typename T> void imShow(T* img, int ImgW, int ImgH); template <typename T1, typename T2> void imShow(T1* img1, T2* img2, int ImgW, int ImgH); I am then calling the template with unsigned char* im1 and char* im2: imShow(im1, im2, ImgW, ImgH); This compiles fine, but i get a link error "unresolved external symbol" for: imShow<unsigned char,char>(unsigned char *,char *,int,int) I don't understand what I did wrong!

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  • Pass temporary object to function that takes pointer

    - by Happy Mittal
    I tried following code : #include<iostream> #include<string> using namespace std; string f1(string s) { return s="f1 called"; } void f2(string *s) { cout<<*s<<endl; } int main() { string str; f2(&f1(str)); } But this code doesn't compile. What I think is : f1 returns by value so it creates temporary, of which I am taking address and passing to f2. Now Please explain me where I am thinking wrong?

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  • Help with Oracle SQL Count function! =)

    - by user363024
    Hi guys.. The question im struggling with is this: i have a list of helicopter names in different charters and i need to find out WHICH helicopter has the least amount of charters booked. Once i find that out i need to ONLY display the one that has the least. I so far have this: SELECT Helicopter_Name COUNT (Distinct Charter_NUM) FROM Charter_Table GROUP BY Helicopter Name ^ this is where i am stuck, i realise MIN could be used to pick out the value that is the smallest but i am not sure how to integrate this into the command. Something like Where MIN = MIN Value Id really appreciate it

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  • [C++] My First Go With Function Templates

    - by bobber205
    Thought it was pretty straight forward. But I get a "iterator not dereferencable" errro when running the below code. What's wrong? template<typename T> struct SumsTo : public std::binary_function<T, T, bool> { int myInt; SumsTo(int a) { myInt = a; } bool operator()(const T& l, const T& r) { cout << l << " + " << r; if ((l + r) == myInt) { cout << " does add to " << myInt; } else { cout << " DOES NOT add to " << myInt; } return true; } }; void main() { list<int> l1; l1.push_back(1); l1.push_back(2); l1.push_back(3); l1.push_back(4); list<int> l2; l2.push_back(9); l2.push_back(8); l2.push_back(7); l2.push_back(6); transform(l1.begin(), l1.end(), l2.begin(), l2.end(), SumsTo<int>(10) ); }

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  • linq delegate function checking from objects

    - by Philip
    I am trying to find the list of objects which can be replaced. Class Letter{ int ID; string Name; string AdvCode; int isDeleted; } Class Replacers{ int ID; string MainAdvCode; string ReplacesAdvCode; } example data: Replacers 0 455 400 1 955 400 2 955 455 such that if a Letter has and Advcode of 455 and another has a code of 400 the 400 gets marked for deletion. And then if another Letter has a 955 then the 455 gets marked for deletion and the 400 (which is already marked) is marked for deletion. The problem is with my current code the 400 and 455 is marking itself for deletion?!?!? Public class Main{ List<Letter> Letters; List<Replacers> replaces; //select the ones to replace the replacements aka the little guys //check if the replacements replacer exists if yes mark deleted var filterMethodReplacements = new Func<Letter, bool>(IsAdvInReplacements);//Working var filterMethodReplacers = new Func<Letter, bool>(IsAdvInReplacers);//NOT WORKING???? var resReplacements=letters.Where(filterMethodReplacements);//working foreach (Letter letter in resReplacements) { //select the Replacers aka the ones that contain the little guys var resReplacers = letters.Where(filterMethodReplacers); if (resReplacers != null) letter.isDeleted = 1; } } } private bool IsAdvInReplacements(Letter letter) { return (from a in Replacables where a.ReplaceAdvCode == letter.AdvCode select a).Any(); } private bool IsAdvInReplacers(Letter letter) { //?????????????????????????????? return (from a in Replacables where a.MainAdvCode == letter.AdvCode select a).Any(); } }

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  • Double indirection and structures passed into a function

    - by ZPS
    I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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  • Multithreading A Function in VB.Net

    - by Ben
    I am trying to multi thread my application so as it is visible while it is executing the process, this is what I have so far: Private Sub SendPOST(ByVal URL As String) Try Dim DataBytes As Byte() = Encoding.ASCII.GetBytes("") Dim Request As HttpWebRequest = TryCast(WebRequest.Create(URL.Trim & "/webdav/"), HttpWebRequest) Request.Method = "POST" Request.ContentType = "application/x-www-form-urlencoded" Request.ContentLength = DataBytes.Length Request.Timeout = 1000 Request.ReadWriteTimeout = 1000 Dim PostData As Stream = Request.GetRequestStream() PostData.Write(DataBytes, 0, DataBytes.Length) Dim Response As WebResponse = Request.GetResponse() Dim ResponseStream As Stream = Response.GetResponseStream() Dim StreamReader As New IO.StreamReader(ResponseStream) Dim Text As String = StreamReader.ReadToEnd() PostData.Close() Catch ex As Exception If ex.ToString.Contains("401") Then TextBox2.Text = TextBox2.Text & URL & "/webdav/" & vbNewLine End If End Try End Sub Public Sub G0() Dim siteSplit() As String = TextBox1.Text.Split(vbNewLine) For i = 0 To siteSplit.Count - 1 Try If siteSplit(i).Contains("http://") Then SendPOST(siteSplit(i).Trim) Else SendPOST("http://" & siteSplit(i).Trim) End If Catch ex As Exception End Try Next End Sub Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim t As Thread t = New Thread(AddressOf Me.G0) t.Start() End Sub However, the 'G0' sub code is not being executed at all, and I need to multi thread the 'SendPOST' as that is what slows the application.

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  • Function pointers to member functions

    - by Jacob
    There are several duplicates of this but nobody explains why I can use a member variable to store the pointer (in FOO) but when I try it with a local variable (in the commented portion of BAR), it's illegal. Could anybody explain this? #include <iostream> using namespace std; class FOO { public: int (FOO::*fptr)(int a, int b); int add_stuff(int a, int b) { return a+b; } void call_adder(int a, int b) { fptr = &FOO::add_stuff; cout<<(this->*fptr)(a,b)<<endl; } }; class BAR { public: int add_stuff(int a, int b) { return a+b; } void call_adder(int a, int b) { //int (BAR::*fptr)(int a, int b); //fptr = &BAR::add_stuff; //cout<<(*fptr)(a,b)<<endl; } }; int main() { FOO test; test.call_adder(10,20); return 0; }

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  • c++ function overloading, making fwrite/fread act like PHP versions

    - by Newbie
    I'm used to the PHP fwrite/fread parameter orders, and i want to make them the same in C++ too. I want it to work with char and string types, and also any data type i put in it (only if length is defined). I am total noob on c++, this is what i made so far: size_t fwrite(FILE *fp, const std::string buf, const size_t len = SIZE_MAX){ if(len == SIZE_MAX){ return fwrite(buf.c_str(), 1, buf.length(), fp); }else{ return fwrite(buf.c_str(), 1, len, fp); } } size_t fwrite(FILE *fp, const void *buf, const size_t len = SIZE_MAX){ if(len == SIZE_MAX){ return fwrite((const char *)buf, 1, strlen((const char *)buf), fp); }else{ return fwrite(buf, 1, len, fp); } } Should this work just fine? And how should this be done if i wanted to do it the absolutely best possible way?

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  • Cryptic C++ "thing" (function pointer)

    - by m00st
    What is this syntax for in C++? Can someone point me to the technical term so I can see if I find anything in my text? At first I thought it was a prototype but then the = and (*fn) threw me off... Here is my example: void (*fn) (int&,int&) = x;

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  • C++ compilation error when passing a function into remove_if

    - by garsh0p
    So here's a snippet of my code. void RoutingProtocolImpl::removeAllInfinity() { dv.erase(std::remove_if(dv.begin(), dv.end(), hasInfCost), dv.end()); } bool RoutingProtocolImpl::hasInfCost(RoutingProtocolImpl::dv_entry *entry) { if (entry-link_cost == INFINITY_COST) { free(entry); return true; } else { return false; } } I'm getting the following error when compiling: RoutingProtocolImpl.cc:368: error: argument of type bool (RoutingProtocolImpl::)(RoutingProtocolImpl::dv_entry*)' does not matchbool (RoutingProtocolImpl::*)(RoutingProtocolImpl::dv_entry*)' Sorry, I'm kind of a C++ newb.

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  • Assigning function within function object without invoking the function itself.

    - by webzide
    Dear experts, I am trying to assign an function within an function object property without actually invoking then function itself. for instance, I have the following function object class definition function objectOne(name, value, id){ this.name=name; this.value=value; this.id=id; this.methodOne=methodFunction(this); } the last line this.methodOne=methodFunction(this); I want to pass the current object to the function but at the same time i don't want to execute the function right now. But if I do it this way without the bracket this.methodOne=methodFunction then the argument of this object would not be passed as a parameter to the function. Is there a way to work through this. Thank you in advance

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  • And now for a complete change of direction from C++ function pointers

    - by David
    I am building a part of a simulator. We are building off of a legacy simulator, but going in different direction, incorporating live bits along side of the simulated bits. The piece I am working on has to, effectively route commands from the central controller to the various bits. In the legacy code, there is a const array populated with an enumerated type. A command comes in, it is looked up in the table, then shipped off to a switch statement keyed by the enumerated type. The type enumeration has a choice VALID_BUT_NOT_SIMULATED, which is effectively a no-op from the point of the sim. I need to turn those no-ops into commands to actual other things [new simulated bits| live bits]. The new stuff and the live stuff have different interfaces than the old stuff [which makes me laugh about the shill job that it took to make it all happen, but that is a topic for a different discussion]. I like the array because it is a very apt description of the live thing this chunk is simulating [latching circuits by row and column]. I thought that I would try to replace the enumerated types in the array with pointers to functions and call them directly. This would be in lieu of the lookup+switch.

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  • Xpath help function

    - by NA
    Hi i have a document from which i am trying to extract a date. But the problem is within the node along with the date their is some text too. Something like <div class="postHeader"> Posted on July 20, 2009 9:22 PM PDT </div> From this tag i just want the date item not the Posted on text. something like ./xhtml:div[@class = 'postHeader'] is getting everything. and to be precise, the document i have is basically a nodelist of this elements for eg i will get 10 nodes of these elements with different date values but to be worse the problem is sometime inside these tags some random other tags also pops us like anchors etc. Can i write a universal expath which will just get the date out of the div tag?

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  • Function pointers uasage

    - by chaitanyavarma
    Hi All, Why these two codes give the same output, Case - 1: #include <stdio.h> typedef void (*mycall) (int a ,int b); void addme(int a,int b); void mulme(int a,int b); void subme(int a,int b); main() { mycall x[10]; x[0] = &addme; x[1] = &subme; x[2] = &mulme; (x[0])(5,2); (x[1])(5,2); (x[2])(5,2); } void addme(int a, int b) { printf("the value is %d\n",(a+b)); } void mulme(int a, int b) { printf("the value is %d\n",(a*b)); } void subme(int a, int b) { printf("the value is %d\n",(a-b)); } Output: the value is 7 the value is 3 the value is 10 Case -2 : #include <stdio.h> typedef void (*mycall) (int a ,int b); void addme(int a,int b); void mulme(int a,int b); void subme(int a,int b); main() { mycall x[10]; x[0] = &addme; x[1] = &subme; x[2] = &mulme; (*x[0])(5,2); (*x[1])(5,2); (*x[2])(5,2); } void addme(int a, int b) { printf("the value is %d\n",(a+b)); } void mulme(int a, int b) { printf("the value is %d\n",(a*b)); } void subme(int a, int b) { printf("the value is %d\n",(a-b)); } Output: the value is 7 the value is 3 the value is 10

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  • Function pointers usage

    - by chaitanyavarma
    Hi All, Why these two codes give the same output, Case 1: #include <stdio.h> typedef void (*mycall) (int a ,int b); void addme(int a,int b); void mulme(int a,int b); void subme(int a,int b); main() { mycall x[10]; x[0] = &addme; x[1] = &subme; x[2] = &mulme; (x[0])(5,2); (x[1])(5,2); (x[2])(5,2); } void addme(int a, int b) { printf("the value is %d\n",(a+b)); } void mulme(int a, int b) { printf("the value is %d\n",(a*b)); } void subme(int a, int b) { printf("the value is %d\n",(a-b)); } Output: the value is 7 the value is 3 the value is 10 Case 2 : #include <stdio.h> typedef void (*mycall) (int a ,int b); void addme(int a,int b); void mulme(int a,int b); void subme(int a,int b); main() { mycall x[10]; x[0] = &addme; x[1] = &subme; x[2] = &mulme; (*x[0])(5,2); (*x[1])(5,2); (*x[2])(5,2); } void addme(int a, int b) { printf("the value is %d\n",(a+b)); } void mulme(int a, int b) { printf("the value is %d\n",(a*b)); } void subme(int a, int b) { printf("the value is %d\n",(a-b)); } Output: the value is 7 the value is 3 the value is 10

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  • SEO: Nested List vs List, Split Over Divs vs Definition List

    - by Jon P
    From an SEO perspective which, if any, is better: Option 1: Nested lists with h2 tags <ul id="mainpoints"> <li><h2>Powerful Analysis</h2> <ul> <li>Charting and indicators</li> <li>Daily trading signals</li> <li>Company health checks</li> </ul> </li> <li><h2>World Market Data</h2> <ul> [List Items removed for brevity] </ul> </li> <li><h2>Daily Market Data</h2> <ul> [List Items removed for brevity] </ul> </li> </ul> Option 2: Divs with h2 and lists <div id="mainpoints"> <div> <h2>Powerful Analysis</h2> <ul> <li>Charting and indicators</li> <li>Daily trading signals</li> <li>Company health checks</li> </ul> </div> <div> <h2>World Market Data</h2> <ul> [List Items removed for brevity] </ul> </div> <div> <h2>Daily Market Data</h2> <ul> [List Items removed for brevity] </ul> </div> </div> Option 3: Definition List <dl id="mainpoints"> <dt>Powerful Analysis</dt> <dd>- Charting and indicators</dd> <dd>- Daily trading signals</dd> <dd>- Company health checks</dd> <dt>World Market Data</dt> [List Items removed for brevity] <dt>Daily Market Data</dt> [List Items removed for brevity] </dl> My instincts tell me that semanticaly the pure list options (1 & 3) are the best and that h2 may be more SEO friendly (1 & 2) which would point to option 1 as being the best option. I do love the lean makeup of the definition list but will I take an SEO hit by losing the h2 tags? Before anyone asks, h2 is not valid markup in a dt tag. Are my instincts right with a nested list being the way to go?

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  • C# Function Inheritance--Use Child Class Vars with Base Class Function

    - by Sean O'Connor
    Good day, I have a fairly simple question to experienced C# programmers. Basically, I would like to have an abstract base class that contains a function that relies on the values of child classes. I have tried code similar to the following, but the compiler complains that SomeVariable is null when SomeFunction() attempts to use it. Base class: public abstract class BaseClass { protected virtual SomeType SomeVariable; public BaseClass() { this.SomeFunction(); } protected void SomeFunction() { //DO SOMETHING WITH SomeVariable } } A child class: public class ChildClass:BaseClass { protected override SomeType SomeVariable=SomeValue; } Now I would expect that when I do: ChildClass CC=new ChildClass(); A new instance of ChildClass should be made and CC would run its inherited SomeFunction using SomeValue. However, this is not what happens. The compiler complains that SomeVariable is null in BaseClass. Is what I want to do even possible in C#? I have used other managed languages that allow me to do such things, so I certain I am just making a simple mistake here. Any help is greatly appreciated, thank you.

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  • How to use will_paginate with a nested resource in Rails?

    - by Sue Petersen
    I'm new to Rails, and I'm having major trouble getting will_paginate to work with a nested resource. I have two models, Statement and Invoice. will_paginate is working on Statement, but I can't get it to work on Invoice. I know I'd doing something silly, but I can't figure it out and the examples I've found on google won't work for me. statement.rb class Statement < ActiveRecord::Base has_many :invoices def self.search(search, page) paginate :per_page => 19, :page => page, :conditions => ['company like ?', "%#{search}%"], :order => 'date_due DESC, company, supplier' end end statements_controller.rb <irrelevant code clipped for readability> def index #taken from the RAILSCAST 51, will_paginate podcast @statements = Statement.search(params[:search], params[:page]) end I call this in the view like so, and it works: <%= will_paginate @statements %> But I can't figure out how to get it to work for Invoices: invoice.rb class Invoice < ActiveRecord::Base belongs_to :statement def self.search(search, page) paginate :per_page => 19, :page => page, :conditions => ['company like ?', "%#{search}%"], :order => 'employee' end end invoices_controller.rb class InvoicesController < ApplicationController before_filter :find_statement #TODO I can't get will_paginate to work w a nested resource def index #taken from the RAILSCAST 51, will_paginate podcast @invoices = Invoice.search(params[:search], params[:page]) end def find_statement @statement_id = params[:statement_id] return(redirect_to(statements_url)) unless @statement_id @statement = Statement.find(@statement_id) end end And I try to call it like this: <%= will_paginate (@invoices) % The most common error message, as I play with this, is: "The @statements variable appears to be empty. Did you forget to pass the collection object for will_paginate?" I don't have a clue what the problem is, or how to fix it. Thanks for any help and guidance!

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