Some reading through C++ code I come across template deceleration without any type , I have tested the code it compiles too
Code:
template<>
class abc {
}
similarly template usage
Code:
abc<> a;
example of such usage can be found here [URL] ....
I decided to make a linked list program using classes and templates.I implemented my linked list and added some basic functions, everything worked just fine. Then I proceeded to add templates...First, the error list:
#pragma once
template<class T>
class Node {
private:
Node* next;
[code]....
To sum up: Something's wrong with the templates that I used in "List.cpp" and what it could be.
I'm currently learning templates -- & my logic is in a knot with what I am trying to do which is the following:
-Create a function name load
-Accepts a filename (the filename is a text file of integers)
-Open the file
-Create an array(dynamically allocating an array) filling it with the elements read in from the file & returns the array(so that the return type of the array is a pointer to the element type of the array).
//Header file:
#ifndef BUBBLE_SORT_H
#define BUBBLE_SORT_H
#include <iostream>
template <typename T>
void load(std::string filename, T *&arr, int *size);
[code].....
how to allocate memory when it comes to using templates..
After asking the user to input 2 values i expect my program to read them and then output whether they are equal, bigger or smaller than one another. However i am getting no output what so ever when i input the values
code below:
#include <iostream>
#include <cmath>
#include <cstring>
#include <string>
#include <string.h>
using namespace std;
int intInput1, intInput2;
float floatInput1, floatInput2;
int x, n;
[Code] .....
Let us consider the following two classes:
class case1
{
public:
int n;
float x;
[code]....
Now, let's suppose that I instantiate an array of 100 elements of each class:
case1 c1[100];
case2<20> c2[100];
My question is this: will c2 occupy roughly half of the memory than c1?will the value c1.n be allocated 100 times, while the value c1.n wil be allocated only once?
Why wouldn't this code compile when adding '<double>' after the function call?
template<class T>
T add(T& a, T& b){
return a + b;
}
int main() {
int a, b;
cin >> a >> b;
cout << add<double>(a,b);
}
Compiler error:
cannot convert 'a' (type 'int') to type 'double&'
How templates are implemented internally?
Theoretically templates are nothing but a generic routines. But how it has been implemented internally?What complier exactly does?
Having issues calling my arguments from my templates, when i declare x and n in the main it comes up with errors
code below:
#include <iostream>
#include <cmath>
#include <cstring>
#include <string>
#include <string.h>
using namespace std;
int intInput1, intInput2;
[code].....
Suppose you have a templated class, such as
template <typename T>
class Matrix {
// some stuff and some methods
};
and let's say that you have some methods that need to do some type-dependent stuff, like, for example,
template <typename T>
Matrix<T> Matrix<T>::transpose() const {
// get this->rowCount, this->columnCount
// create a Matrix that has rowCount amount of columns and columnCount amount of rows
// copy (*this)[j][k] to theMatrix[k][j] (for all of the entries in *this)
// if the entries are complex, take the complex conjugate of them all
}
Would it be good practice to check explicitly for the typename parameter (or is this, somehow, defeating the purpose of templates)? std::cout << "I know that this is a design question, but it needs to be asked... ";
I was just wondering how is this generally resolved. Let say you have this large function that runs in two modes. In the first mode it evaluates the data passed to a function as a map the the second mode it fills the map. example:
Code:
template <typename Map, typename Int>
void func(Map & map, Int i){
int z = 0;
string zz;
[Code] ....
The point is i do not want to write a large function just to include different modes so i decided to set "i" to be a mode identifier. However when i want to compile my function given two modes i get an error since the modes are not recognized (obviously). if i pass map as
Code: map<int,int>
and mode 1 i get an error here :
Code: map[z] = z; besause map
Code: map[z] expects z to be an int not string and the other way around (though in practice this cannot happen since i set the modes). So am i restricted to writing my function for both modes separately (polimorf.) or there is a way to make my example work.
What I'm trying to do is create a class for constructing an 'op tree' for parsing infix notation.
I started with a base class that uses a map of lambdas to actually calculate the operations (since they are mostly 1 line functions) of passed in integer or float values.
This base class just uses a templated T type as the lvalue and rvalue. I realized though that if I overload the math operators, +, -, etc.. I could also use the class itself as a type for the lvalue and rvalue. This lead me to think I could easily create the op tree by using Operation class members themselves as operands, which I think makes sense but I'm having some trouble expressing the code.
Heres what I have thus far
Code:
#include <map>
#include <string>
#include <algorithm>
#include <iostream>
namespace Calc {
[Code] .....
Example, if you look at the main() function I create normal operations easily with integer values. I then try to create a "tree" operation that includes 2 sub-operations as it's rvalue and lvalue, that is where I'm having some conceptual problems as far as implementing the code to do that.
I am trying to implement BST using templates. This is the code that i have written.
Code: template <class T>
struct node
{
struct node *left;
[Code].....
There are no errors but the program hangs. What is the mistake with this program ?
For my project I have to sort 5 numbers and 5 names using a template bubble sort. I have one header for the numbers, and one for the names. This is what I have so far for my testing page:
#include "Floatheader.h"
#include "Nameheader.h"
#include <string>
int main ()
myFloat obj1;
myFloat obj2( 2.2, 5.1);
[Code] .....
I have to create a template to look like this: template<>....with a class inside the arrows. Then, I have to use bubble sort to sort the 5 names and number objects I have created. Sorting the names and numbers and also using templates?
A static method named readFromFile that takes a C-string as the first parameter, and an orderedLinkedList<MemberDO> object as the second parameter. The first argument is the filename that contains data for existing members. This method should read the data for each individual member from the input file (one line of data per member), create a new MemberDO object, and insert this object into the linked list specified in the second argument.
How do I take the second parameter in, do I need to create the Linked List first? Here is the code I have so far
#include<iostream>
#include<string>
#include <fstream>
using namespace std;
class MemberDO {
[Code] ....
What to do with the readFromFile static method?
i'm new to C++ i came across this bubblesort program earlier relating to class templates i was wondering how to make this into simple function templates
#include<iostream>
#include<iomanip.h>
#include<conio.h>
#include<stdio.h>
using namespace std;
template <class t>
class bubble
[Code] ....
I want to create an abstract base class having a member function that can accept a templatized structure as its parameter, something that according to C++'s rules can't be done for a good reason.
That good reason it is because an abstract base class is intended to provide interface rules to the classes that will derive from it and should not deal with data.
But how would you go about doing something like the following which is probably a reasonable design decision?
template<typename T>
class Matrix { /* ... */ };
class iFile {
public:
virtual ~iFile() {} = 0;
virtual void Process(const Matrix<T>&) = 0;
[Code] .....
I am having problems implementing ArrayList using templates. I was given a program and I have to create this implementation to make it work. It keeps giving me an error "invalid operands to binary expression" .....
ifndef Final_4_ArrayList_hpp
#define Final_4_ArrayList_hpp
#define MAX 10;
#include "List.hpp"
template <class T>
class ArrayList : public List <T> {
[Code] ....
template <class T>
void Arreglo<T> :: Registro (ifstream& Entrada) {
Entrada >> Cantidad;
Dealer = new T [Cantidad];
for (int i = 0; i < Cantidad; i++) {
[Code] .....
It says the following error when I comile it:
error: expected type-specifier before 'Detail'
(*(Dealer + i)).Modelo = new Detail[(*(Dealer + i)).AmountModels];
error: expected ';' before 'Detail'
Why will i use explicit instantiation of a template, for a type? If I do not use explicit instantiation, the template is used to create the necessary function then what is the use of explicit instantiation?
template <class Any>
void Swap (Any &, Any &);
// template prototype
template <> void Swap<job>(job &, job &);
// explicit specialization for job
[Code] ....
In the above eg. explicit instantiation is done for char type. What is the use of this?? If the compiler can make use of the template to make a fn for char type.
<eg. taken from C++ Primer>
Let's say I have a variadic type A and a non-variadic type B:
Code:
template <typename ... Args>
class A
{};
template <typename T>
class B
{};
Now, I'd like to do the following (pseudocode since I don't know how to do this yet):
Code:
template <typename ... Args>
class C: public A<B<Args1>,B<Args2>,B<Args3>....>
{};
Essentially, I'd like to take the parameter pack used for C and compose B around each element individually, then pass the result to A.
how I can do this?
I'm trying to learn how to use variadic templates, and I decided a great example would be serializing a series of types into a stringstream:
Code:
// Send a fully constructed message.
virtual void send(ostringstream &msg) = 0;
// Construct a message from the arguments and send it.
// This is the usual entry point.
template <typename ...Args>
void send(Args ...args {
[Code] ....
This works fine, so far as I can tell. However, I decided to see if I could specialize the way certain types are serialized. I tried using a Google Protocol Buffer object as an example, and added this:
Code:
// Handle a protocol buffer type while constructing a message.
template <typename ...Args>
void send(ostringstream &msg,
const google::protobuf::MessageLite &protobuf, Args ...args) {
std::string msg_str = protobuf.SerializeAsString();
msg << msg_str;
send(msg,args...);
}
I would expect this overload to be preferred over the generic T overload when a protobuf object (which always inherits from MessageLite) is passed into send() anywhere in the list. However, this is not happening. I am getting an error message to the effect that << doesn't know how to deal with my concrete type, pointing at the T overload.
This code is from my text book it shows how to implement code that is embedded I have modified it somewhat but I was wondering how I could get the user to implement the size of the array and enter the integers with the size of array that was implemented.
#include<iostream>
#include<cstdlib>
#include<iomanip>
using namespace std;
[Code].....
I'm struggling a bit to combine templates and operator overloading.
I'm writing a program that will be able to perform various matrix arithmetic at the end. However I'm stuck at the overloaded << and >> functions. I've defined them as I'm used to, without working with templates, however they are incorrect as I have defined them, and I'm not sure how to fix it.
I want to overload the stream insertion operator >> to read matrix data from either the keyboard or a file stream. I want to use >> to input a 3 x 3 matrix stored in a text file in the following format:
2 4 3
5 2 3
7 1 0
And similarly I want to overload the stream extraction operator << to output a matrix to the screen or file in the following format:
3 2 -1
1 -1 2
2 3 -1
Here is my work so far:
matrix.h
#ifndef MATRIX_H
#define MATRIX_H
#include <cassert>
#include <iostream>
using namespace std;
template <class T> class Matrix;
[Code] ....
I am trying to implement a linked list using a class template, however each of my classes that I want in the list all inherit from an Account class. I have attempted to template the linked list class as account however Ive come into errors I can't resolve. How I can go about this?
The error exists within the customer.cpp class where it says
14IntelliSense: a value of type "Account *" cannot be assigned to an entity of type "CurrentAccount *"f:Further C++Assignment with TemplatesAssignmentCustomer.cpp229Assignment
Customer class:
#ifndef CUSTOMER_H
#define CUSTOMER_H
#include <iostream>
#include <string>
#include "Account.h"
#include "AccountLinkedList.h"
[Code] .....
//////////////////////////////////////////////
struct FaceTemplate {
public byte [] templateData;
}
List <FaceTemplate> faceTemplates;
////////////////////////////////////////////
I want to create this structure as globally to access this list in every window form. how can i create and how cam i access.
Let's say I have a templated base class:
Code:
template <typename Input>
class Consumer
{
public:
void consume(Input input)
{
// do something
}
};
Now, I have a class which derives from this twice (A and B are unrelated, but otherwise unimportant classes):
Code:
class A;
class B;
class Derived: public Consumer<A>, public Consumer<B>
{
};
Now, elsewhere in the code I do this:
Code:
{
A myA;
Derived myDerived;
myDerived.consume(myA);
}
This looks like it should be simple enough, but g++ 4.8.1 is giving me a "request for member is ambiguous" error.