C++ :: Templates / Lambdas And Overloaded Operators
Feb 16, 2015
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.
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Feb 16, 2013
I'm having an issue with output, luckily everything else works!! I'm working with Mixed Numbers and operations on them. So, here's the code I'm testing with:
int main() {
Mixed m1(5), m2(1,1,1), m5(2,2,3);
cout << "m1+m2= " << m1+m2 << endl;
cout << "m1 + 10=" << m1+10 << endl;
cout << "m1 - 10=" << m1-10 << endl;
return 0;
}
And here is the output for that code:
File name: fract.h
#ifndef fract_H
#define fract_H
#include <iostream>
using namespace std;
const int DEFAULT_VAL = 0;
[Code] ....
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Jan 10, 2013
I believe I have the syntax correct but I'm having difficulty calling my overloaded == operator in main (last snip-it of code). Below are several files explaining the code.
Commission.h here is where the friend bool operator == exists and I believe I have it initialized correctly.
#ifndef COMMISSION_H_INCLUDED
#define COMMISSION_H_INCLUDED
using namespace std;
class Commission {
public:
Commission();
Commission(int, double, double, double );
~Commission();
[Code] .....
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Dec 6, 2014
I am working on a school project and am stuck in the debugging. I am compiling with g++ and am using c++11.
Error message
In file included from /usr/include/c++/4.7/algorithm:63:0,
from date.h:7,
from date.cpp:1,
from schedule.h:1,
from schedule.cpp:1,
from date_driver.cpp:1:
[Code] ....
Here are my overloaded operators for my date class.
bool Date :: operator == (Date otherDate){
if (((otherDate.getDay () == getDay ()) && (otherDate.getMonth () == getMonth ())) && (otherDate.getYear () == getYear ()))
[Code] .....
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Oct 30, 2013
When compiling the code
#include "tensor.h"
int main() {
Tensor<2,-2> m = {{1,2},{1,3}};
Tensor<2> v = {1,5};
std::cout<<m*v<<"
[Code] ....
Why do I get an ambiguity and why is not the wanted operator*-overload (the last one in the tensor.h file) not even mentioned as one of the candidates? Is it clear what I want to do? And if so, what can I do to make the call unambiguous?
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Sep 13, 2013
I'm implementing a rational number class:
#include <iostream>
#include <stdint.h>
using namespace std;
typedef int64_t RAT_INT;
struct RAT{
RAT_INT Num, Den;
RAT(RAT_INT num = 0, RAT_INT den = 1){
Num = num;
Den = den;
[Code].....
Two questions:
1) In the second line in main, how does C++ know to convert 2 to the appropriate RAT?
2) Is it possible to make the third line in main valid without adding global operators for all the member operators to support plain integers?
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Apr 10, 2015
This code is meant to open a file and use overloaded operators for a complex number class. I am getting a lot of errors in my class declaration/definition but I am not sure why.
#include <iostream>
#include <cmath>
#include <fstream>
class CN {
public:
double real;
double im;
[Code] ....
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Feb 24, 2014
I have a program that has been broken into View/Model/Control plus another class to handle RS232 output.
When the View requests something to be sent via RS232, an event is sent to the control, which then raises an event for the serial class.
Is there a way of using only one event without the serial knowing anything about the view?
If there was, I'd imagine it would be something with Lamdas.
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Oct 6, 2013
I've been playing around with this piece of code:
#include <iostream>
#include <string>
#include <algorithm>
template <void(*funky)(const std::string&)>
void callback()
{funky("Hello World!");}
[Code] ....
But when I try to build it, I get this error on line 24:could not convert template argument 'lambda' to 'void (*)(const string&) {aka void (*)(const std::basic_string<char>&)}'|
I thought the lambda expression I wrote would decay to a function pointer matching the template parameter. I can guess that the constexpr qualifier might have changed the type, but without it my compiler complains that lambda needs to be declared as constexpr...
So is there a way to pass lambda expressions as template parameters?
Without having to use std::function
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Jan 22, 2013
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] ....
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May 27, 2014
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.
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Oct 25, 2013
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..
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Mar 14, 2013
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] .....
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Dec 15, 2013
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?
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Aug 26, 2014
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&'
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Feb 25, 2013
How templates are implemented internally?
Theoretically templates are nothing but a generic routines. But how it has been implemented internally?What complier exactly does?
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Mar 14, 2013
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].....
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Mar 6, 2014
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... ";
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Sep 2, 2013
I have to implement the following class:
class MyString {
private:
char *str; // Pointer to the char array that holds the string
int strLength; // Variable to store the length of the string
public:
// Default constructor to initialize the string to empty string
MyString();
[Code] .....
How can I define overloaded constructor at line 12.
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Dec 5, 2014
I am currently having trouble to have getline to read line from the file. Error is: "no instance of overloaded function "getline" matches the argument list"
code is as follows:
std::ifstream config("config.txt");
string process[4];
int linecount = 1;
if (config.is_open)
{
while (config.peek() !=EOF)
{
getline(config, process);
linecount++;
}
}
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Feb 21, 2014
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.
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Oct 27, 2014
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 ?
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May 7, 2013
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?
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Feb 10, 2014
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?
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Jun 21, 2013
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] ....
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Oct 3, 2014
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] .....
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