Error in template class constructor

Question

0.00/5 (No votes)

See more:

I write 3 class with template:

class Parent
class SWAP
class insertionSort : public SWAP<t> , public Parent<t>

when I complie code , compiler return this error:

Error 1 error C2512: 'Parent<int>' : no appropriate default constructor available

Code :

C++

// searches-sorts.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>

using namespace std;

template <class T>
class Parent
{
public:
	T *arr;
	int len;
	virtual void Sort();
	
	

	Parent(T *a, int l)
	{
		len = l;
		arr = new T[l];
		for (int i = 0; i < l; i++)
		{
			arr[i] = a[i];
		}
	}
};


//Swap
template <class T>
class SWAP
{
public:
	void swap(T *a, int l ,int i, int j)
	{
		T temp = a[i];
		a[i] = a[j];
		a[j] = temp;
	}
};


//insertion Sort
template <class T>
class insertionSort : public SWAP<T> , public Parent<T>
{
public:
	insertionSort(T *a, int l)
	{
		Parent::Parent(a, l);
	}

	void Sort()
	{
		int j;

		for (int i = 0; i < len; i++)
		{
			j = i;
			while (j > 0 && arr[j] < arr[j - 1])
			{
				SWAP::swap(arr, len,j, j - 1);
				j--;
			}
		}
	}
};


//
int main( )
{
	int *a = new int[5];
	for (int i = 0; i < 5; i++)
	{
		a[i] = i;
	}
	a[3] = 10;

	Parent<int> *ex = new insertionSort<int>(a, 5);
	

	for (int i = 0; i < 5; i++)
	{
		cout << a[i] << ", ";
	}

	return 0;
}

Posted 21-Nov-14 1:04am

farhad bat

Updated 21-Nov-14 1:14am

v3

Add a Solution

2 solutions

Solution 1

As it says in the error message, where's your default constructor for parent?

If the compiler doesn't see an explicit reference to a base class constructor in the derived class initialiser list it'll try and generate a call to the base class default constructor.

To avoid this you need something like:

C++

insertionSort(T *a, int l) : Parent(a, l)
{
}

and not the syntax you used.

Incidentally should SWAP be a public base class of insertionSort? What sort of operations does SWAP provide that clients of insertionSort want to use? Looking at the lack of data members are you even sure that SWAP is a class and not a function? Actually the entire thing looks like a bunch of functions rather than being classes but maybe that's me.

Posted 21-Nov-14 1:14am

Aescleal

Comments

farhad bat 21-Nov-14 7:19am

I know swap must be function but my professor insist write it as class!!

Aescleal 21-Nov-14 8:27am

I'd suggest getting a new professor - unless there's something very subtle he's trying to demonstrate he's not got a clue about how to use C++

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

farhad bat · Accepted Answer · 2014-11-21T01:39:00

I solve it

C++

// searches-sorts.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>

using namespace std;

template <class t="">
class Parent
{
public:
	T *arr;
	int len;
	virtual void Sort()
	{
	}
	

	Parent(T *a, int l)
	{
		len = l;
		arr = new T[l];
		for (int i = 0; i < l; i++)
		{
			arr[i] = a[i];
		}
	}

	void print()
	{
		for (int i = 0; i < len; i++)
		{
			cout << arr[i] << ", ";
		}
		cout << endl;
	}
};


//Swap
template <class t="">
class SWAP
{
public:
	SWAP()
	{
	}
	void swap(T *a, int l ,int i, int j)
	{
		T temp = a[i];
		a[i] = a[j];
		a[j] = temp;
	}
};


//insertion Sort
template <class t="">
class insertionSort : public SWAP<t> , public Parent<t>
{
public:
	insertionSort(T *a, int l)
		:SWAP(),Parent(a, l)
	{
	}

	void Sort()
	{
		int j;

		for (int i = 0; i < len; i++)
		{
			j = i;
			while (j > 0 && arr[j] < arr[j - 1])
			{
				SWAP::swap(arr, len,j, j - 1);
				j--;
			}
		}
	}
};


//
//
int main( )
{
	int *a = new int[5];
	for (int i = 0; i < 5; i++)
	{
		a[i] = i;
	}
	a[3] = 10;

	Parent<int> *ex = new insertionSort<int>(a, 5);
	ex->Sort();
	ex->print();

	

	return 0;
}


</int></int></t></t></class></class></class></iostream>