473,706 Members | 5,882 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

ambiguous call to overloaded

Hi,

I am having a class template which is used to convert from one type another.
I am having a problem when i use the copy constructor with same type.

code.
#include "stdio.h"
template <class T>
class SPtr
{
public:
// Default constructor
SPtr() : mSptr(NULL){}
// constructor to convert. takes a different type i.e. T2
template<class T2>
SPtr(T2& p){}
// copy constructor.
template<>
SPtr(const SPtr<T>& p) {}
private:
T* mSptr;
};

void main()
{
const SPtr<int> p1;
SPtr<int> p2(p1);
}

here the SPtr<int> p2(p1) gives me an "ambiguous call to overloaded
function" error.
but if i put a const in the template for SPtr(const T2&p), it reolves the
ambiguity,
template<class T2>
SPtr(const T2& p){} // this will correct the problem.

Could someone explain this behaviour?

TFH
shekar


Jul 23 '05 #1
7 3948
* ishekara:

void main()


That is not valid C++.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
Jul 23 '05 #2
here is the revised post. is this C++??

Hi,

I am having a class template which is used to convert from one type another.
I am having a problem when i use the copy constructor with same type.

code.
#include "stdio.h"
template <class T>
class SPtr
{
public:
// Default constructor
SPtr() : mSptr(NULL){}
// constructor to convert. takes a different type i.e. T2
template<class T2>
SPtr(T2& p){}
// copy constructor.
template<>
SPtr(const SPtr<T>& p) {}
private:
T* mSptr;
};

int main()
{
const SPtr<int> p1;
SPtr<int> p2(p1);
return 0;
}

here the SPtr<int> p2(p1) gives me an "ambiguous call to overloaded
function" error.
but if i put a const in the template for SPtr(const T2&p), it reolves the
ambiguity,
template<class T2>
SPtr(const T2& p){} // this will correct the problem.

Could someone explain this behaviour?

TFH
shekar
"Alf P. Steinbach" <al***@start.no > wrote in message
news:42******** ********@news.i ndividual.net.. .
* ishekara:

void main()


That is not valid C++.

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Jul 23 '05 #3

ishekara wrote:
Hi,

I am having a class template which is used to convert from one type another. I am having a problem when i use the copy constructor with same type.

code.
#include "stdio.h"
template <class T>
class SPtr
{
public:
// Default constructor
SPtr() : mSptr(NULL){}
// constructor to convert. takes a different type i.e. T2
template<class T2>
SPtr(T2& p){}
// copy constructor.
template<>
SPtr(const SPtr<T>& p) {}
This should just be:

// copy constructor
SPtr(const SPtr& p) {}

(i.e., without "template <>" or "<T>").

Hope this helps,
-shez-


private:
T* mSptr;
};

void main()
{
const SPtr<int> p1;
SPtr<int> p2(p1);
}

here the SPtr<int> p2(p1) gives me an "ambiguous call to overloaded
function" error.
but if i put a const in the template for SPtr(const T2&p), it reolves the ambiguity,
template<class T2>
SPtr(const T2& p){} // this will correct the problem.

Could someone explain this behaviour?

TFH
shekar


Jul 23 '05 #4
ishekara wrote:
here is the revised post. is this C++??

Hi,

I am having a class template which is used to convert
from one type another. I am having a problem when i use
the copy constructor with same type.

code.
#include "stdio.h"
template <class T>
class SPtr
{
public:
// Default constructor
SPtr() : mSptr(NULL){}
// constructor to convert. takes a different type i.e. T2
template<class T2>
SPtr(T2& p){}
// copy constructor.
Remove this line from your code: template<>

SPtr(const SPtr<T>& p) {}
private:
T* mSptr;
};

int main()
{
const SPtr<int> p1;
SPtr<int> p2(p1);
return 0;
}

here the SPtr<int> p2(p1) gives me an "ambiguous call to
overloaded function" error.
but if i put a const in the template for SPtr(const
T2&p), it reolves the ambiguity,
template<class T2>
SPtr(const T2& p){} // this will correct the problem.

Could someone explain this behaviour?

TFH
shekar
"Alf P. Steinbach" <al***@start.no > wrote in message
news:42******** ********@news.i ndividual.net.. .
* ishekara:

void main()


That is not valid C++.

--
A: Because it messes up the order in which people
normally read text. Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in
e-mail?


You must remove template<> before the copy constructor, see above. Yes, this is
C++
Jul 23 '05 #5
* ishekara:
[top-posting]
Do not top-post. See the FAQ. Corrected.


here is the revised post. is this C++??


With regard to the declaration of 'main', yes.

The following code compiles fine with GNU and Visual C++, spot
the significant difference:
#include <cstddef>

template <class T>
class SPtr
{
public:
// Default constructor
SPtr() : mSptr(NULL){}
// constructor to convert. takes a different type i.e. T2
template<class T2>
SPtr(T2& /*p*/){}
// copy constructor.
SPtr(const SPtr<T>& /*p*/) {}
private:
T* mSptr;
};

int main()
{
const SPtr<int> p1;
SPtr<int> p2(p1);
}

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?
Jul 23 '05 #6
Hi all,

thanks for your reply
I removed the template<>, still it is giving ambiguous error for me. i am
using VC++ for compiling.

The ambiguity goes away by adding const in front of T2, as in
template<class T2>
SPtr(const T2& /*p*/){}

any idea why this const is required?

TFH
shekar

"Shezan Baig" <sh************ @gmail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

ishekara wrote:
Hi,

I am having a class template which is used to convert from one type

another.
I am having a problem when i use the copy constructor with same type.

code.
#include "stdio.h"
template <class T>
class SPtr
{
public:
// Default constructor
SPtr() : mSptr(NULL){}
// constructor to convert. takes a different type i.e. T2
template<class T2>
SPtr(T2& p){}
// copy constructor.
template<>
SPtr(const SPtr<T>& p) {}


This should just be:

// copy constructor
SPtr(const SPtr& p) {}

(i.e., without "template <>" or "<T>").

Hope this helps,
-shez-


private:
T* mSptr;
};

void main()
{
const SPtr<int> p1;
SPtr<int> p2(p1);
}

here the SPtr<int> p2(p1) gives me an "ambiguous call to overloaded
function" error.
but if i put a const in the template for SPtr(const T2&p), it reolves

the
ambiguity,
template<class T2>
SPtr(const T2& p){} // this will correct the problem.

Could someone explain this behaviour?

TFH
shekar

Jul 23 '05 #7
ishekara wrote:
Hi all,

thanks for your reply
I removed the template<>, still it is giving ambiguous error for me. i am
using VC++ for compiling.


1. VC6 and VC.NET are known to have template issues. VC.NET 2K3 is
fairly good with regard to them.

2. Copy constructors should always use const references anyways, unless
there is an EXTREMELY good reason not to.
Jul 23 '05 #8

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

1
10004
by: Alex Zhitlenok | last post by:
Hi, My question is how to resolve in C# ambiguous overloaded operators? Let say, I have two unrelated classes A and B, each one implements overloaded operator + with the first parameter of type A, and the second one of type B. Let say, these are not my classes and I know nothing about the implementation. As system doesn't know what code must be used for resolving the language construction a+b (where A a; and B b;), it returns "The call...
5
10991
by: rolandz | last post by:
Hi, Maybe somebody has been fighting with the problem that I do, currently. I have a class that has method f(). The two versions of the f() method accept different objects: Int and Short. These objects have constructors that allow implicit conversions from simple types. All this has been defined as follows: <code> class Int
2
2456
by: pvl_google | last post by:
Hi, I'm trying to extend an STL class with additional iterator functionality. In the simplified example below I added an extra iterator class with a dereferencing operator. This operator internally relies on the at function of the superclass. #include <vector>
6
3822
by: c1t1z3n | last post by:
hiya, i'm having this weird error on my project. As far as I know "ambiguous call to overloaded function" should only occur when the compiler must choose from several methods, but here i don't think it's the case. I've got the following class: class item { public: item(string id_,string datatype_); //item(string id_,string datatype_,int periodo_); //item(string id_,string datatype_,string headerfile_); //item(string id_, string...
1
2955
by: subramanian100in | last post by:
Consider the following program: #include <iostream> using namespace std; void print(char c) { cout << "from print(char c) : " << c << endl; return;
4
2910
by: Joseph Turian | last post by:
I have a templated class with the following methods: Vocab(const T& t); Vocab(unsigned uid); However, when T = unsigned, and I call Vocab(unsigned(0)) then the compiler rightly complains about an ambiguous call to the overloaded function. How can I specify which method I want called in this case? Thanks,
8
5095
by: Nikola | last post by:
Hello, I'm writing a String class for C++ and I'm getting the following error message when using operator: test.cpp: In function ‘int main()’: test.cpp:7: error: ISO C++ says that these are ambiguous, even though the worst conversion for the first is better than the worst conversion for the second: string.h:19: note: candidate 1: char Types::String::operator(unsigned int) const
32
2107
by: Anna Smidt | last post by:
I am having an "ambiguous call to overloaded function" error again. This is the function: int nGetProfWidth (int ncols, unsigned ProfSpec) { if ((ProfSpec & PROF_2d) == 0) return ncols; return int(sqrt(ncols)); //HERE THE ERROR IS THROWN }
3
6400
by: mathieu | last post by:
Could someone please tell me what is wrong with the following -ugly- piece of c++ code. Why when I explicititely set the template parameter my gcc compiler start getting confused: bla.cxx: In function 'int main()': bla.cxx:25: error: call of overloaded 'foo(short unsigned int*&)' is ambiguous bla.cxx:2: note: candidates are: void foo(OutputType*) bla.cxx:10: note: void foo(PixelType*)
0
8780
marktang
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look ! Part I. Meaning of...
0
9285
Oralloy
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
0
9155
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
0
8989
tracyyun
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the choice of these technologies. I'm particularly interested in Zigbee because I've heard it does some...
0
7901
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
1
6614
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
0
5938
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert into image. Globals.ThisAddIn.Application.ActiveDocument.Select();...
0
4445
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
3
2092
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.