Problem with implicit conversion (GCC 3.4.1)

Problem with implicit conversion (GCC 3.4.1)

[Boris von Loesch]

Hello,

I have written a program that compiles just fine with GCC 3.3. With
GCC 3.4.1 it results in this error:

g++ -O0 -g3 -Wall -c -oTestp.o ../Testp.c
../Testp.c: In function `int main()':
../Testp.c:26: error: no match for 'operator<=' in 't <= 2.0e+0'

Please help me, I have no idea where the problem is.

Here is the code:

template <class T> class BasisF;
	
template <class T> inline bool operator<=(const BasisF<T> &a, const
BasisF<T> &b){return a.x <= b.x;}

template<class T> class BasisF{

public:
	T x;
	BasisF(const T &_x = T()): x(_x){}
	BasisF(const BasisF &_b): x(_b.x){}
	~BasisF(){}
	BasisF& operator= (const T &_x){
		 x(_x);
		 return *this;
	}
	friend bool operator<=<>(const BasisF &a, const BasisF &b);
	};

#define min(a,b) ((a) <= (b) ? (a) : (b))

int main(){
	BasisF<double> t(1);
	if (min(t,2.0)<=0) return 1;
	return 0;
}

Regards,
Boris

RE: Problem with implicit conversion (GCC 3.4.1)

[lrtaylor]

Well, you've declared a <= operator that can compare to BasisF objects,
but you're trying to compare a BasisF object with a double, which you
haven't created an operator for:

min(t,2.0)  -> ((t) <= (2.0) ? (t) > (2.0))

So, in your min macro, you are trying to compare the object t with the
double 2.0.  You don't have an operator for that.

Thanks,
Lyle

-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [mailto:gcc-help-owner@gcc.gnu.org] On
Behalf Of Boris von Loesch
Sent: Thursday, August 26, 2004 3:55 AM
To: gcc-help@gcc.gnu.org
Subject: Problem with implicit conversion (GCC 3.4.1)

Hello,

I have written a program that compiles just fine with GCC 3.3. With
GCC 3.4.1 it results in this error:

g++ -O0 -g3 -Wall -c -oTestp.o ../Testp.c
../Testp.c: In function `int main()':
../Testp.c:26: error: no match for 'operator<=' in 't <= 2.0e+0'

Please help me, I have no idea where the problem is.

Here is the code:

template <class T> class BasisF;
	
template <class T> inline bool operator<=(const BasisF<T> &a, const
BasisF<T> &b){return a.x <= b.x;}

template<class T> class BasisF{

public:
	T x;
	BasisF(const T &_x = T()): x(_x){}
	BasisF(const BasisF &_b): x(_b.x){}
	~BasisF(){}
	BasisF& operator= (const T &_x){
		 x(_x);
		 return *this;
	}
	friend bool operator<=<>(const BasisF &a, const BasisF &b);
	};

#define min(a,b) ((a) <= (b) ? (a) : (b))

int main(){
	BasisF<double> t(1);
	if (min(t,2.0)<=0) return 1;
	return 0;
}

Regards,
Boris

RE: Problem with implicit conversion (GCC 3.4.1)

[Suresh Lakshmanan]

Try the code below. You could use std::min template in STL, so that you can 
force conversion
to the template parameter.

template<class T> class BasisF {
	T x;
public:

	BasisF(const T &_x = T()): x(_x) {}
	BasisF(const BasisF &_b): x(_b.x) {}
	~BasisF() {}

	BasisF& operator= (const T &_x){
		 x(_x);
		 return *this;
	}

	friend bool operator<=(const BasisF &a, const BasisF &b) {
		return a.x <= b.x;
	}
};

#define min(a,b) ((a) <= (b) ? (a) : (b))

int main(){
	BasisF<double> t(1);
	if (min(t, 2.0)<= 0) {
		return 1;
	}

	return 0;
}

Thanks,
L.Suresh.

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Re: Problem with implicit conversion (GCC 3.4.1)

[Boris von Loesch]

Thanks for your replay.

This code works, but why does your code work and my not? Why does it
not compile with gcc 3.4.1 but with gcc 3.3?

Boris

On Thu, 26 Aug 2004 17:27:36 +0000, Suresh Lakshmanan
<suresh_lakshmana@hotmail.com> wrote:
> Try the code below. You could use std::min template in STL, so that you can
> force conversion
> to the template parameter.
> 
> template<class T> class BasisF {
>         T x;
> public:
> 
>         BasisF(const T &_x = T()): x(_x) {}
>         BasisF(const BasisF &_b): x(_b.x) {}
>         ~BasisF() {}
> 
>         BasisF& operator= (const T &_x){
>                  x(_x);
>                  return *this;
>         }
> 
>         friend bool operator<=(const BasisF &a, const BasisF &b) {
>                 return a.x <= b.x;
>         }
> };
> 
> #define min(a,b) ((a) <= (b) ? (a) : (b))
> 
> int main(){
>         BasisF<double> t(1);
>         if (min(t, 2.0)<= 0) {
>                 return 1;
>         }
> 
>         return 0;
> }