Re: warning: ISO C++ says that these are ambiguous

TheFlyingDutchman <>
Fri, 13 May 2011 04:44:01 -0700 (PDT)
On May 13, 2:44 am, Johannes Schaub <>

TheFlyingDutchman wrote:

given ClassA methods:

ClassA operator+(const long& ) const;
ClassA operator+(const int& ) const;
ClassA operator+(const double& ) const;

ClassA operator+(const ClassB&) const;

I get a warning:
warning: ISO C++ says that these are ambiguous even though the worst
conversion for the first is better than the worst conversion for the

I can get rid of the warning if I remove the ClassB constructor that
takes a double:

ClassB(double &);

But I would prefer to leave it in if there was some other way to clear
up the ambiguity.

You have given too little information. You hit a case similar to this:htt=


I am not having any luck reproducing it with a minimum subset of the
code. I did find out that I had another statement

ClassA operator+(const ClassB&);

in addition to

ClassA operator+(const ClassB&) const;

The warning occurs on:

ClassA operator++(int) { ClassA temp = *this;
           *this = temp + (long) 1; return (temp);}

I found that I can get rid of the warning by either eliminating the
extra operator+ with the ClassB input or by using "explicit" on the
ClassB constructor as someone suggested.

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