Error: Overloading ambiguity between "operator+(const RWCString&, const RWC

Question

We always get the following error when we are compiling our source codes:
Error: Overloading ambiguity between "operator+(const RWCString&, const RWCString&)" and "RWCString::operator const char*() const"
Our compiler is Workshop 6 update 1. We can compile the same source codes in Workshop 5.0. We found out that we can solve this problem if we explicitly cast the const strings to RWCString. However, since we are building on previous source codes and modules, we find this solution close to impossible. Is there other solution for this problem? Are there any patch which we can use?
Thanks!

Answer 1

The code really does have an ambiguity in it.
The RWCString class operator() member function, which you invoke as str1(...) with an integer value, returns a char. You then have the operation
        RWCString + char
The RWCString class does not have an associated operator+ that takes a RWCString and a character. The compiler could convert the string to a char* via "operator const char*" and add the value of the char to it, or it could convert the char to a RWCString via a constructor and use the operator+ that takes two RCWCstrings.
The compiler has no way to prefer one choice over the other.
You can write an explicit cast, or you can store the result of the str1(...) operation in an explicit RWCString temp, or you could use the += operator:
str2 = str2 + RWCString(str1(str1.length()-1));
RWCString temp = str1(str1.length()-1);
str2 = str2 + temp;
str2 += str1(str1.length()-1);
BTW, this problem illustrates why it's usually a bad idea to have multiple constructors and also type conversion operators in a class. It's hard to write code that doesn't lead to ambiguities.