Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
In defining a function in an interface :
virtual void ModifyPreComputedCoeffs ( std::vector < IndexCoeffPair_t > & model_ ) = 0;
we want to specify that the vector model_ should not be altered in the sense push_back etc operations should not be done on the vector, but the IndexCoeffPair_t struct objects in the model_ could be changed.
How should we specify that ?
virtual void ModifyPreComputedCoeffs ( const std::vector < IndexCoeffPair_t > & model_ ) = 0;
does not work I think.
The C++ const-correctness concept is IMO way overrated. What you just discovered is one of the big limitations it has: it doesn’t scale by composition.
To be able to create a const vector of non-const objects you need to implement your own vector type. Note that for example even the standard library had to introduce new types for const_iterators.
My suggestion is to use const-correctness where you are forced to, and not everywhere you can. In theory const correctness should help programmers, but comes at a very high cost because of the syntax and is very primitive (just one bit, doesn’t scale by composition, even requires code duplication).
Also in my experience this alleged big help is not really that big… most of the errors it catches are related to the const-correctness machinery itself and not to program logic.
Ever wondered why most languages (including ones designed after C++) didn’t implement this idea?