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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.
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No. A reference is simply an alias for an existing object. const is enforced by the compiler; it simply checks that you don't attempt to modify the object through the reference r .
A const vector will return a const reference to its elements via the [] operator . In the first case, you cannot change the value of a const int&. In the second case, you cannot change the value of a reference to a constant pointer, but you can change the value the pointer is pointed to.
You can't put items into a const vector, the vectors state is the items it holds, and adding items to the vector modifies that state.
The reference is to a vector that is const, so its contained type is also considered const. That means you can't directly change the contents of the vector or the contained items.
Rather than passing the vector into the function, do what the standard library does and pass a pair of iterators instead.
virtual void ModifyPreComputedCoeffs ( std::vector < IndexCoeffPair_t >::iterator & model_begin, std::vector < IndexCoeffPair_t >::iterator & model_end ) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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