convert vector of strings/doubles to arrays

Question

I am using matheval library. Its functions take c-style parameters, for example:

    #include<matheval.h>

    char * evaluator_evaluate(void * evaluator, int count, char **names, double *values);

In my case, I want to convert std::vector of names and std::vector of values to char ** and double *

Also, every name correspond to a unique value, and there could be repetitions. What is the best way to arrange names and values elegantly in terms of data structures? For now, I use vectors, and both contains repetitions.

Edit Please keep in mind that order of names and values matters and should match.

Thanks

Answer 1

Internally, the standard requires that a vector<> is equivalent to an array. You can take the address of vector[0] and the resulting pointer will point to a contiguous area of memory where the data is stored, in the same order as the vector. This pointer is valid until or unless the vector<> is resized.

For std::string values (or any other object, for that matter), though, you will only get an array of string objects.