On Sun, Mar 27, 2011 at 10:07 AM, Thomas Heller <thom.heller@googlemail.com> wrote:
On a separate note, is there any way I can prevent the following `factor = 0` from compiling (e.g., making factor a const within the Phoenix function expression)?
#include <boost/spirit/include/phoenix.hpp> #include <iostream> #include <vector> #include <algorithm>
int main() { double sum = 0.0; int factor = 10;
std::vector<double> v(3); v[0] = 1.0; v[1] = 2.0; v[2] = 3.0;
std::for_each(v.begin(), v.end(), ( factor = 0, // <==== Can I prevent this with a compiler error?
No, because this is just plain old C++. assigning zero to a value ... there is nothing what phoenix can do here.
Ok, I understand. Thanks.
The guy who wrote the code could have said: const int factor = 10; assignment would then be impossible^W not allowed.
Yes, but the use case would be to have factor const *only* within the "function" passed to for_each while keeping it mutable in the enclosing scope. Therefore, programmers have to declare factor not-const within main() and I was wondering if there was a way using Phoenix to add the const only locally within the "function" passed to for_each (this is done by Boost.Loccal using "constant-binding" as in `const bind& factor`). -- Lorenzo