[Boost-users] [array] range check (at compile time)

20 Feb 2010

      Hi,

 Lately I find myself using boost::array intesively, specially in
small demo programs. Sometimes, when "manually" accessing the elements
I type a index out of range. The library can detect these errors once
the program is running but I found this a waste, also I was surprised
not to see this kind of static check not implemented in the library.
So I wanted to see if I could enforce range checking at compile time,
and I come out with this solution.

namespace boost{ //sorry about the namespace name
	template<size_t IDX, typename T, size_t N>
	const T& get(boost::array<T, N> const& arr){
		BOOST_STATIC_ASSERT(IDX<N);
		return arr[IDX];
	}
	template<size_t IDX, typename T, size_t N>
	T& get(boost::array<T, N>& arr){
		BOOST_STATIC_ASSERT(IDX<N);
		return arr[IDX];
	}
}

#include<iostream>

void main(){
  boost::array<double, 3> a = {1,2,3};
  std::clog<<boost::get<2>(a)<<std::endl; // ok, (namespace
specification needed, why?)
  std::clog<<boost::get<5>(a)<<std::endl; //does not compile
  return 0;
}

(I though about using enable_if instead of BOOST_STATIC_ASSERT but
that would be too much overengineering.)

Is this implemented already in some other way?

Alfredo

[Boost-users] [array] range check (at compile time)

alfC