Question

Often I have some compile-time constant number that is also the upper limit of possible values assumed by the variables. And thus I’m interested in choosing the smallest type that can accomodate those values. For example I may know that variables will fit into <-30 000, 30 000> range, so when looking for a suitable type I would start with signed short int. But since I’m switching between platforms and compilers I would like a compile-time assert checking whether the constant upper values really fit within those type. BOOST_STATIC_ASSERT( sizeof(T) >= required_number_of_bytes_for_number ) works fine but the problem is:
How to automatically determine the number of bytes required for storing a given compile-time constant, signed or unsigned? I guess a C macro could do this job? Could anyone write it for me?
I might use std::numeric_limits::max() and min() instead of computing the bytes but then I would have to switch to run-time assert 🙁

Answer 1

Now that this is tagged with c++, I suggest using Boost.Integer for appropriate type selection. boost::int_max_value_t< MyConstant >::least would give the type you are looking for.