How to use those constant ? It rather simple. Things like double k = pi_; int u = ten_; works as intended by auto-casting the valeu to the destination type.
You can force a constant to be of a given type : abs( float(log2_) ); Alternatively, the basic operator (+,-,*,/,unary -, ~, ! and comparison) are overlaod to autocast the constant into a proper type when used like :
double k,v; k = v + pi_; bool test = x > log10_;
A set of result_of enabled traits also allows to computes the correct type of a constant when used in a complex expression. Most constant type-cast is performed at compile-time, unless if you use a user-defined type-casting overload.
I am overthinking it or could this be viable ?
Well.... this is one of those "complex" solutions that was suggested last time this was discussed that I've been trying to avoid ;-) Off the top of my head, the main problems I see are: * What is the result of 2 * pi? How about 2 * pi * r where r is a real? * If you mistakenly call a function passing a constant as argument, for example foo(2.0, pi), then if foo is a template you will likely get an inscutable failure very deep inside foo's body (or worse some other function that foo calls). * In order to avoid ODR violations I presume the constants have to be defined in an anonymous namespace? Does this cause code bloat simply by #including the constants header? Now I suspect that all of these issues are probably solvable to some degree, it's a question of whether it's worth the hassle, and/or whether the resulting code is likely to turn into a problem to maintain. Cheers, John.