From: Dave Abrahams
So the question is, is there any way to get from a literal string to an MPL list of literal char for each character. Nope. constexpr is somewhat crippled: although a constexpr function executes at compile-time, it has to obey the same rules as any other function. For example, its return type can depend on the type, but never on the *value*, of its arguments, and once you're inside the function, the contents of the argument are not treated as compile-time constants. So, I think constexpr actually doesn't promise it.
Well, there goes all my excitement. How then would the original proposal by Martin to use constexpr to "parse strings in C++ at compile time" work? You and Eric seemed to know what Marin had in mind and agree that a constexper string-based regex library was feasible, though differed on whether it was worthwhile. What am I missing? I was afraid of thatly yours, Luke