on Sun Jan 08 2012, "Simonson, Lucanus J" <lucanus.j.simonson-AT-intel.com> wrote:
From: Of John Bytheway
Literals can be extended in both raw and cooked forms, with the exception of string literals, which can only be processed in cooked form. This exception is due to the fact that strings have prefixes that affect the specific meaning and type of the characters in question.' - source: wikipedia - http://en.wikipedia.org/wiki/C%2B%2B11#User-defined_literals . Right below that Wikipedia describes a variadic template-based mechanism, where the compiler instantiates a template operator and passes the characters as template arguments to it. The return type of that operator could be an MPL list of boxed characters and we could access it using decltype - at least this is the idea. That interface is only available for integer and floating-point literals, not string literals (which that page also says). The only way to get at characters of a string literal at compile time is through constexpr functions.
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.
From there it is just simple metaprogramming to do whatever with the string. It seems the constexper approach promises this, but I'd like to see the code example for what it looks like to use it and also how it works.
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. -- Dave Abrahams BoostPro Computing http://www.boostpro.com