Now that __ctfe has officially been folded into the compiler, is anyone else already planning on making most of std.math CTFE-compatible?  If not, I'll probably start working on this.  Also, as far as the design, I think there should probably be a separate etc.ctfemath module under the hood (though not exposed to the user).  std.math would import this module and do something like:

real someFun(real num) {
     if(__ctfe) {
         return etc.ctfemath.someFun(num);
    }

     // RTFE implementation.
}

This would make things a lot easier to test, etc.