https://issues.dlang.org/show_bug.cgi?id=15227
--- Comment #3 from Doug Nickerson <[email protected]> --- In addition to the undocumented syntax I've further noticed: - grammar for 'Integer' technically allows leading 0's and disallows negative integers - 'Integer' is used in the grammar for both non-negative (Position) and negative (Width, Precision) purposes - the 'r' (raw) and 'u' (unsigned) format spec characters are not documented anywhere (neither in the grammar or the rest of the text) That last bullet is probably more important than any other. Caveat on the original issue: there is indeed a hyperlink very early on in the formattedWrite documentation, which goes to an external page that does explain the positional syntax/semantics: "%n$" and "*m$" but not the forms involving ':' Incidentally, that page (2004 edition) indicates a newer version is available: http://pubs.opengroup.org/onlinepubs/9699919799/ (2013 edition). However, it doesn't appear to have anything new regarding positional notation. Related question: is there a reason, or should std.format support the 'i', 'p', or 'n' format spec characters from the *printf family of functions? --
