So let me just say that this is a bike shed topic -- I've been in the shed a decade ago on the subject -- but hey why not :) I dropped the proposal below bc it was clear to me that no agreement was possible on the topic. The proposal in isn't variadic because that feature didn't exist at the time, but you can see how it would be trivially changed to be -- why it is begging to be variadic. It brings together many of the discussed libraries format, string_algo, regex into an interface that is simple and clear. It allows for both formatting and appending. Extremely small sample super_string <http://www.crystalclearsoftware.com/libraries/super_string/classbasic__super__string.html> s(" (456789) [123] 2006-10-01 abcdef "); s.to_upper(); cout << s << endl; s.trim(); //lop off the whitespace on both sides cout << s << endl; double dbl = 1.23456; s.append(dbl); //append any streamable type s+= " "; cout << s << endl; date d(2006, Jul, 1); s.insert_at(28, d); //insert any streamable type cout << s << endl; super_string s; double dbl = 1.123456789; int i = 1000; s.append_formatted <http://www.crystalclearsoftware.com/libraries/super_string/classbasic__super__string.html#67740abfd6224fab0402b3dd7076f216>(dbl, i , dbl, i, "a string", "%-7.2f %-7d %-7.2f %-7d %s"); //s == "1.12 1000 1.12 1000 a string" //other overloadings available with less parameters super_string s1; s1.append_formatted <http://www.crystalclearsoftware.com/libraries/super_string/classbasic__super__string.html#67740abfd6224fab0402b3dd7076f216>(dbl, "This is the value: %-7.2f"); //s1 == "This is the value: 1.12" main page http://www.crystalclearsoftware.com/libraries/super_string/index.html My justification for *why* I did this as a type against all the *standard judgement* of the c++ experts http://www.crystalclearsoftware.com/libraries/super_string/index.html#why_ty... My original post in 2006 http://lists.boost.org/Archives/boost/2006/07/107087.php Jeff On Mon, Jan 23, 2017 at 4:14 PM, Gavin Lambert <gavinl@compacsort.com> wrote:
On 24/01/2017 07:26, Olaf van der Spek wrote:
1. scope for formatting tags:
concat(format::hex<int>, 42, " is hex for ", concat(42)).str();
Here the inner concat will convert the 42 to its decimal representation, while the outer one converts the first 42 to its hex representation.
Wouldn't concat(hex(42), " is hex for", 42) make more sense?
+1. If you like persistent formatting states (and all the unexpected fun they cause when you forget to cancel them), use iostreams instead.
3. results from concat() in a boost::range that is passed to join():
join(separator("\n"), my_files | transformed([](const std::filesystem::path& f) -> auto { return concat(f.filename, ": ", std::filesystem::file_size(f)); })).str();
Maybe I missed something, but what was the intended distinction between concat() and join()?
To me, as vocabulary words, concat() implies "concatenate without separator" and join() implies "concatenate with separator"; as such it seems unnecessary to explicitly decorate the separator here since it's a required parameter.
(Both should accept either variadics or ranges, if that's not too complicated to arrange, though it's likely for join() to be used more often on ranges; concat() might be more evenly split, though probably leaning toward variadics.)
Although I suppose http://www.boost.org/doc/libs/ 1_63_0/doc/html/string_algo/reference.html#header.boost.algo rithm.string.join_hpp and http://www.boost.org/doc/libs/ 1_63_0/libs/range/doc/html/range/reference/utilities/join.html might not entirely agree on this vocabulary...
(Loads the bikeshed on the back of a bike and rides away.)
If "concat" is the outer layer anyway, I would return a std::string
directly for convenience. It is easy to forget the trailing .str() and it does not look elegant.
Of course better proposals are welcome :-) Would you prefer the implicit conversion? If so, why?
Implicit is problematic with auto..
While that's true, I think the flexibility of returning a factory from concat() is more useful than the discomfort of either remembering the str() or using std::string explicitly as the type instead of auto (or using auto combined with explicit std::string construction).
_______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman /listinfo.cgi/boost