Michael Caisse wrote:
I've been trying to think of when I might use such a library. Without the symmetry (input as well as output) I can think of few instances where this functionality might come in handy. Other than potential debug output, what else do you envision? What am I missing?
Yes, I mostly think of this for debug output. But that does come up a lot. Similar to debug output would be testcase output. Something the customer still does not see, but is certainly useful. An example of something in production code might be printing a container out as an html table.
What about: os << karma::format_delimited( "<ol>" << *verbatim["<li>" << stream << "</li>"] << "</ol>", // format description '\n', // delimiter c // data ) << std::endl; (ok, not a table, but a list, but you get the idea) where c could be any container type holding any data type. And with some preparation it is easily possible to create a special html framework allowing to write this as: html::ol[*html::li[stream]] or html::table[*html::row[stream]]
I'm also finding little improvement over the following example based on your samples. Here I am using Karma to produce the same output as Explore. It is a bit more verbose; however, it is infinitely more flexible.
In BoostCon 2007, we wanted something that worked like 'print(c)' where 'c' is any container. Other languages have this capability. We did consider using Karma during that conference and somebody presented this. It was decided to not be simple enough. The code samples you provided are compelling, but it's not as dead simple as 'print(c)' or the more C++ oriented 'cout << c'.
'cout << c' just doesn't work because of the need to use UB (extending namespace std). So you will end up writing cout << explore::format(c); which would have the Karma equivalent of (Boost V1.41): cout << karma::format(*stream, c); or even (post V1.41): cout << karma::format(auto_, c); or cout << karma::format(c); Regards Hartmut