From: mfdylan (dylan_at_[hidden])
Date: 2002-01-24 01:55:05
--- In boost_at_y..., Karl Nelson <kenelson_at_e...> wrote:
>
> That would not well serve the purpose of allowing
internationalization.
> String translation services use printf. It is a large standard
which
> we really should obey. This point has been discussed multiple
> times on the list. Positional simply does not serve the needs of
> a formating tool.
>
> > By the way, Robert's approach doesn't mention about how to write
Surely it's fair to assume most translation services understand the %
1 %2 %3 style? It's used by the Win32 FormatMessage API if nothing
else. As for the problem of how to deal with a number directly after
the digit, has anyone seriously ever needed more than 9 positional
parameters in a sentence? And does it really happen so often that
breaking the string up into two is going to cause a major problem?
If not, then you just take the first digit after the % and you're
done. Simplifies parsing, and the pretty rare cases where you might
want a fixed number directly after a positional parameters aren't
likely to upset anyone too much. If they do, then make the number a
parameter too.
So
"Renaming file %1 in folder %2 to %12. OK?"
becomes
"Renaming file %1 in folder %2 to %1%3. OK?"
Even if the number is always '2' for now, there's a moderate chance
in the future it might change, so inserting dynamically at runtime is
doing no harm.
As for the formatting options (width/precision specifications and so
forth), I really can't see a lot of point of encouraging continued
use of the cryptic printf-style, which can hardly make translators'
jobs easier. The only reason I can see for keeping them part of the
string is the possibility that in you want different hardcoded
specifications across multiple languages. I'm willing to hear a
reasonable justification of why this is necessary (as opposed to
dynamically determined specs where they may need to be different for
different languages), but I certainly can't think of any.
As for using [], I was only finally warming to using % as an insertor
when the [] idea was sprung on us all.
Now we are supposed to something like write
format("array\[[1]\] = [2]") [i] [array[i]];
as opposed to
format("array[%1] = %2") % i % array[i];
At least using '%<n>' the only time you'd require escaping of '%' is
if you actually want to display % followed by a number - and %
generally goes at the end of a number so that's pretty unlikely. I
guess something like:
"n mod 2 (notated n%%2) returns the least significant bit"
I'd prefer
format("array[%1] = %2", i, array[i]);
Although if you allow for manipulators between parameters, even with
only 9 parameters you would have to support a helluva lot of template
variants. And I guess it's handy to be able to insert parameters one-
by-one if necessary. To be honest I never really understood the
argument against using '<<' - I assume the only reason was that the
statement
cout << format("array[%1] = %2") << i << array[i] << ".\n";
Could either be an error (inserting too many parameters), or an
intended insertion of ".\n" into the stream after the formatted
message. I probably opt on the safe side and say it's error and
require extra parentheses:
cout << (format("array[%1] = %2") << i << array[i]) << ".\n";
I think I showed in another post how this can implemented with
minimal code and fairly efficiently.
Dylan