Re: formatter

From: vonosan (alnsn_at_[hidden])
Date: 2001-12-13 09:34:36

Thank you David,
I started to read these threads and I'll continue later.
I want to note that many problems arise when mixing format 
functionality with ostream functionality. I think they shouldn't mix. 
First you format and then output result to ostream. Operator << can 
be used without any troubles in this case. In one posted message I 
read that operator<< is reserved for ostream functionality. IMO, it's 
not true, "interaction" between the outputed object and ostream is 
reserved! Such "interaction" is defined between my formatter and 
formatted object (which is actually redirect output to ostringstream, 
possibly several times).
Ok, let me briefly describe the format I used. Two different forms 
exist: single param and param block (I'm not strong in English, you 
are welcome to improve that names).
Single param is single percent sign followed by sequence of digits, 
for example %0 or %123456789. First non-digit character outputed as-
is. Double percent outputed as single percent is usual.
Block param enclosed in curl brackets and has such specification:
{ ['/' fill_char ] [ width ] [.[precision]] [flags] param_sequence }
where flags are letters having the same same effect as ostream 
manipulators:
letter  ostream manips
----------------------
l       left
r       right
i       internal
d       dec
x       hex
X       hex, uppercase
o       oct
g       setf ( ios_base::fmtflags (), ios_base::floatfield )
f       fixed
e       scientific
E       scientific, uppercase
a       boolalpha
b       showbase
p       showpoint
+       showpos
u       uppercase

param_sequence is sorted sequence of one or more parameters (for 
example %0%1%4). Normally, there should be exactly one parameter. 
Additional params can be used for manipulators. Example:
formatter fmt ( "{%0%1}, {%0%2}!" );
  fmt << my_manip // my_manip is user defined manipulator
      << "Hello"
      << "world";
  string str = fmt.str ();
  cout << str << endl;

It is equvalent to this code:
  cout << my_manip  // %0
       << "Hello"   // %1
       << ", "
       << my_manip  // %0
       << "world"   // %2
       << '!';
  cout << endl;

Unfortunately, I'll go offline till Monday.