----- Original Message -----
From: "Will Coleda" <[EMAIL PROTECTED]>
To properly support $tcl_precision in tcl, I need to change how I'm
currently implementing {$tcl_precision == 0}. Right now, I just fake
it by setting the precision to 16, but that isn't right.
where something like
{expr acos(0)} should output:
1.5707963267948966
it outputs (with the above C code)
1.5708
And in partcl's current state, it outputs
1.570796326794897
A few points to ponder.
1) The default precision for %g in C is 6 significant digits, i.e.
1.57080 (but sprintf drops trailing zeroes)
2) 1.5707963267948966 actually corresponds to 17-digit precision (which
is the limit for double), not 16
3) tcl uses its own special handling for tcl_precision = 0, refer to
http://www.tcl.tk/cgi-bin/tct/tip/132.html for more information
4) Look at David Gay's code (see http://www.netlib.org/fp/index.html,
specifically gdtoa) for similar logic
5) Although I haven't looked, the tcl source code must contain their
actual implementation
I don't know whether we expect enough usage of Parrot in mathemetical
circles to be worthwhile adding one of these implementions to our
version of sprintf.
Regards
Peter Gibbs
