[boost] Re: Insufficient significant digits using lexical_cast

From: Daryle Walker (dwalker07_at_[hidden])
Date: 2003-08-12 02:56:10

[Paul claims that lexical_cast prints (floating-point) numbers with too 
few precision digits.  Currently, limits::digits10 + 1 is used.  Paul 
wants to change it to "int significant_digits10 = int(ceil(1 + 
limits::digits * log10Two));" where "limits" is the numeric-limits 
traits class and "log10Two" is the base-10 logarithm of 2.]

You used an article on IEEE 754 arithmetic.  Shouldn't you check if the 
number type is compliant with that format?  Or can this work for any 
suitable type?  You also have to check if "limits::digits" is 2!

Looking at the numbers you had, couldn't you just change 
"limits::digits10 + 1" to "limits::digits10 + 3"?  It could be argued 
that there's just a bug in the definitions of "limits::digits10" (it's 
too low).

On Saturday, August 9, 2003, at 5:48 PM, Paul A. Bristow wrote:
[CHOP OFF really long article, with long attachments]