From: Wybo Dekker <wybo@...4all.nl>
Date: 2012-06-08T21:17:50+09:00
Subject: number printing like in my spreadsheet

When I need to print numbers without knowing how large or small they may
become, in a fixed width of n characters and an accuracy of (at least) m
figures, I mostly use the "%n.mg" format. For example:

-10.upto(10) do |i| puts "%12.6g" % [1.234234234*10**i] end

would print the first column below.
However, my spreadsheet (LibreOffice) does a better job; it would print
the second column below, keeping more significant figures and using less
scientific formats.
Finally, I would appreciate the third column even better, as it keeps
the maximum number of significant figures within the available width.

Is there an elegant way to do this in Ruby?

 1.23423e-10 1.2342e-010 1.23423e-10
 1.23423e-09 1.2342e-009 1.234234e-9
 1.23423e-08 1.2342e-008 1.234234e-8
 1.23423e-07 1.2342e-007 1.234234e-7
 1.23423e-06 1.2342e-006 1.234234e-6
 1.23423e-05 1.2342e-005 1.234234e-5
 0.000123423 0.000123423 0.000123423
  0.00123423 0.001234234 0.001234234
   0.0123423  0.01234234  0.01234234
    0.123423   0.1234234   0.1234234
     1.23423    1.234234    1.234234
     12.3423    12.34234    12.34234
     123.423    123.4234    123.4234
     1234.23    1234.234    1234.234
     12342.3    12342.34    12342.34
      123423    123423.4    123423.4
 1.23423e+06     1234234     1234234
 1.23423e+07    12342342    12342342
 1.23423e+08   123423423   123423423
 1.23423e+09  1234234234  1234234234
 1.23423e+10 12342342340 12342342340

-- 
Wybo