ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
2000-1992.2
=> 7.79999999999995
ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
2000-1992.2
=> 7.79999999999995
2009/3/6 S2 [email protected]:
ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
2000-1992.2
=> 7.79999999999995
2000-1992.2
=> 7.79999999999995
It is known non-bug:
http://docs.sun.com/source/806-3568/ncg_goldberg.html
Regards,
Rimantas
2009/3/6 S2 [email protected]:
ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
2000-1992.2
=> 7.79999999999995
The use of inexact floating point numbers by default in Ruby (which
follows C and most, but not all, other programming languages) is a
design choice, not a bug. One might dispute whether or not its a good
design choice (personally, I prefer Scheme’s numeric tower and exact
numbers by default with conversion to inexact numbers only when an
inexact operation is applied to an exact number or an explicit
designation of an inexact number is given), but its a point about
which people could debate endlessly, and since BigDecimal is at least
in the standard library, its not a matter of whether Ruby can do exact
math, but just how verbose the code is to do it.
ex:
require ‘bigdecimal’
require ‘bigdecimal/math’
class BigDecimal
def pretty
digits, magnitude = to_s.split(‘.’)[1].split(‘E’)
magnitude=magnitude.to_i
digits.insert(0,‘0’*[(1-magnitude),0].max)
digits.insert([magnitude,1].min,‘.’)
end
end
include BigMath
(2000-BigDecimal(‘1992.2’)).pretty
=> “7.8”
On Fri, Mar 6, 2009 at 7:42 PM, Christopher D. [email protected]
wrote:
design choice, not a bug. One might dispute whether or not its a good
require ‘bigdecimal’
endinclude BigMath
(2000-BigDecimal(‘1992.2’)).pretty
=> “7.8”
Or, while that works for the case presented, if you want it to work
right in general:
class BigDecimal
def pretty
return to_i.to_s if self==to_i
digits, magnitude = to_s.split(‘.’)[1].split(‘E’)
magnitude = magnitude.to_i
digits.insert(0,‘0’*[(1-magnitude),0].max)
digits.insert([magnitude, 1].max,‘.’)
end
end
Hi,
2009/3/7 Christopher D. [email protected]:
design choice, not a bug. One might dispute whether or not its a good
require ‘bigdecimal’
endinclude BigMath
(2000-BigDecimal(‘1992.2’)).pretty
=> “7.8”
Why not use BigDecimal.to_s(‘F’) ?
Refer to
http://www.ruby-doc.org/stdlib/libdoc/bigdecimal/rdoc/classes/BigDecimal.html#M000032
Regards,
Park H.
On Fri, Mar 6, 2009 at 8:15 PM, Heesob P. [email protected] wrote:
  digits.insert(0,‘0’*[(1-magnitude),0].max)
Refer to http://www.ruby-doc.org/stdlib/libdoc/bigdecimal/rdoc/classes/BigDecimal.html#M000032
Because that would be sane?
No, seriouly, I knew there was a BigDecimal formatter somewhere that
I’d seen (and even used, though not recently), but I thought it was
external. Clearly, it’s better to use that than to try to reinvent the
wheel.
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