From: "Michael W. Ryder" <_mwryder@...>
Date: 2007-06-22T17:40:10+09:00
Subject: Re: Ruby doesn't know how to multiply

Pe�a wrote:
> From: Michael W. Ryder [mailto:_mwryder@worldnet.att.net] :
> # My simple calculator is more precise for some math operations than my 
> # expensive PC.  Maybe we need to implement something like 
> # General Decimal 
> # Arithmetic which is available for C++ and Java at 
> # http://www2.hursley.ibm.com/decimal/ in Ruby.  It may be as simple as 
> # writing wrappers for the operations, I haven't had to time to look 
> # closer at the package.
> 
> have you tried bigdecimal?
> 
> irb(main):001:0> require 'bigdecimal'
> => true
> irb(main):002:0> a=BigDecimal("14.95")
> => #<BigDecimal:2867a5c,'0.1495E2',8(8)>
> irb(main):003:0> b=BigDecimal("0.6")
> => #<BigDecimal:28614b8,'0.6E0',4(8)>
> irb(main):004:0> c=BigDecimal("8.97")
> => #<BigDecimal:28e47b4,'0.897E1',8(8)>
> irb(main):005:0> d=BigDecimal("8.970000001")
> => #<BigDecimal:28dffe8,'0.8970000001E1',16(16)>
> irb(main):006:0> a*b == c
> => true
> irb(main):007:0> a*b == d
> => false
> irb(main):008:0> c == 8.97
> => true
> 
> bigdecimal notation is very handy for calculator-like applications since the raw input usually is of type string.
> 
> kind regards -botp
> 
> 
I'm not trying to denigrate the project but it looks like it is still in 
alpha stage while the IBM project seems to have been releasing 
production code for a while.  It also is an IEEE standard, which may or 
may not mean anything.
I hadn't known about the bigdecimal project before and may try comparing 
the results of it to the general decimal arithmetic package if I get time.