From: Harry Truax <htruax@...>
Date: 2004-08-17T02:34:38+09:00
Subject: Re: A method for summing several variables

Thanks Austin,

But unfortunately $SAFE needs to be set to 3 which will preclude the use of
eval( ).

Harry

----- Original Message ----- 
From: "Austin Ziegler" <halostatue@gmail.com>
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Monday, August 16, 2004 1:13 PM
Subject: Re: A method for summing several variables


> On Tue, 17 Aug 2004 01:48:09 +0900, Harry Truax <htruax@stf.com> wrote:
> > Hi everyone,
> >
> > Just wanted to say thank you for all of your suggestions and coding
examples. I will be studying your ideas closely to see if I can implement
them in our product. I really
> > do not have the leeway to alter our product's code structure, I have to
live with this fact (argh!!).
> >
> > Our field variables (the ones we do arithematic on) are set up like:
> >
> > box1_1 = ''
> > box1_2 = ''
> > box1_3 = ''
> > box1_4 = ''
> > box1_5 = ''
> > box1_6 = ''
> > box1_7 = ''
> > box1_8 = ''
> > box1_9 = ''
> > box1_10 = ''
> > box1_11 = ''
> > etc.
> >
> > The actual amount and thus naming of these variables vary from
application to application. Some of the summing operations are quite lengthy
as in:
> >
> > box5_189 = $CUR % (box5_5.to_f + box5_10.to_f + box5_15.to_f +
box5_20.to_f + box5_25.to_f + box5_30.to_f + box5_35.to_f + box5_40.to_f +
box5_45.to_f + box5_50.to_f + box5_55.to_f + box5_60.to_f + box5_65.to_f +
box5_70.to_f + box5_75.to_f + box5_80.to_f + box5_85.to_f + box5_90.to_f +
box5_95.to_f + box5_100.to_f + box5_105.to_f + box5_110.to_f + box5_115.to_f
+ box5_120.to_f + box5_125.to_f + box5_130.to_f + box5_135.to_f +
box5_140.to_f + box5_145.to_f + box5_150.to_f + box5_155.to_f +
box5_160.to_f + box5_165.to_f + box5_170.to_f + box5_175.to_f +
box5_180.to_f + box5_185.to_f + box5_187.to_f)
> >
> > I will try to find a shortcut method to handle this based on your
suggestions, but if I have to manually type in each box name in setting up
the implementation, I may
> > as well just type in the lengthy sum operation as shown above.
>
> I didn't participate in the initial round, but why not do a generator
> and then eval your generated string in the current binding?
>
>   s = (5..185).to_a.select { |e| e % 5 == 0 }.map { |e| "box5_#{e}.to_f" }
>   s << "box5_187.to_f"
>   box5_189 = $CUR % [eval("(#{s.join(' + ')})", binding)]
>
> This will work so long as there's some kind of pattern you can deal
> with (I don't get the box5_187 in your example, but I added it as an
> exception).
>
> I tested in irb with:
>
>   v = (5..187).to_a
>   v = v.select { |e| (e % 5 == 0) or (e == 187) }.map { |e| "box5_#{e}" }
>   v << "box5_187"
>   b = binding
>   v.each_with_index { |e, i| eval("#{e} = 1.25", b) }
>   puts box5_10 # => 1.25
>   $CUR = "%020.10f"
>
>     # the above set the test data; the below is the implementation
>   s = (5..187).to_a.select { |e| (e % 5 == 0) or (e == 187) }
>   s.map! { |e| "box5_#{e}.to_f" }
>   box5_189 = $CUR % [eval("(#{s.join(' + ')})", binding)
>   puts box5_189 # => 000000047.5000000000
>   puts v.size  * 1.25 # => 47.5
>
> -austin
> -- 
> Austin Ziegler * halostatue@gmail.com
>                * Alternate: austin@halostatue.ca
>
>