From: Joel VanderWerf <vjoel@...>
Date: 2006-02-14T05:15:11+09:00
Subject: Re: Working with kernel.eval

Ian Whitney wrote:
> I'm trying to calculate the results of formulas that are stored in text
> files.
> 
> For example, a file may contain the line: 1+2/3
> 
> I want to take that line & get the result of the formula, 1.66 (roughly)
> 
> The way to do this seems to be Kernel.eval. But I can't get it to work
> correctly. Here's my irb session:
> 
> irb(main):001:0> a = "1+2/3"
> => "1+2/3"
> irb(main):002:0> b = eval(a)
> => 1
> irb(main):004:0> b.class
> => Fixnum
> 
> I would think that eval(a) should return a Float, not a Fixnum.

It's nothing to do with eval, but rather that if you start with fixnums,
you do fixnum arithmetic. Try replacing 2 with 2.0. That invokes float
division, and every result depending on that input will be float. In
general, you can use x.to_f if you want to force a value to be treated
as float.

-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407