From: Ian Whitney <iwhitney@...>
Date: 2006-02-14T05:07:01+09:00
Subject: Working with kernel.eval

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.

I thought maybe that eval wasn't following the standard order of  
operations, which could explain the return value of 1. So then I  
tried this:

irb(main):005:0> a = "2/3"
=> "2/3"
irb(main):006:0> b = eval(a)
=> 0
irb(main):007:0> b.class
=> Fixnum


So, it's not an order of operations thing.

Maybe I shouldn't be using eval. But I can't find another option. Any  
thoughts?

Thanks,

Ian