From: Ian Whitney <iwhitney@...>
Date: 2006-02-14T11:58:47+09:00
Subject: Re: Working with kernel.eval

That does appear to be the best solution. I plugged that in & my unit  
tests look good.

Thanks,

Ian

On Feb 13, 2006, at 2:19 PM, David Vallner wrote:

> require "mathn" for a batch of tweaks that will make Ruby maths  
> expression
> more maths-like than C-like.
>
> David Vallner
>
> Dňa Pondelok 13 Február 2006 21:07 Ian Whitney napísal:
>> 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
>