From: Robert Klemme <shortcutter@...>
Date: 2011-03-30T18:09:20+09:00
Subject: Re: Why can a floating point number be used as an array index?

On Tue, Mar 29, 2011 at 10:02 PM, Sniper Abandon
<sathish.salem.1984@gmail.com> wrote:
> Jeff Dik wrote in post #989828:
>> Why can a floating point number be used as an array index?  Anybody
>> know of a good use case for this?
>>
>> irb(main):020:0> [1, 2, 3][0.3]
>> 1
>> irb(main):021:0> [1, 2, 3][0.9]
>> 1

> arr = [1,2,3,4....]
> arr[(anyhting).to_i]

No, it's using #to_int

irb(main):001:0> idx = Object.new
=> #<Object:0x1091fd74>
irb(main):002:0> %w{foo bar}[idx]
TypeError: can't convert Object into Integer
        from (irb):2:in `[]'
        from (irb):2
        from /opt/bin/irb19:12:in `<main>'
irb(main):003:0> class <<idx
irb(main):004:1> def to_i;p "to_i";1;end
irb(main):005:1> end
=> nil
irb(main):006:0> %w{foo bar}[idx]
TypeError: can't convert Object into Integer
        from (irb):6:in `[]'
        from (irb):6
        from /opt/bin/irb19:12:in `<main>'
irb(main):007:0> class <<idx
irb(main):008:1> def to_int;p "to_int";1;end
irb(main):009:1> end
=> nil
irb(main):010:0> %w{foo bar}[idx]
"to_int"
=> "bar"

#to_i is just a convenience conversion (e.g. String#to_i) while
#to_int is only used for things which *are* actually an integer.  You
can see all implementators with "ri '#to_int'".

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/