From: Robert Dober <robert.dober@...>
Date: 2007-07-10T19:09:09+09:00
Subject: Re: Beautiful Code : Pity he didn't ask here...

On 7/10/07, John Carter <john.carter@tait.co.nz> wrote:
> Just got the O'Reilly announcement of the book "Beautiful
<snip>
> In Example 4.3 he has...
> 1 counts = {}
> 2 counts.default = 0

>
> Personally I prefer...
>   counts = Hash.new(0)
>    or
>   counts = Hash.new{|hash,key| hash[key]=0}
> buts that's personal preference I guess.
>
> In example 4.4 he rightly identifies line 10 as a little ugly and bemoans the lack of sort_by_value in hash.
>    10 keys_by_count = counts.keys.sort { |a, b| counts[b] <=> counts[a] }
> it seems he doesn't know about..
>
> count.keys.sort_by{|key| count[key]}
>
> Of course he could have done...
>
> class Hash
>    def sort_keys_by_value
>      keys.sort_by{|key| fetch(key)}
>    end
> end
or

tops = counts.sort_by{|*kv| kv.last}.reverse[0..9]
puts tops.map{ |k,v| "#{v}: #{k}"}

#each is just a primitive for Enumerables, right?

>
>
> Example 4.5 looks like a poster child for the Hash.new block approach...
> 4 @hash = {}
> .
> .
>
> 9 if @hash[s[0]]
> 10 @hash[s[0]] << [ s[1], article ]
> 11 else
> 12 @hash[s[0]] = [ s[1], article ]
> 13 end
>
>
> Replace that with...
>
> 4 @hash = Hash.new{|hash,key| hash[key] = []}
>
> 10 @hash[s[0]] << [ s[1], article ]
>
>
> That makes it real pretty code.

Save for

   File.open(some_name).each_line

Let the GC close the file!? It is not going to happen !!

<snip>
Robert

-- 
I always knew that one day Smalltalk would replace Java.
I just didn't know it would be called Ruby
-- Kent Beck