From: Chuck Remes <cremes.devlist@...>
Date: 2008-08-08T07:12:34+09:00
Subject: Re: Most compact command for associate array 'totalling'?


On Aug 7, 2008, at 4:59 PM, John Pritchard-williams wrote:

> Ok - in 'awk' you can do this: (Where 'array' is empty initially)
>
> array[<string>]++
>
>
> For instance:
>
> array["abc"]++; => a["abc"]=1
> array["abc"]++; => a["abc']=2
> ...
>
> Which is really useful for tallying up a complete column of varying
> values from a text file where you don't know in advance the what may
> appear in a column etc...
>
> In Ruby, I have worked out a similar the equivalent to be: (with a  
> Hash
> now...)
>
>
> a={};
> a["abc"]=a["abc"].to_i+1;
>
>
> But I"m sure there is a shorter way ? Better trick available here?
>
> As an aside to 'to_i' is to turn the 'nil' into zero: is this safe to
> assume this?
>
> Thanks - sorry if this is stupid question....

No stupid questions; they're all good.

Here's a minor reworking of what you did to eliminate the #to_i.

a = Hash.new { |h,k| h[k] = 0 }
a["abc"] += 1

The special form of Hash.new that I used above will automatically  
initialize the bucket to 0 for any new key it receives, so you avoid  
the problem with nil and #to_i.

cr