From: "Kroeger, Simon (ext)" <simon.kroeger.ext@...>
Date: 2005-12-09T00:34:53+09:00
Subject: Re: increasing counter whithin loop?


> Hi Simon,

Hi Steve,
 
> I just ran your code, and got the exact output you got, but I 
> don't understand 
> a bit of it. 

:/

> First, I'm unclear as to the use of variables starting with 
> colon. What are 
> they, when are they used? 

actually these aren't variables but values, symbols to be
specific:

http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_symbol.html

they aren't used for any purpose in this example, the array just
had to contain something.
 
> Also, are prv, this and nxt just any old variables, or are 
> they somehow 
> supplied by enumerator? 

no they are not supplied by enumerator, each_cons yields arrays
do the block (containing 3 elements in this case). 

because of the magick of ruby's assign operator you can write

a, b, c = [1, 2, 3] 

which is equal to

a, b, c = 1, 2, 3

or

a = 1; b = 2; c = 3

this is used here to give the 3 elements of the array yielded by
each_cons more meaningfull names.
 
> Is variable a a string, an array, or something else?

an array. [...] creates arrays, see

http://www.ruby-doc.org/docs/ProgrammingRuby/html/tut_containers.html#UA

> Why did you place an array containing only nil before and 
> after a in the 
> parentheses?

because, well because I would have missed the first and the last
element of a otherwise. (I would have seen them in 'prv' or 'nxt'
but never in 'this')

> Thank you for this code. When I asked my question about how 
> to stop writing 
> Ruby with a Perl accent, I was hoping to understand 
> constructs like this one. 
> I have about 8 days experience with Ruby and so have some 
> catching up to do.

just hang on 

cheers

Simon