From: "Hal E. Fulton" <hal9000@...>
Date: 2001-11-17T04:12:08+09:00
Subject: [ruby-talk:25604] Re: Arrays, iterators, and map/collect

----- Original Message ----- 
From: Robert Feldt <feldt@ce.chalmers.se>
To: ruby-talk ML <ruby-talk@ruby-lang.org>
Sent: Friday, November 16, 2001 4:19 AM
Subject: [ruby-talk:25403] Re: Arrays, iterators, and map/collect


> On Fri, 16 Nov 2001, Hal E. Fulton wrote:
> 
> > But what if I want to do an operation 
> > conditionally? Is this still a good way to do it,
> > in a case where the mapped value is
> > sometimes/always the same as the original?
> > 
> >   strings.map! { |s| if s[0]==?a then s else "pre." + s end }
> > 
> I would do it like this but allow myself to shorten it to
> 
>   strings.map! {|s| s[0]==?a ? s : ("pre." + s)}
> 
> since its a one-liner.
> 
> Don't you feel it is natural? Why?
> 

I'm having difficulty expressing myself.

This example is natural enough.

One problem I have is: When I travel through
an array, I expect to use an iterator. 

What if the map! operation is really only a
side effect? I guess it is possible to do 
other stuff inside the block, but that makes
it less obvious what is happening.

I guess I would like to iterate through an array
performing arbitrary operations and have the
option to change the values of array elements
if I wished. "replace" is OK I suppose... I haven't
tried it.

I don't like the idiom of explicitly indexing into 
the array for this case...

Thanks,
Hal