From: "Guy N. Hurst" <gnhurst@...>
Date: 2002-02-26T16:46:55+09:00
Subject: Re: Question with for loop

Steve Shreeve wrote:
> 
> I've got a quick question. Sort of a minor issue, but I was wondering about
> Ruby's syntax a special situation. I have a bit of code that looks like this:
> 
> b.rpc('ORWU TOOLMENU',[nil])
> b.rpc('ORWU HASKEY',['XUPROGMODE'])
> b.rpc('ORQQPX NEW REMINDERS ACTIVE')
> ['O RX', 'I RX', 'UD RX', 'IV RX'].each { |val| b.rpc("ORWORDG IEN", [val]) }
> b.rpc('ORWU DT', ['NOW'])
> b.rpc('ORWCH LOADAL')
> 
> Notice how the third to last line is sort of "doing it's own thing". It would
> be nice have all these lines "look the same". Something like this would work:
> 
> b.rpc("ORWORDG IEN", [val]) for val in ['O RX', 'I RX', 'UD RX', 'IV RX']
> 

How about:

b.rpc("ORWORDG IEN",[val||=nil]) while val=(tmp||=['O RX', 'I RX', 'UD RX', 'IV
RX']).shift if (tmp=nil).nil?

The trailing "if" is only to ensure tmp is nil (to avoid an endless loop), and
the "||=" construct is a conditional assignment.

This construct can be tested with the following code:

irb(main):001:0> def s(t); p t+2; end
nil
irb(main):002:0> s(val||=nil) while val=(tmp||=[1,2,3]).shift if (tmp=nil).nil?
3
4
5
nil
irb(main):003:0>



Guy N. Hurst