From: Eric Hodel <drbrain@...7.net>
Date: 2005-03-03T11:54:21+09:00
Subject: Re: optparse:  on() vs on_tail()

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On 02 Mar 2005, at 18:45, James Edward Gray II wrote:

> Can someone tell me the difference between the on() and on_tail() 
> methods of OptionParser.  I can't seem to figure it out.  Thanks.

from optparse.rb:

=begin
--- OptionParser#on(*opts) [{...}]
--- OptionParser#def_option(*opts) [{...}]
--- OptionParser#on_head(*opts) [{...}]--- 
OptionParser#def_head_option(*opts) [{...}]
--- OptionParser#on_tail(*opts) [{...}]
--- OptionParser#def_tail_option(*opts) [{...}]
     Defines option switch and handler. (({on_head})), 
(({def_head_option}))
     and (({on_tail})), (({def_tail_option})) put the switch at head
     and tail of summary, respectively.

     cf. ((<OptionParser#switch>)).
=end #'#"#`#

If you read down from there, on_tail/on add things to the end, of the 
args list summary while on_head adds them to the front.

It looks like on_tail only exists to make things pretty.

-- 
Eric Hodel - drbrain@segment7.net - http://segment7.net
FEC2 57F1 D465 EB15 5D6E  7C11 332A 551C 796C 9F04

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