optparse: on() vs on_tail()

[James Edward Gray II]

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

James Edward Gray II

[Eric Hodel]

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

[James Edward Gray II]

On Mar 2, 2005, at 8:54 PM, Eric Hodel wrote:

> 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.

Thanks much.

James Edward Gray II

[James Edward Gray II]

On Mar 2, 2005, at 8:54 PM, Eric Hodel wrote:

> 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.

While we're on the subject, if you just use on(), are options added to
the summary in order? Thanks again.

James Edward Gray II

[Thomas Kirchner]

* On Mar 3 12:22, James Edward Gray II (ruby...@ruby-lang.org) wrote:
> While we're on the subject, if you just use on(), are options added to
> the summary in order? Thanks again.

Yeah, they're added in the order that you declare them. on_head is useful
for general, common options that most everyone needs, so that they appear
first. on() adds everything to the middle in order. on_tail is good for
generic options like --help or --version that aren't vital, but should be
there. Or at least that's how I use it :)

There's some decent documentation and a good example here:
http://www.ruby-doc.org/stdlib/libdoc/optparse/rdoc/classes/OptionParser.html
Hope that helps.
Tom