From b.rowlingson at lancaster.ac.uk  Sat Jul 10 14:24:36 2010
From: b.rowlingson at lancaster.ac.uk (Barry Rowlingson)
Date: Sat, 10 Jul 2010 13:24:36 +0100
Subject: [Rd] Defining a method that behaves like '$'?
In-Reply-To: <4C371FB0.9040700@cbio.uct.ac.za>
References: <4C371398.80603@cbio.uct.ac.za> <4C371645.6030204@gmail.com>
	<4C371AE3.9060801@cbio.uct.ac.za>
	<8D37932C-62F7-44C0-BAFA-9A77ABADE59F@me.com>
	<4C371FB0.9040700@cbio.uct.ac.za>
Message-ID: <AANLkTimRISCE4AjmCThITuF9qYaUyzuvhaSottcYXxuK@mail.gmail.com>

On Fri, Jul 9, 2010 at 2:10 PM, Renaud Gaujoux
<renaud at mancala.cbio.uct.ac.za> wrote:
> I do not want to access the slot itself but its content: a:toto would be
> a at slot1[['toto']].
> The thing is that I would like to have two different methods: '$' (that I
> already have) and another one to define, ideally that behaves like '$'.
> So in brief:
> - a:toto would be for a at slot1[['toto']]
> - a$tata would be for a at slot2[['tata']]
>
> But apparently it might not be possible.
>

 Even if possible, definitely not desirable. As already mentioned, a:b
is the sequence a to b (as in 0:10), so it's going to look weird to
anyone who hasn't noticed your definition. Also, it looks fairly
meaningless. By which I mean there's no obvious reason why a colon
should do what you want it to do. There's also no obvious reason why a
dollar sign does what it does (whats it got to do with dollars?) but
we've had it for 20 years so we're stuck with it.

 Write a method for your objects and force your users to do a bit more
typing as a trade-off for legibility:

 slot1(a,"toto")

 is a lot more readable than a:toto (assuming you replace 'slot1' with
something meaningful).

 Remember, code is most likely to be written once, and read many times
- so make it easy for readers!

Barry



[Rd] Defining a method that behaves like '$'?
Barry Rowlingson