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

Barry Rowlingson b.rowlingson at lancaster.ac.uk
Sat Jul 10 14:24:36 CEST 2010

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:


 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!


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