From: Brian Candler <B.Candler@...>
Date: 2007-04-24T04:31:05+09:00
Subject: Re: Arrow operator with dash instead of equals (->)

On Tue, Apr 24, 2007 at 02:25:33AM +0900, Andrew Green wrote:
>         (x -> last_names).to_s + ", " + (x -> first_names).to_s
>         
> Using a dot instead of an arrow here is not an option for various
> reasons.
> 
> Any ideas as to how to hack around this limitation in Ruby, then?

As you say, you could use >>, although it has a fairly low operator
precedence, so

   x >> last_names + x >> first_names

would be parsed, I think, as

   x >> (last_names + x) >> first_names

If you're going to run through a preprocessor to substitute ->, then "." may
be a better substitution.

> Our interpreter eventually gets the code blocks as strings, so I could
> just substitute the -> for >> behind the user's back, but that would be
> messy, because it would substitute all occurrences of ->, even if
> they're in quotes or interpretable by Ruby in some other, unforseen way.
> Or is there some clean way of doing this? With ri or something similar,
> maybe?

The cleanest way I suspect would be to define a grammar for your own
language, and write a parser for it. I believe there's a Ruby parser
generator out there.

Then you are not bound by the rules of Ruby syntax at all.

Regards,

Brian.