Yet Another useless Ruby 2 Idea

[David A. Black]

Hi --

There are just too many problems that can quickly be solved by
multi-dimensional arrays and hashes not to have them and have them easily.
I used the hack from "matz" today to make a 2d hash, and it's ugly and
unworthy of Ruby. You should be able to do this without any extra steps
just like in Perl. If the project ends up getting bigger THEN you
refactor it, but YOU JUST GOT TO HAVE THAT.

I don't know how to do it with Array, because Array doesn't
seem to accept a block for its default value generation like
Hash does.

But with Hash:

hoh = lambda { Hash.new {|h,k| h[k] = hoh.call} }

Thank you. I used this just yesterday, and it helped a lot with a report
reorganization I wanted to do.

The first time I used Perl for a web report (Perl IV I think) I believe it
didn't have multi-dimensional hashes either. Once I got Perl5, I could do a
lot more much more easily and still clearly. I agree with what the one
fellow said that I don't use multi-dimensional arrays nearly as much as
multi-dimensional hashes, but for instance it would be nice to have as a
memory item on a multi-dimensional hash read.

I know in the long run it's better to use more formal constructs for a lot of
things in order to make a program clear and maintainable, but really n>2
arrays and hashes are really the thing I love most about Perl, and I think it
allows you to do organizations that aid understanding in very important ways
with reports that can be written ad hoc very quickly.

Let's be fair, though: you can't just airlift what Perl does into
Ruby. In Perl you can do things like:

$x[2]{"y"}[0] = 1;

and have things created automatically because there's no ambiguity.
In Ruby, you can't do this without prior initialization:

x[2]["y"][0] = 1

because there's no way to tell what the objects should be -- and not
just as between arrays and hashes, but at all. They could be anything
that responds to '[]'. Even if x is an array, you can't infer what
x[2] is supposed to be, except that it is something that can take "y"
as an argument to #[]. That could be a hash, a Proc, the class object
Array, or arbitrarily many things that you might create in your
program.

I completely understand your love of how this works in Perl. I just
wanted to clarify the fact that it's not an omission or gap in Ruby;
it's a consequence of the whole language design. So there are
compensations (And see the other responses for ways to achieve
something close to what you want.)


David

 

[Dave Brown]

The first time I used Perl for a web report (Perl IV I think)

I quite liked Perl IV, but I always thought Perl 77 was a big
improvement.

--Dave