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comp.lang.ruby

Array#to_s in Ruby 1.9 Head

Gary Wright

10/19/2006 9:35:00 PM

Mauricio Fernandez writes in http://eigenclass.org/hiki.rb?...
+Ruby+1.9+update+5
that Ruby 1.9 Head has changed Array#to_s to be an alias for
Array#to_inspect.

What is the motivation for that change?
print a
becomes
a.each { |x| print x }

It seems like an unnecessary change that takes away a very nice
default behavior.

I have a situation where I represent a tree of objects as nested
arrays. I can convert the
entire tree to a string via a pre-order traversal as:

text = tree.to_s

I like that.


Gary Wright
3 Answers

Ross Bamford

10/20/2006 11:25:00 PM

0

On Fri, 2006-10-20 at 06:34 +0900, gwtmp01@mac.com wrote:
> Mauricio Fernandez writes in http://eigenclass.org/hiki.rb?...
> +Ruby+1.9+update+5
> that Ruby 1.9 Head has changed Array#to_s to be an alias for
> Array#to_inspect.
>
> What is the motivation for that change?
> print a
> becomes
> a.each { |x| print x }
>
> It seems like an unnecessary change that takes away a very nice
> default behavior.

FWIW I find I need 'puts ary.inspect' much more often than 'puts ary',
so I think this is a good change.

--
Ross Bamford - rosco@roscopeco.REMOVE.co.uk

Joel VanderWerf

10/21/2006 12:04:00 AM

0

Ross Bamford wrote:
> On Fri, 2006-10-20 at 06:34 +0900, gwtmp01@mac.com wrote:
>> Mauricio Fernandez writes in http://eigenclass.org/hiki.rb?...
>> +Ruby+1.9+update+5
>> that Ruby 1.9 Head has changed Array#to_s to be an alias for
>> Array#to_inspect.
>>
>> What is the motivation for that change?
>> print a
>> becomes
>> a.each { |x| print x }
>>
>> It seems like an unnecessary change that takes away a very nice
>> default behavior.
>
> FWIW I find I need 'puts ary.inspect' much more often than 'puts ary',
> so I think this is a good change.

(Why 'puts ary.inspect' instead of 'p ary' ?)

I suspect there is a fair amount of code that depends on

print a

being the same as

print *a

This would be the case if you are thinking of an array of strings as an
array of lines. For example, if you are writing a method whose input, a,
is the contents of a text file _either_ as a string _or_ as an array of
lines, then

print a

has the same behavior on all inputs.

With the change in Array#to_a, you don't have this nice duck-typing, but
you get it back if you use splat:

print *a

(that works when a is a string, at least in 1.8.4)

I'm not against the change, just thinking about damage control.

--
vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

Ross Bamford

10/21/2006 9:26:00 AM

0

On Sat, 2006-10-21 at 09:04 +0900, Joel VanderWerf wrote:
> Ross Bamford wrote:
> > On Fri, 2006-10-20 at 06:34 +0900, gwtmp01@mac.com wrote:
> >> Mauricio Fernandez writes in http://eigenclass.org/hiki.rb?...
> >> +Ruby+1.9+update+5
> >> that Ruby 1.9 Head has changed Array#to_s to be an alias for
> >> Array#to_inspect.
> >>
> >> What is the motivation for that change?
> >> print a
> >> becomes
> >> a.each { |x| print x }
> >>
> >> It seems like an unnecessary change that takes away a very nice
> >> default behavior.
> >
> > FWIW I find I need 'puts ary.inspect' much more often than 'puts ary',
> > so I think this is a good change.
>
> (Why 'puts ary.inspect' instead of 'p ary' ?)

Good point. I'm not sure where that 'puts' came from anyway, I blame
late-night typing ;)
Thinking about it now, the more common case where this would save me
typing is string interpolation.

> I suspect there is a fair amount of code that depends on
>
> print a
>
> being the same as
>
> print *a
>
> This would be the case if you are thinking of an array of strings as an
> array of lines. For example, if you are writing a method whose input, a,
> is the contents of a text file _either_ as a string _or_ as an array of
> lines, then
>
> print a
>
> has the same behavior on all inputs.
>

> With the change in Array#to_a, you don't have this nice duck-typing, but
> you get it back if you use splat:
>
> print *a
>
> (that works when a is a string, at least in 1.8.4)
>
> I'm not against the change, just thinking about damage control.
>

Certainly, I have such code myself that would need to be changed to deal
with this. I'm already resigned to the fact that some of my code will
break when 1.9 becomes mainstream so I guess this would cause extra
typing in the immediate, but I'm still sure it'd save me keystrokes in
the long run.

Generally, MHO is that arrays (and hashes too - should this change
encompass Hash#to_s as well?), as data structures, should retain some
indication of that structure when asked for a string representation. For
me at least, the current behaviour of simply joining the elements is
rarely useful - I almost always need to either join(', ') or map { .. }
arrays somehow for non-debug output anyway.

--
Ross Bamford - rosco@roscopeco.REMOVE.co.uk