From: gwtmp01@...
Date: 2006-10-22T06:04:51+09:00
Subject: Re: Array#to_s in Ruby 1.9 Head


On Oct 20, 2006, at 12:57 AM, Yukihiro Matsumoto wrote:
> The official purpose of #to_s method is that returning string
> representation of the object.  No more, no less.  So it's up to our
> expectation for the string representation of the object.  I changed
> the behavior to make string representation of arrays more
> distinguishable from other objects.
>
> I don't think to_s _SHOULD_ work as replacement of Array#join.  But
> there may be another reason I missed to keep it compatible with 1.8.

OK, I grabbed ruby 1.9 so that I could actually play with it.

I always assumed that Array#join simply called Array#to_s on each  
element
and then constructed the final string by inserting the separator between
each element, but it actually seems to flatten the array first:

Ruby 1.8:
    a = [1,2]
    b = [3,4]
    c = [a,'foo',b]
    c.to_s               # 12foo34
    c.inspect		# [[1, 2], "foo", [3, 4]]
    c.join               # 12foo34
    c.join('-')		# 1-2-foo-3-4

When the separator is the empty string, the two algorithms are the  
same, but
if the separator is not empty then they give different results.  The
non-flattening algorithm would produce: 12-foo-34 in the above example.

My objections to the Array#to_s behavior in 1.9 were based on  
thinking about
Array#join as simply calling #to_s on each element (without the  
flattening step),
which would make it more difficult to work around.

So in 1.9, the above example produces:
    c.to_s               # [[1, 2], "foo", [3, 4]]
    c.inspect		# [[1, 2], "foo", [3, 4]]
    c.join               # 12foo34
    c.join('-')		# 1-2-foo-3-4

I think the documentation for Array#join should mention the  
flattening step.
Something like:

      Returns a string created by flattening the array, converting  
each element of
      the result to a string via #to_s, and concatenating the strings  
with _sep_ as
      the separator.


Gary Wright