From: Daniel DeLorme <dan-ml@...42.com>
Date: 2006-06-28T11:00:29+09:00
Subject: Re: Unicode roadmap?

Daniel Martin wrote:
> I'll point you at my solution to ruby quiz #83: (short but unique)
> 
> http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/197973
> 
> How would you write the method string_similarity without access to
> each character?  (This method computes the length of the longest
> common substring)
> 
> How would you compute the Levenshtein distance (edit distance) between
> two strings without access to each character?

I'll grant that I don't have enough imagination and that there *are* cases where 
you want character access. But it seems to me that the main use case is for 
something like this:
    str = "cogito <b>ergo</b> sum"
    i = str.index("<b>") + 3
    j = str.index("</b>",i)
    str[i...j]
    => "ergo"
and for that common case, regexes are far more appropriate:
    str.match(/<b>(.*?)<\/b>/)[1]
    => "ergo"

Advocating regexes-only for character manipulation is certainly extreme. I'm 
just saying that byte access and character access needs to have different 
semantics. If you look at the current ruby String API, bytes are accessed 
through integer positions and characters are accessed through regexes. The byte 
are char APIs are quite distinct, it's just that everybody is using the byte API 
and expecting to get characters as a result.

 From what I understand (and please correct me if I'm wrong), ruby2 will fix 
that by changing the api so that integer positions represent characters instead 
of bytes. For binary strings, those two concepts map to the same reality so it 
won't be such a backward-incompatible change. I just wonder what will be the 
behavior of str[0]. Will it return a 0..255 integer in the case of binary string 
and a 1-character string in the case of encoding-set string? Now *that* would be 
an API nightmare.

> How would you pull strings out of a file with fixed-width fields?
> With regular expressions?  Really?  What if you had a hundred fields?

Hmm, fixed width records and fields were created for the purpose of fast access 
to data, i.e. seek to position recnum*reclength and extract reclength bytes; 
they only make sense in the case of single-byte characters. So this is more a 
case of byte access.


Daniel