Re: ${^var} and word splitting

[Stephane Chazelas <stephane.chazelas@gmail.com>]

2014-11-24 15:55:24 +0000, Peter Stephenson:
[...]
> Consequently it's easy to change the behaviour in the second case...
> This doesn't cause any test failures.  Unless anyone has any ideas why
> we do this, maybe we should simplify it like this?  If anyone does have
> ideas, we should write a test for that case.
[...]

I'd say no. People expect:

IFS=:
PATH=/bin::/usr/bin
setopt shwordsplit
set -- $PATH

to split $PATH into /bin, "" and /usr/bin. That's how all the
shells (except the Bourne shell) behave (and POSIX requires) and
is the whole point of having _IFS white space_ in the first
place.

(BTW, POSIX also requires :/bin::/usr/bin: to be split into "",
"/bin", "" and "/usr/bin" (not another "") as IFS is the
internal field _delimiter_ there, not _separator_. I tend to
prefer the zsh way (also yash's and older versions of pdksh)
though.)

What I don't like much is IFS white spaces (or x's with (s:x:))
to be collapsed *but not removed from head and tail*.

The whole point of having /IFS white spaces/ was to split
strings the /natural/ way (like words in a text, like awk's
fields or like the Bourne shell did for any character of $IFS,
not just the whitespace ones). That means considering sequences
of blanks as one *and* leading and trailing blanks not to create
fields. A string like " : foo : bar : : baz  " would be split
into "", foo, bar, "" and baz.

I don't see the point in doing one and not the other. IOW in:

~$ a=' a  b ' zsh -c 'print -l ${(s, ,)a}'
a
b
~$ a=' a  b ' zsh -c 'print -l "${(s, ,)a}"'

a
b

~$ a=' a  b ' zsh -c 'print -l "${(s, ,@)a}"'

a

b

~$


I'd rather 2 above behave either like 1 or 2. I'm fine with 1
and 3 behave like they do now.

It may be too late to change the behaviour now, though I'd find
it hard to imagine people relying on "$=var" to make empty
arguments at the beginning and end but not in the middle.

-- 
Stephane