Re: PATCH: pws-19: document minor syntactic innovation

["Bart Schaefer" <schaefer@xxxxxxxxxxxxxxxxxxxxxxx>]

On Jun 1, 11:56am, Peter Stephenson wrote:
} Subject: PATCH: pws-19: document minor syntactic innovation
}
} I should note that things like ${"foo"} only work by accident: you'll find,
} for example, that ${"foo"%bar} doesn't work.  That would require swallowing
} nulled out quotes at another point in paramsubst(), which I hinted at
} before.  I didn't do this because I didn't see a use for it, but maybe it's
} more consistent that way?

If it's messy, I think it could be left out, but yes, it is more consistent
that way.

} > What's the right way to document this change, including odd stuff like
} > the above?
} 
} Here's a possible chunk for 3.1.5-pws-20.
[...]
} +Note that double quotes may appear around nested quotations, in which case

Perhaps "nested expansions" rather than "nested quotations"?

} > Should the FAQ recommend using this form in some circumstances because
} > of the (@) change in 3.1.5?
} 
} Well, the new nested substitution section (3.22) is really about getting a
} parameter evaluated as a parameter name and I'm not sure it's a good idea
} to put in a lot of stuff about other flags and their uses, which could get
} quite involved.  Maybe it needs a separate question, but I'm not sure I can
} even remember the full effect of the changes.

The full effect of the (@) changes?  It's pretty simple, really.  In 3.0,
once something becomes an array as a result of (@) or (f) or (s//), it is
always an array, even inside quotes, no matter how deeply nested the ${ }
get.  In 3.1.5-pws-XX for XX > 15 (I think it was), array-ness persists
only for the current level of ${ }; if there's another ${ } around that,
quoted-ness takes over again.

So to get certain quoted array expansions to behave the same in 3.0.6 and
3.1.5-pws-20+, you must either put in an (@) at every ${ } (which is ugly
and, in 3.0.6, redundant), or you must `push in the quotes' as deeply into
the nested ${ } as possible, e.g. to immediately surround the ${(@)...}.

For example, in 3.0.6-pre-4 and later, the following all are (will be)
equivalent:

	"${${${(f)$(print -l *)}}}"		(1)
	${"${${(f)$(print -l *)}}"}		(2)
	${${"${(f)$(print -l *)}"}}		(3)
	${${${(f)"$(print -l *)"}}}		(4)

In 3.1.5-pws-20, (1) == (2) [both are strings] and (3) == (4) [both are
arrays], but [obviously] (1) != (4).

Oh, and of course the [@] subscript and subscript number ranges behave
just like the (@) flag as far as this is concerned.

I admit I haven't worked out whether there are other ramifications when
SH_WORD_SPLIT is set .... 

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com