Re: [PATCH] Enable further expansion of parameter name by ${!...}

[Bart Schaefer <schaefer@brasslantern.com>]

On Jan 26,  3:00pm, Tomoki Sekiyama wrote:
}
}                     # ksh       bash     zsh(default)       zsh(KSH)
} echo $aaa           # bbb       bbb      bbb                bbb
} echo ${!aaa}        # aaa       ccc      bad substitution   bbb

OK, but the point is that ideally in that last row the zsh(KSH) case
would be "aaa".  I guess this is no worse than the difference of
${array[1]} with or without ksharrays set.  (If "nameref aaa=bbb",
then the first column of the last row would be "bbb".)

}                     # ksh       bash     zsh(default)       zsh(KSH)
} echo ${!foo[bar]}   # foo[bar]  piyo     bad substitution   bar

I find this one interesting, because the ksh doc says it "expands to the
name of the subscript" which would seem to me to fit the zsh(KSH) column
more than the ksh column.

Ksh also has the special case ${!foo[bar..baz]} which treats the array
keys as an alphabetical list and generates a sub-list of them from "bar"
through "baz" (uninteresting in this example).

} According to this, introducing bash-like behaviors instead of "bad
} substitution" error will not hurt zsh even in ksh emulation mode.

My question is, why choose the bash behavior for the zsh default and
not the ksh behavior?  If we make the bash behavior the default, then
also adding namerefs as a default leaves us deviating from ksh on the
meaning of ${!aaa} for identifiers that are not namerefs.