Odd behavior of quoted Zsh array subtraction

Odd behavior of quoted Zsh array subtraction

[Zach Riggle]

I'm sure there's a section of the manual that explains this.

I'm also sure I don't know what section it is.

    $ a=( aa bb cc dd ee  )

    $ b=( cc )

    $ echo ${a:|b}
    aa bb dd ee

    $ echo "${a:|b}"
    aa bb cc dd ee # <-- WHAT

    $ echo "${(@)a:|b}"
    aa bb dd ee

    $ echo "${a[@]:|b}"
    aa bb dd ee

All results except the first quoted expression is the expected result.

Why does the marked, quoted array-subtraction result in a different
set of values?  I would expect that array operators have precedence
over array-converted-to-scalar.  Maybe this is an "outward-in"
expansion issue?

Re: Odd behavior of quoted Zsh array subtraction

[Mikael Magnusson]

On 7/23/21, Zach Riggle <zachriggle@gmail.com> wrote:
> I'm sure there's a section of the manual that explains this.
>
> I'm also sure I don't know what section it is.

If you search for "brain damage" in the zshall manpage, you will find
it. You are in particular interested in the ordering relation between
item 5 and item 7.

>     $ a=( aa bb cc dd ee  )
>
>     $ b=( cc )
>
>     $ echo ${a:|b}
>     aa bb dd ee
>
>     $ echo "${a:|b}"
>     aa bb cc dd ee # <-- WHAT
>
>     $ echo "${(@)a:|b}"
>     aa bb dd ee
>
>     $ echo "${a[@]:|b}"
>     aa bb dd ee
>
> All results except the first quoted expression is the expected result.
>
> Why does the marked, quoted array-subtraction result in a different
> set of values?  I would expect that array operators have precedence
> over array-converted-to-scalar.  Maybe this is an "outward-in"
> expansion issue?

Your expectation is simply not matching what the code does, if the
current level is double quoted then words will be joined before
history modifiers are applied.

-- 
Mikael Magnusson

Re: Odd behavior of quoted Zsh array subtraction

[René Neumann]

> If you search for "brain damage" in the zshall manpage, you will find
> it. 

For those readers who think this is some sarcastic remark (like I did at 
first): No, it yields exactly the right spot.

</PSA>

- René

Re: Odd behavior of quoted Zsh array subtraction

[Bart Schaefer]

On Fri, Jul 23, 2021 at 2:51 AM Mikael Magnusson <mikachu@gmail.com> wrote:
>
> You are in particular interested in the ordering relation between
> item 5 and item 7.  [...] if the
> current level is double quoted then words will be joined before
> history modifiers are applied.

This is correct, but item 7 sort of sweeps up :| and :* (etc.) by
accident, because they aren't really history modifiers.  For example,
// is called out explicitly there, but :/ is not.  Item 7 has not been
kept up to date with several of the more recently added forms of
parameter manipulation.