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From: Bart Schaefer <schaefer@brasslantern.com>
To: zsh-users@zsh.org
Subject: Re: easy calling of associative array?
Date: Mon, 2 Nov 2015 08:28:08 -0800	[thread overview]
Message-ID: <151102082808.ZM17640@torch.brasslantern.com> (raw)
In-Reply-To: <563784B5.3040901@eastlink.ca>

On Nov 2,  7:43am, Ray Andrews wrote:
}
}     get_v ()
}     {
}     #$3=${(P)${:-${1}[$2]}}     #nothing works
}     eval "$3=\$${1}[$2]"        #this works
}     }

This has nothing to do with associative arrays and everything to do with
assignment syntax.  "$3" is not a valid identifier, so "$3=" is not an
assignment; this all decided before $3 is expanded, which is why putting
the "eval" around it works (it delays the "is an identifier" check until
after $3 has expanded).

Probably the most cogent way to do this is

    get_v () {
      typeset -g $3="${(P)${:-${1}[$2]}}"
    }

}     set_v ()
}     {
}     # {(P)${:-${1}[$2]}}=$3       #nothing works
}     eval "${1}[$2]=$3"            #this works
}     }

Same assignment-syntax problem.

    set_v () {
      # typeset -gA $1		# optional
      typeset -g "${1}[$2]=$3"	# quotes so [ ] isn't globbing
    }

Here you don't need the (P) indirection because ${1} and $2 are both
expanded before being passed to typeset, so you already extracted the
name that was passed in $1.

Also note I'm ignoring all possible error checking, e.g. if $1 is not
an identifier (in the worst case, contains an "="), things go badly.

}     test_v ()
}     {
}     #eval "${1}[$2]"            #nothing works
}                                  #this works
}     [ ${(P)${:-${1}[$2]}} = $3 ] && echo 'all too true' || echo 'alas, no.'
}     }

I'm not exactly sure what you're wanting as either output or exit
status here, but except that I'd recommend [[ ]] instead of [ ] as
the test syntax, what you wrote for "this works" is sensible.


  reply	other threads:[~2015-11-02 16:28 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-01 23:12 Ray Andrews
2015-11-01 23:55 ` ZyX
2015-11-02  0:49   ` Ray Andrews
2015-11-02  3:08     ` Bart Schaefer
2015-11-02  3:33       ` Ray Andrews
2015-11-02  6:51         ` Bart Schaefer
2015-11-02 15:43           ` Ray Andrews
2015-11-02 16:28             ` Bart Schaefer [this message]
2015-11-02 18:32               ` Ray Andrews
2015-11-02 19:37                 ` ZyX
2015-11-02 22:10                   ` Bart Schaefer
2015-11-02 22:50                     ` Ray Andrews
2015-11-02 21:05                 ` Bart Schaefer
2015-11-02 23:01                   ` Ray Andrews
2015-11-03 15:57                     ` Bart Schaefer
2015-11-04 14:48                       ` Ray Andrews
2015-11-04 16:39                         ` Bart Schaefer
2015-11-04 18:31                           ` Ray Andrews
2015-11-02 19:33             ` ZyX
2015-11-02 23:04               ` Ray Andrews

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