value of a key pointed by (P) ?

value of a key pointed by (P) ?

[Marc Chantreux]

Hi all, 

typeset -A a
a=(
	this is 
	something special
	for you
)
b=a
k=this
print ${${(P)b}[$k]}

i expect 'is', i get 'you'. Why ? how to fix ?
thanks a lot for help.

regards.
mc

-- 
téléphone : 03.90.24.00.19
courriel  : marc.chantreux@ulpmm.u-strasbg.fr
---------------------------------------

Re: value of a key pointed by (P) ?

[Peter Stephenson]

Marc Chantreux <marc.chantreux@ulpmm.u-strasbg.fr> wrote:
> typeset -A a
> a=(
> 	this is 
> 	something special
> 	for you
> )
> b=a
> k=this
> print ${${(P)b}[$k]}
> 
> i expect 'is', i get 'you'. Why ? how to fix ?

The expression generated by ${(P)b} is passed back as an ordinary array, so
it isn't indexed properly by the $k.

I don't think there's an easy answer; you have to resort to something like

eval print '${'$b'[$k]}'

-- 
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Re: value of a key pointed by (P) ?

[Marc Chantreux]

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le 15/09/2006,
Peter Stephenson nous écrivait :
> The expression generated by ${(P)b} is passed back as an ordinary array,

isn't it a bug? do you think it's possible to fix it in future versions
of zsh ? 

> so it isn't indexed properly by the $k.

it's clear now ... thanks for explain, Peter
> 
> I don't think there's an easy answer; you have to resort to something like
> eval print '${'$b'[$k]}'

i've done it but it isn't as sexy as the way i tried to write.

regards
mc

-- 
téléphone : 03.90.24.00.19
courriel  : marc.chantreux@ulpmm.u-strasbg.fr
---------------------------------------

Re: value of a key pointed by (P) ?

[Bart Schaefer]

On Sep 15, 10:17pm, Marc Chantreux wrote:
} Subject: Re: value of a key pointed by (P) ?
}
} le 15/09/2006,
} Peter Stephenson nous écrivait :
} > The expression generated by ${(P)b} is passed back as an ordinary array,
} 
} isn't it a bug?

No, it's not.  ${(P)b} is "the value of the thing named by the value of
b" and the value of the parameter a is an ordinary array consisting of
all the values of the associative array.

What you want are name references, that is, "the thing named by the
value of b" (note the difference -- missing one "value of").  Zsh
doesn't have those yet, and when it does they probably won't be
implemented via parameter expansion flags.

Also consider:

    b="a[$k]"
    print ${(P)b}

Re: value of a key pointed by (P) ?

[Bart Schaefer]

On Sep 15,  6:56pm, Peter Stephenson wrote:
}
} I don't think there's an easy answer; you have to resort to something like
} 
} eval print '${'$b'[$k]}'

print ${(e):-'${'$b'[$k}]'}