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comp / comp.lang.tcl / Re: How do I correctly access this variable?

SubjectAuthor
* How do I correctly access this variable?Luc
`* Re: How do I correctly access this variable?Colin Macleod
 `* Re: How do I correctly access this variable?Ralf Fassel
  `- Re: How do I correctly access this variable?et99

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Subject: How do I correctly access this variable?
From: Luc
Newsgroups: comp.lang.tcl
Organization: A noiseless patient Spider
Date: Fri, 4 Oct 2024 06:36 UTC
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From: luc@sep.invalid (Luc)
Newsgroups: comp.lang.tcl
Subject: How do I correctly access this variable?
Date: Fri, 4 Oct 2024 03:36:48 -0300
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I am stumped by this:

array set CONTROL {
InitialStartUpDir "$env(HOME)"
}

puts $env(HOME)
/home/luc

OK.

Now,

oo::define NewTab {
constructor {} {
blah blah blah...
$newtab configure -text "$::CONTROL(InitialStartUpDir)"
}
}

The button label becomes "$env(HOME)" instead of /home/luc.

What am I doing wrong?

--
Luc
>>

Subject: Re: How do I correctly access this variable?
From: Colin Macleod
Newsgroups: comp.lang.tcl
Date: Fri, 4 Oct 2024 08:15 UTC
References: 1
Path: eternal-september.org!news.eternal-september.org!cmacleod.me.uk!.POSTED!not-for-mail
From: user7@cmacleod.me.uk.invalid (Colin Macleod)
Newsgroups: comp.lang.tcl
Subject: Re: How do I correctly access this variable?
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Date: Fri, 04 Oct 24 08:15:02 GMT
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Luc <luc@sep.invalid> posted:

> I am stumped by this:
>
> array set CONTROL {
> InitialStartUpDir "$env(HOME)"
> }
>
> puts $env(HOME)
> /home/luc
>
> OK.
>
> Now,
>
> oo::define NewTab {
> constructor {} {
> blah blah blah...
> $newtab configure -text "$::CONTROL(InitialStartUpDir)"
> }
> }
>
> The button label becomes "$env(HOME)" instead of /home/luc.
>
> What am I doing wrong?

Variable references do not get expanded inside braces {}.
Try:
array set CONTROL "
InitialStartUpDir $env(HOME)
"

--
Colin Macleod.

Subject: Re: How do I correctly access this variable?
From: Ralf Fassel
Newsgroups: comp.lang.tcl
Date: Fri, 4 Oct 2024 09:01 UTC
References: 1 2
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From: ralfixx@gmx.de (Ralf Fassel)
Newsgroups: comp.lang.tcl
Subject: Re: How do I correctly access this variable?
Date: Fri, 04 Oct 2024 11:01:35 +0200
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* Colin Macleod <user7@cmacleod.me.uk.invalid>
| Luc <luc@sep.invalid> posted:
>
| > I am stumped by this:
| >
| > array set CONTROL {
| > InitialStartUpDir "$env(HOME)"
| > }
--<snip-snip>--
| > What am I doing wrong?
>
| Variable references do not get expanded inside braces {}.
| Try:
| array set CONTROL "
| InitialStartUpDir $env(HOME)
| "

Or safer, in case the expanded value contains spaces:

array set CONTROL [list InitialStartUpDir $env(HOME)]

HTH
R'

Subject: Re: How do I correctly access this variable?
From: et99
Newsgroups: comp.lang.tcl
Organization: A noiseless patient Spider
Date: Fri, 4 Oct 2024 19:17 UTC
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From: et99@rocketship1.me (et99)
Newsgroups: comp.lang.tcl
Subject: Re: How do I correctly access this variable?
Date: Fri, 4 Oct 2024 12:17:33 -0700
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On 10/4/2024 2:01 AM, Ralf Fassel wrote:
> * Colin Macleod <user7@cmacleod.me.uk.invalid>
> | Luc <luc@sep.invalid> posted:
>>
> | > I am stumped by this:
> | >
> | > array set CONTROL {
> | > InitialStartUpDir "$env(HOME)"
> | > }
> --<snip-snip>--
> | > What am I doing wrong?
>>
> | Variable references do not get expanded inside braces {}.
> | Try:
> | array set CONTROL "
> | InitialStartUpDir $env(HOME)
> | "
>
> Or safer, in case the expanded value contains spaces:
>
> array set CONTROL [list InitialStartUpDir $env(HOME)]
>
> HTH
> R'

One wonders why Luc wouldn't just simply use array notation:

set ::CONTROL(InitialStartUpDir) $env(HOME)

[array set] with a list is useful when the list has more than one key/value pair, while with just a single pair takes about twice the time (as determined with [time]} to run.

BTW I have one little nitpick with the docs on this one. It states:

"Each odd-numbered element in list is treated as an element name within arrayName ..."

In Tcl, list indices invariably begin at 0, and yet odd-numbered here would indicate beginning at 1, and oddity in itself :)

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