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Date: Tue, 10 Jan 2017 15:43:18 +0000
From: Peter Stephenson <p.stephenson@samsung.com>
To: zsh-workers@zsh.org
Subject: Re: Bug in parameter expansion with :-    ?
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On Tue, 10 Jan 2017 16:35:00 +0100
Ronald Fischer <ynnor@mm.st> wrote:

> This expands correctly to a '+':
> 
>       ${unset_variable:-+}
> 
> This however doesn't expand to a '-', but to the empty string:
> 
>     ${unset_variable:--}

You may be getting into confusions with options to builtins rather than
the expansion.

% print -r -- ${unset_variable:--} 
-

pws