Hmm, it appears fish indeed does some tricky things with expansion. Separate
arguments are expanded left to right:
> set foo first
> echo $foo (set foo second) $foo (set foo third) $foo
first second third
>
But within one argument the command substitution is done first:
> set foo first
> echo $foo-(set foo second; echo)-$foo-(set foo third; echo)-$foo
third--third--third
>
Without the echo's inside the command substitutions the command gives an
empty line as output. Don't know if that's a bug or a feature. Does anyone
know if that's supposed to happen?
> set foo first
> echo $foo-(set foo second; echo)-$foo-(set foo third)-$foo
>
Jan
On Mon, Feb 21, 2011 at 08:39, Isaac Dupree
<m...@isaac.cedarswampstudios.org>wrote:
> On 02/19/11 12:45, weakish wrote:
> > In fish's user doc (section "Combining different expansions"):
> >
> >> When combining multiple parameter expansions, expansions are performed
> >> in the following order:
> >>
> >> * Command substitutions
> >> * Variable expansions
> >
> > So command substitutions get performed before variable expansions?
> >
> > But give fish the following code:
> >
> > echo $(echo HOME)
> >
> > fish said:
> >
> > echo $(echo HOME)
> > ^
> >
> > It seems variable expansion happens first here?
>
> Well, parsing happens first, and prevents the above (As it turns out, $
> can syntactically only accept literal variable names (and whatever else
> it specifically accepts)).
>
> (At least, that's how a sane shell might do it. I don't trust fish's
> parsing enough to be certain.)
>
> Anyway, command substitution and variable expension probably don't
> happen in a fixed order relative to each other. If you have (cat
> $variable) then the variable has to be expanded before the command is
> executed, obviously. On the other hand $SomeArray[(seq 3)] clearly has
> to execute the command before expanding the variable.
>
> -Isaac
>
>
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Pinpoint memory and threading errors before they happen.
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Locate bottlenecks in serial and parallel code that limit performance.
http://p.sf.net/sfu/intel-dev2devfeb
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