* Determining whether a function is used in an arithmetic context
@ 2017-07-25 3:47 dana
2017-07-25 7:03 ` Bart Schaefer
0 siblings, 1 reply; 3+ messages in thread
From: dana @ 2017-07-25 3:47 UTC (permalink / raw)
To: zsh-users
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Hey there,
I was playing with arithmetic functions recently and i wanted to have one
of them behave differently depending on whether it's used in an arithmetic
context or not. I can't seem to figure out a *reliable* way to detect that,
though.
The %_ prompt expansion seemed like it might be the way to go — it produces
math when used in an arithmetic command... but not an arithmetic
*substitution*, strangely. (Is that expected?)
The best luck i had was giving the function a different name when used in
arithmetic context, and then checking to see if %N matches $0. However,
this only works when function_argzero is enabled, and unfortunately i think
i need that turned off, since ZSH_ARGZERO is not available in zsh <5.3.
See below for the result of my experiments. Have i missed something?
Cheers
dana
% zsh --version
zsh 5.3.1 (x86_64-apple-darwin16.6.0)
% cat /tmp/foo
myfunc() {
(( $1 ))
printf ' $zec %s\n' ${zsh_eval_context:-\?}
printf ' $ft %s\n' ${functrace:-\?}
printf ' $fs %s\n' ${funcstack:-\?}
printf ' $0 %s\n' ${0:-\?}
printf ' $_ %s\n' ${_:-\?}
printf ' $ZAZ %s\n' ${ZSH_ARGZERO:-\?}
printf ' %%N %s\n' ${${(%):-%N}:-\?}
printf ' %%_ %s\n' ${${(%):-%_}:-\?}
}
functions -M func 1 1 myfunc
print 'Normal context:'
myfunc 1
print 'Arithmetic substitution context:'
: $(( func(1) ))
print 'Arithmetic command context:'
(( func(1) ))
% zsh /tmp/foo
Normal context:
$zec toplevel
$zec shfunc
$ft /tmp/foo:16
$fs myfunc
$0 myfunc
$_ myfunc
$ZAZ /tmp/foo
%N myfunc
%_ ?
Arithmetic substitution context:
$zec toplevel
$zec shfunc
$ft /tmp/foo:19
$fs myfunc
$0 func
$_ func
$ZAZ /tmp/foo
%N myfunc
%_ ?
Arithmetic command context:
$zec toplevel
$zec shfunc
$ft /tmp/foo:22
$fs myfunc
$0 func
$_ func
$ZAZ /tmp/foo
%N myfunc
%_ math
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Determining whether a function is used in an arithmetic context
2017-07-25 3:47 Determining whether a function is used in an arithmetic context dana
@ 2017-07-25 7:03 ` Bart Schaefer
2017-07-25 21:20 ` dana
0 siblings, 1 reply; 3+ messages in thread
From: Bart Schaefer @ 2017-07-25 7:03 UTC (permalink / raw)
To: Zsh Users; +Cc: dana
On Mon, Jul 24, 2017 at 8:47 PM, dana <dana@dana.is> wrote:
>
> I was playing with arithmetic functions recently and i wanted to have one
> of them behave differently depending on whether it's used in an arithmetic
> context or not. I can't seem to figure out a *reliable* way to detect that
I guess I'd do it like this:
myfunc() {
if [[ ${funcstack[2]} == myfunc_math ]]
then print In math context
else print Not in math context
fi
}
myfunc_math() {
myfunc "$@"
}
functions -M myfunc 1 1 myfunc_math
> The %_ prompt expansion seemed like it might be the way to go — it produces
> math when used in an arithmetic command... but not an arithmetic
> *substitution*, strangely. (Is that expected?)
Yes, it's expected, because it's the parser state -- by the time the function is
actually executing, the parser is done. %_ is only meaningful during program
input (typically interactively) or in an execution trace, not during
execution itself.
I think it's accidental that it has a value during arithmetic commands.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Determining whether a function is used in an arithmetic context
2017-07-25 7:03 ` Bart Schaefer
@ 2017-07-25 21:20 ` dana
0 siblings, 0 replies; 3+ messages in thread
From: dana @ 2017-07-25 21:20 UTC (permalink / raw)
To: Zsh Users; +Cc: Bart Schaefer
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I suppose that'll do. Thanks!
On 25 July 2017 at 02:03, Bart Schaefer <schaefer@brasslantern.com> wrote:
> On Mon, Jul 24, 2017 at 8:47 PM, dana <dana@dana.is> wrote:
> >
> > I was playing with arithmetic functions recently and i wanted to have one
> > of them behave differently depending on whether it's used in an
> arithmetic
> > context or not. I can't seem to figure out a *reliable* way to detect
> that
>
> I guess I'd do it like this:
>
> myfunc() {
> if [[ ${funcstack[2]} == myfunc_math ]]
> then print In math context
> else print Not in math context
> fi
> }
> myfunc_math() {
> myfunc "$@"
> }
>
> functions -M myfunc 1 1 myfunc_math
>
> > The %_ prompt expansion seemed like it might be the way to go — it
> produces
> > math when used in an arithmetic command... but not an arithmetic
> > *substitution*, strangely. (Is that expected?)
>
> Yes, it's expected, because it's the parser state -- by the time the
> function is
> actually executing, the parser is done. %_ is only meaningful during
> program
> input (typically interactively) or in an execution trace, not during
> execution itself.
> I think it's accidental that it has a value during arithmetic commands.
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-07-25 21:21 UTC | newest]
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