Re: [babel] passing strings in

[Dan Davison <davison@stats.ox.ac.uk>]

"Eric Schulte" <schulte.eric@gmail.com> writes:

> Hi Maurizio,
>
> The ip addresses in your table are being interpreted as source/reference
> names which org-babel is trying to resolve.  In order to differentiate
> between strings and reference names, we either must surround all strings
> in double quotes (as below) or we must end all references with "()" and
> disallow any strings which end in "()".

Hi Eric,

Thanks for the much better answer. I think my vote goes for your second
option. In other words, :var x=blockname passes the string "blockname",
whereas :var x=blockname() passes the result of evaluating a block
called "blockname".

One argument for this is that in order to pass arguments to a block
being evaluated as a reference, users are already obliged to use the
parenthetic function call syntax:

:var x=blockname(arg1=val1)

so demanding the parentheses in the absence of arguments is natural (and
perhaps even serves to remind users of the possibility of passing
arguments).

Also I think that users will probably pass strings more often than they
will pass the results of block reference evaluations, so
interpreting :var=blockname as a string literal may also be justified by
Least Surprise for naive users (e.g. apparently me...).

Dan




>  Currently we are taking the
> former approach, which means your table will require the following to
> work...
>
> #+TBLNAME: system-host-ping :var host=system-hosts
> | name   | ip               |           ping |
> |--------+------------------+----------------|
> | host 1 | "192.168.10.200" | 192.168.10.200 |
> | host 2 | "192.168.10.24"  |  192.168.10.24 |
> | host 3 | "192.168.42.24"  |  192.168.42.24 |
> #+TBLFM: $3='(sbe system-ping (ip $2))'
>
> #+source: system-ping
> #+begin_src sh :var ip=0
> # This is what I eventually want
> #ping -w 10 -c 1 -q $ip >/dev/null 2>&1
> #echo $?
>
> # Testing
> echo $ip
> #+end_src
>
> I'd be open to discussion on this issue.  I suppose if reference
> resolution fails we could try using the name as a string literal, but
> that could lead to debugging nightmares...
>
> Cheers -- Eric
>
> Maurizio Vitale
> <mav@cuma.i-did-not-set--mail-host-address--so-tickle-me> writes:
>
>> In the table/block pair below, I'm trying to pass an IP number to some
>> shell code. It seems like in the table formula I can only have
>> numbers. Is that right?
>>
>> #+TBLNAME: system-host-ping :var host=system-hosts
>> | name      |             ip | ping   |
>> |-----------+----------------+--------|
>> | host 1    | 192.168.10.200 | #ERROR |
>> | host 2    |  192.168.10.24 | #ERROR |
>> | host 3    |  192.168.42.24 | #ERROR |
>> #+TBLFM: $3='(sbe system-ping (ip $2))'
>>
>> #+source: system-ping
>> #+begin_src sh 
>> # This is what I eventually want
>> #ping -w 10 -c 1 -q $ip >/dev/null 2>&1
>> #echo $?
>>
>> # Testing
>> echo $ip
>> #+end_src
>>
>> Any way to pass arbitrary strings?
>>
>> Thanks a lot,
>>
>>        Maurizio
>>
>>
>>
>>
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>
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