Re: [ferret_users] reusing information from variable definitions

["Fiedler, Russell (O&A, Hobart)" <Russell.Fiedler@xxxxxxxx>]

Hi Marco,

It looks like the /LIKE qualifier could be what you're after.

https://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/commands-reference/DEFINE#_VPINDEXENTRY_1348

All attributes are inherited (apart from missing_value, scaling and offset). You can override some if you want.

e.g. (From the examples)

yes? let/like=temperature/title="Surface Temperature" sst = temperature[z=0:5@MAX]

so

let/like=aa bb=aa+666

let/like=bb/title="`bb,return=original_definition`" cc = bb

which should be the same as

let/like=aa/title="`bb,return=original_definition`" cc = bb

Cheers,

Russ

---

From: owner-ferret_users@xxxxxxxx <owner-ferret_users@xxxxxxxx> on behalf of Marco van Hulten <Marco.Hulten@xxxxxx>
Sent: Tuesday, 11 February 2020 3:46 AM
To: ferret_users@xxxxxxxx <ferret_users@xxxxxxxx>
Subject: [ferret_users] reusing information from variable definitions

 

Hi all—

I am looking for a way to use information of a variable without user
intervention (in a script).  For instance,

  let/units="m/s" aa = 123.
  let bb = aa + 666.
  sh var bb
bb = AA + 666.

Recently, Ansley pointed out that even more information can be
retrieved from variables, e.g. by SHOW VARIABLE/TREE.  But can I use
any of this information?  Say, that I want to define a third variable
cc as bb but with the units bb's terms that I don't know, so

  say `bb,return=original_definition`
aa + 666.
  let/title="`bb,return=original_definition`" cc = bb

I also want to get to use aa.units, by referring only to bb (I don't
know aa).  If a return function or method exists to retrieve the
information, I could then just spawn AWK:

  def symb Units = spawn( "echo '`bb,return=original_definition`' | awk '{ print $1 }'" )
  let/title="Original _expression_: `bb,return=original_definition`"/units="($Units)" cc = bb

To recap: my goal is to get the units from a previous _expression_; to
that end, I think I need a way to make use of SHOW VARIABLE[/TREE]
information, or even more generally stdout.  Is there a last-output
symbol, maybe?  (There is FER_LAST_ERROR.)

—Marco