| Good practices with hashes [message #84502] |
Wed, 22 May 2013 03:39 |
Fabzi
Messages: 305
Registered: July 2010
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Senior Member |
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Dear IDLers,
I'm trying to be "up to date" and use the new neat syntax offered by IDL
8. My apologies in advance if my question is trivial.
I was thinking about using hashes of hashes to store a kind of dynamic
database. For example:
table = hash()
table['lake_1'] = hash('id', 1, 'depth', 100, 'name', 'lake1', $
'temperature', 14.5)
table['lake_2'] = hash('id', 2, 'depth', 56, 'name', 'lake2', $
'temperature', 11.8)
table['lake_3'] = hash('id', 3, 'depth', 12, 'name', 'lake3', $
'temperature', 18.1)
table['lake_4'] = hash('id', 4, 'depth', 167, 'name', 'lake4', $
'temperature', 7.2)
in this example, the attributes are scalars but temperature could be a
vector or more complex things. I used hashes because I can dynamically
fill the table as I read the data (lake per lake).
However, the resulting table is not as easy to use as I expected. Most
of the time (not always), I would want to read the attribute for all
lakes. So I would do:
depth = !NULL
foreach h, table, lake do depth = [depth, h['depth']]
But this is not "as easy" as if the table would be "swappable", for
example if I was able to do:
depth = table['depth']
Second problem: since hashes are not sorted, I have to keep track of the
lake ids to get the data arrays in the right order.
Long talk, two questions: is this the "right way" to use hashes? Is
there a better solution for this quite simple problem?
(I am quite sure I am not the first one using tables...)
Thanks a lot for your advices!
Fab
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