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Re: HASH -- bug, or "feature"? [message #75873 is a reply to message #75871]

Wed, 20 April 2011 15:09

penteado
Messages: 866
Registered: February 2018

Senior Member
Administrator

On Apr 20, 6:26 pm, Gray <grayliketheco...@gmail.com> wrote:
> This all makes perfect sense... except that it isn't really useful for
> me. I had been using a hash so that I could retrieve and store
> information (in the form of structures) about particular stars by
> indexing with star IDs and not having to search over arrays or lists
> for individual members. When I had information for a set of stars
> where some but not all were already in the hash, I would do something
> like this:
>
> tmp = replicate({star},n_new)
> old = where(star_hash.haskey(new_ids),n_old)
> if (n_old gt 0) then tmp[old] =
> (star_hash[new_ids[old]].values()).toarray()
> tmp.info = new_info & tmp.id = new_ids
> star_hash[new_ids] = tmp

I have a subclass for ordered hashes, which I could clean up and make
public if there is interest. However, I do not see why it is needed
above. If I understand it right, you want to put the new elements in
the hash, without overwriting any preexisting elements. Would it not
be the same as just

tmp=replicate({star},n_new)
tmp.info=new_info
tmp.id=new_ids
new=where(~star_hash.haskey(new_ids),/null)
star_hash[new_ids[new]]=tmp[new]

?

The work being just to avoid overwriting the preexisting elements. If
they could be overwritten, it would be just

tmp=replicate({star},n_new)
tmp.info=new_info
tmp.id=new_ids
star_hash[new_ids]=tmp

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[Message index]

		Re: HASH -- bug, or "feature"? By: Gray on Thu, 21 April 2011 04:20
		Re: HASH -- bug, or "feature"? By: penteado on Wed, 20 April 2011 15:09
		Re: HASH -- bug, or "feature"? By: Gray on Wed, 20 April 2011 14:26
		Re: HASH -- bug, or "feature"? By: Mark Piper on Wed, 20 April 2011 13:33
		Re: HASH -- bug, or "feature"? By: Paul Van Delst[1] on Wed, 20 April 2011 12:50
		Re: HASH -- bug, or "feature"? By: Michael Galloy on Wed, 20 April 2011 12:19

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