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From: sirkm@ssyx.ucsc.edu (Greg Anderson)
Newsgroups: comp.sys.mac.hypercard
Subject: Re: Association lists in hypercard?
Message-ID: <8947@saturn.ucsc.edu>
Date: 31 Aug 89 15:37:23 GMT
References: <37303@bu-cs.BU.EDU>
Sender: usenet@saturn.ucsc.edu
Reply-To: sirkm@ssyx.ucsc.edu (Greg Anderson)
Organization: UC Santa Cruz; Division of Social Sciences
Lines: 46

In article <37303@bu-cs.BU.EDU> gasp@bucsd.bu.edu (Isaac Kohane) writes:
>Hi,
>
>	I'm a relative novice to hypercard and have some trouble
>finding a clean solution to the creation of association lists. That is,
>I'd like to store pairs of keys and their values and wish to be able
>to retrieve the value given the key. Any ideas?
>
>
>				-zak

You could use the 'grep' XFCN to do this.  Store keys and values in
a field like this:

	key1,value1
	key2,value2
	key3,value3

... and so on.  Then:

	get grep("key2",bg field "whateveritsnameis")

will return

	key2,value2

Use 'item 2 of it' to reference the value, or just say 'get item 2 of grep('.

To delete a key and its value:

	put grep(v,"key2",bg fld "xx") into bg fld "xx"

To add a key, just put it after the field.  Don't forget the return --
grep works on lines.

To change the value of a key, just delete and re-add it.

An alpha version of the grep XFCN is attached to the HyperUnix home
stack, available for anonymous ftp from ssyx.  There's still a bug
in wildcard searching, though.  As soon as I fix that, I'll put grep
and replace (sed?) up for anonymous ftp.

  ___\    /___               Greg Anderson              ___\    /___ 
  \   \  /   /         Social Sciences Computing        \   \  /   /
   \  /\/\  /    University of California, Santa Cruz    \  /\/\  /
    \/    \/              sirkm@ssyx.ucsc.edu             \/    \/