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From: taylorj@yvax.byu.edu
Newsgroups: comp.sys.mac.hypercard
Subject: Re: EvalExpr() callback in XCMDs
Message-ID: <1388taylorj@yvax.byu.edu>
Date: 9 Jul 90 20:22:19 GMT
Lines: 17
X-Local-Date: 9 Jul 90 13:22:19 PDT

In article <2608@network.ucsd.edu>, pbiron@weber.ucsd.edu (Paul Biron) asks
why using EvalExpr for the Exists function in the Dartmouth collection
works from the XFCN but not from HyperCard.

The difference is that X-commands have error results returned to them, as
opposed to an error dialog popping up.  This is so that the X-command can
handle the error appropriately without bothering the user.  The writer of
the Exists XFCN brilliantly took advantage of this.

The "go to non-existant card" thing works the same way.  An error message is
returned in "the result" instead of a dialog popping up so that a script
can handle things without user intervention.


Jim Taylor
Microcomputer Support for Curriculum   |
Brigham Young University               |   Bitnet: taylorj@byuvax.bitnet
101 HRCB, Provo, UT  84602             |   Internet: taylorj@yvax.byu.edu