Xref: utzoo comp.sys.mac.hypercard:4097 comp.sys.mac.programmer:16275
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!stadler
From: stadler@Apple.COM (Andy Stadler)
Newsgroups: comp.sys.mac.hypercard,comp.sys.mac.programmer
Subject: Re: global variables in code resources
Keywords: global variables, code resources, XCMD's, XFCN's
Message-ID: <43407@apple.Apple.COM>
Date: 27 Jul 90 22:16:11 GMT
References: <12642@june.cs.washington.edu>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 21

>How much do callbacks to HyperCard from externals slow the execution
>of an Xternal?

The callback mechanism itself is very quick and direct.  Low overhead.

>Along the same lines is it faster to execute HyperTalk
>commands from within a script of is it faster to make callbacks
>from the Xternal's code?

If you are doing something which can be handled through one of the specific
function callback (like SetGlobal or GetFieldByXXX or NumToStr) then by all
means use the callback - it will be quite efficient.

If you are just sending single lines of HyperTalk, through SendCardMessage,
SendHCMessage, or EvalExpr, however, the interpreter will actually have to
parse, tokenize, interpret, and execute your line.  This won't make much
difference if you do it a single time;  but the interpreter tokenizes scripts
and keeps the tokens around, which means that -repeated- execution of a given
line will be much faster if it's in a script.

--Andy      stadler@apple.com