shinberd@unioncs.UUCP (David Shinberg) (02/21/89)
Hello,
I am working on HyperCard for a programming languages course and have run
into a few questions involving the implementation of HyperCard. I realize
that some information may only be known inside apple and not available
to the public. Here goes it anyway.
1) Why do certain commands generate errors when invoked from the MessageBox?
e.g. if, repeat, etc
2) What method of memory allocation does HyperCard use?
e.g. Stack, heap, etc
3) How are global variables stored and referenced?
Thanks Much
David A. Shinberg
88_shinb@union.BITNET Box 2073
uunet!steinmetz!unioncs!shinberd Union College
Schenectady NY, 12308dan@Apple.COM (Dan Allen) (02/22/89)
In article <1184@unioncs.UUCP> shinberd@unioncs.UUCP (David Shinberg) writes: > 1) Why do certain commands generate errors when invoked from the MessageBox? > e.g. if, repeat, etc > 2) What method of memory allocation does HyperCard use? > e.g. Stack, heap, etc > 3) How are global variables stored and referenced? Structured statements like repeat and if are not allowed currently in the message box. They must be in a script. HyperCard uses both the standard Macintosh stack (the stack pointer is register A7 of the 68000) as does all Macintosh applications. In addition, HyperTalk has its own stacks for pushing and poping variables and scopes and the like. These stacks are not available to HyperTalk programmers in any way. Bitmaps and cards and backgrounds and text is all manipulated with the standard Macintosh Memory Manager which uses the application heap. For more information on this, read Inside Macintosh. Global variables are stored by HyperTalk in a private manner, i.e., if we documented it we couldn't change it, which we are planning to do for various reasons including performance. Dan Allen HyperCard Team Apple Computer
desnoyer@Apple.COM (Peter Desnoyers) (02/22/89)
In article <26170@apple.Apple.COM> dan@Apple.COM (Dan Allen) writes: > >Structured statements like repeat and if are not allowed currently in >the message box. They must be in a script. > Is there any particular reason for this? It would be very convenient to be able to use these statements from the message box. Peter Desnoyers
carterbk@apple.com (Bryan K. Carter) (02/22/89)
In article <26177@apple.Apple.COM> desnoyer@Apple.COM (Peter Desnoyers) writes: > In article <26170@apple.Apple.COM> dan@Apple.COM (Dan Allen) writes: > > > >Structured statements like repeat and if are not allowed currently in > >the message box. They must be in a script. > > > Is there any particular reason for this? It would be very convenient > to be able to use these statements from the message box. In order to execute a repeat there needs to be more than just one line of code, i.e.: repeat 3 do this do that end repeat As far as 'if' statements being in the message handler, the same concept may apply. There are so many possibilities for an if/then/else/end if statement, that one line of code is not going to cut it. However, something like 'if the msg box is not empty then beep' should conceivably execute, but it doesn't. If/then/else statements are usually called to check prior values which the code (script) may/may not have generated. If/then/else's and repeats are 'structured' (operative word here) statements in programming, not single line statements. Bryan K. 'STAKMan' Carter carterbk@apple.com <<There are two kinds of every snow flake in the world, it just depends upon who's second grade class you are in.>>
mithomas@bsu-cs.UUCP (Michael Thomas Niehaus) (02/22/89)
In article <26177@apple.Apple.COM>, desnoyer@Apple.COM (Peter Desnoyers) writes: > In article <26170@apple.Apple.COM> dan@Apple.COM (Dan Allen) writes: > > > >Structured statements like repeat and if are not allowed currently in > >the message box. They must be in a script. > > > Is there any particular reason for this? It would be very convenient > to be able to use these statements from the message box. I was under the impression that the message box only has one line in it. If there are more of them hiding somewhere, someone should let all of us know. Seriously, it seems to me that you can't use repeat and if and other multi-line statements just because there is only one line to enter them on. If this is not true (e.g. if there is any way to put more than one statement in the message box to be executed at one time) let me know. (It would be nice to be able to say 'domenu new card; domenu new field', but that is too *NIX like. This could also be 'if <whatever>;<dowhatever>;end if'.) HyperCard never ceases to amaze me. I don't think I will ever be able to remember all of the shortcuts (anyone have a good "cheat sheet" that lists them?) or all of the different HyperTalk constructs and functions. Now I can't wait to see version 2.0. I read in Computerworld that "they" were considering adding AI type constructs (ala LISP) to HyperTalk. I may not like AI languages in general, but this sounds like it could be a lot of fun. AI for the masses... Michael Niehaus Apple Student Rep Ball State University UUCP: ..!{pur-ee,iuvax}!bsu-cs!mithomas AppleLink: ST0374 Disclaimer: No one would be stupid enough to let me speak for them (not even this university).