earl@cogdev.cognet.ucla.edu (Earl Williams) (06/05/91)
Is there really no 'case' statement in Hypertalk, or am I missing its
equivalent? For simple keypress trapping, I'd like to do something like
the following:
on keyDown key
case
key = 'a' then do this else
key = 'b' then do that else
key = 'c' then do the other
end
end keyDown
Instead, I have to use standard if-then-else statements which, when
formatted, give the false impression that I'm doing nesting.
on keyDown key
if key = 'a' then do this else
if key = 'b' then do that else
if key = 'c' then do the other
end if
end if
end if
end keyDown
This is extremely inelegant, if not confusing (when used in a more
complex example than this, of course.
Any suggestions? What am I missing here? Any help will be
much appreciated.
-----------------------------------------------------------
Earl M. Williams ?8-) UCLA Psychology Department
earl@cognet.ucla.edu 2344B Franz Hall
"No matter where you go, there you are." -Buckaroo Banzaijdevoto@Apple.COM (Jeanne A. E. DeVoto) (06/06/91)
In article <1991Jun4.234844.1280@cognet.ucla.edu> earl@cogdev.cognet.ucla.edu (Earl Williams) writes: >Is there really no 'case' statement in Hypertalk, or am I missing its >equivalent? For simple keypress trapping, I'd like to do something like >the following: > >on keyDown key > case > key = 'a' then do this else > key = 'b' then do that else > key = 'c' then do the other > end >end keyDown > >Instead, I have to use standard if-then-else statements which, when >formatted, give the false impression that I'm doing nesting. > >on keyDown key > if key = 'a' then do this else > if key = 'b' then do that else > if key = 'c' then do the other > end if > end if > end if >end keyDown > >This is extremely inelegant, if not confusing (when used in a more >complex example than this, of course. Write your conditional like this: if key is "a" then do this else if key is "b" then do that else if key is "c" then do the other Or, if your statements are more than one line (even if they're not, if you're a neatness freak or want complete clarity when using nested ifs): if key is "a" then do this else if key is "b" then do that else if key is "c" then do the other end if You can embellish this with an exception case at the end: if key is "a" then do this else if key is "b" then do that else if key is "c" then do the other else do something else end if Just one end if, at the end, and no Vogage to the Righthand Edge of the Script Editor. -- ========= jeanne a. e. devoto ======================================== jdevoto@apple.com | You may not distribute this article under a jdevoto@well.sf.ca.us | compilation copyright without my permission. ______________________________________________________________________ Apple Computer and I are not authorized | CI$: 72411,165 to speak for each other. |
fwb@pollux.tmc.edu (Fred Brehm) (06/06/91)
In article <1991Jun4.234844.1280@cognet.ucla.edu> earl@cogdev.cognet.ucla.edu (Earl Williams) writes: >Is there really no 'case' statement in Hypertalk, or am I missing its >equivalent? The equivalent is "else if" > ... For simple keypress trapping, I'd like to do something like >the following: > >on keyDown key > case > key = 'a' then do this else > key = 'b' then do that else > key = 'c' then do the other > end >end keyDown on keyDown key if key = 'a' then do this else if key = 'b' then do that else if key = 'c' then do the other end if end keyDown -- Frederic W. Brehm Siemens Corporate Research Princeton, NJ fwb@demon.siemens.com -or- ...!princeton!siemens!demon!fwb
stadler@Apple.COM (Andy Stadler) (06/07/91)
In article <1991Jun4.234844.1280@cognet.ucla.edu> earl@cogdev.cognet.ucla.edu (Earl Williams) writes: >Is there really no 'case' statement in Hypertalk, or am I missing its >equivalent? For simple keypress trapping, I'd like to do something like > > [..hypothetical case statement syntax described..] > >Instead, I have to use standard if-then-else statements which, when >formatted, give the false impression that I'm doing nesting. > >on keyDown key > if key = 'a' then do this else > if key = 'b' then do that else > if key = 'c' then do the other > end if > end if > end if >end keyDown Instead, type it like this: on keydown key if key is 'a' then dosomething else if key is 'b' then dosomethingelse else if key is 'c' then doyetanother end keydown I think this is what you want. Andy Stadler Apple Computer, Inc.
johnston@oscar.ccm.udel.edu (06/07/91)
Still simpler (forget all the else statements): on keyDown key if key is "a" then beep if key is "b" then beep 2 if key is "c" then beep 3 pass keyDown end keyDown Bill (johnston@minnie.me.udel.edu)
Harry.Myhre@p2.f863.n102.z1.fidonet.org (Harry Myhre) (06/07/91)
Earl Williams writes in a message to All on 05 Jun 91
EW> Is there really no 'case' statement in Hypertalk, or am I missing
EW> its equivalent?
You're right, HyperTalk doesn't have a case statement. You could have coded
your if statement:
on keyDown key
if key = 'a' then do this else
if key = 'b' then do that else
if key = 'c' then do the other
end if
end if
end if
end keyDown
like this instead:
on keyDown key
if key = 'a' then
do this
else if key = 'b' then
do that
else if key = 'c' then
do the other
end if
end keyDown
Either way you do it, it's uglier than a nice case statement. And harder to
read and understand what's going on.
--
: Harry Myhre - via FidoNet node 1:102/851 (818)352-2993
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: Compu$erve: >internet:Harry.Myhre@p2.f863.n102.z1.fidonet.orgbcarter@claven.idbsu.edu (Bruce Carter) (06/07/91)
In article <55655@nigel.ee.udel.edu> johnston@oscar.ccm.udel.edu writes: >Still simpler (forget all the else statements): > >on keyDown key > if key is "a" then beep > if key is "b" then beep 2 > if key is "c" then beep 3 > pass keyDown >end keyDown Simpler, but slower. In this construction all of the if statements have to be evaluated individually. <-> Bruce Carter, Courseware Development Coordinator bcarter@claven.idbsu.edu Boise State University, Boise, ID 83725 duscarte@idbsu.bitnet (This message contains personal opinions only) (208)385-1250@phone
scasterg@magnus.acs.ohio-state.edu (Stuart M Castergine) (06/08/91)
In article <55655@nigel.ee.udel.edu> johnston@oscar.ccm.udel.edu writes: >Still simpler (forget all the else statements): > >on keyDown key > if key is "a" then beep > if key is "b" then beep 2 > if key is "c" then beep 3 > pass keyDown >end keyDown > >Bill (johnston@minnie.me.udel.edu) But much slower -- you force the script to evaluate all the expressions, which is time-consuming if there are very many. If you insert else statements, flow will exit the construct after it finds a condition that tests true, saving you many needless expression evaluations. -- scasterg@magnus.acs.ohio-state.edu Stuart M Castergine "Step by step they were led to practices which disposed to vice -- the lounge, the bath, the elegant banquet. All this in their ignorance they called civilisation, when it was but part of their servitude."
EIVERSO@cms.cc.wayne.edu (06/15/91)
Harry.Myhre@p2.f863.n102.z1.fidonet.org (Harry Myhre) writes >Earl Williams writes in a message to All on 05 Jun 91 >EW> Is there really no 'case' statement in Hypertalk, or am I missing >EW> its equivalent? >You're right, HyperTalk doesn't have a case statement. You could have coded >your if statement: >on keyDown key > if key = 'a' then do this else > if key = 'b' then do that else > if key = 'c' then do the other > end if > end if > end if >end keyDown >like this instead: >on keyDown key > if key = 'a' then > do this > else if key = 'b' then > do that > else if key = 'c' then > do the other > end if >end keyDown >Either way you do it, it's uglier than a nice case statement. And harder to >read and understand what's going on. I'd write it like this: on keyDown if key = "a" then doThis if key = "b" then doThat if key = "c" then doTheOther end keyDown Fewer lines, fewer indents, more legible code. Closer to what you like about a case statement. I'd save the "else if" for multi line proceedures after an if. If you want to debate that, be my guest. A few "nigling" little points... Double quotes are for containing literal strings, not single quotes. "Do" and "The" are reserved words. --Eric
psych@watserv1.waterloo.edu (R. Crispin - Psychology) (06/16/91)
In article <1991Jun14.175048.20051@cs.wayne.edu> EIVERSO@cms.cc.wayne.edu writes: >I'd write it like this: > >on keyDown > if key = "a" then doThis > if key = "b" then doThat > if key = "c" then doTheOther >end keyDown > This is a slower technique since no matter what value KEY has all 3 statements are executed. The only time this is faster is if key is unassigned. A better technique is as follows on keyDown Key if key = "a" then doThis else if key = "b" then doThat else if key = "c" then doTheOTher end keydown I ran some tests and this can be up to 25% faster but usually it is 10% faster. Richard Crispin Phone: (519)888-4781 Dept. of Psychology EMail: psych@watdcs.uwaterloo.ca University of Waterloo psych@watserv1.uwaterloo.ca Waterloo, Ont. Canada N2L 3G1
estier@uni2a.unige.ch (06/19/91)
In article <1991Jun4.234844.1280@cognet.ucla.edu> earl@cogdev.cognet.ucla.edu (Earl Williams) writes: > Is there really no 'case' statement in Hypertalk, or am I missing its > equivalent? For simple keypress trapping, I'd like to do something like > the following: > > on keyDown key > case > key = 'a' then do this else > key = 'b' then do that else > key = 'c' then do the other > end > end keyDown In fact, there is no need of a case statement in HyperTalk since the handler mechanism can very conveniently be substituted to it. So instead of writing borrowing sequences of "if-then-else-end if" for your example, why not writing: on keyDown key if key is in "a b c" then send key end keyDown on a do this end a on b do that end b on c do the other end c (Please don't write me that it takes too much time to execute, just wait for the next (hopefully more powerfull) Mac ;-) Thibault +----------------------------- | estier@macmail.unige.ch or | estier@cui.unige.ch or | ESTIER@CGEUGE51 +-----------------------------