Topic: @switch and switch()
Author: Trispis
Summary: Due to numerous inquiries, Trispis presents a brief summary lecture
on @switch and switch().

<101> Trispis says, "Okay. I'm ready to begin."

<101> Trispis says, "I'll be running from a hastily written script up through
the first example. After that, it'll slow down a bit while I type stuff
manually."

<101> Trispis gives a brief introduction.

<101> Trispis says, "My purpose here is, in a nutshell, to give me a rough
text to edit, refine, and upload to the 101 webpage about the basic (very
basic) functionality and syntax of @switch and switch() (with nominal
references to if() and ifeles() for a few simpler things)."

<101> Trispis says, "The basic function of a SWITCH is to determine what, if
any, action should be taken in a given circumstance."

<101> Trispis says, "For example, restricting a $command so that it can only
be used to affect an object of type PLAYER."

<101> Trispis says, "A more complex example would be a $command that can act
on any type of object, but must do different things depending on which type
(PLAYER, ROOM, EXIT, THING)."

<101> Trispis says, "Another more complex example would be a $command which
has options itself without making multiple commands (e.g., +finger/brief,
+finger/detail could be made from $+finger/* *)."

<101> Trispis says, "Before I give any more confusing examples, let's dive in
and take a look at @switch."

<101> Trispis recommends we begin by typing: help @switch

@SWITCH
@switch [/<switch>] <string> = <expr1>, <action1> [,<exprN>,
<actionN>]... [,<default>]
For those of you familiar with programming, this command acts like
if/then/else or switch/case. It compares <string> against whatever
each <expr> evaluates to. If <string> and <expr> match, the action list
associated with that <expr> is carried out. If no match is found, the
<default> action list is carried out.

The string "#$" in <action>'s will be expanded to the evaluated result
of <string> before it is acted on.

@switch/all will carry out the action lists for -all- of the
expressions that match <string>. This is the default.
@switch/first will carry out the action list for only the -first-
expression that matches <string>. This is the same as
@select, and it is less computationally expensive than
/all in many cases.

(continued in help @switch2)


<101> Trispis says, "One of the problems which migh be confusing people is
that the syntax for @switch wraps to the second line. So, I'm going to scrunch
it together onto one line so that it can be seen as a whole. -- To do this
(and since I'm only worried about the BASIC functionality), I'm going to
remove the [/switch] portion and some of the excess whitespace."

<101> Trispis says, "Here is the syntax for @switch all on one line

@switch <string> = <expr1>, <action1> [,<exprN>, <actionN>][...] [,<default>]

Much easier to picture when it's not all broken apart like in the help file."

<101> Trispis says, "Now, I'm going to skip the first sentence thereafter (cuz
I'm assuming part of the misunderstanding is due to the fact that some people
AREN'T familiar with programming)."

<101> Trispis says, "Beginning with the second sentence, the help file reads:
It compares <string> against whatever each <expr> evaluates to. If <string>
and <expr> match, the action list associated with that <expr> is carried out.
If no match is found, the <default> action list is carried out. [NOTE: The
<default> is optional. Therefore if no <default> is given and no matches
occurred, then nothing happens.]"

<101> Trispis pauses to allow time for that to sink in to any actual newbies
who may be trying to learn this right now.

<101> Trispis adds the next sentence of the help file.

<101> Trispis says, "Right after that, it says: The string "#$" in <action>'s
will be expanded to the evaluated result of <string> before it is acted on.
[NOTE: This means that you can use the substitution #$ in your actions, rather
than retyping <string> in them.]"

<101> Trispis says, "I'll begin with an example that can be typed directly
into the keyboard for your own experimentation."

<101> Trispis says, "do this...

@switch [words(cwho(101))]=0,think There are no players on the 101
channel,think There are #$ players on the 101 channel.

and see how it behaves."

<101> Trispis says, "pretend that @switch command was all on one line of
input."

<101> Trispis says, "That's all I haved pre-written, so it's gonna slow down
drastically now."

<101> Trispis says, "What that example does is... it checks how many people
are on the 101 channel ( [words(cwho(101))] ) and then, if that is a zero (0),
it does the action immediately following the zero. Then (since it's a very
basic example), if it's anything other than zero (the default) it performs the
final action."

<101> Trispis says, "This is a very basic switch."

<101> Trispis says, "The next example won't be doable from your keyboard, and
it assumes you've been through the Code Basics and the More Code Stuff
lectures."

<101> Trispis says, "This one uses our $wave command from our Lab Project...
to prevent us from being spoofed by a puppet."

<101> Trispis says, "We can have our waver check for the TYPE of object that
we're waving to... and make sure it's a PLAYER before executing the wave."

<101> Trispis says, "like this..."

<101> Trispis says, "$wave *:@switch [type(locate(%#,%0,*))]=PLAYER,@remit
%l=%N waves."

<101> Trispis says, "This command (as all of these examples will do)
introduces other functions (you really should read the help files on these...
they're added bonuses to the lecture). Specifically, this command looks for an
object in the location of the user (locate does that) and checks
its type. If the type matches PLAYER, the @remit occurs. Since there is no
default, nothing else happens."

<101> Trispis says, "er... it looks for an object in the location of the user
WHICH MATCHES THE INPUT %0 (like: wave Trispis)"

<101> Trispis says, "If I had been running a puppet around there named
Trispis, your waver would not have waved to it."

<101> Trispis says, "That's the basic syntax of @switch."

<101> Trispis says, "Now, to make that example more complex, we can make it do
something for a PLAYER... and SOMETHING ELSE for a PUPPET... as follows..."

<101> Trispis says, "$wave *:@switch 1=[hastype(%0,PLAYER)],@remit %l=%N waves
to the real %0.,[hasflag(%0,PUPPET)],@remit %l=%N waves to the immitation %0."

<101> Trispis says, "Notice in this example, I changed the order of things a
bit (this is to show the versatility of switches). I used a plaintext <string>
(1) with functions for the <expr1> and <expr2>."

<101> Trispis says, "This command only does 2 possible things. 1) wave to the
real (PLAYER) object, or 2) wave to the immitation (PUPPET) object."

<101> Trispis says, "Two final things to note about @switch."

<101> Trispis says, "One: It can have as many paired <expr>,<action> sets as
you wish (well... there may be a limit, but if you reach it you're probably
trying to do too much with it)."

<101> Trispis says, "And two: the <default> is optional."

<101> Trispis says, "Now, I'm going to change and cover the switch() function,
which basically works almost identical to the @switch command."

<101> Trispis recommends reading: help switch()

SWITCH()
switch(<string>, <expr1>, <list1>, [<exprN>, <listN>], ...[<default>])

This function matches <string> against the <expr>essions, returning the
corresponding <list>. If nothing is matched, the <default> is returned.
This is similar to @switch/first, but instead of executing the list,
it simply returns it. Wildcard patterns are allowed. There may be
a maximum of ten arguments total to the function.

If the string "#$" appears in the <list> to be executed, it will be
replaced with the evaluated value of <string> before execution.

Example:
> say switch(test, *a*, foo, *b*, bar, *t*, neat, baz)
You say, "neat"
> say switch(ack, *a*, foo, *b*, bar, *t*, neat, baz)
You say, "foo"
> say switch(moof, *a*, foo, *b*, bar, *t*, neat, baz)
You say, "baz"
> say switch(moof, *a*, foo, *b*, bar, *t*, neat, #$)
You say, "moof"


<101> Trispis says, "Rather than go over all of the examples again using
switch(), I'm just going to use the final one to illustrate the syntax of
switch() for doing the same thing..."

<101> Trispis says, "$wave *:@remit %l=[switch(1,[hastype(%0,PLAYER)],%N waves
to the real %0.,[hasflag(%0,PUPPET)],%N waves to the immitation %0.)]"

<101> Trispis says, "Notice two things: 1) I moved the @remit to the beginning
(@commands cannot be put INSIDE of functions), and 2) I used the exact same
switch conditions to get the same result as the previous example."

<101> Trispis says, "If you have a situation where you only have one condition
to match, you can use if() or ifelse() rather than switch()."

<101> Trispis says, "You should read those help files, too."

<101> Trispis says, "example: @remit %l=if(hastype(%0,PLAYER),%N waves to %0)"

<101> Trispis says, "example2: @remit %l=ifelse(hastype(%0,PLAYER),%N waves to
%0,%N yawns)"

<101> Trispis says, "This is basically all I intended to cover, so I'll take
any specific questions now."

<101> Yosh raises his hand? :)

<101> Trispis says, "yes?"

<101> Trispis assumes Yosh is typing a well stated question. (:

<101> Halatir says, "He's going to use T-spam (tm)?"

<101> Yosh says, "Okay..whenever I mix nested switches..and @pemit..I always
get messed Up..say..@switch [get(me/status)]=on,{@switch
[get(me/password)]=%0,{@pemit Right password},{@pemit Wrong password}},{@pemit
The thing is not on..} ...Whenever the password is wrong it @pemits 'Wrong
password,{@pemit The thing is not on.."

<101> Halatir says, "Yep."

<101> Yosh pants ;)

<101> Trispis says, "That's a trick with @pemit"

<101> Yosh says, "Trick?"

<101> Cball has been wondering how to make a password object similar to that
also..so will just be perceptive and listen...

<101> Trispis says, "Move some (just the appropriate ones) of your {}'s do
wrap only the pemit contents like this: @pemit {blah blah blah}"

<101> Yosh says, "Okay.."

<101> Trispis says, "And probably do the same for your inner @switch"

<101> Yosh nods..okay..

<101> Trispis offers a complete rewrite for confirmatioin...

<101> Trispis takes that last one back. Just the @pemit one is accurate.

<101> Yosh says, "Okay"

<101> Yosh says, "Thanks :)"

<101> Trispis says, "here's my rewrite of what you asked about..."

<101> Trispis says, "+1 @switch [get(me/status)]=on,{@switch
[get(me/password)]=%0,@pemit %#={Right password},@pemit %#={Wrong
password}},@pemit %#={The thing is not on.}"

<101> Trispis says, "Does that make sense, Yosh?"

<101> Yosh says, "Yeah :)"

<101> Trispis says, "It's a feature of the @pemit command."

<101> Yosh nods..

<101> Trispis says, "If the first character of the <message> is a {, it ends
the message at the first } it comes to afterwards. ... Otherwise, it pemits
everything after the equal sign."

<101> Yosh ahs..

<101> Trispis says, "That's a very good question, btw. Second to completely
misunderstanding the @switch syntax, it's probably the most common problem
I've seen with @switch (the @pemit sending everything after the equal sign and
not stopping at the end of the intended message)."

<101> Trispis says, "Any other questions?"

<101> Trispis concludes this mini-lecture and stops logging.