Okay I've got round to putting it on the wiki
(http://amsn-project.net/wiki/Dev:TclTk_Tutorial). I didn't put
anything about multiline commands yet. But I think everything else is
there!
- Tom
On 5/31/07, Youness Alaoui <[EMAIL PROTECTED]> wrote:
> Yeah, you reminded me of something...
> Most 'common problems' with tcl/tk are the "lists theory", substitution
> theory, and command theory.
> In short, the 'lists theory' is that everything is a list, and tcl works a
> lot with list manipulations.
> substitution theory is that, if I do "function $arg" the $arg will be
> substituted, and if it had a space, the
> 'function' will get two arguments, if I do {function $arg} (the {} means it's
> a list) the $arg will not be
> substituted and the argument will be the same as if I wrote "function \$arg".
> If I do [list function $arg] then
> $arg will be substituted but if it had a space in it, it will still count as
> one argument (not two like
> before).. actually $arg will become a list element.
> Example :
> set file "c:\My documents\file.txt"
> if you do
> button .b -command "open $file"
> then it will fail because it would be the same as doing :
> button .b -command "open c:\My documents\file.txt"
> (this is what will be stored), so once evaluated, it will evaluate "C:\My" as
> the first argument and
> "documents\file.txt" as the second argument.
> If you do :
> button .b -command {open $file}
> then it will fail because it will say "$file : file not found" unless you
> create a file named "$file"
> if you do :
> button .b -command [list open $file]
> then it will work because Tcl will store the callback as : {open {C:\My
> documents\file.txt}} (a list with two
> elements, the first being the command, the second being the argument).
> and finally, about the 'command theory', it's to say that EVERYTHING is a
> command. even 'if'.. so the if is a
> command which takes :
> if expression body ?elseif body? ?elseif body? ... ?else body?
> so if you do :
> if $a return
> it works, if you want to do :
> if $a == $b return
> it won't work because you sent "$a" as one argument "==" as a second argument
> (the body '==' is invalid, it
> would say that '==' is not a valid command) and $b as the third argument
> (again error because it only accepts
> else and elseif) and return as the 4th argument. So you group them into a
> list :
> if {$a == $b} return
> the {$a == $b} becomes a list. You could have also done :
> if [list $a == $b] return
> but it's better to put braces, and the 'if' command will evaluate the
> expression and *substitute in the parent
> namespace* (which is why it works, even if { } will disable substitution).
> Also, you CAN'T do :
> if {$a == $b} {
> return 0
> }
> else
> {
> return 1
> }
>
> because it will say "else : invalid command". The commands are delimited by
> either a ';' or by a newline, so
> when you close the brace after the if and go to the next line, it means that
> you finished with the 'if'. This
> means you HAVE to put the 'else' on the same line as the closing brace of the
> body, like this :
> if {$a == $b} {
> return 0
> } else {
> return 1
> }
> The same applies for the 'else' you can't put a newline after the 'else',
> otherwise it will say "{ : invalid
> command".
> You can put newlines inside the body of the if only because we do a { } (if
> you do [list] you'll need to put a
> backslash at the end of each line otherwise it will say "missing close
> bracket", like this :
> if {$a == $b} [list \
> return 0 \
> ] else [list \
> return 1
> ]
> but you DON'T WANT TO DO THIS because... well, remember { } allows you to
> disable substitution, so if you do for
> example :
> if {$a == $b} [list return [exit]]
> then when evaluation the 'if', the [list return [exit]] will be evaluated (to
> go as an argument of the if) and
> 'exit' will be called even if $a != $b.
> So to continue, when you do the { }, nothing is evaluated, so if you do
> if { $a == $b } {
> return 0
> }
> then if will get 2 arguments, the first being the expression and the second
> being a list containing multiple
> elements : a newline, a series of spaces, a 'return', a '0' and a newline.
> When the 'if' will evaluated that
> list, it will be evaluated as code and the variables/commands will be
> substituted/evaluated and the newlines
> will be interpreted as command delimiters.
> You can also do something like this :
> set body { whatever_function $arg
> return 0
> }
> if {$a == $b} $body
> and since $body is not between { } it will be replaced by the code above...
> beware, if you did :
> if {$a == $b} {$body }
> then $body will only be substituted AFTER the if is entered and will be
> evaluated as one command, it will say
> that :
> {whatever_function $arg
> return 0
> } : invalid command
>
> oh and yes, if you were meant to ask, yes, you can put newlines and put
> spaces in a command, so if you do :
> proc {a
> b
> c} { } {puts 'abc called'}
>
> a command called {a
> b
> c} will be created. And you can call it with
> {a
> b
> c}
> or with :
> set command "a\nb\nc"
> $command
>
> it's fun Tcl, right ? you just need to understand those three basics,
> anything is a command getting executed..
> the tcl keywords are just 'built-in' commands (like if), understand lists and
> substitutions... and once you get
> that, you can do a lot of fancy stuff (like commands with spaces or newlines
> in them :p)
>
> Finally, here are three interesting links in the forums in which I explained
> what I just explained in this mail,
> a bit differently, maybe better, with other examples, and probably with a bit
> more info. So please read them
> too.
> http://www.amsn-project.net/forums/viewtopic.php?p=17467
> http://www.amsn-project.net/forums/viewtopic.php?p=5801#5801
> http://www.amsn-project.net/forums/viewtopic.php?p=4461#4461
>
> and I would REALLY love it if someone could summarize all this (or just
> copy/paste it?) to the wiki in a page
> like Dev:Tcl/Tk_Tutorials
>
>
>
> p.s.: I never tried/tested the commands with newlines, but I'm guessing they
> will work,I know that if I had put
> $body, it will tell me an error trying to execute a command containing the
> newline, but I never created one in
> itself.
>
> Thanks and have fun!
> KaKaRoTo
>
>
> On Thu, May 31, 2007 at 12:05:49AM +0200, Mirko Hansen wrote:
> > Wow thanks a lot everybody for this nice welcome. It's a real pleasure to
> > me. I think I should introduce myself roughly. Well, I think you all already
> > know, but my name is Mirko. ;) I'm 24 years old, living in Germany, and
> > actually I'm studying computer science at university. It's sometimes really
> > time-consuming, especially if we have those really nice homeworks like the
> > last two days, but I hope I'll be of use for the team, anyway I'll give my
> > best to. As Youness said, I'm very new to TCL, I never had to deal with it
> > before, so I would be really grateful if you advise me of my possibly made
> > mistakes, to be able to learn from them. :)
> >
> > I think you'll hear from me soon. To a great teamwork! :)
> >
> > Bye,
> > Mirko
> >
> > 2007/5/30, Youness Alaoui <[EMAIL PROTECTED]>:
> > >
> > >yeah, sounds intriguing right ?
> > >well, baaazen is the username of Mirko. And this mail is to announce that
> > >he's been added as part of the team.
> > >So everyone, please welcome Mirko into the team, and please be helpful.
> > >Mirko, if you need anything, don't hesitate to ask. I think you've been
> > >following the ML for a little while now
> > >so you should know how we work. in short ;
> > >1 - a bugfix, you can commit
> > >2 - a change to the UI should be discussed
> > >3 - a change of behavior should be discussed
> > >4 - a new feature should be discussed.
> > >
> > >Mirko is still studying and won't have much time (like everyone else) but
> > >he promised to do his best to try and
> > >help. He doesn't know much Tcl but from the patches he sent, it shows that
> > >he's very skilled and I'm sure he'll
> > >learn it all pretty soon.
> > >
> > >KaKaRoTo
> > >
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