egghelp.org community

[Fill]

Hi folks,

I'm trying to create a script that sends a warning message some seconds after a user joins the channel, but it is not working. The script is like this:

[arfer]

Using square brackets suggests that what they contain is a command and its arguments, if there are any. Command substitution will occur and the result fed back into the utimer statement. In your case the output command executes immediately and returns nothing. Hence the code will be interpreted as simply

utimer 15

Use the command [list] to return the appropriate arguments to the utimer command and have the output occur when the utimer triggers

[Fill]

ahmmm I see. But we must use square brackets with utimers isn't it?
I understood now, but how would I make to execute another proc after the 15 secs.?

Thanks for the help and great explanation

[arfer]

It rather depends on whether the proc you want to execute requires arguments to be passed to it, because the syntax for the command utimer is :-

utimer seconds command

That is why, taking the example above, you could not have simply written as follows :-

utimer 15 puthelp "PRIVMSG $chan :message"

That would result in the Tcl error :-

wrong # args: should be "utimer seconds command"

The square brackets group together the command name and its arguments into a single command. However, as we have seen, that will bring about command substitution during a preliminary pass through the interpreter. We simply used the list command to prevent immediate output (during command substitution). A Tcl list of arguments is passed to the utimer command instead of the return value of an output command (in actuality nothing).

Therefore, to answer your question. If the proc you want to execute after a delay does not take any arguments then you don't need square brackets :-

utimer 15 procName

If the proc does take arguments, then you do need square brackets to group them. In which case substitution will occur and to prevent immediate execution you would generally make use of the list command :-

utimer 15 [list procName arg1 arg2]

I think that's just about the best explanation I can manage from my understanding of Tcl. There are more knowledgeable folk here that could perhaps give you a technically better answer.

I will tell you this with some degree of certainty. Everybody learning Tcl has fallen foul of this or similar.
_________________
I must have had nothing to do

[nml375]

To get technical:
The reason we recommend using the list command when using timer/utimer is to avoid "double substitution and evaulation". This problem arises because of the way variable and command substitutions are done in tcl.

Contrary to many other programming languages, when you prefix a variable name with $ in tcl, this causes the tcl interpreter to read the variable and replace the $variable with it's content. Same goes for command substitutions ( [command] ). In essence, the command will never see the variable, let alone be aware of it's existence.

The problem with timer/utimer, is that the command line argument gets passed to the tcl interpreter as the timer expires. As such, the interpreter will first check for any variable and command substitutions before executing the command. Hence, we got a second substitution.

The effect of this is perhaps best illustrated with an example:

[Fill]

NIce, understood everything!!! Your explanation was great, thanks for the great help nml375 and arfer. We're always learning

Once again, thanks a lot. I appreciate this website.

See ya