Playing Music and Global Variables

[LegendsEnd]

I thought I could do my program without using a global variable but I've run into a problem when it comes to music, I'm using Turing 4.03 if it makes a difference.

code:

process PlayMusic (file : string)     loop         Music.PlayFile (file)     end loop end PlayMusic procedure Program fork PlayMusic ("BG.mp3") %Program end Program

When I use Music.PlayFileStop, it just restarts the process, if I make the process like so:

code:

process PlayMusic (file : string, stop : boolean)     loop         exit when stop = true         Music.PlayFile (file)     end loop end PlayMusic

While that works if I were to just do fork PlayMusic ("a.wav",true), if I played a file first then did that, the second process would end and the first process would just continue again. I can't think of a way to stop it from another procedure however, so only thing I can think of now is a global variable. Should I be trying to make a class and find a workaround that way?

[Delos]

Does Music.PlayFileReturn() work on your version? If so, you won't need to use processes at all.

As for the lack of globabl variables, it is quite possible - as long as your play your cards correctly. Bottle things up into modules or classes, which each can have their own local variables that pervade the structure. Then, parameters, parameters, parameters - you'll be passing and parsing more than you ever thought possible, but it will all end up in your favour, as you won't have to worry about hard-coded lines floating around the place! (That's really whay global variables introduce, levels on hard-coding that are not as dynamic as parameter-passed vars).

[LegendsEnd]

Music.PlayFileReturn does not work on my version, is there a way to create it manually? If not, would it be proper programming if I were to just throw that part of my program into a module and have a global variable type thing in it?

[LegendsEnd]

Hmm I just did the whole module method but it doesn't seem to work. My module:

code:

unit module PlayMusic     export Start, Stop     var stop : boolean     process Start (file : string)         stop := false         loop             exit when stop = true             Music.PlayFile (file)         end loop         Music.PlayFileStop     end Start     procedure Stop         stop := true     end Stop end PlayMusic

Simple program:

code:

import PlayMusic fork PlayMusic.Start ("tes4title.mp3") PlayMusic.Stop

[Delos]

Looking at your Play process, it seems as though it will continuously attempt to play the file until a Stop is called - which would result it a staticy 'buzz' screaming through your speakers.

If you have access to a newer version of Turing through your school, see if you can get it since PlayFileReturn() is definitely a useful procedure.

If you can't, and you want to keep plugging away with processes, then do the following:
- read the basic tuts on processes
- read the warning tuts on processes explaining their evils
- read Tony's advanced tuts on processes and concurrency
- look into Monitors. These are rarely used constructs that you could allow you to switch processes on and off (I believe the commands are something to the ring of 'wait' and 'wake'...or such analagous terms).

I don't suggest this though, since it's a lot more work than would seem necassary. If I understand, you're trying to loop some music while playing? And this music might change during the programme? In which case, you might be able to get away with changing the name of the track that is pulled by your play process...
Oh, and what was the specific error you got when you tried your Module?

[LegendsEnd]

After a lot of messing around I got it working. It wasn't that the program wasn't working, it was just my stop procedure didn't stop it. I fixed this by playing a 1 millisecond delay after forking the play process and THEN calling the stop procedure. Apparently calling a process and then a procedure right afterwards is a bad idea.