************************************************************************* A GUIDE TO AMOS 6 - MORE ON PROCEDURES BY BRUCE LAING © 1994 Bruce Laing for Megadisc Digital Publishing ************************************************************************* Easy AMOS users please see the Errata at the bottom of this file! -S 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43 Welcome to part 6 of the "guide to AMOS" series. In this article, I will be concluding our look at procedures as well as having a look at the more advanced structured commands available in AMOS professional. In the previous Megadisc, i showed you two ways of passing variables into procedures from the main program. As i mentioned, there are ways of passing variables to procedures, and the third is to enclose the variables in square brackets in the Procedure statement. E.G. A=1 : B=2 PR[A,B] Procedure PR[A,B] Print A,B End Proc What if you wish to pass variables back to the main program from the original procedure? you can do this using a modified version of the End Proc command as well as the param function. First i will explain the modified End Proc command. this has the same function as the procedure command. That is: End Proc[A,B] but for the command to have any use, we must use the param function. This has three versions of the same command. and these are: Param (for interger variables) Param$ (for string variables) Param# (for floating point [or real] numbers) Below is an example: A=5 _MUL[A] Print Param Procedure _MUL[A] A=A*5 End Proc _MUL[A] What if you don't wish to let the procedure do it's full course? You can get out of it by using the Pop Proc command. this command will exit back to your main program without going through the full routine. Here's a quick example: Procedure _GET_OUT Main: CT=CT+1 If CT=10 then Pop Proc Print "I'm Stuck!" goto MAIN End Proc  IS IT OR ISNT IT? Previously, i started to talk about the IF/THEN/ELSE/ENDIF structure. The If function tests to see if a condition is met. if the condition is met, the command after the THEN statement will be executed. If the condition fails, it will go to the next line. The Else command simplify things. Take a look at the listing below..... A=Rnd(2) If A=2 Then Goto _NEXT Print "A is less than 2" _NEXT: program continues..... Compare that to the next listing...... A=Rnd(2) If A=2 Then Goto _NEXT : Else Print "A is Less than 2" ... ..... _NEXT: Program continues..... However, there is a slightly different structure using the ENDIF statement. The difference will be that the THEN cannot be used in a If/End If combination. A=Rnd(2) If A=1 Goto _NEXT Else Print "A is less than 2" End If AMOS Professional users have an additional string to their programming bow. This command is called the Else If command, and allows you to have multiple tests. Take a look at the listing below.... If A=1 Print "one" Else If A=2 Print "Two" Else Print "Three End If ON ..... PROC COMMAND We can simplify the above listings much easier by using the ON command. This can have a number of formats. The possible combinations are: On Goto line1,line2,line3 (for the goto command) On Gosub line1,line2,line3 (for the Gosub command) and of course... On Proc Proc1,proc2,proc3 (for procedures) The above commands are the equivalent of the If/Then commands earlier. The only thing you cannot do is check for negative values. This will cause an error. If the value is higher than the listing in the On... command, it will then jump straight to the next line. for example, if the variable A has a value of 4 and you only had three options in the On..... command, it would then jump straight to the next line in the program. Every little thing that you do..... Kate Ceberano, 1991 Here's something if you wish to run a procedure (or subroutine) every few 50ths of a second. (or if you live in America, 60ths of a second). This command is called the EVERY command. This command can either be used for procedures or subroutines. All you have to do is to specify the length of time between every call in either 50ths (or 60ths) of a second. The thing is you must complete the routine before the specified interval time, otherwise an error will be called. While the routine is being called, the EVERY system is disabled automatically. So if you wish to call the routine continuously, you must insert an Every On command before the final End Proc (or return) is called. Take a look at this quick example: Every 50 Proc TEST Do Print At(0,0);"Loop" Loop Procedure TEST Shared A Inc A:Print :This is call number";A Every On End Proc  AND NOW... THE END OF THIS ARTICLE This marks the end of this editions article. you will find on this disk a short example program explaining most of the commands mentioned in this article. In the next MD, I will have a look at some of the excellent extensions available. The article will include a quick tutorial on the CText extension, as well as the excellent music extension EME (the enhanced music extension) and explain the new (and modified) commands in this extension. So Until next time BCNU © Bruce Laing, December, 1994 - = - = - = - = - = - = - = - = - = -  ERRATA for routine Easy AMOS users, please note that the EVERY command is not implimented in your version. You will have to rem out the procedure in the listing, otherwise, a "Command not available in Easy AMOS" error will rear its ugly head. Sorry. Bruce, December, 1994 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43 !¡ 43