Local Variables

[kevin]

Local Variables

  Here's some examples to help those new to this PlayBASIC programming stuff, get some idea of Variable Scope.    


  Local Variables Inside User Defined functions

PlayBASIC Code: [Select]

   Setfps 60

  Do
        Cls 0
        
      print BumpCounterFunction()
      print BumpStaticCounterFunction()

  
      Sync     
  loop



Function BumpCounterFunction()
   // When this function is entered, all variables are set to zero

    // add one to the local COUNTER variable.  This variable only exists inside this function.
    Inc Counter

   // Since Counter is local and will be initialized to zero each time we call this function
   // upon exiting Counter will always be 1 

EndFunction Counter




Function BumpStaticCounterFunction()
   // Tell PB that Counter variable should retain it's value between calls
      Static Counter

    // add one to the local COUNTER variable
      Inc Counter

   // The counter variable inside this function retains it's value between calls, so
   // each time we call this function the local counter variable will be increased by 1
   
EndFunction Counter

   Make a Global variable accessible inside a function.

PlayBASIC Code: [Select]

  // Tell PB that the variable COUNTER should be visible from inside Functions & Subs
  // 
  Global Counter 


   Setfps 60

  Do
        Cls 0
        
      print BumpCounterFunction()
  
      Sync     
  loop



Function BumpCounterFunction()

    // add one to the GLOBAL COUNTER variable.
    Inc Counter

    // Since counter exists outside of the function it's not created/destroyed each time 
    // a function is called.  So if we change it's value inside a FUNCTION or PSUB
    // the changes will be visible program wide.

EndFunction Counter

 Using LOCAL to tell PlayBASIC to ignore any global instances of a variable.

PlayBASIC Code: [Select]

  // Tell PB that the variable COUNTER should be visible from inside Functions & Subs
  Global Counter 

  Setfps 60

  Do
        Cls 0
        
      print BumpCounterFunction()
      print BumpLocalCounterFunction()
  
      Sync     
  loop



Function BumpCounterFunction()

    // add one to the GLOBAL COUNTER variable.
    Inc Counter

    // Since counter exists outside of the function it's not created/destroyed each time 
    // a function is called.  So if we change it's value inside a FUNCTION or PSUB
    // the changes will be visible program wide.

EndFunction Counter





Function BumpLocalCounterFunction()

   // Tell PB that inside this function you want a local variable Called COUNTER

   
       Local Counter

    // When PB sees the Counter varibale,  it first looks are any local variables
    // of that name.. If it can't find one, it looks in the Globals declarations.
    // In this case, it'll find the LOCAL copy first.  So this Counter is not the 
    // global version, but the local. Which  
    
    Inc Counter

   // Since Counter is local and will be initialized to zero each time we call this function
   // upon exiting Counter will always be 1 


EndFunction Counter