variable ramping

Comments

• Mike G Posts: 2,702

  2012-12-06 13:22 edited 2012-12-06 13:22

  Increment volume until 32 is reached (limit maximum). Please see the Propeller manual page 155 for a detailed explanation of <#. Page 152 has information on pre/post increment (++).
  http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/Web-PropellerManual-v1.2.pdf
• MagIO2 Posts: 2,243

  2012-12-06 14:03 edited 2012-12-06 14:03

  ++volume is called a pre increment. This means that the variable is incremented first and the result of the increment is used in the rest of the expression. You could translate this code into:
  
  volume := volume + 1
  volume := volume <# 32
  
  If you write volume++ in an expression, that's called a post increment. So, first the value of volume is read and used in the rest of the expression and then it is increased. This of course would not make sense in this expression.
• stilgar Posts: 47

  2012-12-06 14:57 edited 2012-12-06 14:57

  thanks for the info
  stilgar
• JonnyMac Posts: 9,556

  2012-12-06 14:57 edited 2012-12-06 14:57

  You can do the same thing with pre-decrement:
  
  volume := --volume #> 0
• lardom Posts: 1,659

  2012-12-07 10:12 edited 2012-12-07 10:12

  I use a memory aid to remember the difference between the maximum limit '<#' and the minimum limit '#>' ; This '<' represents an eye looking right which = 'maximum'. This '#' represents the eyeball 'highlight'. So one 'highlighted eye' looks toward 'maximum' '<#' and the other toward 'minimum' '#>'.

  volume := ++volume <# 32
  

  
  Every time this line is executed 1 is added to the 'volume' variable up to a maximum of 32. I think it helps to learn to state a line of code in plain english.
• cavelamb Posts: 724

  2012-12-07 12:55 edited 2012-12-07 12:55

  However, we often find that ramping may need something more than ++1 increment.
  
  As in the following example.
  LED Throb - steps up and down by 2.
  
  

  { Throb.Spin }
  CON     
  _CLKMODE=XTAL2
  _XINFREQ =5_000_000
  MSec   = _XINFREQ / 1_000
  USec   = _XINFREQ / 1_000_000
  T500U = Usec * 500                                          
  T300M = Msec * 300                                  
  Tsteps= 50                       
  VAR
  Byte X, LED
  PUB  Throb
     LED := 23
    dira [LED] :=1
      Repeat                              
        ' going up
        Repeat X from 1 to Tsteps step 2   
           outa[LED] := 1                                     
           waitCNT ((X*T500U) +cnt)        
           outa[LED] := 0                                      
           waitCNT ((Tsteps-X+1)*T500U+cnt)
        outa[LED] := 1                      
        waitcnt(T300M +cnt)
  
        'going down
        Repeat X from 1 to Tsteps step 2          
           outa[LED] := 1    
           waitCNT ((Tsteps-X+1)*T500U+cnt)
           outa[LED] := 0                                         
           waitCNT ((X*T500U) +cnt)
        waitcnt (T300M*2 +cnt)      
  
  
• Duane Degn Posts: 10,588

  2012-12-07 18:37 edited 2012-12-07 18:37

  lardom wrote: »

  I use a memory aid to remember the difference between the maximum limit '<#' and the minimum limit '#>' ; This '<' represents an eye looking right which = 'maximum'. This '#' represents the eyeball 'highlight'. So one 'highlighted eye' looks toward 'maximum' '<#' and the other toward 'minimum' '#>'.

  
  I always think of the "> <" symbols as hungry mouths. They're always open to the larger item, and when used as a limit they also get to eat a number sign.