Loops - variable or command?

[stevmjon]

just wondering when using a loop is it best to use variables or commands?

#1 :

For lp = 0 to GetScreenWidth()

#2 :

width = GetScreenWidth()
For lp = 0 to width

i am not sure if the #1 command is read once or is it read each iteration of the loop?
i have always used variables as these are fast access.

[kevin]

Expressions are pre-evaluated into temp variables.

So GetScreenWidth() is only called once to compute the end of the range.

PlayBASIC Code: [Select]

setfps 30

Do
    cls
    
    For xlp=0 to _GetScreenWidth()
        print xlp
    next

    sync
    
loop spacekey()
end


function _GetScreenWidth()
      print "Called _GetScreenWidth()"
EndFunction 10