求值顺序

    1. var v = 0
    2. proc getI(): int =
    3.   result = v
    4.   inc v
    5.  
    6.  
    7. proc someCopy(a: var int; b: int) = a = b
    8.  
    9. a[getI()] = getI()
    10.  
    11.  
    12. v = 0
    13. someCopy(b[getI()], getI())
    14.  
    15. doAssert b == [1, 0, 0]