Re: Iterating through a list

[Paul E Johnson]

Doug Donalson wrote:
> 
> Suppose I have a list, call it aList.  aList can have members or be empty.
> Suppose that aList is empty and I do the following:
> 
>     index=[aList create: self];
>     while(  (aListMember=[index next]) )
>    {
>       do some stuff
>    }
> 
1. The while loop will terminate after it finds a nil object in your
list.

2. From swarm 2.1 forward, I believe, you get a seg fault if you send
any message to nil. so if in your"do  some stuff" you have [aListMember
doSomething] then this is guaranteed to crash.  

3. Instead, do

        for (aListMember=[index next];[index getLoc]==Member;aListMember=[index
next])
        {
           if (aListMember != nil)
               do some stuff
        }       

the getLoc method returns Member for anything in the list, even nils.
-- 
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ukans.edu/~pauljohn
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66045                FAX: (785) 864-5700

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