[Swift-user] still stuck on fold9.swift

[Ben Clifford]

On Tue, 16 Jun 2009, Hodgess, Erin wrote:

> Ok.  We're back to fold9.swift again, but it's saying that there are 
> multiple writers.
> These are in /home/erin/swift1.
> 
> Is it because of the recursive nature of the a[v+1] setup, maybe?

This is a static compile time analysis problem - Swift looks at the source 
code and sees that you are assigning to the a[] array in one place (the 
a[0] statement, outside of iterate) and again in another place (the a[v+1] 
place inside of iterate).

Its bothered me in the past that this hasn't worked, but I hadn't realised 
that it did at one stage actually work (which it must have done to be 
written in the tutorial).

Its probably useful to file a bug about this, then - its a comment I have 
from doing things with the 3rd provenance challenge over the past couple 
of months too. I think in the long term its a use that should be accepted, 
but the syntax of Swift makes this kind of analysis incredibly awkward to 
get right.

You can maybe around this by something like this (untested):

replace 

  a[v+1] = countstep(a[v]);  

with
  if(v==0) { a[v+1] = countstep(startfile); } 
  else { a[v+1] = countstep(a[v]); } 

and replace the a[0] assignment line with:

countfile startfile = echo("793578934574893");


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