[darcs-devel] [patch1997] index: fix import layout (and 8 more)

Ben Franksen bugs at darcs.net
Fri Feb 28 00:18:02 UTC 2020


Ben Franksen <ben.franksen at online.de> added the comment:

>>   * index: no longer rely on the special behavior of appendPath
> 
>> -          then dirlength state -- must be 0 in this case
>> +          Nothing -> dirlength state
> 
> Isn't that "must be 0" comment still valid?

Hm, yes. Can't remember why I removed it. Should probably re-add.

>> -           tree' = makeTree [ (n, fromJust $ treeitem s) | (n, s) <- inferiors, isJust $ treeitem s ]
>> +           tree' = makeTree [ (n, fromJust $ treeitem s) | (Just n, s) <- inferiors, isJust $ treeitem s ]
> 
> What's going on here, i.e. how do we know it isn't a behaviour change?

We change the type of 'nameof' to return Maybe, where Nothing is
returned only for the root item. The 'inferiors' in the above snippet is
a bad name for 'subtrees' and is the result of calling 'subs $ start
substate' a few lines above that code. 'subs' in turn recursively
enumerates the "states" (think of a state as a cursor) pointing to the
subitems under the current one. It in turn calls 'nameof' which must
return Just because by definiton sub items are not the root item.

Clear now?

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