haskell at list.mightyreason.com
Sat Apr 8 15:27:47 EDT 2006
Aaron Denney wrote:
> On 2006-04-08, Chris Kuklewicz <haskell at list.mightyreason.com> wrote:
>>> Is the head of the inits of undefined really an error?
>>> Since the head of inits  is also  ...
>>> But if you really want that undefined to produce an error.. you could
>>> just :
>>> inits' xn@(_:_) = zipWith take [0..] $ map (const xn) $ undefined:xn
>>> inits' _ = undefined
>> Exactly. Now inits' *is* a drop in replacement for inits.
> Right, but the new spiffy inits seems to be a strict superset. Does
> anything plausibly depend on the strictness of the original. I think it
> was written that way for clarity, not for the strictness properties.
I have nothing that depends on the difference.
And it really only affects (inits undefined).
There is a certain progressions to this though
(A) inits undefined is undefined
(B) inits [undefined] is :[undefined]
(C) inits [1,undefined] is ::[1,undefined]
The original replacement made (A) behave like (B), which breaks the nice
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