Re: inits

Aaron Denney wrote:

On 2006-04-08, Chris Kuklewicz wrote:

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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.

The inits' _ = undefined can be left out, but may be useful to some clarity. On the other hand, I think the new spiffy inits is quite clear once you notice why its map (const xn) $ undefined:xn This version doesn't use a weird recursive function. Its just.. the definition of inits I think. first element of inits, take the first element. 2nd element of inits, take the first plus the next element ... But that's just my logic... probably why I wrote it like this in the first place ( just wanted to see if I could write the inits without using a book ;) )