Re: [Haskell-cafe] Please add a method for optimized concat to the Semigroup class

Am 03.05.2011 um 13:39 schrieb Stephen Tetley:

Does it have an obvious default implementation, bearing in mind it we might really want a total function?

sconcat [] = error "Yikes - I wish this was total!" sconcat [a] = a sconcat (a:as) = a <> sconcat as

You have to provide the "neutral" element by yourself: infixl 4 <>> a <>> [] = a a <>> (b:bs) = a <> b <>> bs

Best wishes

Stephen

On 3 May 2011 12:12, Yitzchak Gale wrote: [SNIP]

...

It has the obvious default implementation, but allows for an optimized implementation for specific instances. That turns out to be something that comes up all the time (at least for me) in real life.

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